Keywords: Geothermal power plants Resource assessment Geothermal reservoirs Drilling Injection testing Core samples. Volume 2: Application in Hawaii

Transcription

1 EPRI Electric Pwer Research Institute Keywrds: Gethermal pwer plants Resurce assessment Gethermal reservirs Drilling Injectin testing Cre samples EPRI TR V2 Prject Final Reprt December 1993 Gethermal Reservir Assessment Based n Slim Hle Drilling Vlume 2: Applicatin in Hawaii Prepa'red by The Unl~@rsity f Hawaii at Mana Hnlulu, Hawaii

2 EPRI Leadership in Science and Technlgy R E p R T s u M M A R y Gethermal Reservir Assessment Based n Slim Hle Drilling Vlumes 1 and 2 EPRI tested and dcumented slim hle drilling as a gethermal resurce evaluatin methd. The results f this wrk cnfirm that lwer cst reservir evaluatins can be perfrmed using slim hle methds. On the basis f this reprt's prbabilistic reservir size estimate, the Kilauea East Rift Zne n the island f Hawaii culd supprt MWe f gethermal pwer capacity. INTEREST CATEGORY Renewable generatin and fuels KEYWORDS Gethermal pwer plants Resurce assessment Gethermal reservirs Drilling Injectin testing Cre samples BACKGROUND Utilities spnsring gethermal pwer plant prjects face financial risk and expense in finding and cnfirming reservirs. A lesser, but imprtant, risk invlves underprductin and/r lwer-than-design temperature frm prductin wells drilled t deliver gethermal ht water t the pwer plant. Drilling and flw testing full-size prductin wells in advance f pwer plant cnstructin is an expensive way t mitigate risks. The State f Hawaii and EPRI cspnsred the prject reprted here t use smaller, less-expensive "slim hles" as a means f discvering and evaluating a gethermal reservir. OBJECTIVE assessment. T test and dcument the slim hle methd f gethermal reservir APPROACH The prject team cnsisted f university researchers, a gethermal resurce/reservir assessment firm, and varius suppliers f gethermal drilling and field-testing services. They planned and dcumented the slim hle methd and its applicatin t the Kilauea East Rift Zne (KERZ), the gethermal resurce area f greatest near-term ptential in Hawaii. Next, they designated a series f fur slim hles, knwn as scientific bservatin hles (SOHs) 1, 2, 3, and 4. Using injectin flws, they drilled and tested three f the fur SOHs. Finally, they prepared this final reprt, dcumenting the methd, the SOH experience, the results, and the cnclusins f the Kilauea test. RESULTS The Hawaii applicatin cnfirms the viability f the slim hle apprach. Specifically, the three hles drilled and tested suggest that csts can be reduced by half cmpared with a full-size well. In additin, the slim hles prvided results cnsistent with an analysis based n a mre cmplete data set. A prbabilistic analysis f the variatin in crucial gethermal reservir parameters, as measured r estimated frm SOH and ther available data, led t a KERZ reservir size estimate with the fllwing prbability distributin: a mean f 288 MWe, a mde f 180 MWe, and a standard deviatin f 177 MWe. A prbabilistic analysis using nly data frm the three SOHs prvided similar results: a mean f 173 MWe, a mde f 100 MWe, and a standard deviatin f 116 MWe. A 28-MWe cmmercial gethermal pwer plant is nw lcated at this reservir. The SOH-nly analysis shws a 95% prbability that the lwer KERZ reservir will supprt this plant's full capacity fr 25 years. The three hles drilled were 7.6 cm (3.0 in) in diameter at their narrw final depth. Drilled t ttal depths f km ( ft), the hles indicated reservir EPRI TR s-V1-2 Electric Pwer Research Institute

3 temperatures ranging between C ( F). SOH-1 exhibited high flw capacity (6100 millidarcy-ft) behind a thin impermeable barrier that partially bscured the reservir flw capacity. The ther tw hles exhibited lw flw capacity (abut 1330 millidarcy-ft). On the basis f flw capacity and the related permeability measurements, a rck prsity range f 3-7% was used in reservir mdeling. Vlume 1 f this reprt cntains the slim hle analytical methd. Vlume 2 describes its specific applicatin t KERZ. EPRI PERSPECTIVE The reprt shws hw t prceed with a slim hle reservir assessment prject. The particular example f KERZ n the island f Hawaii ffers mre f a guide t reveal lessns learned than a mdel t be emulated. Csts were abut twice as high as planned, but the prject revealed methds f reducing csts that were successfully emplyed n the last f the hles (SOH-2). Csts t drill and cmplete the hles ranged frm nearly $3001ft fr SOH-1 at 5526 ft (1684 m) dwn t $1601ft fr SOH-2 at 6802 ft (2073 m). With cnventinal industry cmpletin practices and use f rtary drilling t the bttm f the hle (withut recvery f cre samples), csts as lw as $100/ft culd be targeted fr ft ( km) deep slim hles. Full-size wells wuld cst $300-$400/ft in this depth range under Kilauea cnditins. PROJECT RP Prject Manager: Evan Hughes Generatin & Strage Divisin Cntractr: The University f Hawaii at Mana Fr further infrmatiri n EPRI research prgrams, call EPRI Technical Infrmatin Specialists (415)

4 Gethermal Reservir Assessment Based n Slim Hle Drilling Vlume 2: Applicatin in Hawaii TR V2 Research Prject Final Reprt, December 1993 Prepared by THE UNIVERSITY OF HAWAII AT MANOA Hawaii Natural Energy Institute Hlmes Hall Dle Street Hnlulu, Hawaii Principal Investigatr H. J. Olsn GEOTHERMEX, INC Central Avenue, Suite 201 Richmnd, Califrnia Prepared fr State f Hawaii Department f Business, Ecnmic Develpment and Turism 335 Merchant Street, Rm 110 Hnlulu, Hawaii Electric Pwer Research Institute 3412 Hillview Avenue Pal Alt, Califrnia EPRI Prject Manager E. Hughes Hydrelectric Generatin & Renewable Fuels Prgram Generatin & Strage Divisin

5 DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES THIS REPORT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN ACCOUNT OF WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC. (EPRI). NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) NAMED BELOW, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM: (A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS REPORT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) THAT THIS REPORT IS SUITABLE TO ANY PARTICULAR USER'S CIRCUMSTANCE; OR (B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS REPORT OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS REPORT. ORGANIZATION(S) THAT PREPARED THIS REPORT: THE UNIVERSITY OF HAWAII AT MANOA ORDERING INFORMATION Requests fr cpies f this reprt shuld be directed t the EPRI Distributin Center, 207 Cggins Drive, P.O. Bx 23205, Pleasant Hill, CA 94523, (510) There is n charge fr reprts requested by EPRI member utilities. Electric Pwer Research Institute and EPRI are registered service marks f Electric Pwer Research Institute, Inc. Cpyright 1993 Electric Pwer Research Institute, Inc. All rights reserved.

6 ABSTRACT The Hawaii Scientific Observatin Hle (SOH) prgram was planned, funded, and initiated in 1988 by the Hawaii Natural Energy Institute, an institute within the Schl f Ocean and Earth Science and Technlgy, at the University f Hawaii at Mana. Initial funding fr the SOH prgram was $3.25 millin supplied by the State f Hawaii t drill six, 4,000 ft scientific bservatin hles n Maui and the Big Island f Hawaii t cnfirm and stimulate gethermal resurce develpment in Hawaii. After a lengthy permitting prcess, three SOHs, ttaling 18,890 feet f mstly cre drilling were finally drilled alng the Kilauea East Rift Zne (KERZ) in the Puna district n the Big Island. The SOH prgram was highly successful in meeting the highly restrictive permitting cnditins impsed n the prgram, and in develping slim hle drilling techniques, establishing subsurface gelgical cnditins, and initiating an assessment and characterizatin f the gethermal resurces ptential f Hawaii - even thugh permitting specifically prhibited pumping r flwing the hles t btain data f subsurface fluid cnditins. The first hle, SOH-4, reached a depth f 2,000 meters, recrded a bttm hle temperature f C, and established subsurface thermal cntinuity alng the KERZ between the HGP-A and the True/Mid-Pacific Gethermal Venture wells. Althugh evidence f fssil reservir cnditins were encuntered, n znes with bvius reservir ptential were fund. The secnd hle SOH-I, was drilled t a depth f 1,684 meters, recrded a bttm hle temperature f C, effectively dubled the size f the Hawaii Gethermal Prject - Abbtt/Puna Gethermal Venture (HGP-A/PGV) prven/prbable reservir, and defined the nrthern limit f the HGP-A/PGV reservir. The final hle, SOH-2, was drilled t a depth f 2,073 meters, recrded a bttm hle temperature f C, and has sufficient indicated permeability t be designated as a ptential "discvery". iii

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8 Sectin CONTENTS 1 INTRODUCTION CONCLUSIONS PROJECT HISTORY Lcatin and Setting Previus Activity The Slim Hle Drilling Prgram DATA OBTAINED FROM THE SLIM HOLES DATA ANALYSIS Interpretatin f Dwnhle Data Subsurface Temperature Distrib~tin 5.3 Analysis f Permeability... ESTIMATION OF RESOURCE PARAMETERS ESTIMATION OF RECOVERABLE ENERGY RESERVES REFERENCES v

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10 TABLES State f Hawaii Slim Hle Drilling Prject: Cllectin State f Hawaii Slim Hles: Basic Cmpletin Data Status f Data 4.3 Dwnhle Surveys Cnducted in Slim Hle SOH Dwnhle Surveys Cnducted in Slim Hle SOH Dwnhle Surveys Cnducted in Slim Hle SOH Histry f Injectin Rates and Pressures, Injectin Test f Slim Hle SOH Histry f Injectin Rates and Pressures, Injectin Test f Sl im Hle SOH Histry f Injectin Rates and Pressures, Injectin Test f Slim Hle SOH Reservir Parameters Estimated frm Injectin Testing f Slim Hles Summary f Estimated Resurce Parameters Summary f Prbabilistic Estimatin f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel A) Summary f Prbabilistic Estimatin f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel B) Estimated Prbability Distributins f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel A) Estimated Prbability Distributins f Recverable Ener~y Reserves, Kilauea East Rift Zne (Mdel B) vii

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12 I LLUSTRA TI ONS Figure 3.1 Map f the island f Hawaii including the East Rift Zne f the Kilauea vlcan Reginal map f the lwer Kilauea East Rift Zne shwing gelgic features and well lcatins Cmpletin diagram, slim hle SOH Cmpletin diagram, slim hle SOH Cmpletin diagram, slim hle SOH Dwnhle summary plt - slim hle SOH-l Dwnhle summary plt - slim hle SOH Dwnhle summary plt - hle SOH Water levels measured while drilling - hle SOH Explanatin fr dwnhle summary plts Dwnhle pressure respnse during injectin test f slim hle SOH Dwnhle pressure respnse during injectin test f slim hle SOH Dwnhle pressure respnse during injectin test f slim hle SOH Temperature distributin at -1,000 feet, msl Temperature distributin at -2,000 feet, msl Temperature distributin at -3,000 feet, msl Temperature distributin at -4,000 feet, msl Temperature distributin at -5,000 feet, msl Temperature distributin at -6,000 feet, msl Hrner semi-lg plt, well SOH-1 pressure fallff ix

13 Figure 5.8 Cmparisn f measured and calculated pressure data, well SOH Well SOH-2 pressure fallff test: Hrner semi-lg plt 5.10 Cmparisn f measured and calculated pressure data, well SOH Hrner semi-lg plt, well SOH-4 pressure fallff 5.12 Cmparisn f measured and calculated pressure data, well SOH Estimatin f reservir area based n slim hles nly 6.2 Estimated prbability distributin f reservir area 6.3 Estimatin f reservir area based n all wells and slim hles 6.4 Estimated prbability distributin f reservir thickness 6.5 Estimated prbability distributin f reservir vlume 6.6 Estimated prbability distributin f reservir depth 6.7 Estimated prbability distributin f average reservir temperature 6.8 Estimated prbability distributin f rck prsity 6.9 Estimated prbability distributin f energy recvery factr 7.1 Histgram f megawatt capacity based n slim hles nly (mdel A) 7.2 Histgram f megawatt capacity based n all well data (mdel B) 7.3 Histgram f megawatt capacity, mdels A & B 7.4 Cumulative prbability plt f MW capacity, mdels A & B 7.5 Histgram f MW per square mile, mdels A & B Page Cumulative prbability plt f MW per square mile, mdels A & B Histgram f recvery efficiency, mdels A & B Cumulative prbability plt f recvery efficiency, mdels A & B x

14 1. INTRODUCTION The State f Hawaii has an nging prgram t determine the extent f the gethermal resurce base within the State. As part f this prgram, the State, EPRI and the Hawaiian Electric Cmpany (HECO) have c funded a prject t assess the resurce base using deep, slim explratin hles as the primary surce f infrmatin fr resurce identificatin and quantificatin. S far this prject has included the drilling f three slim hles within the Kilauea East Rift Zne (KERZ) f the island f Hawaii, t depths between 5,500 and 6,800 feet. Vlume 1 f this reprt described in detail the thery and practice f assessing gethermal energy resurces using slim hle data. This vlume reviews the results t date f the slim hle drilling prgram in the KERZ, and applies the assessment methdlgy f vlume 1 t the infrmatin btained frm the slim hles. A ttal f three hles is insufficient t fully characterize a resurce as extensive as that f the KERZ. Therefre this vlume, in additin t using the slim hle results t illustrate the applicatin f the resurce assessment methdlgy, cnsiders several ther imprtant aspects f the prgram, including: The extent t which the available data are adequate r inadequate fr resurce assessment. The quality f the data cllected during drilling and testing f the slim hles, as regards their use in the assessment prcess. 1-1

15 The ptential integratin f infrmatin frm existing prductin-diameter deep wells in the KERZ. Sectin 2 summarizes the main cnclusins drawn frm the assessment f the KERZ slim hles. Sectin 3 reviews the histry f the explratin and develpment f the KERZ and f the slim hle drilling prgram. Sectin 4 describes the infrmatin cllected during the. drilling, lgging and testing f the hles, and sectin 5 discusses the reductin and analysis f the data. Sectins 6 and 7 present the applicatin f the resurce assessment methdlgy using the slim hle data. In sectin 6 the primary and secndary resurce parameters are estimated, using the techniques described in vlume 1. Sectin 7 presents a prbabilistic estimatin f recverable energy reserves based n the estimated resurce parameters. 1-2

16 2. CONCLUSIONS 1. Explratin and develpment drilling f prductin-diameter gethermal wells in the Kilauea East Rift Zne s far has been lcalized and nn-systematic, guided by the leasehld interests f peratrs as well as technical evaluatins f the resurce. Slim hle drilling prvides an pprtunity t add significantly t the resurce data base, and thereby aid in develping an integrated cnceptual mdel and reginal assessment f the KERZ gethermal resurce. 2. Data frm the slim hles are available in the frm f daily drilling reprts, well cmpletin reprts, limited analysis f cre samples, results f dwnhle lgging, and results f injectin testing. Gelgic mnitring f drilling peratins (mud lgging), detailed analysis f cres, prductin testing and fluid sampling have nt been perfrmed. 3. Mst f the ptentially available categries f data that are necessary f useful fr resurce assessment were cllected t sme extent during drilling and testing peratins, except as prevented by regulatry restrictins. Data availability and quality culd be imprved mst by greater attentin t data cllectin during drilling, and by the use f mre reliable dwnhle lgging instruments. 4. Cmpilatin and analysis f dwnhle data frm the slim hles indicates that all 3 hles penetrated gelgically similar envirnments cnsisting almst entirely f subaerial, submarine and intrusive basaltic rcks. SOH-4 appears t be structurally 2-1

17 lwer and penetrates a greater prprtin f dike rcks than the ther tw hles. 5. Existing dwnhle surveys are adequate t characterize the stable temperature prfiles f the slim hles. All the hles exhibit a similar prfile: a cld, isthermal zne extends t a depth f several thusand feet, belw which temperatures increase linearly, reaching 400 t 660 F belw elevatins f -4,000 feet msl. 6. Temperature data frm the slim hles, in cmbinatin with data frm ther deep wells in the lwer KERZ, are sufficient t develp a mdel f subsurface temperature distributin alng a prtin f the rift zne. The mdel shws higher temperatures ccurring alng the rift axis, decreasing rapidly with distance away frm the axis t the nrthwest and sutheast. A hightemperature (greater than 350 t 400 F) zne a mile r mre in width may be present at drillable depths alng the rift. 7. Evidence frm dwnhle surveys indicates that permeability in the deep subsurface near the rift axis (where temperatures are high enugh fr cmmercial explitatin) is restricted t lcalized znes f tectnic r vlcanic fracturing. Analysis f injectin testing suggests that reservir permeability is typically lw, yielding well flw capacities in the range f 1,000 t 6,000 md ft. 8. Prbability distributins f a number f imprtant resurce parameters can be characterized by the available slim hle data. In this study, prbability distributins have been estimated fr reservir area, thickness, vlume, depth, average 2-2

18 temperature, rck matrix density, rck prsity, rck heat capacity, and energy recvery factr. 9. Tw separate estimates f the prbability distributin f reservir area have been made: ne based nly n data frm the slim hles, and ne based n the slim hles plus data available frm ther lwer-kerz wells. Bth estimated distributins are asymmetric, due t uncertainty as t the maximum pssible size f the reservir, and the additin f mre well data increases the verall estimate f reservir area. This means that the gethermal resurce f the lwer KERZ is still far frm cmpletely defined by drilling. 10. The estimated prbability distributins f the resurce parameters have been used t calculate tw estimates f recverable energy reserves f the lwer KERZ, by means f a prbabilistic calculatin methd. The first estimate mdels reserves based n the slim hles nly, whereas the secnd mdels reserves based n all f the lwer KERZ wells. 11. The c~lculatin based nly n the slim hles indicates a recverable energy reserve whse prbability distributin has a mean f 173 megawatts, with a mde r mst likely value f abut 100 MW and a standard deviatin f 116 MW, assuming a pwer plant f typical efficiency with a 25 year lifetime and an average capacity factr f 90%. The prbability distributin f reserves based n all wells has a mean f 288 MW, a mde f abut 180 MW, and a standard deviatin f 177 MW. 12. The applicatin f the methdlgy presented here, and in vlume 1 f this reprt, t the data frm the KERZ slim hle 2-3

19 prgram indicates that even limited slim hle drilling can be useful in making a preliminary estimate f cmmercial reserves, defining requirements fr and benefits f additinal drilling, and characterizing the degree f resurce risk that exists when planning cmmercial develpment. The resurce assessment prcess itself is useful in assessing the relative benefits f different drilling methds, well designs and well lcatins, and therefre may assist in planning further drilling. 2-4

20 3. PROJECT HISTORY 3.1 Lcatin and Setting The Hawaiian scientific bservatin (slim) hle (SOH) drilling prgram is a central part f the nging prgram f the University f Hawaii t investigate the state's gethermal resurces, with the bjectives f assessing their ptential and stimulating their develpment by private investrs. The Kilauea East Rift Zne was chsen as the area f greatest interest fr initial slim hle explratin, because f its resurce that had been discvered and evaluated, in part, by previus drilling, its nging explratin and develpment by private peratrs, and its relative accessibility. The KERZ extends eastward t nrtheastward frm the summit f Kilauea vlcan, and lies within the Puna district f Hawaii Cunty (figure 3.1). Active injectin f magma int the rift frm the summit regin, ften accmpanied by eruptin f lava at the surface, maintains high temperatures and therefre prvides a heat surce fr hydrthermal activity within the rift zne. Althugh the hydrlgical and thermal structure f the Puna district is far frm fully defined, results frm explratin s far have tended t cnfirm the expectatin that gethermal resurces f cmmercial temperature are largely cnfined t areas alng and near the rift zne axis. The uppermst prtin f the KERZ, near the summit f Kilauea, lies within Hawaii Vlcanes Natinal Park and ther areas prtected frm cmmercial develpment. Explratin and develpment has therefre taken place within the lwer prtin f the rift, where the State has designated znes fr cmmercial gethermal activities (figure 3.2). 3-1

21 In the area where explratin has ccurred, the rift zne has a typical width f abut 1.5 miles, as indicated by bth surface mrphlgy and aermagnetic anmalies. The extent f gethermal reservirs within the 1.5 mile rift zne is nt clearly limited. Gethermal reservirs have nt been discvered utside the rift zne. At the surface parts f the rift zne are marked by pen fissures and lines f cinder and spatter cnes. Frm knwledge f lder rifts in the Hawaiian Islands, nw expsed by ersin, rift znes in the subsurface cnsist f swarms f clsely spaced, nearly vertical, and nearly parallel dikes. The dikes are cmpsitinally similar t the repetitive basalt flws int which they are intruded; the basalt flws make up the bulk f the vlcanic edifice and differ frm each ther mre in texture than in cmpsitin. Flws ccurring clser t the present grund surface are subaerial and include pahehe and a'a flws, ften with internal textural variatins, and rarer pyrclastic depsits. With increasing depth a transitin t submarine lavas ccurs, s that cmpact pillw lavas and lesser hyalclastites (water-lain pyrclastics) predminate. Other rck types, including mainly cral reef carbnate, are rare. The gethermal system r systems f the KERZ therefre ccur in a vlcanically and tectnically active rift setting that is cmpsitinally simple but structurally and texturally cmplex, dminated by the prevailing rift structure. 3.2 Previus Activity Explratin activity in the KERZ began in the early 1960s, when a subsidiary f Magma Pwer Cmpany drilled a series f 4 wells up t 700 feet deep at scattered lcatins. Several f these wells encuntered mderately high temperatures, but nne discvered a 3-2

22 cmmercial gethermal resurce. than a decade thereafter. Significant explratin ceased fr mre A number f gvernment-funded gephysical surveys were carried ut in the 1970s. These included gravity, magnetic, seismic, and a variety f electrical surveys, including DC (biple-diple and plediple), EM (time dmain, variable frequency inductive sunding and transient sunds), mise-a-la-masse and self-ptential (S.P.). These surveys lcated several anmalies, which tended t cnflict with each ther and therefre culd nt be used cnclusively fr delineating a gethermal reservir. Results f these and ther gephysical and gechemical surveys have since been used fr siting sme f the deep wells that have been drilled in the KERZ, but fr the mst part surface studies have guided deep drilling in nly a general way. In 1976 the first gethermal discvery in the KERZ was made by the State when a scientific test well, HGP-A, was drilled t a depth f 6,435 feet, encuntering cmmercial permeability and temperatures in excess f 600 F. A three megawatt (MW) demnstratin pwer plant was cnstructed and began peratin in 1982, using well HGP-A as its steam surce. The HGP-A plant perated until 1989, when it was decmmissined. Encuraged by the success f the HGP-A well, cmmercial peratrs resumed explratin activity during the 1980s. Thermal Pwer Cmpany btained a lease psitin in the vicinity f Kaph and carried ut an explratin prgram leading t the drilling f three prductindiameter wells (KS-1, KS-1A and KS-2) up t 8,000 feet deep during Each f these wells successfully encuntered cmmercial temperatures and permeability, and had measured prductivities f up t several MW. Hwever, all three wells were affected by sme degree f 3-3

23 mechanical damage, leaving n mre than ne f them in cnditin fr ptential cmmercial use. Thermal's explratin effrts, thugh encuraging, ended with the drilling f these wells, and the leases were eventually sld. Barnwell Industries, which acquired a leasehld that included acreage adjacent t Thermal's, drilled three wells plus ne sidetrack (Ashida 1, Lanipuna l/st, and Lanipuna 6) up t 8,400 feet deep during These wells shwed indicatins f high-temperature gethermal resurces, but nne was cmmercially prductive. In the late 1980's, the Puna Gethermal Venture (PGV) acquired the Thermal Pwer leasehld and a cntract t supply 25 MW f pwer t Hawaiian Electric Cmpany (HECO). Develpment drilling fr the prject began in late 1990, and t date three wells (KS-3, KS-7 and KS-8) have been drilled. These wells, drilled near the existing KS wells and HGP A, cntinue t indicate the presence f a viable gethermal resurce, but unanticipated subsurface cnditins have led t drilling and envirnmental prblems, the mst ntable being uncntrlled flws while drilling wells KS-7 and KS-8. This has resulted in regulatry delays in the prgress f field develpment. At the time f this reprt, PGV had nly recently resumed its develpment activities. Over the past several years the True/Mid-Pacific Gethermal Venture has als been cnducting an explratin prgram in the Wa Kele Puna area, several miles up the rift frm the Kaph area. T date this prgram has cnsisted mainly f drilling ne deep explratin well, which was cmpleted in 1990 after fur sidetracks (additinal well bres drilled utside the riginal track). The peratr reprted a discvery in this well based n encuntering a high-temperature steam zne; hwever, n results frm the well were released at the time this reprt 3-4

24 was written. A secnd site t the east f the existing well has been permitted, but n new drilling has cmmenced. In summary, t the present time the gethermal explratin f the KERZ has been characterized by relatively nn-systematic drilling and ther explratry activities ver limited areas. The drilling f deep wells has been guided mainly by: The large-scale structure f the rift zne. Results f previusly drilled wells (leading in many cases t limited step-uts). Available lease psitins and regulatry cnstraints. Quite limited infrmatin frm surface explratin techniques. As a result, while substantial infrmatin frm deep drilling in the KERZ has been accumulated ver the past three decades, it is nt f a systematic r cmprehensive type that facilitates the develpment f an integrated cnceptual mdel and reginal assessment f the gethermal resurce. This cnditin, alng with the State f Hawaii's interest in the rderly develpment f gethermal resurces, has prmpted the investigatin f slim hle drilling as a means f resurce assessment. 3.3 The SOH Prgram The need fr a systematic assessment f the gethermal resurces f Hawaii led the University f Hawaii t cnceive and plan the current SOH prgram, beginning in In 1989 the University, in 3-5

25 cnjunctin with EPRI, develped a scpe f wrk, and cntractrs were selected t perfrm the drilling, testing and investigatin f the results f a series f slim hles. It was decided that the hles shuld be drilled by diamnd cring, in rder t btain cntinuus cre samples, and Tnt Drilling Services was selected as the drilling cntractr frm prpsals based n specificatins published by the State. GethermEx prvided specificatins fr dwnhle data cllectin during drilling, and planned and carried ut lgging and testing peratins as the hles were cmpleted. The University f Hawaii crdinated and perfrmed scientific studies f samples and ther infrmatin btained frm the hles. Drilling peratins began in December f 1989 with hle SOH-4, lcated near Iilewa crater (figure 3.2). This hle utilized the access prvided by the rad cnstructed by the True/Mid-Pacific venture fr its peratins sme distance t the west. SOH-4 was drilled ver a perid f 142 days t a depth f 6,562 feet. Significant cst and time verruns ccurred fr a variety f reasns, including difficulties with drilling techniques. In additin, the well was drilled deeper than its planned depth f 4,000 feet, when it was determined that temperatures at the prgrammed depth were lwer than desired. Figure 3.3 shws a schematic f the cmpletin f SOH-4. The next site t be drilled was SOH-I, lcated in the Kaph area near HGP-A and the PGV wells. Cnsiderable difficulties ccurred while drilling this hle, and it was eventually cmpleted in 205 days at a depth f 5,526 feet. Figure 3.4 shws the cmpletin f SOH-I. Hle SOH-2 was drilled during January-June 1991, and was cmpleted at a depth f 6,802 feet in a ttal f 126 days. This hle is 3-6

26 lcated dwn-rift (nrtheastward) frm SOH-1 in the Kaph area. 3.5 shws the cmpletin diagram fr SOH-2. Figure Lgging and testing peratins were carried ut as the hles were cmpleted; these peratins and their results are described in subsequent sectins f this reprt. At present all planned testing has been cmpleted. Hwever, the hles remain useful as mnitring wells t bserve the behavir f the KERZ reservir ver time as additinal explratin and develpment wrk is carried ut. Currently the slim hles are instrumented t mnitr subsurface pressure, in rder t identify and measure any changes in reservir pressure that may ccur in respnse t prductin and injectin by PGV r ther peratrs. Initially it was planned that the SOH drilling prgram wuld include fur hles n the island f Hawaii t a nminal average depth f 4,000 feet, and tw additinal hles t be drilled n the island f Maui. F~ a variety f reasns, including financial, regulatry and plitical cnsideratins, the drilling prgram was interrupted after three hles, but additinal drilling may take place in the future. Additinal details f the backgrund f the prgram, drilling peratins, and planned future activities are prvided in several published reviews f the prject, including Olsn (1988), Olsn and Deymnaz (1992a), and Olsn et al. (1990a and 1990b). A summary f the drilling results and csts f the prgram (Olsn and Deymnaz, 1992b) is included as an appendix t this reprt. The remainder f this reprt fcuses n the infrmatin btained frm the three cmpleted slim hles, and its impact n the assessment f the gethermal resurce f the KERZ. 3-7

27

28 4. DATA OBTAINED FROM SLIM HOLES Infrmatin abut subsurface cnditins is generated as sn as drilling begins, and valuable infrmatin is ptentially available at any stage f the drilling, testing and mnitring prcess until a slim hle is eventually abandned r therwise rendered unavailable. This sectin reviews the data that have been gathered frm the KERZ slim hles during all phases f activity. Table 4.1 presents a summary f the data that have been made available frm the drilling, lgging and testing f the slim hles. This table summarizes the availability and quality f infrmatin in a variety f categries, based n the data requirements discussed in vlume 1 f this reprt. Sme f these categries are relatively mre imprtant than thers in the resurce assessment prcess. Fr example, static dwnhle temperature surveys are f critical imprtance in assessing a variety f resurce parameters, whereas caliper lgs d nt nrmally impact the assessment f the resurce directly. Hwever, all categries f data may be imprtant in analyzing well and reservir characteristics, interpreting test data, and develping a cherent cnceptual mdel f the gethermal system. Therefre it is advisable t cllect all infrmatin that can be gathered rutinely during drilling and testing, and t carefully cnsider the cst/benefit rati f any types f data that require special testing r ther peratins t btain. Data cllected during the drilling f the KERZ slim hles were recrded mainly in the daily drilling reprts that are prduced rutinely in mst drilling peratins. These reprts cntain a recrd f drilling activities perfrmed each day, and sme infrmatin 4-1

29 regarding dwnhle cnditins as drilling prceeds, such as drilling fluid temperatures, bttmhle measurements f temperature and pressure, and preliminary lithlgic identificatins. This infrmatin allws the histry f drilling peratins t be recnstructed and the final cnfiguratin f the hle t be understd, and prvides sme data fr interpreting subsurface cnditins. Nrmally it is preferable that a gelgist r ther specialist maintain a lg f the hle as it is drilled, systematically cmpiling all pertinent bservatins that may eventually be useful in resurce assessment (such a lg is frequently termed a "mud lg"). This prevents the lss f imprtant infrmatin that frequently is frgtten r nt bserved as drilling prceeds. Lgging f this type was nt perfrmed during the drilling f the KERZ hles. Well cmpletin reprts prepared fr the SOH-1 and SOH-4 hles were als available fr this reprt. These reprts cntain summaries f the histry f drilling peratins, and infrmatin abut the mechanical cmpletin f the wells, usage f materials and equipment, and dwnhle measurements. Als included are analyses f drilling peratins and prblems, drilling time and csts, and related subjects. Rck cres were cllected ver the drilled depths f the slim hles, with the exceptin f sme intervals that were drilled nly by rtary methds. Sme f the latter were drilled withut return f drilling fluid t the surface, and n samples f rck cuttings culd be btained; such intervals ccur mainly in SOH-2. In the cred intervals, cre recvery rates tended t be high, and frequently were 100%. Hwever, recvery in a number f cring runs was much prer and at times there was n recvery. The cre samples have been preserved and are the subject f nging study by University f Hawaii persnnel. Sme f the results f these studies were available fr this reprt. 4-2

30 A variety f standard dwnhle lgging peratins were carried ut in the slim hles as they were drilled and cmpleted. These included a number f dwnhle temperature and pressure surveys, and in sme cases spinner lgs and selected gephysical lgs. Additinal temperature and pressure surveys were run after drilling, as the hles thermally equilibrated. Prductin f fluids frm the slim hles was prhibited under the terms f their permits. Therefre n prductin testing r sampling f prduced fluid culd be carried ut. Injectin. testing was pssible, hwever, and a thrugh injectin test f each hle was carried ut after it was cmpleted. Details f these tests are presented belw. Table 4.1 presents an evaluatin f the availability and quality f the data cllected t date frm each f the slim hles. Fr each data categry, availability is rated 0, 1, 2 r 3, representing "absent", "minimal r sparse", "adequate", and "abundant r fully adequate", respectively. These ratings are based n judgements f what is desirable r pssible under ideal cnditins. Lack f data in any particular categry may be due ne r mre f a variety f causes (fr example, permit restrictin, lack f funds, lack f time, r lss f pprtunity). Data quality in each categry is rated 1, 2 r 3, representing "pr", "adequate", and "excellent". These ratings represent an assessment f the reliability and utility f the data fr characterizing the quantities they measure; this is subjective but it is based n cmparisn with standard methds f data cllectin, cmpilatin and review. 4-3

31 The data cllected in each categry frm the slim hles are reviewed belw. Als discussed in this sectin are the specific prcedures used fr data cllectin, especially in lgging and testing peratins. Basic Cmpletin Data The basic infrmatin describing the drilling and cmpletin f the hles is readily available frm the daily drilling reprts and well cmpletin reprts. This includes verall hle depths and diameters, and the depths, sizes and types f casings and any ther equipment set in the hles. Table 4.2 summarizes the cmpletin infrmatin fr each hle. Drilling Penetratin Rates N detailed recrd f penetratin rates was kept during drilling; the nly infrmatin f this type available is the recrd f daily cring ftages. Mre detailed knwledge f penetratin rates is desirable because it prvides an bjective indicatin f rck cmpetency, which ften reflects imprtant variatins in reservir cnditins. Hwever, it is less cmmn and mre difficult t btain this infrmatin while cre drilling, as ppsed t rtary drilling. Directinal Surveys Measurements f hle deviatin frm vertical were made in SOHand SOH-4, ver nly a prtin f each hle. It appears that n deviatin measurements were made in SOH-2. Hwever, the results frm the ther tw hles suggest that the maximum deviatin in any f the hles is likely t be several degrees r less, which means that the 4-4

32 hles can be treated as vertical fr the purpse f interpreting subsurface cnditins frm dwnhle data. Drilling Fluid Prperties Basic drilling fluid prperties (density, viscsity and ph) were recrded each day in the daily drilling reprts, alng with the amunts f mud materials cnsumed. This infrmatin is sufficient t be f use in interpreting drilling fluid temperatures, circulatin lsses, and ther aspects f the drilling prcess as needed. Mre sphisticated mnitring f the drilling fluids, such as measurement f gas r chlride cntents, was nt perfrmed. Drilling Fluid Temperatures The temperature "in" and "ut" f the mud r ther fluid used fr drilling was reprted n a daily basis in the drilling reprts. Nrmally it is preferable t have a mre clsely mnitred recrd f mud temperatures as the hle is deepened, but in this case many f the intervals f greatest interest were drilled with little r n fluid return. Therefre the ptential infrmatin t be gained frm clse mnitring f mud temperatures was relatively minr. Bttmhle Temperatures Bttmhle temperatures were measured rutinely in each hle during drilling, using a maximum recrding thermmeter. Figures 4.1 t 4.3 shw the bttmhle temperatures measured in each hle, pltted versus depth. Als shwn in figures 4.1 t 4.3 are the dwnhle temperature prfiles measured in the hles after cmpletin (these are discussed in detail belw). As these figures shw, the trend f 4-5

33 bttmhle temperatures in each hle is quite similar t the verall stabilized temperature trend in the wellbre. Therefre, the bttmhle temperatures are useful during drilling t estimate expected stabilized temperatures; such infrmatin may be used t guide mdificatins t the drilling prgram as it prgresses. In fact, hle SOH-4 was eventually deepened n the basis f bttmhle temperature measurements, which indicated that the hle had nt penetrated the desired reservir cnditins at its planned depth f 4,000 feet. Figures 4.1 t 4.3 indicate that the frequency and quality f the measurements made during drilling are sufficient t characterize adequately the bttmhle temperature behavir. Water Levels r Bttmhle Pressures Water levels were measured rutinely in SOH-4 when the cre barrel was retrieved at the end f a cring run. It appears that water levels were measured nly infrequently in SOH-1 and SOH-2. Figure 4.4 shws the water levels measured in SOH-4 as a functin f hle depth at the time f measurement. This graph shws tw intervals f relatively shallw water levels dwn t abut 2,700 feet depth, pssibly reflecting "perched" aquifers abve the general water table. Belw this depth, the water level becmes much deeper (abut 1,000 feet belw grund surface), and then gradually shallws with increasing depth. This trend may reflect in part an increase in hydrstatic pressure with depth. Hwever, frm water level measurements alne it is nt pssible t distinguish quantitatively a true pressure trend frm wellbre thermal effects: because temperature increases steadily with depth, it is pssible that the changes in water level are due in large part t water density changes that ccur as the wellbre 4-6

34 becmes htter. Fr this reasn fluid level measurements are mainly useful as a qualitative indicatr f reservir cnditins. It is mre desirable in general t measure bttmhle pressure~ rutinely r at selected depths, as this measures reservir pressure mre directly. Such measurements are time cnsuming and expensive. Circulatin Lsses Lsses f circulatin were nted and characterized t sme degree in the daily-drilling reprts. Hwever, n analysis r cmpilatin f the lss znes by n-site technical persnnel is available; therefre interpretatin f the distributin and magnitude f lsses must be made frm relatively limited data. In additin, a relatively large interval f each hle was drilled with n returns r with nly partial returns f fluid. This makes it relatively difficult t determine frm the recrd f fluid lsses where permeable znes ccur and t estimate their relative magnitudes. Fr the SOH hles, therefre, the lcatin and characteristics f permeable znes are best investigated using infrmatin ther than circulatin lsses. Static Dwnhle Temperature and Pressure Surveys A number f dwnhle temperature and pressure surveys were run in each f the slim hles during and after well cmpletin and, in several cases, during drilling. The mre reliable f these surveys are shwn in figures 4.1 t 4.3 as plts f temperature and pressure versus depth. The dwnhle surveys cme frm a number f surces, including: 4-7

35 Surveys run by the Hthle cmpany. These emplyed an electrnic tl fr temperature measurement. Surveys run by GethermEx using mechanical (Kuster-type) temperature and pressure recrding tls belnging t GethermEx and the University f Hawaii. Surveys run using the United States Gelgical Survey (USGS) lgging truck. These utilized an electrnic temperature tl alng with pressure, spinner and ther lgs. Surveys run by Pruett Industries using Kuster temperature and pressure tls. Of these measurements, the surveys run using Kuster tls were fund t be fr the mst part reliable and cnsistent. Sme f the temperature surveys run with the USGS lgging truck were successful, while sme f the temperature surveys and all f the pressure surveys failed. The Hthle surveys prduced nly limited results, and it was determined that their reliability was nt sufficient t allw cmparisn with ther surveys r results frm ther hles. The failure f varius lgging tls appears t have resulted in part frm the high temperatures encuntered in the hles. Tables 4.3 t 4.5 list the temperature/pressure and ther dwnhle surveys and lgs run in each f the slim hles. In each hle a number f temperature surveys were successfully cmpleted. In hles SOH-2 and SOH-4 ne r mre pressure surveys were als cmpleted; hwever, in hle SOH-l n reliable pressure results culd be btained. Additinal pressure surveys wuld nrmally be desirable in rder t mre reliably estimate reservir pressures. The temperature surveys are 4-8

36 sufficient t characterize the stable dwnhle temperature prfile "in each hle. Spinner Surveys Pr results were btained frm all spinner surveys run in the slim hles, fr a variety f reasns. The Hthle spinner unit prvided sme infrmatin frm SOH-4, but n scale was ever prvided fr the lgs and the data were ambiguus, useful nly in a very qualitative way. The USGS spinner unit failed n each ccasin that it was run. Pruett's spinner tl run in SOH-2 appeared t perate crrectly, but was clgged by burrs frm the slts in the tubing run in the hle. As a result, n useful spinner data are available fr analysis. Gephysical and Caliper Lgs A limited amunt f ther lgging was attempted in additin t the temperature, pressure and spinner surveys. This cnsisted mainly f gamma ray lgging in SOH-l and SOH-2 using the USGS lgging unit, use f the USGS brehle televiewer in SOH-2, and caliper lgs run in SOH-l and SOH-2. The gamma ray tl failed in bth instances, and n results have been made available frm the ther lgs. The lack f lgging infrmatin is nt particularly critical in this case, because gephysical lgs typically d nt prvide much help in interpreting terranes such as the KERZ that cnsist f mntnus vlcanic rcks. Lithlgy Lithlgic infrmatin available frm the KERZ hles cnsists mainly f limited descriptins recrded in the daily drilling reprts, and summary lithlgic clumns cmpiled by University f Hawaii 4-9

37 persnnel based n bservatins f the cres frm each hle. The latter infrmatin prvides a useful lithlgic and stratigraphic framewrk fr cmparing lithlgy with ther dwnhle infrmatin. The fllwing rck units are distinguished in the lithlgic summaries f the hles: ~ Subaerial lava flw units, including pahehe, a'a and transitinal flw units. Znes f strng thermal xidatin are identified. Intrusive rcks (dikes and ther intrusins) Ash beds Cral reef rck, which was identified in a few limited znes Pillw lavas (dense, cmpact submarine lava flws) Hyalclastite (shattered r ashy rck frmed frm lava flws erupted int a shallw cean envirnment) With the exceptin f the cral reef rck, all f the abve units are basaltic in cmpsitin; the main differences between the different rck types are in their texture and structure. The mst imprtant distinctins fr examining larger-scale vari~tins in rck prperties are between subaerial and submarine lavas, and between lava flws and intrusive rcks. Less abundant units such as ash and cral beds, althugh they cause lcal hetergeneity, are nrmally t thin t represent n a large scale. Therefre, figures 4.1 t 4.3 shw summaries f lithlgy that distinguish znes dminated by subaerial 4-10

38 lavas, submarine rcks, and intrusives. Figure 4.5 presents a legend shwing the key t the different lithlgy symbls. Lithlgy is imprtant in the KERZ slim hles nt nly fr its impact n the interpretatin f subsurface cnditins fr resurce assessment, but als because f its effect n drilling. It was bserved in drilling the slim hles that certain znes, particularly hyalclastite znes within the submarine rcks, created extremely difficult cnditins fr cring relative t ther rck types. This infrmatin is useful in guiding the selectin f drilling techniques in individual hles and in the verall drilling prgram. Rck Alteratin Very little infrmatin regarding rck alteratin in the slim hle cres has been made available. Such infrmatin is nrmally desirable in rder t investigate pssible large-scale variatins in rck prperties caused by alteratin, t enhance understanding f the subsurface gelgy as part f cnceptual mdeling, and, in sme cases, t prvide additinal infrmatin regarding the nature and distributin f permeability. Injectin Test Results Injectin tests were perfrmed in each f the slim hles during r after the time f well cmpletin. These tests prvided imprtant infrmatin fr assessing the distributin f permeable znes in the hles and fr estimating well and reservir parameters, including reservir flw capacity and the well skin factr. 4-11

39 The injectin tests fllwed standard prcedures. Typically, static temperature and pressure surveys were run befre the start f each test, then water was injected at as ne r mre rates, as allwed by the limitatins f water supply, equipment, and well characteristics. In each test the fllwing data were cllected: Static temperature and (if pssible) pressure prfiles in the wellbre befre and after injectin. A histry f injectin flw rates and times. Pressure respnse during and after injectin (pressure fallff) at a selected depth dwnhle. The histry f wellhead pressure while injecting. The dwnhle temperature prfile during injectin (in SOH-2 and SOH-4). Spinner surveys were attempted during several f the injectin tests. As discussed abve, nne f the surveys were successful, fr a variety f reasns. Due t the wide spacing f the slim hles it was nt pssible t cllect useful interference data during injectin testing by instrumenting ne r mre additinal hles fr dwnhle pressure mnitring. The injectin test f hle SOH-l was perfrmed at the time f well cmpletin, during January 5-10, Static temperature, pressure and ther lgs were run using the USGS lgging truck during 4-12

40 January 5-9, hwever, ther than the temperature lg these were mstly unsuccessful. Water was injected fr a perid f time t cl the wellbre, and n January 10 dwnhle pressure mnitring was started using Kuster tls, while injecting water fr a ttal f 6 hurs at rates f 80 and 110 gallns per minute (gpm). After injectin stpped the pressure fallff was mnitred fr a perid f several hurs. Table 4.6 shws the histry f injectin rates, and figure 4.6 shws the dwnhle pressure respnse as a functin f time. Results f the injectin test analysis are discussed in sectin 5. An injectin test f hle SOH-2 was cnducted when the well was cmpleted, during June 5-9, Again the USGS lgging truck was used fr dwnhle surveys, but the tls wuld nt perate prperly, s Pruett Industries was cntracted t prvide dwnhle temperature and pressure measurements. Static surveys were run n June 6, and water was injected t cl the well beginning n June 7. Kuster pressure tls were run in the hle t 4,500 feet and water was injected at 135 t 275 gpm ver perid f 3 hurs. Pressure fallff was mnitred fr a further 9 hurs. The injectin rate histry during the test is shwn in table 4.7, and figure 4.7 shws the pressure respnse during and after injectin. An injectin test f SOH-4 was carried ut when the hle was cmpleted, during May 17-23, This test was similar t the tests cnducted in SOH-1 and SOH-2, but it was limited by the lack f equipment necessary t inject water at psitive wellhead pressures. Therefre a secnd injectin test was cnducted during January 11-13, In the secnd test a static temperature survey was first run, then the well was cled by injecting water at a lw rate. Pressure tls were hung at 4,500 feet, and water was injected at 150 and 235 gpm ver a perid f 6 hurs. Fur hurs f pressure fallff data were 4-13

41 gathered. The histries f injectin rate and dwnhle pressure respnse are shwn in table 4.8 and figure 4.8, respectively. Sectin 5 discusses the results and analysis f the injectin tests fr SOH-4 and the ther tw slim hles. Prductin Test Results Fr reasns discussed abve, it was nt pssible t cnduct any prductin testing f the slim hles, and s n prductin data are currently available fr analysis. It is thught that ne r mre f the hles culd be prductive if stimulated prperly, particularly SOH-I, which has a higher estimated flw capacity than either SOH-2 r SOH-4 (sectin 5). Dwnhle Fluid Samples N dwnhle samples f reservir fluids have been cllected frm the slim hles. Particularly in view f the restrictin against prducing any f the hles, it wujd be advantageus t cllect such samples in rder t gain infrmatin regarding reservir fluid chemistry. Several types f sampling apparatus are available that culd be used t cllect fluid samples, including unbiled water and gases, frm the reservir interval f each f the hles. It is recgnized that lst drilling fluids may cntaminate samples. Dwnhle water samples were cllected in the early stages f drilling by each f the hles by bailing. These samples were apparently taken in rder t meet regulatry requirements. They represent cld grundwater abve the reservir zne, therefre they are nt f direct interest fr gethermal resurce assessment. 4-14

42 Summary A review f table 4.1 shws that data were cllected frm the KERZ slim hles in mst f the imprtant categries that were nt restricted by regulatry cnsideratins. Hwever, the availability and quality f data in a number f categries, as shwn in table 4.1 and discussed abve, is less than ptimum and culd be imprved upn in a number f ways. The tw mst imprtant reasns fr failure t gather ptimum data frm the KERZ hles are the failure f dwnhle lgging instruments, and inadequate attentin t and crdinatin f data gathering effrts during drilling peratins. The first prblem can be remedied thrugh experience and thrugh investigatin f the suitability f particular lgging and measurement techniques t the envirnment encuntered in the reservir intervals f the slim hles. The lcatin f the KERZ, which limits rapid access t a wide variety f lgging equipment, persnnel and services, is likely always t have an impact n the ability t cnduct reliable dwnhle surveys at a reasnable cst. The use f less sphisticated techniques (such as the use f mechanical rather than electrnic dwnhle tls) may be a necessary tradeff in rder t maximize the chance f btaining reliable infrmatin. The needs f data gathering during drilling must be addressed by cnsidering and priritizing the bjectives f the drilling prgram, analyzing the cst/benefit relatinships f varius activities, and implementing necessary changes by ensuring that apprpriate equipment and persnnel are available when drilling takes place. The cst f data gathering peratins, such as well site gelgy r mud lgging, is ften difficult t justify within the cntext f already burdened drilling budgets. Hwever, it is precisely the high cst f drilling activities 4-15

43 that makes it imperative t carefully plan and carry ut a prgram that will avid the lss f ptentially imprtant infrmatin. 4-16

44 5. DATA ANALYSIS As discussed in vlume 1 f this reprt, a large variety f analysis techniques may be applied t the data btained frm wells r slim hles. Nrmally the available infrmatin is prcessed and analyzed with the bjective f develping a cnceptual hydrgelgic mdel f the gethermal system, which may be used in cnjunctin with specific types f data t estimate resurce parameters and t carry ut further, mre quantitative mdeling. Cmprehensive examinatin f the data by a number f different methds may be required t determine the mst significant characteristics f the system and the relative emphasis t be placed n particular categries f infrmatin. This sectin fcuses n the methds f analysis that are mst critical t the resurce assessment methdlgy presented in vlume 1, and in particular the t estimatin f recverable energy reserves frm the slim hle results. The mst imprtant cmpnents f this analysis are the determinatin f subsurface temperature distributin, and characterizatin f the distributin f permeability within the reservir vlume. Cmpilatin and interpretatin f dwnhle data make up the first step in this prcess. 5.1 Interpretatin f Dwnhle Data The mst imprtant dwnhle infrmatin cllected frm the three KERZ slim hles is summarized in figures 4.1 t 4.3. These graphs include details f well cmpletin, summaries f dwnhle lithlgy, bttmhle temperatures measured during drilling, and the mre reliable f the temperature and pressure surveys cnducted in each hle. The fllwing cnclusins may be drawn frm examinatin f these figures: 5-1

45 The transitin frm subaerial t submarine vlcanics ccurs much deeper in SOH-4 (abut 4,200 feet belw mean sea level, r msl) than in the ther tw hles (arund -1,500 feet msl). This suggests that SOH-4 ccupies a structurally lw psitin with respect t the ther hles. The abundance f dike rck is greater in SOH-4 (50% r mre f all rcks) than in the ther tw hles, where intrusives cmprise less than 30%. The reprducibility f the later temperature surveys run in each hle indicates that they are representative (within abut 10 F) f the stable temperature prfiles that wuld be expected after a lengthy perid f heat-up. The stable temperature prfile f each f the hles appears t have a relatively cld «200 F), isthermal zne up t several thusand feet thick, belw the static water level. This is presumably a zne f cld grundwater abve the gethermal system, and is cnsistent with the absence f surface hydrthermal features alng the rift zne. Belw the isthermal zne, temperatures increase steeply with depth and temperature gradients are relatively linear. Each f the hles has characteristic gradient in this interval. The gradient is highest in SOH-I, but this hle has the greatest depth t the bttm f the isthermal zne, and its temperatures are lwer at a given depth than in the ther hles. SOH-2 has a higher gradient than SOH-4 and ultimately reaches a higher bttmhle temperature f abut 660 F. The temperature gradient in each f the three hles can be 5-2

46 prjected t mre than 600 F at elevatins deeper than -6,000 msl. Relatively lw permeability in the uncased intervals f the hles is suggested by their linear temperature prfiles, and by the very limited perturbatins f the prfiles in respnse t cld water injectin. This is particularly true f hles SOH-2 and SOH-4, which shw nly very limited thermal effects frm injectin f cld water. Nte that a large interval f each hle, particularly the upper prtin (nw behind casing), was drilled with partial r ttal lsses f circulatin. This indicates that permeability may be greater in the first several thusand feet belw the surface, abve the depth f cmmercial reservir temperatures. The temperature prfiles frm SOH-4 are smewhat ambiguus, pssibly due t inaccurate measurements in ne r mre surveys. Hwever, cmparisn f surveys run befre, during and after injectin f cld water suggest that minr znes f permeability are present between depths f abut 2,400 and 3,650 feet. A distinct temperature inflectin als ccurs at abut 4,500 feet; this may reflect sme degree f permeability at this depth. In SOH-2 all permeability appears t ccur shallwer than a depth f 5,000 feet. A permeable zne appears t be present within the interval frm 4,000 t 4,900 feet, based n the temperature surveys run during and after injectin. Additinal permeable znes may be present at depths shallwer than 3,500 feet. 5-3

47 In hle SOH-I, a distinct zne f significant permeability is present between 4,000 and 4,500 feet. This is the nly imprtant permeable zne in the uncased prtin f the hle. This zne is within an interval where frmatin temperatures are relatively lw (less than 250 F). 5.2 Subsurface Temperature Distributin Stable temperature prfiles measured in the slim hles cnstitute the mst direct surce f infrmatin available t characterize the subsurface distributin f temperature. Nrmally the three-dimensinal temperature distributin is best visualized and quantified by means f a set f cntur maps drawn at varius levels thrugh the reservir, r by a set f isthermal maps that shw the depth r elevatin f the surfaces defined by specific temperatures, ver the reservir area. T cnstruct the level r isthermal maps, temperature data are cntured (by hand r by cmputer techniques) ver the area where the data density is sufficient fr interplatin. Hwever, the KERZ slim hles are spaced t widely t permit interplatin and cunturing with any reliability. Therefre, each hle is capable f cntributing nly an islated pint that defines the lcal temperature ver sme limited radius f influence. Additinal infrmatin is available that can help in estimating the temperature distributin ver a mre cntinuus area in the KERZ. This includes (a) knwledge f the structure f the rift zne, and (b) temperature data available frm wells drilled previusly in the Kaph area by PGV and thers. The latter data serve t define temperatures reliably ver a subzne f the rift, and the rift zne structure can be 5-4

48 used as a basis fr interplating temperatures between slim hles, by assuming that a cntinuus surce f heat (in the frm f injected magma) is lcalized alng the rift axis, yielding a pattern f temperatures that decrease perpendicular t the axis. Figures 5.1 thrugh 5.6 present an estimatin f temperature distributin in the explred part f the KERZ, based n the data available frm the slim hles and previusly existing wells, and n assumptins abut the rift zne structure. These temperature level maps shw temperature cnturs at 1,000 ft intervals frm -1,000 feet t -6,000 feet msl. As these maps shw, the temperature distributin is well defined ver an area f abut ne square mile where the density f wells is high, and is mre speculative in ther areas. The densely drilled area reveals the anticipated pattern f highest temperatures alng the rift axis, with temperature decreasing rapidly t the nrthwest and sutheast. This gives supprt t the interplatin f temperatures based n the rift zne structure. The level maps indicate that temperatures f cmmercial interest ( F and greater) begin t be encuntered arund -2,000 feet msl, at least within limited areas. Temperatures prbably increase with depth ver mst r all f the rift zne, s that at ~5,000 feet. there is a "crridr" f high temperatures up t a mile wide r mre ver much f the explred area. Temperature gradients in existing wells suggest that at mst places alng the rift axis it is likely that temperatures f 600 F r mre ccur at elevatins belw -5,000 feet, r at drilled depths f 6,000 t 10,000 feet. 5-5

49 5.3 Analysis f Permeability The distributin and characteristics f permeability may be examined by bth qualitative and quantitative means using the data acquired frm the slim hles. Qualitatively, the lcatins and relative magnitudes f permeable znes intercepted by the hles can be interpreted frm temperature surveys cnducted under different cnditins, frm the recrd f circulatin lsses during drilling, and frm ther less direct infrmatin. Quantitative analysis f permeability cnsists mainly f the estimatin f reservir flw capacity frm the results f injectin r prductin testing. The mst imprtant inferences regarding permeability that can be drawn frm dwnhle data were discussed in sectin 5.1. The qualitative interpretatin f permeability based n the slim hles can be summarized as fllws: Significant permeable znes appear t be present at shallw depths (dwn t 3,000 t 4,000 feet belw the grund surface), based n the ccurrence f circulatin lsses in all f the hles. Much r all f this permeability is likely due t the prus and finely fractured nature f the subaerial basalts that make up the shallwer interval. The shallw permeable znes ccur fr the mst part where the temperature is t lw t be f cmmercial interest. At greater depths, permeability is lwer and appears t be restricted t specific znes. This may indicate that the permeability in the deeper znes is due nt t riginal rck prperties but t tectnic r vlcanic fracturing. Based n the slim hle results, much f the reservir vlume appears t 5-6

50 be relatively impermeable, but scattered permeable znes are likely present in sufficient numbers t allw extractin f heat via prductin wells. The injectin test data discussed in sectin 4 have been analyzed t estimate flw capacity and ther reservir parameters fr each f the slim hles, using the methdlgy described in vlume 1. These analyses are summarized here. Figure 5.7 shws the "Hrner plt" f the dwnhle pressures measured in the injectin test f SOH-I. The plt can be used t estimate reservir flw capacity and skin factr prvided that the data are cllected fr a sufficient length f time t clearly reveal the true reservir respnse; this is generally indicated by a straight line n the Hrner plt. Hrner pltting can be used t estimate flw capacity and skin factr in finite reservirs as well as in infinite-acting reservirs, because the bundary effects influence nly late time data. The pltted data shw the end f the wellbre strage effects at the dimensinless Hrner time value f apprximately 13. By definitin, the small values f the Hrner time crrespnd t large shut-in times and a Hrner time f 1 crrespnds t an infinite shut-in time. Past the wellbre strage perid, a semi-lg straight line can be apprximated thrugh the data pints. Frm the analysis f the slpe f the semi-lg straight line, and the injectin rate, the reservir flw capacity (kh) is calculated t be 6,100 md-ft. Frm the bserved pressure change behavir and the Hrner line, the well skin factr is estimated t be

51 These values calculated fr flw capacity are cnsidered relatively lw, and the psitive skin factr values indicate sme type f flw restrictin in the near wellbre regin. Fr such lw flw capacity values, it is difficult t estimate either the flw capacity r the skin factr value accurately. The same values calculated by the Hrner methd fr reservir flw capacity and skin factr, were used in matching the entire pressure histry presented in figure 5.8. A very gd match was btained, cnfirming the results f the Hrner analysis. Figure 5.9 shws the Hrner plt f the measured dwnhle pressure data frm the injectin test f hle SOH-2. The straight line shwn in figure 5.9 is believed t be the crrect straight line fr estimating reservir flw capacity, while the shape f the pressure respnse is characteristic f either a fractured frmatin r duble prsity behavir. We have therefre used a duble prsity mdel t analyze the test data. The analysis f the pressure fallff data give a value f reservir flw capacity f 1,300 md-ft and a well skin factr f The value f transmissivity is very lw but is cnsistent with the estimates btained fr well SOH-4. The values f reservir flw capacity and skin factr estimated frm the pressure fallff data were then used in matching the entire pressure histry and the match between the measured and calculated respnses is presented in figure A reasnable match is btained t the measured data, indicating that the reservir parameters are 5-8

52 reasnable. The lw value f flw capacity is als cnsistent with the qualitative interpretatin made frm examinatin f the dwnhle temperature surveys. The dwnhle pressure data btained frm the secnd injectin test run in SOH-4 were analyzed using the same analysis methd as fr SOH-I. Figure 5.11 shws the Hrner plt f the dwnhle pressure data measured in SOH-4 during the tw-step injectin test f January 12, The plt shws that the pressure fallff measurements were taken fr a sufficient length f time t clearly reveal the semi-lg straight line, after the wellbre strage effects had cncluded. The Hrner analysis indicates a reservir flw capacity f 1,360 md-ft, and a skin factr f The negative value fr the skin factr prbably reflects that the wellbre has intersected fractured rck. As with the ther hles, the flw capacity and skin factr estimated frm the Hrner plt have been used t match the entire pressure histry. The results are shwn n figure The fallff data have been reasnably matched, but the well's pressure respnse during injectin can rit be matched using the same hydraulic parameters, indicating that the hydraulic cnditins that prevailed in the well during and after the injectin perids were different. It is pssible t alter the hydraulic respnse in a damaged well by mud cleanut r by fracturing. In this case, the wellhead pressures during injectin were nt sufficient t induce fracturing at the depth f the casing she, but the pressure data indicate the well being mre "stimulated" during the injectin than during the fallff perid. This effect has been bserved 5-9

53 previusly during injectin testing f shallw wells elsewhere, and has been explained as a reversible phenmenn, where the flw capacity f the existing fractures imprves with the increment f wellhead pressure. This fracture stimulatin is bserved while the high wellhead pressure cnditins are maintained, but ceases immediately after they are interrupted. Therefre, the hydraulic respnse f the well during the test, varies prprtinally with the injectin pressure, and returns t its natural stage during fallff. Table 5.1 summarizes the reservir parameters calculated fr the three slim hles based n the results f their injectin tests. Estimated flw capacities range frm 1,300 t 6,100 md-ft; this is in the lw range fr cmmercial gethermal reservirs. Hwever, it appears t be cnsistent with results btained frm the ther wells drilled in the KERZ. Althugh flw capacities are lw in the wells in the Kaph area, the high reservir temperatures permit cmmercial levels f prductin t be achieved in a number f wells. 5-10

54 6. ESTIMATION OF RESOURCE PARAMETERS The methds and guidelines fr estimating primary and secndary resurce parameters using results frm slim hles are described in detail in vlume 1 f this reprt. As discussed in that vlume, a wide variety f parameters ptentially may be estimated frm slim hle data. These encmpass a brad range f physical prperties, such as hrizntal and vertical extent, temperature, pressure, density, permeability, and chemical cmpsitin, as well as the perfrmance characteristics f wells drilled int the reservir. All f the parameters may ultimately be useful in describing and understanding the gethermal resurce, and in qualitatively r quantitatively characterizing the resurce fr further mdeling f its behavir. Typically, attentin will be fcused n the estimatin f a limited set f parameters that are mst useful in meeting the needs f the resurce identificatin and assessment prject being carried ut. This sectin examines fr the KERZ the estimatin f a set f parameters that include, primarily, thse needed t calculate the recverable reserves f gethermal energy within the resurce. The parameters estimated are: Reservir area. Reservir thickness. Reservir vlume. Reservir depth. 6-1

55 Reservir temperature. Rck matrix density. Rck prsity. Rck heat capacity. Energy recvery factr. The prbabilistic reserves calculatin methd described in vlume 1 and applied in sectin 7 f this vlume requires that prbability distributins, rather than single values, f the key resurce parameters be estimated. Fr simplicity, the prbability distributins f the parameters estimated in this sectin are mdeled as either triangular (defined by a minimum, mst likely, and maximum value) r rectangular (defined by a minimum and maximum value) prbability functins. Althugh this study is primarily cncerned with the use f slim hle data in the assessment prcess, any thrugh assessment f a prspect wuld take int accunt all available infrmatin, particularly any infrmatin frm ther existing drillhles. In the KERZ, infrmatin frm existing explratin wells (in additin t the SOH slim hles) is extensive and has a ptentially imprtant impact n any assessment f the KERZ resurce. Here the effect f the additinal data prvided by these wells is examined by making tw separate estimatins f reservir area: ne using data frm the slim hles nly, and ne using infrmatin frm all available drillhles in the lwer KERZ. 6-2

56 The estimatin f mst parameters is affected t sme degree by the inclusin f the additinal well data, but the mst significant impact is n the estimatin f reservir area. Therefre this parameter alne has been selected fr a separate estimate. In sectin 7, the calculatin f energy reserves is made using bth estimates fr reservir area, and the single estimates f the ther parameters. The gethermal reservir must be defined in terms f a cutff temperature in rder t estimate parameters ver the reservir vlume. Nrmally this cutff temperature depends n the ecnmics f field develpment, and n the requirements f the planned pwer generatin methd. Fr this study a cutff temperature f 400 F has been selected. Generally, the use f a lwer cutff temperature will result in a higher estimate f ttal reserves, but it will be mre cstly r even unecnmic t fully explit the reserves. Cnversely, a higher cutff temperature will lead t an estimate that is lwer but shuld be less cstly t explit. Reservir Area The distributin f temperature determined in sectin 5 is the primary tl used t estimate the reservir area, defined as the area within which temperatures abve the selected cutff will be encuntered at r abve the maximum depth frm which cmmercial wells can extract fluids. Given this definitin, the estimate f reservir area is smewhat dependent n drilling technlgy and ther technical and ecnmic cnsideratins. Hwever, given the current understanding and explratin histry f the KERZ, it is reasnable t estimate reservir area based n the temperature distributin at the maximum depth f the slim hles, which is abut 6,000 feet belw grund surface r abut - 5,000 feet msl. The dwnhle temperature prfiles frm the slim hles 6-3

57 (figures 4.1 t 4.3) and the map f temperature distributin at -5,000 feet therefre can be used as a guide fr reservir area estimatin. The three slim hles are by themselves t widely spaced fr cntinuus cnturing f temperature with reasnable cnfidence. Therefre, except in an ptimistic case, the estimated reservir area is limited t a distinct area f influence arund each slim hle that penetrates r shws evidence f nearly penetrating temperatures abve the cutff. Hles SOH-2 and SOH~4 penetrate substantial intervals abve the cutff temperature, and SOH-l penetrates a small interval abve the cutff. Figure 6.1 shws the estimated reservir area, in the frm f a map shwing the utlines f the minimum, maximum and mst likely areas. The minimum and mst likely areas cnsist f discrete areas arund each f the slim hles; because f the knwn elngatin f the gethermal anmaly alng the rift axis, these areas have been given an elliptical frm, rather than the circular frm they wuld have in the absence f such infrmatin. Fr hles SOH-2 and SOH-4, bth f which penetrate an interval abve cutff temperature f abut 2,000 feet, a minr radius f 1,000 feet is chsen fr the minimum area, and a minr radius f 2,000 feet is chsen fr the mst likely area. Fr hle SOH-I, which reaches the cutff temperature nly at bttmhle, smaller minr radii f 500 and 1,000 feet are selected fr the minimum and mst likely areas, respectively. Summing these separate areas f influence yields a minimum area f 0.5 square miles and a mst likely area f 2.0 square miles. T estimate the maximum area frm the sparse slim hle data, it is acceptable t make the ptimistic assumptin, based n the structure f the rift zne, that high temperatures ccur cntinuusly between the 6-4

58 hles. Therefre a cntinuus zne slightly wider than the "mst likely" zne arund the slim hles can be used t represent the maximum area; this zne is utlined in figure 6.1. The area within this zne is 8.0 square miles. Cmbined with the minimum and mst likely areas, this prduces the triangular prbability distributin f reservir area shwn in figure 6.2. The parameters f the distributin are listed in table 6.1. The estimated prbability distributin f area is asymmetric, being skewed tward the lw end f the range with a "tail" n the high end. This is the result f a lack f sufficient data t define the temperature distributin with a high degree f cnfidence. Althugh the slim hle data are sufficient t frecast the pssible presence f an extensive reservir area, the shape f the estimated distributin indicates uncertainty (and therefre risk) in assuming that such an area exists. Typically, as mre hles are drilled, the width f the distributin narrws, indicating a higher level f cnfidence in the estimate. Additin f the data frm the existing deep wells in the KERZ extends and refines the mdel f subsurface temperature distributin, as shwn in the temperature cnturing f figures 5.1 t 5.6. Mst f the wells are cncentrated in the Kaph area near SOH-I, s it is in this area that the highest level f cnfidence is achieved. Figure 6.3 shws the utlines f the minimum, mst likely and maximum reservir areas estimated using all the available drilling data. As this figure shws, the minimum and mst likely areas are extended cnsiderably in the vicinity f SOH-I, whereas the islated SOH-2 and SOH-4 still have discrete areas f influence. The verall distributin f temperature alng the rift is better defined, allwing a brader zne up-rift frm SOH-l t be included in the mst likely area. 6-5

59 The minimum, maximum and mst likely areas based n all drilling data are 1.3 square miles, 3.5 square miles, and 12.5 square miles, respectively. The triangular distributin defined by these values is shwn in figure 6.2. Despite the additinal data there remains an asymmetry that reflects a need fr further drilling t define the extent f the reservir with a high degree f cnfidence. Reservir Thickness The temperature prfiles measured in the slim hles (figures 4.1 t 4.3) serve as a basis fr estimating the thickness f the reservir in the KERZ. As nted abve, bth SOH-2 and SOH-4 penetrate an interval f abut 2,000 feet in which the temperature is abve the cutff f 400 F. In additin, the temperatures in these hles increase steadily t bttmhle, indicating that the temperatures remain at r abve cutff t greater depths. Althugh SOH-1 des nt penetrate a substantial interval abve cutff temperature, it als has a steep temperature gradient at bttmhle,,and therefre it is reasnable t assume that a significant reservir interval is present at greater depth. Even' if temperature reversals were present belw the depths reached by the slim hles, temperatures in excess f 400 F wuld persist t depths f 8,000 t 9,000 feet, yielding a reservir thickness f at least 4,000 feet. This value is therefre selected as the minimum reservir thickness in a triangular prbability distributin. Based n knwledge f the KERZ t date and the temperature prfiles f the slim hles, it is mre likely that temperatures cntinue t increase r becme isthermal with depth. Therefre the reservir thickness may be substantially greater than the minimum estimate. 6-6

60 The maximum reservir thickness, like the reservir area, is smewhat dependent n prject ecnmics and available drilling technlgy. Hwever, it is cnservative t assume that prductin wells can be successfully drilled t depths f 10,000 t 11,000 feet. Therefre a maximum reservir thickness f 6,000 feet is an acceptable estimate. There is nt a strng basis fr selecting a mst likely thickness frm the limited data available, given uncertainties regarding temperature behavir with depth and limitatins n drilling capabilities. A mst likely value f. 5,000 feet has been selected, yielding a symmetrical prbability distributin fr reservir thickness (figure 6.4). A separate estimate f reservir thickness based n existing prductin-diameter wells, in additin t the slim hles, has nt been made here. Generally, the existing wells shw temperature prfile characteristics similar t thse f the slim hles, and an estimate based n all f the wells wuld be similar t that shwn in figure 6.4. Reservir Vlume Reservir vlume may be calculated directly frm the estimated reservir area and average thickness, t the extent that they are statistically independent f each ther. The calculatin fr a single pair f estimated values is a simple multiplica~in f thickness times area t yield the parallelepiped vlume. Hwever, as discussed in vlume 1, cmputatin f the cmpsite prbability distributin derived frm the area and thickness distributins is nt s straightfrward, and is best accmplished using a numerical methd. Figure 6.5 shws the prbability distributins f reservir vlume derived using the randm-sampling numerical methd described in 6-7

61 vlume 1, and the distributins r reservir area and thickness discussed abve. Bth f the vlume distributins were cmputed by cmbining 200,000 randm samplings frm the reservir area and thickness distributins. The cmpsite distributins indicate mst likely reservir vlumes f 2.1 cubic miles and 3.5 cubic miles, based respectively n the slim hles nly and n all KERZ drillhles. The cmputed distributin f reservir vlume is nt used directly in the calculatin f recverable energy reserves (sectin 7). Hwever, the calculatin is made implicitly in the reserves estimatin prcess, which uses independently the estimated distributins f reservir thickness and area. Reservir Depth Reservir depth, defined as the vertical depth t the tp f reservir rck abve the cutff temperature, can be estimated by examinatin f the stable temperature prfiles measured in the slim hles (figures 4.1 t 4.3). These prfiles shw sme variatin in the depth t the 400 F cutff, ranging frm 4,700 feet in SOH-4 t 5,500 feet in SOH-l. Cnsidering the wide spacing f the slim hles, hwever, these depths are relatively clse t ne anther and suggest that the average reservir depth is likely t fall within r near t this range. Based n this infrmatin, a relatively narrw range f 4,500 feet (minimum) t 5,500 feet (maximum) is selected as the estimated average reservir depth. The mst likely value is estimated t be 4,800 feet, based n the similar depths t cutff temperature in SOH-2 and SOH-4. Figure 6.6 shws the triangular prbability distributin f average reservir depth based n these estimated values. 6-8

62 The prbability distributin f average reservir depth is nt used directly in the calculatin f reserves. Hwever, it can be imprtant in ther aspects f develpment planning, particularly in selecting well depths and designs. Reservir Temperature Estimatin f average reservir temperature shuld ideally be carried ut using a cmprehensive mdel f subsurface temperature based n measurements frm slim hles (r ther drillhles). In the KERZ the slim hles are t widely spaced t permit cntinuus, reliable cnturing f temperature, and therefre average temperature must be estimated frm the measured temperature prfiles in the individual hles. Hwever, these are relatively cnsistent in frm, and s the prbability distributin f average temperature can be estimated with sme degree f cnfidence. Figures 4.1 thrugh 4.3 indicate that the vertical temperature prfile thrugh at least the first 2,000 feet f the reservir zne is cnsistent and is characterized by temperatures increasing steadily t 600 F r gre~ter. Belw the depth explred t date, temperatures may cntinue t increase, r the temperature prfiles may becme isthermal r reverse. Even if a strng reversal were encuntered belw the depths drilled s far, a substantial interval f temperatures in excess f 500 F wuld be available fr explitatin. Based n the similarity f the prfiles between the widely spaced hles, and n the high and increasing temperatures at depth, the minimum average reservir temperature (in the vlume abve the 400 F cutff) is estimated t be abut 500 F. 6-9

63 Theretical cnsideratins and infrmatin frm ther hydrthermal systems wrldwide suggest that temperatures in the ecnmically useful reservir zne are unlikely t greatly exceed F, and therefre it is expected that the temperature prfiles f wells drilled t greater depths than the slim hles will tend t becme isthermal at depths belw abut 7,000 t 9,000 feet. If temperatures in the deeper reservir are in the F range, then the average reservir temperature culd be as high as 650 F, and therefre this value has been selected as the maximum fr the prbability distributin (table 6.1). Due t the few hles available t define the temperature distributin within the reservir, there is n strng basis fr chsing a mst likely average temperature. A temperature f 575 F, midway between the estimated minimum and maximum temperatures, has been selected as mst likely. Figure 6.7 shws the triangular prbability distributin f ~verage reservir temperature defined by these parameters, which are listed in table 6.1. Rck Matrix Density N measurements f rck matrix density are yet available frm cres r ther samples cllected frm the slim hles. Therefre there is n direct evidence frm the slim hles frm which t estimate density. Hwever, the lithlgy f the rcks penetrated by the slim hles has been defined by examinatin f the cres, cnfirming as expected that the reservir rck is almst entirely basalt and intrusive equivalents, altered t varying degrees. This allws rck density t be estimated based n the knwn characteristic density f basaltic rck. 6-10

64 The range f variatin in the rck matrix density f unaltered basalts is small, and is centered near abut 2.8 grams per cubic centimeter, f 2,800 kg per cubic meter. Alteratin t hydrthermal minerals tends t change the riginal rck density, but the degree f change is likely t be relatively small. Therefre a rck matrix density f 2,800 kg per cubic meter, r 175 punds per cubic ft, is estimated t be mst likely (table 6.1). Because f the small pssible variatin in density, this parameter is cnsidered t be a fixed value rather than a prbability distributin in the calculatin f recverable energy reserves. Rck Prsity N measurements f prsity are available frm the slim hle cres. In any case, such measurements might tend t be misleading if used t estimate verall rck prsity in the reservir, because fractures are nt likely t be adequately represented in the cre samples. Therefre it is apprpriate t estimate prsity frm mre generalized studies f hydrthermal systems. A cmmnly accepted range f pssible average rck prsity in gethermal reservirs is 0.03 t 0.07, r 3% t 7%. These prsities are used here as the limits f a rectangular prbability distributin, shwn in figure 6.8 and table 6.1. Rck Heat Capacity As with density and prsity, there are n direct measurements f the heat capacity f the KERZ reservir rcks, nr are such measurements cmmnly carried ut. Like density, the ptential range f 6-11

65 heat capacity in a particular rck type is relatively small, and s it is nrmally acceptable t mdel the distributin f heat capacity as a fixed value. Here a value f BTU/lb/F is selected fr the average heat capacity f the reservir rck (table 6.1). Multiplying by the selected average rck matrix density f 175 punds per cubic ft yields a vlumetric heat capacity f BTU/cu. ft/f. This value is equivalent t abut 0.6 cal/g/c, which is a value cmmnly used fr estimating energy reserves in gethermal fields (e.g. White and Williams, 1975). Energy Recvery Factr The energy recvery factr, r fractin f the energy in the reservir vlume that can be recvered fr cmmercial use, can be difficult t estimate even if a large amunt f reservir data is available. The recvery factr depends t a large degree n the distributin f permeability within the reservir vlume: the mre cntinuusly distributed the permeability, the larger the fractin f energy that can be extracted by heat transfer t prduced fluids. The spatial distributin f permeability nrmally cannt be characterized with as much certainty as ther parameters such as temperature and pressure, and the small number f slim hles present ver a relatively large area f the KERZ prvides a further limitatin. Therefre, a rectangular prbability distributin with brad limits is apprpriate fr estimating recvery factr in the KERZ. The limits f the prbability distributin must take int accunt the evidence frm dwnhle data and injectin testing that reservir permeability in the KERZ is relatively lw, and may ccur 6-12

66 mainly in limited znes (figures 4.1, 4.2 and 4.3; table 5.1). Therefre, the maximum pssible recvery factr shuld be lwer than the 25% that is cnsidered as a typical best case fr many gethermal fields (White and Williams, 1975; Muffler, 1978). An upper limit f 15% (0.15) has been selected here fr the prbability distributin (table 6.1). A minimum recvery factr f 2.5% (0.025) has been chsen, based n the pssibility that permeability may be absent in significant prtins f the estimated reservir area nt yet investigated by the slim hles, r at depths deeper than thse yet drilled. Figure 6.9 shws the prbability distributin defined by the selected minimum and maximum values. 6-13

67

68 7. ESTIMATION OF RECOVERABLE ENERGY RESERVES Sectin 2 f vlume 1 f this reprt discusses the theretical and cmputatinal backgrund f the Mnte Carl technique fr the prbabilistic estimatin f recverable reserves f gethermal energy. In this sectin the Mnte Carl technique is applied t the gethermal resurce f the Kilauea East Rift Zne, using the resurce parameters estimated in sectin 6 (table 6.1). A separate estimate f reserves within the KERZ~ based n slightly different assumptins and n a mre extensive data base, has recently been carried ut by GethermEx (1992). That estimate prvided results cnsistent with thse f this reprt. In additin t the resurce parameters, the calculatin f energy reserves requires that certain parameters related t pwer generatin methds be assumed, in rder t express recverable energy in terms f available megawatts f electric pwer generatin ptential. These parameters, and their values assumed fr the KERZ estimatin, are: Pwer plant life: 25 years Pwer plant lad factr r capacity factr: 90% Pwer plant energy utilizatin factr: 45% Rejectin temperature (average annual ambient temperature): 60 F Tw separate mdels f recverable energy reserves have been calculated: ne using the reservir area prbability distributin estimated frm the slim hle results nly, and ne based n the 7-1

69 reservir area distributin estimated frm all available well data (table 6.1). These mdels are referred t here as the "slim hles nly" mdel r "Mdel A", and the "all wells" mdel r "Mdel B", respectively. Fr each mdel, the jint prbability distributin f energy reserves has been calculated using the Mnte Carl technique, frm 1,000 sets, r iteratins, f randmly selected values fr the resurce parameters within their respective prbability distributins. Tables 7.1 and 7.2 summarize the characteristics f the resulting prbability distributins fr Mdels A and B, respectively, in terms f their means, standard deviatins, and selected percentiles. Fr the mdel based nly n the slim hle data (Mdel Ai table 7.1), the mean capacity fr an installatin with the assumed pwer plant parameters is 173 megawatts, with a standard deviatin f 116 MW. The mdel incrprating all the well data, with its larger estimated reservir area, has a mean f 288 MW, with a standard deviatin f 177 MW. The loth percentiles f capacity calculated by the tw mdels are 53 MW and 96 MW, respectively. These numbers represent the 90% cnfidence level fr resurce availability, assuming that the resurce parameters have been apprpriately estimated. Als calculated fr bth mdels are the jint prbability distributins f megawatts per square mile f reservir area, and f resurce recvery efficiency. Fr Mdel A the mean capacity per square mile is 50.4 megawatts, with a standard deviatin f 21.2 MW per square mile. The prbability distributin calculated fr Mdel B is similar, with a mean f 50.1 MW per square mile and a standard deviatin f 21.2 MW per square mile. Fr bth mdels, the mean recvery efficiency is calculated t be 1.22% with a standard deviatin f 0.49% %. 7-2

70 The jint prbability distributins f recverable energy reserves are mst easily interpreted by cnstructing histgrams that display the relative frequency r prbability that the level f reserves falls within a certain categry, and cumulative prbability plts that aid in determining the prbability that reserves are greater than r equal t a specified level. T cnstruct such graphics, the relative frequency f MW capacity, MW capacity per square mile and recvery have been cmputed fr unifrm intervals. The results are tabulated in tables 7.2 (Mdel A) and 7.3 (Mdel B), and used as the basis fr figures 7.1 t 7.8. Figure 7.1 shws a histgram f the jint prbability distributin f megawatt capacity fr Mdel A, based n the slim hle data nly. The histgram shws clearly the shape f the prbability distributin, which has a mde, r mst likely value, near abut 100 MW. Mst f the distributin lies between values f abut a and 300 MW, with a small prbability f lwer values (arund 20 MW r less), and steadily decreasing prbabilities f higher values (300 t 700 MW). Overall the distributin is slightly asymmetric, with a IItailll n the high side extending t the higher values which have very lw prbabilities. Based n figure 7.1, the slim hle.data are useful in characterizing the available resurce t within abut plus r minus 120 t 150 MW f capacity, at least within the limited znes explred by the slim hles. Additinal drilling that further explred and delineated the gethermal system wuld better define the limits f the resurce, and therefre better define the prbability distributin. Figure 7.2 presents a histgram f MW capacity fr Mdel B, based n all available well data. Althugh based n a greater number f wells, the distributin is brader and mre asymmetric than that fr Mdel A, with a lnger IItailll extending t mre than 1000 MW n the high 7-3

71 end (thugh at extremely lw prbabilities). In additin, the mst likely value f MW capacity is abut 180 MW, substantially higher than fr Mdel A. This indicates that the additin f data frm mre wells has had the effect f extending, rather than delineating, the knwn resurce, and that a significant number f additinal wells r slim hles might be required t define the resurce t the extent that the prbability distributin begins t narrw nce again. This is particularly true if the resurce extends farther up and dwn the rift than the current limits f explratin drilling (figures 3.2, 6.1, 6.2). Figure 7.3 shws the histgrams f MW capacity fr bth Mdel A and Mdel B pltted tgether in utline frm. This figure emphasizes the difference in shape between the tw distributins, and suggests that with additinal drilling the eventual prbability distributin shuld reach a still-higher mde. Additinal drilling wuld als be expected t make the distributin mre symmetric and narrwer (i.e. with a mde clser t the mean, and a smaller standard deviatin relative t the mean). Figure 7.4 shws a cumulative prbability plt f the MW capacity distributins fr,bth Mdel A and Mdel B. A plt f this type is useful fr estimating the prbability that a certain level f reserves exists, r fr estimating reserves at a specific cnfidence level. Fr example, Mdel A indicates a SO% prbability that recverable reserves exceed abut 140 MW. In Mdel B, the SO% cnfidence level fr reserves is slightly mre than 2S0 MW. The calculated prbability distributins f capacity per unit area (in this case expressed as MW per square mile) fr bth Mdel A and Mdel B are shwn in figure 7.S. As this figure shws, the distributins are quite similar fr bth mdels. This is because bth 7-4

72 mdels are based n the same set f parameters except fr reservir area, which by definitin des nt affect the calculatin f capacity per unit area. The differences between the tw distributins are therefre due mainly t randm differences between the trial values used in the Mnte Carl technique. The distributin f MW per square mile is nearly symmetric, and shws either a slight bimdality, r a mean and mde falling near 50 MW. Mst f the values fall between 15 and 80 MW per square mile. Figure 7.6 shws the cumulative prbability plt f MW square mile fr bth Mdel A and Mdel B. per Figure 7.7 presents the histgram f recvery efficiency fr Mdel A and Mdel B. As fr capacity per unit area, the distributins fr Mdel A and Mdel B are similar, as recvery efficiency is insensitive t reservir area. Figure 7.8 shws the cumulative prbability plt f recvery efficiency fr the tw mdels. The distributin f recvery efficiency is rughly symmetric, althugh the mde appears t be n the high side f the distributin, near 1.6%, whereas the mean is abut 1.2%. Mst f "the values within the distributin fall between abut 0.3% and 2.1%. This example f the calculatin f recverable gethermal energy reserves using resurce parameters estimated frm slim hle drilling helps illustrate sme imprtant cnclusins regarding slimhle-based resurce assessment methdlgy in general, and the KERZ slim hle drilling prgram in particular. As shwn here, even a limited number f slim hles, in cmbinatin with an understanding f the gelgical terrane based n surface studies, can be useful in 7-5

73 identifying a gethermal resurce, and making a preliminary quantitative estimate, r at least a minimum estimate, f ptential cmmercial reserves. The estimatin prcess als helps characterize the need fr additinal infrmatin frm further drilling, by shwing hw the definitin f the gethermal resurce imprves with incremental data prvided by additinal hles. This may enable preliminary planning fr cmmercial explitatin t prceed by helping t quantify the degree f uncertainty (and therefre risk) assciated with the understanding f the resurce at any particular stage f explratin. The resurce assessment prcess als may assist in making decisins regarding the planning and management f additinal slim hle drilling, r f large-diameter explratin and develpment drilling. The KERZ example illustrates that, fr the purpses f resurce assessment with the aim f cmmercial develpment, a small number f hles may prvide a limited data base, even if the amunt f infrmatin gained frm each hle is relatively large. Tradeffs such as reducing hle depth r using a less expensive drilling methd in rder t drill mre hles may in many cases result in a higher level f cnfidence in resurce assessment results. The KERZ drilling prgram has been characterized t this.pint by relatively deep and expensive hles, and this in cmbinatin with ther factrs has limited the number f hles drilled t date. Planning fr future drilling culd incrprate cnsideratin f the likely value f alternative hle designs and techniques in cmparisn with the existing hles. Anther significant aspect f the KERZ hles is that prductin testing and fluid sampling, fr reasns discussed earlier, have s far nt been feasible. Althugh this des nt affect the estimatin f recverable energy reserves, it can have an imprtant impact n the characterizatin and mdeling f ther aspects f the resurce, and 7-6

74 indeed n defining the ultimate viability f the resurce. It therefre can affect decisin making and planning fr cmmercial explitatin. In this regard, the presence f infrmatin frm large-diameter wells in the KERZ is an imprtant factr in assessing the resurce, regardless f their lcatin r distributin. In general, the presence r absence f large-diameter wells, r plans fr such a drilling prgram, shuld be a cnsideratin in planning the extent and style f a slim-hle prgram. 7-7

75

76 8. REFERENCES GethermEx, Inc., 1992, Annual Reprt: Gethermal Resurces Assessment: Reprt fr State f Hawaii Department f Business Ecnmic Develpment and Turism. Olsn, H. J., 1988, Hawaiian Prgram fr the Cnfirmatin and Stimulatin f Gethermal Resurces Develpment: Gethermal Resurces Cuncil Transactins, v. 12, p Olsn, H. J. and Deymnaz, J. E., 1992a, Preliminary Results and Status Reprt f the Hawaiian Scientific Observatin Hle Prgram: Seventeenth Wrkshp, Gethermal Reservir Engineering, Stanfrd University. Olsn, H. J. and Deymnaz, J. E., 1992b, Summary f the Drilling Results and Csts f the Hawaiian Scientific Observatin Hle (SOH) Prgram: Reprt fr Electric Pwer Research Institute. Olsn, H. J., Seki, A., Deymnaz, J., and Thmas, D., 1990a, The Hawaiian Scientific Observatin Hle (SOH) Prgram: Gethermal Resurces Cuncil Transactins, v. 14, p Olsn, H. J., Seki, A., Deymnaz, J., and Thmas, D., 1990b, The Hawaiian Scientific Observatin Hle (SOH) Prgram: Gethermal Resurces Cuncil Transactins, v. 14, p Muffler, L. J. P., editr, 1978, Assessment f Gethermal Resurces f the United States : U.S. Gelgical Survey Circular

77 White, D. E. and Williams, D. L., editrs, 1975, Assessment f Gethermal Resurces f the United States : U.S. Gelgical Survey Circular

78 TABLES

79

80 Table 4.1. State f Hawaii Slim Hle Drilling Prject: Status f Data Cllectin SOH-1 SOH-2 SOH-4 A Q A Q A Q Basic cmpletin Data Drilling Penetratin Rates Directinal Surveys Drilling Fluid Prperties Drilling fluid Temperatures Bttmhle Temperatures Water levels/bttmhle Pressures Circulatin Lsses Static Dwnhle Temperature Surveys Static Dwnhle Pressure Surveys Static Spinner Surveys Gephysical Lgs Caliper Lgs Lithlgy Rck Alteratin Injectin Test Flw Rates I Injectin Test Dwnhle T /P Prfiles Injectin Test Spinner Survey Injectin Test Pressure Transients Injectin Test Interference Mnitring Dwnhle Fluid Samples Prductin Test Fluid Rates Prductin Test T /P Prfiles Prductin Test Pressure Transients Prductin Test Interference Data Prductin Flw Test Fluid Samples I A = Data Availability (0-3) Q = Data Quality (1-3) 9-1

81 Table 4.2. State f Hawaii Slim Hles: Basic Cmpletin Data Hle Name SOH-1 SOH-2 SOH-4 Start Date 5/31/90 2/4/91 12/12/89 Cmpletin Date 1/13/91 6/9/91 5/25/90 Drilled Depth (feet) 5,526 6,802 6,562 Surface Elevatin (feet msl) Reference Elevatin (feet msl) Bttmhle elevatin (feet msl) -4,907-6,532-5,367 First Casing Size (inches) 9-5/8 9-5/8 13-3/8 First Casing Depth (feet) Secnd Casing Size (inches) /8 Secnd Casing Depth (feet) 1,996 1, Third Casing Size (inches) 4-1/2 5 7 Third Casing Depth (feet) 3,022 3,721-4,103 2,000 Furth Casing Size (inches) - 4-1/2 HO rds Furth Casing Size (feet) - 1,794-3,721 4,530-5,290 Fifth Casing Size (inches) - 3-1/2 - Fifth Casing Depth (feet) - 4,762-4,998 - Tubing Size (inches) 2-3/4 (NO) 2-3/4 (NO) 2-3/4 (NO) Tubing Depth (feet) 5,526 6,802 6,562 Open Hle Size (inches) 3.83 (HQWL)/2.98 (NQ) 2.98 (NQ) 3.78 (HQ)/2.98 (NQ) Maximum Measured Deviatin (deg.)

82 Table 4.3. Dwnhle Surveys Cnducted in Slim Hle SOH-1 Date Survey Type Hle Cmpany Cnditin Cmments 12/20/90 T 1/5/91 T,P 1/5/91 T 1/6/91 Gamma Ray 1/6/91 Caliper,T 1/8/91 Spinner 1/9/91 Gamma Ray 1/9/91 Spinner 1/10/91 P 1/10/91 T 1/11/91 T 3/1/91 T Univ. f Hawaii Drilling Hle depth 5,526' USGS Static Pressure tl failed GethermEx Static USGS Static Tl failed USGS Static Hle blcked at 4,410' USGS Injecting Tl failed USGS Static Tl failed USGS Injecting Tl failed GethermEx Injecting Pressure fallff test USGS Static Hle blcked at 5,131 ' USGS Static USGS Static T = Temperature P = Pressure 9-3

83 Table 4.4. Dwnhle Surveys Cnducted in Slim Hle SOH-2 Date Survey Type 3/6/91 T,P,S,G,C,V 6/6/91 T,P 6/6/91 T,P 6/7/91 T,S 6/8/91 P 1/8/91 T,P Hle Cmpany Cnditin Cmments USGS Drilling USGS Static Pruett Static Pruett Injecting Spinner failed Pruett Injecting Pressure fallff test Pruett Static T = Temperature P = Pressure S = Spinner G = Gamma Ray C = Caliper V = Brehle Televiewer 9-4

84 Table 4.5. Dwnhle Surveys Cnducted in Slim Hle SOH-4 Hle Date Survey Type Cmpany Cnditin Cmments 5/20/90 Spinner,T Ht Hle Static Abrted at 4,250' 5/21/90 Spinner Ht Hle Injecting 5/21/90 T,P GethermEx Injecting 5/21/90 P GethermEx Injecting, Static Clck failed 5/22/90 P GethermEx Injecting, Static Pressure fallff test 5/22/90 T Ht Hle Static Results unreliable 5/22/90 T Ht Hle Injecting Results unreliable 5/22/90 T Ht Hle Injecting Results unreliable 5/22/90 Spinner Ht Hle Injecting Results unreliable 5/23/90 T Ht Hle Static Abrted at 4,000' 5/23/90 T Ht Hle Static Results unreliable 5/23/90 T,P GethermEx Static 7/11/90 T,P GethermEx Static 1/11/91 T USGS Static 1/12/91 P GethermEx Injecting Pressure fallff survey 1/13/91 T USGS Static Hle blcked at 5,745' T = Temperature P = Pressure 9-5

85 Table 4.6. Histry f Injectin Rates and Pressures, Injectin Test f Slim Hle SOH-1 Dwnhle Wellhead Time Pressure Pressure Flw Rate (minutes) (psi g) 0.0 1, ,056.6 (psi g) 0 0 (gpm) Cmments Clck cnnected Tl at 3,075 feet Start pumping... ~9.... ~.'.~9.~:.~... ~... ~?... g~~~9.~..!!.?~.e~!.~ , Well full 65 1, , u , ~9.... ~.'.~.~~:.~... ~.~~... ~~ , , ~.~~... ~.'.~~.?:.~... ~?g... ~9..?... g~~~9.~..!!.?~.e~!.~ , ~.?g... ~.'.~~.~:9.... ~~g... ~.~ , , , ,"""', , , , Stp pumping , , Ttal injectin vlume = 20,170 gallns 250 1, ??~ ~.'.g.~~:.~ , , , , , , POOH Tl at surface 9-6

86 Table 4.7. Histry f Injectin Rates and Pressures, Injectin Test f Slim Hle SOH-2 Time (minutes) Dwnhle Wellhead Pressure Pressure Flw Rate (psi g) (psi g) (gpm) 1, , Cmments Start pumping water... ~......?!g??:.~......?~~... ~.?~:~... ~~I.~~~.~9... p..~.~~~~~~.j?~~~.i.~.9...?g~~?~~.p.~~ , , , , , ~.~......?!g~~:? ~.~~... ~.~~:.~...!.9.~~~.. ~~j~~.~~~.. ~.. ~.~~.. ~.~E~~.I.~ , , , , ,125.9 Duble injectin rate; use 2 pumps , , , ~.~~...?!.?~~:?... ~~~...??~:~ , , Ttal injected = 189 barrels , , First pump catches air; flw nt stable 154 2, , , Ttal injected = 551 barrels 184 1, Shut bth pumps ff; begin fallff , , , ~?~ ~.!.~?~.:~ ~ ~ , , ,821.0 End f Kuster 12 hur clck 9-7

87 Table 4.8. Histry f Injectin Rates and Pressures, Injectin Test f Slim Hle SOH-4 Dwnhle Wellhead Time Pressure Pressure Flw Rate Flw Rate (minutes) (psig) (psig) (bbl/min) (gpm) Cmments Start cling well ~~... ~:.~ ~.:?....!.~...!.~!~~.g9.9.!!d.~.. ~~~~E.. ~~l~.~~~.~... ~...??.. ~.~.I.~ a Ttal = 92 bbls Cnnect Kuster tl # u a Well full Start running tl in hle... ~.~.~... ~.!.!.~~:~ ~:~...?.~....!.~~~.~!.. ~.'. g.~: ,723.9 a Start pumping... ~.!.~... ~.!.!.~~:~... ~~... ~:~... ~.~!....!.~!~UD1~g~~9... ~... ~~.. ~.~!.~ , Zered flw ttalizer; ttal injected = a 180 1, Ttal = 67 bbls... ~.~.?... ~.!.~~~:~... ~.!..... ~:~ ~.~.!.... Y.Y.~!:.E~~~9.~.. ~~g~!!~~!~jt~y... ~L..?g.J?~! , , ?~.?... ~.!.~.?~:~... ~.~~... ~:.?... ~.~!....!.~!~~.. ~.. ~.!..~.. ~~.~~ , , , Ttal = 270 bbls Ttal = 340 bbls Ttal = 463 bbls , Ttal = 599 bbls Ttal = 701 bbls 374 1, , Add ne pump... ~~.?... ~.!.~.~~:~ ~ g ~:.?...?~.~...!g~~~.. ~..!.~.?.. ~~~~ , , , Ttal = 825 bbls Ttal = 1137 bbls Ttal = 1315 bbls 9-8

88 Table 4.8. Histry f Injectin Rates and Pressures, Injectin Test f Slim Hle SOH-4 (cntinued, page 2) Dwnhle Wellhead Time Pressure Pressure Flw Rate Flw Rate (minutes) (psig) (psig) (bbljmin) (gpm) Cmments 515 1, Ttal = 1466 bbls 545 1, Ttal = 1636 bbls... ~~~... ~.!.~9..~.:~ g ~~g.p...!?~!!!p.!.~ ,811.7 a a a 550 1,741.8 a 0 a... ~~.~... ~.!.~~~:~ ,623.3 a a a 565 1,590.9 a a a... ~! ~!.?~~:~ ,547.2 a a a 580 1,535.9 a a a... ~~?... ~.!.~.?~: ,513.3 a 0 a 595 1,505.2 a a 0... ~9.?... ~.!.~~!.:.~ ,490.7 a a a 635 1,485.8 a a a... ~~.?... ~.!.~.?!.:! ,472.9 a a a 725 1,468.0 a a a 755 1,463.2 a a a... u 780 1,463.2 a 0 a POOH a a a Tl ut f the hle 9-9

89 Table 5.1. Reservir Parameters Estimated frm Injectin Testing f Slim Hles Reservir Flw Capacity Skin Hle (md ft) Factr SOH-1 6, SOH-2 1, SOH-4 1,

90 Table 6.1. Summary f Estimated Resurce Parameters Distributin Minimum Mst Likely Maximum Parameter Units Type Value Value Value Reservir Area (a) Square miles Triangular Reservir Area (b) " " Reservir Thickness Feet Triangular 4,000 5,000 6,000 Reservir Vlume (a) Cubic Miles Cmpsite -0.4* -2.1* -8.6* Reservir Vlume (b) " " -1.2* -3.4* -13.2* Reservir Depth Feet Triangular 4,500 4,800 5,500 Reservir Temperature Degrees F Triangular Rck Matrix Density Ib/cu. ft Fixed Rck Prsity Dimensinless Rectangular 3.0% - 7.0% Rck Specific Heat BTU/cu. ftrf Fixed Energy Recvery Factr Dimensinless Rectangular 2.5% % (a) Estimate based n slim hle results nly (b) Estimate based n results f all wells and slim hles *Apprximate effective values; see figure

91 Table 7.1. Summary f Prbabilistic Estimatin f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel A) Input Parameter Distributins Mst Distributin Minimum Likely Parameter Type Value Value Vl. Heat Capacity (BTU/cu. ftfof) Fixed Rejectin temperature (OF) Fixed 60.0 Utilizatin factr Fixed 45.00% Plant lad factr Fixed 90.00% Pwer plant life (years) Fixed 25.0 Reservir area (square miles) Triangular Reservir thickness (feet) Triangular 4,000 5,000 Rck prsity Rectangular 3.00% Average temperature (OF) Triangular Recvery factr Rectangular 2.50% Maximum Value , % % Summary f Results Mean Standard Minimum Value Deviatin Value MW Capacity MW per square mile Recvery Efficiency 1.22% 0.49% 0.33% Tenth First Percentile Quartile Median MW Capacity MW per square mile Recvery Efficiency 0.53% 0.82% 1.22% Maximum Value % Third Quartile % 9-12

92 Table 7.2. Summary f Prbabilistic Estimatin f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel B) Input Parameter Distributins Mst Distributin Minimum Likely Parameter Type Value Value Vl. Heat Capacity (BTU/cu. ftfof) Fixed Rejectin temperature (OF) Fixed 60.0 Utilizatin factr Fixed 45.00% Plant lad factr Fixed 90.00% Pwer plant life (years) Fixed 25.0 Reservir area (square miles) Triangular Reservir thickness (feet) Triangular 4,000 5,000 Rck prsity Rectangular 3.00% Average temperature CF) Triangular Recvery factr Rectangular 2.50% 0.00% Maximum Value , % % Summary f Results Mean Standard Minimum Value Deviatin Value MW Capacity MW per square mile Recvery Efficiency 1.22% 0.50% 0.32% Tenth First Percentile Quartile Median MW Capacity MW per square mile Recvery Efficiency 0.54% 0.78% 1.21% Maximum Value 1, % Third Quartile % 9-13

93 Table 7.3. Estimated Prbability Distributins f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel A) Prbability Distributin fr MW Capacity Interval Interval Interval Relative Cumulative Number End Midpint Frequency Frequency % 0.00% % 6.30% % 21.20% % 40.20% % 57.10% % 68.00% u % 77.10% % 83.60% % 87.80% % 90.90% % 94.60% % 96.80% % 98.00% % 98.80% % 99.10% % 99.80% % 99.90% % 99.90% % % % % % % % % % % % % % % 25 1, % % 9-14

94 Table 7.3. Estimated Prbability Distributins f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel A) (cntinued, page 2) Prbability Distributin fr MW per Square Mile Interval Interval Interval Relative Cumulative Number End Midpint Frequency Frequency % 0.00% % 0.00% % 0.00% % 1.70% % 8.80% % 14.90% n % 20.60% % 27.40% % 35.40% % 43.10% % 50.60% % 56.50% % 64.00%." Iv % 70.90% % 79.00% % 86.00% % 91.70% % 94.90% % 97.60% % 99.10% % 99.70% u % % % % % % % % % % 9-15

95 Table 7.3. Estimated Prbability Distributins f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel A) (cntinued, page 3) Prbability Distributin fr Recvery Efficiency Interval Interval Interval Relative Cumulative Number End Midpint Frequency Frequency % 0.00% 0.00% % 0.10% 0.00% 0.00% % 0.30% 3.20% 3.20% % 0.50% 11.30% 14.50% % 0.70% 9.80% 24.30% % 0.90% 11.70% 36.00% % 1.10% 12.70% 48.70% % 1.30% 11.00% 59.70% % 1.50% 13.40% 73.10% % 1.70% 11.50% 84.60% % % % % % 2.10% 3.90% % % 2.30% 0.00% % % 2.50% 0.00% % % 2.70% 0.00% % % % % % % 3.10% 0.00% % % 3.30% 0.00% % % 3.50% 0.00% % % 3.70% 0.00% % % % % % % 4.10% 0.00% % % 4.30% 0.00% % % 4.50% 0.00% % % 4.70% 0.00% % % 4.90% 0.00% % 9-16

96 Table 7.4. Estimated Prbability Distributins f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel B) Prbability Distributin fr MW Capacity Interval Interval Interval Relative Cumulative Number End Midpint Frequency Frequency % 0.00% % 0.50% % 7.30% % 15.20% % 26.50% % 37.90% % 46.80% % 56.70% % 65.80% % 71.20% % 77.40% % 81.40% % 86.20% % 89.00% % 91.90% % 93.20% % 94.90% % 95.90% % 97.50% % 98.20% % 98.50% % 99.00% % 99.40% % 99.50% % 99.80% 25 1, % 99.90% 9-17

97 Table 7.4. Estimated Prbability Distributins f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel B) (cntinued, page 2) Prbability Distributin fr MW per Square Mile Interval Interval Interval Relative Cumulative Number End Midpint Frequency Frequency % 0.00% % 0.00% % 0.00% % 2.10% % 7.30% % 15.50% % 22.70% % 29.40% % 35.70% % 43.80% % 50.00% % 57.90% % 64.70% ~'" Iv % 71.30% % 79.60% % % % 91.80% % 95.40% % 97.20% % 98.70% % % % 99.80% % % % % % % % % 9-18

98 Table 7.4. Estimated Prbability Distributins f Recverable Energy Reserves, Kilauea East Rift Zne (Mdel B) (cntinued, page 3) Prbability Distributin fr Recvery Efficiency Interval Interval Interval Relative Cumulative Number End Midpint Frequency Frequency % 0.00% 0.00% % 0.10% 0.00% 0.00% % 0.30% 2.60% 2.60% % 0.50% 11.40% 14.00% % 0.70% 12.10% 26.10% % 0.90% 12.20% 38.30% n % 1.10% 11.40% 49.70% % 1.30% 10.00% 59.70% % 1.50% 12.10% 71.80% % 1.70% 13.40% 85.20% % 1.90% 11.00% 96.20% % 2.10% 3.80% % % 2.30% 0.00% % % 2.50% 0.00% % % 2.70% 0.00% % % 2.90% 0.00% % % 3.10% 0.00% % % 3.30% 0.00% % % 3.50% 0.00% % % 3.70% 0.00% % % 3.90% 0.00% % % 4.10% 0.00% % % 4.30% 0.00% % % 4.50% 0.00% % % 4.70% 0.00% % % 4.90% 0.00% % 9-19

99

100 FIGURES

101

102 /0 Figure 3.1 Map f the Island f Hawaii including the East Rift Zne f the Kilauea Vlcan ~'=' =O'===='==:=dI,0 MILES.NOTE: Elevatin shwn in meters, msl 1992, GethermEx, Inc. EPRIPU31/092B92/H4979 Elt.t'fl =60000/EPRI.JP '. "0' ",.. ~.' '.'.",..... '",,"... '......,".. ' :<) It) ~ c 1 f <D 1 C g l' 10-1

103 ;: :1l N c " ft 'l7q~ + s~ ~ d~g '8 '" /0 N ~ 'tj C- ~ ~ -~r (j)' ~ -YOO~.SOH-2.---\ -_.' \ 100 /?t;!~.,~) / 'KapOh~~ /~ - crate/! N " I--' a I N Elevatin cntur, feet _ Fracture, fault LEGEND Scientific Observatin Hle (SOH) Deep gethermal wells pf ~ Prductin; injectin; dry -e- 0 x Plugged; mnitr; drilling Figure 3.2: Reginal map f the lwer Kilauea East Rift Zne shwing gelgic features and well lcatins. // :::Y II T /1 //>-// I I,,.---""- ). C,1 37. V= A ("'{' "'IC,r-; J-' /', r / /-' /'/ /' l ' / ~. // '. OCE'A.lv ~'i $..., DOO ft I I 5000 feet I mile GethermEx. Inc. EPRPU32/092892/H4979/EI~N1-52!O/I-IAW..!.I.JP N

104 MASTER DRILLING VALVE WKM 6"-300 7" WLG FOSTER SOW WELLHEAD WLG FOSTER 2" --- 3,000# WING VALVE ~ -caa NO x 7" TUBING HANGER -GIG /8" 61# K ' 17-1/2"- 12-1/4"--"' /8" 40# K ', 8-1/ ~-----7" 35# K-80 2,000' HQ 3.8"... 4,570' -. LOST HQ ROD 760' 5,330' -+- NO 3.0" /8" x 2-3/4" PER~ORATED wi 1/2" DIAMETER HOLES 26 PER 1 0' LENGTH 5,290' , ,540' T.D. OF TUBING (CAP WELDED ON TBG END) TD=6,562' (Nt t scale) Figure 3.3. Cmpletin diagram, slim hle SOH , GethermE.x, Inc. EI'R1''H/OOZ09'/....,./Oll'll-l/SO

105 MASTER DRiLLING VALVE WKM 6"-300 7" WLG FOSTER SOW WELLHEAD WLG FOSTER 2" a_- 3,000# WING VALVE NO X 4-1/2" TUBING HANGER 12-1/4"' /8" 40# K ' 8-1/ ~-----7" 35# N-80 1,996' HQ 4.0" NO 3.0" _ /2" 9.5# J-55 3,022' 4,325' 2-3/8" x 2-3/4" PERFORATED wi 1/2" DIAMETER HOLES 26 PER 1 0' LENGTH 3,021 '-5,521' -~ ,521' T.D. OF TUBING (NO BIT ON TBG: END) TO=5,526' (Nt t scale) Figure 3.4. Cmpletin diagram, slim hle SOH-l 1992, GethermEx. Inc. EI'RI"""'/""2.. 2/...,./D''''~'/''''

106 MASTER DRILLING VALVE WKM 6-INCH INCH WLG FOSTER SOW WELLHEAD WLG FOSTER 2-INCH f 3,000# WING VALVE -dioii_---- NO x 7-INCH TUBING HANGER 12-1/4-INCH /8-INCH 40# K ft 8-1/2-INCH INCH 35# N-80 1,800 ft HO 3-3/4+-INCH ,900 ft ~ /8-INCH J-55 4,127 ft 4,147 ft II II I I I 4,127 FT - 6,800 FT II II I,_ /4-INCH x 3/16-INCH I PER~ORATED SLOTS 20 PER 10-FOOT LENGTH TD=6,802 ft (Nt t scale) Figure.3.5. Cmpletin diagram, slim hle SOH GethcrmEx. Inc. EPRlSOH'!OO'.. Z/H.,./ONY'-I/SOH

107 FIGURE 4.1. DOWNHOLE SUMMARY PLOT - SLIM HOLE SOH-1 Cmpletin Temperature (degrees F) rv~v~r-~r-----~-r'-~-.-..-,,-r'-~-r'-~rt-.'-.,-r.-~r-r'-"rt-"o V V tuding II V hanger V V a Cmpleted 6 January T p " casing 0 BOTTOMHOLE TEMPERATURES 0 1/05/91-24 HRS. AFT. COMPL /9 1-5 HRS. AFT. PUMPING x 1/ 10/9 1-8 HRS. AFT. INJ. + 1/ 11 /91-16 HRS. AFT. INJ. \l 3/01 / DAYS AFT. INJ r-1 (/) E -i-j Q) Q) ~ c 0.r-! -i-j 1'0 > Q) r-1 w '1/2' casing. uncmt. : 2-3/8' : perf '0. : tubing ""]... I--' I--' (1) 0. 0 (1) "CJ rt' :::r """ (1) (1) rt' : 3-3/4' pen hle ~ 0 0 < ~ <> a Pressure (ps ig) 10-6 GethermEx, 3000 Inc D: BHOLE.PL T

108 FIGURE 4.2. DOWNHOLE SUMMARY PLOT - SLIM HOLE SOH-2

109 FIGURE 4.3. DOWNHOLE SUMMARY PLOT - HOLE SOH Cmpletin 100 Temperature (degrees F) Cmpleted 25 May 1990 a " casing T P BOTTOMHOLE TEMPERATURES 0 5/21/90 - INJECTING 30 GPM /::, D. 5/23/90 - STATIC, 18 HRS. AFTER INJ. x x 7/11/90 - STATIC, 49 DAYS AFTER INJ. + 1/11/91 - STATIC. 8EFORE INJ. 'V 1/13/91 - STATIC, 18 HRS. AFTER INJ r-1 en E c.1"'1 +J 1'0 > OJ r-1 UJ i v v v i i v v v v v /4" ppen hle x x x J CO 0. CO '0 rl'" ::r /8" : perf 'd, tubing x ~--~------~~~~~~~~~~~~~~~~~~~~~~~ Pressure (ps ig) GethermEx, Inc A: BI-KlLE. PI.. T

110 FIGURE 4.4. WATER LEVELS MEASURED WHILE DRILLING - HOLE SOH-4 Cmpletin /8' 1000 tudlng hanger Measured Water Level (feet GL) " 1000 caslng r-i (/) E V CO D- +J ID 'I CO Q) v e J v v v 3500 '"CI.. ;., r > c c ID M- r-i... + W v v v 3-3/4 " ppen hle J M- :J" /8" 6000 : perf d tubing GethermEx, Inc" ; WLEVEL. PL T

111 FIGURE 4.5. EXPLANATION FOR DOWNHOLE SUMMARY PLOTS LITHOLOGY ~'v v ~ 'v ~ ~ f---- R f------' SUBAERIAL VOLCANICS SUBMARINE VOLCANICS INTRUSIVES NO SAMPLE SYMBOLS Lcatin f liner hanger Lcatin f casing she Sltted prtin f liner Bttm f liner Open hle GethermEx. Inc ~-1992 B: PLOT. PI.. T

112 Figure 4.6: Dwnhle Pressure Respnse During Injectin Test f Slim Hle SOH CJ) - ~ 1400 "-..,; ~ 1350 :::J en... ~ I L 0... (l) ~ Time since start f injectin (minutes) 1992 GethermEx, Inc.

113 Figure 4.8: Dwnhle Pressure Respnse During Injectin Test f Slim Hle SOH I 1 I I I I I I I I I I I T I IT I III I TT In TTT rftt I CJ).- ~ 1800 '-,;I ~ 1750 ::J (j)... ~ I L... N 0._ (1) ~ 1600 ~ ~,,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Time since start f injectin (minutes) 1992 GethermEx, Inc.

114 Figure 4.8: Dwnhle Pressure Respnse During Injectin Test f Slim Hle SOH ,,,,,,,,,,, J,,,,,,, ",,,,,,,, r, I n 1 r r J J -'I..--,.,r-.-.-r , I... w...-, 1850 CJ).- ~ 1800 "'--" ~ 1750 ::::J (f) ~ 1700 L (L (J) ~ : ,, I I I I I I I I I I I I I I I I I J L I I I I I I I J I J I II J Jllii I I I I I I I I I I I I I I LLI Ll I II I J Time since start f injectin (minutes) 1992 GethermEx, Inc.

115 ~ It \ =>:::; \ v ( (\... ~ I g +~ # '%~ " :/a ~ (~r~~--~0,--,ida SOH-2 / [J/G 8 N '" /~ /<OPOhO Crter g N " ~ I ~.j::: & '" ( (137 1, I. " /.//.r '/\ / ~ /j:::r'.. i 0iy.. <.. j. kift:4;/~ Elevatin cntur, feet LEGEND Frcture, fault Scientific Observatin Hle (SOH) Temperature cntur, f Deep gethermal wells flf * Prductin; injectin; dry ~ 0 x Plugged; mnitr; drilling a a I 5000 feet mile Figure 5.1: Temperature distributin at feet. msl GethermEx. Inc. EPRtTCU1/092t192/H49SO/E1WN1.. S2SO!HAWAl.JP

116 ~ 8 = =================:::~~=========::=:=:=~~~:=:=:=:=:=:=:=:=:=~~~:=~~~~===== " '""" r.,~oo " \: /) '~ I '" r:' ~()() (l + 0>0 0 -", 0,; '" 0 " V~ uf\ + Af-v; ~ \ + '-./7 / ~, sq I--' a I I--' U1 g~ ~es, ~I '6 " ~%O /000 "f,:/ ii/ ) ) '" " "1 N & (/'/ /' fl-\..~ r~----, > "Y,,//),) //<j/ (J C E,A.l'/', /' /' ( 1 '-') " ~( j'ja CIF.lC N $ LEGEND ft Elevatin cntur, feet Fracture, fault Scientific Observatin Temperature cntur, Hle (SOH) OF Deep gethermal wells 9! ~ Prductin; injectin; dry -E> 0 x Plugged; mnitr; drilling LOCATION 5000 feet ( I I mile Figure 5.2: Temperature distributin at -2,000 feet, msl 1992, GethermEx, Inc, EPRiTCIO/092892/H4980/EIMN1-52!W/HA.W'!"I.JP

117 ------~ ~ It \00'9'0 V~ + i:?jl + SO /\ /)(\ _ 1! r,m ~ ~ c '6.., '".~ ( 1:.7) - I -'" /\ r // J a a..., N $ LEGEND '00 It Elevatin cntur, feet _ Fracture, fault Scientific Observatin Hle (SOH) Temperature cntur, T Deep gethermal wells ' ~ Prductin; injectin; dry <'> 0 x Plugged; mnitr; drilling LOCATION I a I 5000 leel I mile Figure 5.3: Temperature distributin at -3,000 feet, msl GethermEx. Inc. EPRlTCMJ/092992/H4.9SO/EJMN1-52!D/PJ.WAI.JP

118 ft + 9' r , 0,~ " \:::,..~ co ' / 0; /. /./' ;;q:, "b ///0 \ +~~ 7//~ "RJ./ a a N "... I J ~900 ~ /000 //00 _/ g5~--- ~ ' ---,1 00 "":: 0 4/- r,o --~/-,1." // "-a 500 V ~ 4- '\ r, ',.';_ r / "-/ '0 CJ ~ / /' '& ~.z, ~ C &, ''I' ;::>/,, C.71' 'I "Y / I N ( 1 3j0') OG, EAl~r q; ~, a '" N Elevatin cntur, feet Fracture, fault LEGE:ND Scientific Observatin Hle (SOH) Temperature cntur, "F Deep gethermal wells.;! ~ Prductin; injectin; dry ~ 0 x Plugged; mnitr; drilling a 5000 teet 1 mile ft Figure 5.4: Temperature distributin at -4,000 feet, msl GethermEx. Inc, EPRlTCM4/092992/H4981 /EIMN /H"-W4J.JP

119 ~ It + < , 0 N '" S~ ~,~ <:0 '6 N "'... I / ~ 1"1 N OG.h~1.j'T N $ LEGEND It Elevatin cntur, feet _ Fracture, fault Scientific Observatin Hle (SOH) Temperature cntur, "F Deep gethermal wells ~'+ Prductin; injectin; dry -e- 0 x Plugged; mnitr; drilling I 5000 feet mile Figure 5.5: Temp-erature distributin at -5,000 feet, msl GethermEx. Inc. EPRlTCMS/C92992/H4981 /EIMN1-5280/HAWAI.JP

120 ft + "'Cb '0 '" SO ~... I c>:> '6 ~900 /000 SOH-4 l.j>oo Elevatin cntur, feet _ Fracture, fault LEGEND Scientific Observatin Hl ~ (SOH) Temperature cntur, "F + /' 60 0 "> Deep gethermal wells ft! <1T Prductin; injectin; dry ~ 0 x Plugged; mnitr; drilling & I') "'~L ; ;X~------"----- I...,... /,',/\ ~ /.11 'f J;- / I '" N ij H8 0 /. g.' N "" ~<.',(" '. '-c & '" ::7)/ F'/,\ (11:J. '-.// -. / r / -' // I I i-l $ 5000 feet I mile ft Figure 5.6: Temperature distributin at -6,000 feet, msl GethermEx. Inc. EPRllCIM)/~29:l2/H"981 /EIMN' "'S~!O/HAWAl.JP

121 1250 Figure 5.7: Hrner Semi-lg Plt, Well SOH-1 Pressure Fallff.,..-" CJ) 1225 en 0.. ' ~ 0 I N 0 (l) ~ ::J ~ 1175 (l) ~ 0... a) 1150 I..c c S: measured data semi-lg straight line: kh = 6,100 md.ft, skin = 39 0 ""'0 (J) I... ~ 1100 Q) Q. -<>...,_.&>_ _ Hrner Time GethermEx, Inc.

122 Figure 5.8: Cmparisn f Measured and Calculated Pressure Data, Well SOH measured data -- calculated: kh = 6,100 md.ft, s = 39 " O'l 1450 (J) ,... a I N... ~ 1350 [( 0 ::l 0 (J) (J) Q) 1300 ~r 0 L 0..- Q) n 3: Time since injectin started (hurs) GethermEx, Inc.

123 Figure 5.9: Well SOH-2 Pressure Fallff Test: Hrner Semi-lg Plt 1900 ', ii' iii iii' i 1890 ~ CJ) 1880 (J) 0... '--"" Q) 1870 L. ::J (J) ~ 1860 l- n I N N ~ c c: ~ 1840 ~ 1830 L ::J Ul 1820 Q) ~ 1810 ~ 0 I I kh = 1,300 md.ft; skin = -0.2 (duble prsity mdel) Hrner Time GethermEx. Inc.

124 ... 0 I N w Figure ,..., O'l (J) "---'" 2200 Q) ~ 2150 (J) ~ 2100 ~ Q) c ~ : Cmparisn f Measured and Calculated Pressure Data, Well SOH-2 Cl r~ ~~ I I I ~,~ 0 \ I I I ~ Ia,~,... I I, <f I Q) J \ measured data. - - duble prsity mdel: kh = 1,300 md.ft; skin = MOOD'!!! 0iW0 t:r"o'o"o 0"0 0"0 O"O'U' ern.ctq crt> tj~ ~ ~ 0000"000 cd Time since injectin started (hurs) 1992 GethermEx, Inc.

125 2000 Figure 5.11: Hrner Semi-lg Plt, Well SOH-4 Pressure Fallff "..-, 01 Cf) '--'" (]) 1800!... ~ 1750 U) (]) ct measured datcj semi-lg straight line: kh = 1,360 md.ft, skin = (]) 1650 C> I N +:> 0. : C 1600 ~ ""0 ~ 1500 ::J ~ 1450 (]) 2: ~--.,.. 90~ O O --- 0,.;;; e "--(Y Hrner Time GethermEx, Inc. 1000

126 Figure 5.12: Cmparisn f Measured and Calculated Pressure Data, Well SOH r measured data calculated: kh = ',360 md.ft, s = ~ I 000 (;) 1850 ~ t5' 0 ~ 1800 '--'" ~ 1750 ~ 0 :::J ~ 1700 ~ L N Q) ~ ~...J ~ Time since injectin started (hurs) 1992 GethermEx, Inc.

127 ... I N 0'1 LEGEND Elevatin cntur, feel Deep gethermal wells - Fracture, fault _ ~ ~ Prductin; injectin; dry Scientific Observatin Hle (SOH) -& 0 x Plugged; mnitr; drilling Figure 6.1: Estimatin f reservir area based n slim hles nly. H,} q t~~~~';~1 k:;:::::::1 Maximum area Mst likely area Minimum area 1992, GethermEx, Inc. EPRlPU61/100192/H<9B2/E"'Nl=52BC/HAWAlLJP f2,=~ 5000 fe"t 1 mile

128 Figure 6.2: Estimated Prbability Distributin f Reservir Area SLIM HOLES ONLY ALL WELLS.3 >-' I N -...J > U Z w ::> e w a: LL..2.1 I I I I I, I I, I I I I I I I, I I I I, , ' I, "I I I" I I I I I I, I I I I I I I I I I I I,, 1)1 I I I, I,, I I " I II I I I I -, I I I " I I I RESERVOIR AREA (Square Miles) GethermEx, Inc

129 ... I N ex> Elevatin cntur, feet Fracture, fault LEGEND Scientific Observatin Hle (SOH) Deep gethermal wells 9f ~ Prductin; injectin; dry <70 x Plugged; mnitr; drilling ~ Maximum area,.\'\.,'" ~*~ Mst likely area ~ Minimum area Figure 6.3: Estimatin f reservir area based n all wells and slim hles Getherm Ex. Inc. EPIOPU6J/l00592/H<9B2/El"Nl =52BO/HAW"II.JP I b ~LOCATiON 5000 f'get mile

130 Figure 6.4: Estimated Prbability Distributin f Reservir Thickness I N ~ > U Z w ::> Cl w a: LL I RESERVOIR THICKNESS (Feet) '0 GethermEx. Inc

131 Figure 6.5. Estimated Prbability Distributin f Reservir Vlume ~ SLIM HOLES ONLY --l A '_L WELLS '... I W > U Z LU ::> CI LU 0: IJ I I I I,, I I-,,, I, I, I,,," I I,, '''.", -. ",11, ".. '-, '" \ \I ", -'. """,., V\ ", ",, -.. '.,,...,... I a ---._.J, a I I c RESERVOIR VOLUME (cubic miles) '-\,.2.1 6ethermEx. Inc:

132 Figure 6.6: Estimated Prbability Distributin f Reservir Depth a I w - > u z w ~ CI w a: u I I, I RESERVOIR DEPTH (Feet) GethermEx. Inc

133 Figure 6.7: Estimated Prbability Distributin f Average Reservir Temperature.02 I.02 >- () Z w... :::J 0 e I W W CC N LL.01 t- / \ -l.01 ' r l' AVERAGE RESERVOIR TEMPERATURE (F) GethermEx, Inc

134 Figure 6.8: Estimated Prbability Distributin f Rck Prsity a I w W > U Z W =>.25 el W a: ll I ~ 1 2 I 3 I I 456 ROCK POROSITY (Percent) GethermEx, Inc

135 Figure 6.9:.15 Estimated Prbability Distributin f Energy Recvery Factr.15.1 f- --' I.1 I... I W ~ > U Z w ::> C! W 0: LL.05 f- -...J.05 I I I I I I I I I I I I I I I ENERGY RECOVERY FACTOR (Percent) I I I () 20 GethermEx. Inc

136 00' ' O~6 00'006 00'098 > c:: I/) CI) J: E en c:: "C CI) I/) ca m > == (J ca Q. ca -ca ~ ca C) CD ~ \t O E e C).- -I/) J: 00'Ol8 00'09L OO'OvL OO'OOL 00'099 00'Ol9 00'08g OO'Ovg ~ (.) fts OO'OOg g- 00'09t ~ OO'Olt 00'08 OO'Ot 00'00 00'09l OO'Oll 00'08l OO'Ovl OO'OOl 00'09 OO'Ol ~ ~ CO C\I 0 ~ 0 ~ 0 ~ 0 ~ ~ 0 ~ CD... 'V... C\I A)UdnbaJ j 0-0 ~ 0 ~ e;:::: 0 ~ ~ 0 ~ 0 CO cd 'V N ~

137 00'086 00'0\76 - m (1) 't:j ~ c -CO C 00'098 00'OZ8 00'08L OO'O\7L 00'006 (1) ~ «c 't:j (1) tj) CO m ~ CJ CO c.. CO (.) t: CO ~ Cl (1) ~... E e Cl - -en X N...: E :::I Cl u:: OO'OOL 00'099 00'OZ9 00'08<; OO'Ot<; ~ u ns 00'00<; g. (J 00'09t ~ OO'OZt 00'08r O'tr O'r 00'09Z OO'Oll 00'08 l OO'Otl OO'OOl 00'09 OO OZ ~ ~ ~ ~ 0 0 ~ C\I CO CD,{JuanbaJj ~ 0 ~ ~ t N 0

138 Figure 7.3. Histgram f Megawatt Capacity, Mdels A & B 20.00% 18.00% 16.00% 14.00% 12.00% Mdel A (Slim Hles Only) -D-- Mdel B (All Wells)... >- u 0 c I w -...J Q) ~ ~ 10.00% 8.00% 6.00% 4.00% \ 2.00% 0.00% ~ioo.oo ~ c...r-i - ==-II ~I , MWCapacity

139 Figure 7.4. Cumulative Prbability Plt f MW Capacity, Mdels A & B % :~~I 90.00% 80.00% / 70.00% >-.... u 0 c (l) I w 0- '" (l) ex> w % 50.00% 40.00% Mdel A --D-- Mdel B 30.00% 20.00% 10.00% 0.00% , MWCapacity

140 Figure 7.5. Histgram f MW per Square Mile, Mdels A & B 9.00% 8.00% 7.00% Mdel A (Slim Hles Only) --D- Mdel B (All Wells) 6.00%... u c > % I ~ W ~ ~ 4.00% 3.00%. 2.00% 1.00% 0.00% MW Capacity per Square Mile

141 Figure 7.6. Cumulative Prbability Plt f MW per Square Mile, Mdels A & B % 90.00% 80.00% 70.00% 60.00% I-'.> i:!.b. ~ 50.00% r L % Mdel A (Slim Hles Only) ~ Mdel B (All Wells) 30.00% 20.00% 10.00% 0.00% MW Capacity per Square Mile

142 Figure 1.7. Histgram f Recvery Efficiency, Mdels A & B 14.00% 12.00% 10.00%... >- u 0 c Q) I :::l +:> cr... Q) W- 8.00% 6.00% -.- Mdel A (Slim Hles Only) 4.00% Mdel B (All Wells) 2.00% 0.00% 0.00% 0.50% 1.00% 1.50% 2.00% 2.50% Recvery Efficiency

143 Figure 7.8. Cumulative Prbability Plt f Recvery Efficiency, Mdels A & B % 90.00% 80.00% 70.00% --- Mdel A (Slim Hles Only) ----D-- Mdel B (All Wells) 60.00%... u >-. c Q.) ::::l 0 I ~ 0- N ~ u % 40.00% 30.00% 20.00% 10.00% 0.00% 0.00% 0.50% 1.00% 1.50% 2.00% :~.50% MW Capacity per Square Mile

144 APPENDIX

145

146 TABLE OF CONTENTS Summary f the Drilling Results and Csts f the Hawaiian Scientific Observatin Hle (SOH) Prgram TEXT Backgrund... Page 1 SOH-4.'e.... Page 1 SOH-I.... Page 5 SOH Page 5 Preliminary SOH Prgram Results... Page 6 FIGURES Fig. 1, Vlcanic Features and Areas with Gethermal Ptential n Maui and Hawai i... Page 2 Fig. 2, Lcatin f SOHs n the Big Island... Page 2 Fig. 3, SOH Drilling Perfrmance Depth vs. Cst... Page 4 Fig. 4, SOH Drilling Perfrmance Depth vs. Time... Page 4 Fig. 5, SOH Temperature vs. Elevatin.... Page 4 Fig. 6, HGP-A - PGV Gethermal Reservir... Page 8 TABLES Table 1, SOH-4 Drilling Csts and Activities... in back Table 2, SOH Prject Cst Overview... in back Table 3, SOH-l Drilling Csts and Activities in back Table 4, SOH-2 Drilling Csts and Activities in back A-iii

147

148 SUMMARY OF THE DRILLING RESULTS AND COSTS OF THE HAWAIIAN SCIENTIFIC OBSERVATION HOLE (SOH) PROGRAM by Harry J Olsn University f Hawaii at Mana Hnlulu, Hawaii and Jhn E. Deymnaz Independent Gethermal Drilling Cnsultant Hermistn, Oregn fr Electric Pwer Research Institute SCHOOL OF OCEAN AND EARTH SCIENCE AND TECHNOLOGY UNIVERSITY OF HAWAII AT MANOA August 10, 1992 A-I

149 Summary f the Drilling Results and Csts f the Hawaiian Scientific Observatin Hle (SOHj Prgram BACKGROUND The bjectives f the Scientific Observatin Hle (SOH) prgram as stated in the State f Hawaii enabling legislatin are t stimulate gethermal develpment and t cnfirm the gethermal resurces f Hawaii. The first gal f stimulating gethermal develpment has been met, as tw develpers, Puna Gethermal venture (PGV) and True/Mid-Pacific Gethermal venture (T/MPGV) are currently invlved in explratin and develpment alng the Kilauea East Rift Zne. In spite f the unfavrable permitting and regulatry envirnment, and intense lcal NIMBY and LULU (Nt In My Back Yard & Lcally Unppular [r Unwanted] Land Use) ppsitin t gethermal develpment, the secnd gal f the SOH prgram has been partially met, in that the SOH prgram has assessed a significant prtin f the Kilauea East Rift Zne (KERZ) in which the active gethermal develpers are perating. The prgram has been an utstanding success t date in develping effective drilling techniques, reducing drilling expenses, prviding deep gelgic sectins alng the area f current develpmental activity, establishing thermal cntinuity within the KERZ, defining limits t the HGP-A/PGV reservir, and discvering a ptential reservir in an untested area. As f the cmpletin f the first phase f the SOH prgram, three f the fur permitted SOHs have been drilled. Althugh all the necessary permits were apprved fr the furth hle, SOH-3, the State f Hawaii decidea t defer the drilling f SOH-3 until additinal SOHs are permitted with amended prvisins t allw pumping r flw testing f the hles t btain fluid grundwater and reservir samples. Figure 1 shws the lcatin f the vlcanic features and areas with gethermal ptential n Maui and Hawaii. The lcatin f thesohs, the GRZs, as well as the prductin wells drilled by PGV and T/MPGV alng the KERZ are shwn n Figure 2. SOH-4 The first hle drilled, SOH-4, was drilled t a ttal depth f 2,000.1 meters (6,562 feet), and recrded a bttm hle temperature f 306.1C (5830 F). Althugh evidence f fssil reservir cnditins were fund, n znes with bvius reservir permeability were encuntered. N prblems were encuntered in cre drilling the upper sectin f subaerial basalt flws and dikes. Hwever, severe rtary drilling prblems with lst A-2

150 Mul Vlcan Kahului, LEGEND 19' ~Crater ~ Rift Zne E!J Areas with Geatherma: Ptential c:j Hl,kt KAHOOLAWE Suthwest RUI Zne HAWAII H-uQ-ta-t-Ql---r--~~~~~~------~~ ~-"--- Vlcan 156" t55",i" Fig. 1 Vlcanic fearures and areas with gethermal ptential n Maw and Hawaii (Surce: Gethermal Resurces f Hawaii, 1983),.... rer f / EXPLANATION GRZ Gefhermal Resurc. Sub&n. Getherml Prductin We" SOHs,.... DCE.. N Fig. 2 Lcatin f SOHs n the Big Island A-3

151 circulatin and reaming were encuntered in the upper 610 meters (2,000 feet) f the hle, resulting in large verruns in drilling csts. These prblems were slved by slwly and carefully drilling blind fr 50 t 100 meters (150 t 300 feet) thrugh lst circulatin znes instead f cementing whenever circulatin was lst, and by using thin cement mixtures t regain circulatin. The cre hle then was pened with rtary tls t the final hle size in ne pass instead f tw. After the surface casing was set and cemented, cre drilling prceeded with nly minr prblems t the bttm f the hle in a heated sectin f submarine basalts. At a depth f apprximately 1,200 meters (4,000 feet), state fficials apprved the deepening f the hle t a depth f apprximately 2,000 meters (6,500 feet) because temperatures f C (400F) r higher had nt been recrded during drilling. At this time, the ther scheduled SOHs als were targeted t depths f apprximately 1,825 t 2,000 meters (6,000 t 6,500 feet). Ttal direct drilling csts fr SOH-4 are $1,466,813, r $ per meter ($ per ft) Daily drilling activities and csts fr SOH-4 are listed in Table 1, and a summary f ttal csts fr each SOH by drilling activity in rcks with similar drilling characteristics is given in Table 2. Descriptins f rcks with similar drilling characteristics used in Table 2 (SOH Prject Cst Overview) are as fllws: Type I Type II Submarine vlcanics, sediments and intrusives which have nt undergne extensive thermal alteratin and are pervasively fractured, hard, and abrasive. Subaerial vlcanics and sediments, altered and unaltered. Submarine vlcanics and assciated intrusives and "sediments which have undergne extensive thermal alteratin. Cre drilling csts, usually expressed as ftage charges) tend t increase with depth, even if hle size is reduced resulting in lwer bit csts, due t increased trip time fr cre recvery and bit changes, and fr ther prblems, such as increased risk f twist-ffs, assciated with depth. Drilling perfrmance is shwn graphically fr depth versus cst fr all the SOHs in Figure 3, and fr depth versus time fr all the SOHs in Figure 4. The temperature gradient f SOH-4 and the ther SOHs are shwn in Figure 5. Interestingly enugh, SOH-4 was initially cnsidered t be a "failure" by State fficials because the bttm hle temperature was nt as high as the 3580 C (676F) encuntered in the HGP-A well, because f the large cst verrun, as cmpared t the cst estimated fr the riginal 1,200 meter A-4

152 u -I -z - ) -6-7 ~\ \ \ 0.2 \ \ I a~\ I \ \ SOH-a ~-- -\", \ -1--,, \ '-..'"'\ \ " SOH'4~~, "-- 0.' 0.6 O.B COST (Miliinal I, ~ "'r-,,--'- --.C(OH" ',- ", ' I.' Fig. 3 SOH drilling perfrmance depth vs. cst 0 -I -2 -J." 0 ", " C I,~ r-i I,, SOH Z ~ I I \ \ \"\... '. I 1\ I..!.',-"j'...,,, ~ SOH ft" I, 1'... I"'-J I, s~::b-'4, '., ""-~ "'1- I ", ' I~ DAYS Fig. 4 SOH drilling perfrmance depth vs. rime I " +1 -I "\ Y 2... '..... "...-SOH.. 4 I " \, '. " '. '. -6 TEMPERATURE "e I Fig. 5 SOH temperarure vs. eleva.tin A-5

153 (4,000 ft) depth planned fr the hle, and because the hle did nt encunter a reservir. This resulted in renewed effrts t educate the fficials t the realities f drilling ecnmics, prgrammatic gals, and expected results. SOH-1 The secnd hle, SOH-1, was drilled t a ttal depth f 1,684.3 meters (5,526 feet) and recrded a bttm hle temperature f 206.1C (403 0 F). The drilling and casing plan fr the upper 610 meters (2,000 feet) was mdified, utilizing the experience gained in the drilling f SOH-4, by mitting the initial 305 meters f 9-5/8 inch casing and using 7 inch casing frm the surface t a depth f 610 meters (2,000 feet). This resulted in rapid prgress with nly infrequent and minr drilling prblems, and cst savings f apprximately $240,000 as cmpared t SOH-4 at a similar depth. When cring resumed belw the casing, hwever, very severe drilling prblems were encuntered due t highly fractured, cl «38C r <100F), submarine basalt, sands, and dikes, in the interval between 610 and 1,370 meters (2,000 t 4,500 feet), resulting in shrt bit life, shrt (15 t 45 centimeters r 6 t 18 inches) cre runs, stuck drill rds and massive cst verruns. The fractured submarine basalt and dikes brke ff during drilling int small fragments arund and in frnt f the bit, and rlled abut the drilling surfaces, wearing the bit face matrix and guging ut the diamnds. The exterir gauge f the bits was reduced and the interir gauge enlarged resulting in shrt cre runs which was caused by rck stuck in the cre barrel, and resulted in the necessity f redrilling the hle t reach bttm. Bit life averaged between 3 and 6 meters (10 t 20 feet ), and resulted in cnstant tripping f the rds t replace bits. Belw 1,370 meters (4,500 feet) ~he temperature increased rapidly, resulting in nrmal drilling runs, cre recvery f nearly 100%, and lng bit life, due t.fracture filling r bnding f the fractures by thermal metamrphism. Ttal drilling csts fr SOH-1 are extremely high at $1,643,544 r $ per meter ($ per ft), which caused the hle t be stpped apprximately 300 meters (975 feet) shrt f the its targeted depth. Daily drilling activity and csts are listed in Table 3. SOH-2 The third hle, SOH-2, was drilled t a ttal depth f 2,073.2 meters (6,802 feet) and recrded a bttm hle temperature f C (6630 F). The drilling and casing plan was again mdified t incrprate the lessns learned in the drilling f the first tw hles. T reduce drilling csts, A-6

154 -6- the upper 580 meters (1,900 feet) f the SOH was rtary drilled wltn n cring. Casing was set apprximately 30 meters (100 Feet) higher in SOH-2than in the ther tw SOHs because f a sudden 4 deviatin in the hle in an 8.2 meter (27 ft) interval between a depth f 567 t 575 meters (1,860 t 1,887 feet), which resulted in several drill cllar twist-ffs and fishing jbs. After the casing was set, cring encuntered difficult, time cnsuming, and expensive drilling cnditins similar t thse encuntered in SOH-I. At that time a decisin was made nt t attempt t fight the hle dwn by cring, and the hle, subsequently, was rtary drilled t apprximately 1,250 meters (4,100 feet). As circulatin was lst at the surface, nly a few scattered rck samples were cllected in the upper rtary prtin f the hle. Hwever, the dgleg caused by the sudden hle deviatin, persisted thrugh the casing and drilling cntinued t be plagued by repeated twist-ffs t the bttm f the hle. Luckily all the twist ffs ccurred inside the casing and fishing, althugh time cnsuming and cstly, did nt result in majr delays r lss f the hle. Temperature at a depth f 1,250 meters (4,100 feet) was 132.7C ( F) which was sufficient t bnd the fractured submarine basalts (r the sectin previusly had been subjected t higher temperatures with the same results), and cring prceeded rapidly and smthly t the bttm f the hle. Subsequent injectin testing indicated that a permeable interval between 1,488.3 and 1,505.7 meters (4,883 t 4,940 feet) with a temperature f C ( F) can be designated as a pssible "discvery". Additinal drilling in the vicinity f SOH-2 shuld intersect fracture permeability belw a depth f 1,825 meters (6,000 feet) with fluid temperatures in excess f C (572F) Ttal drilling csts fr SOH-2 are $1,106,684 r $ per meter ($ per ft), which represented a savings f greater than $300,000 while drilling 73 meters (240 feet) deeper than SOH-4, and greater than $460,000 while drilling 389 meters (1,276 feet) deeper than SOH-I. Daily drilling activity and csts are listed in Table 4. PRELIMINARY SOH PROGRAM RESULTS Very preliminary results frm SOH prgram indicate that: Cre (slim) hles can be successfully drilled t depths in excess f 2,070 meters (6,800 feet) and can be used t assess gethermal resurce ptential at substantial savings in drilling and permitting csts and envirnmental impact. Initial drilling results indicate that SOHs in Hawaii can be mst efficiently drilled by a cmbinatin f rtary and cre drilling techniques. A-7