Reconnaissance Study of Low-temperature Geothermal Resources in Southwestern Ontario

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1 PROCEEDINGS, 44th Wrkshp n Gethermal Reservir Engineering Stanfrd University, Stanfrd, Califrnia, February 11-13, 2019 SGP-TR-214 Recnnaissance Study f Lw-temperature Gethermal Resurces in Suthwestern Ontari Sara Shahmhammadi 1, Pneh Maghul 2 1 HYBRIXCEL INC., 2 Civil Engineering Department, University f Manitba, Winnipeg, Canada 1 Sara.Shahmhammadi@hybrixcel.cm, 2 Pneh.Maghul@umanitba.ca Keywrds: Recnnaissance, gethermal resurces assessment, lw temperature, EGS, sedimentary basin, Canada gethermal ABSTRACT The interest in recvering the gethermal energy stred in sedimentary basins fr electricity prductin is grwing. Mst sedimentary basins have been explred fr il and gas and therefre reservir and gephysical data such as depth t basement and frmatin thickness are well knwn. The availability f this data reduces the explratin risk and allws the develpment f gelgic explratin mdels fr each basin. The main gal f this paper is t carry ut a recnnaissance study f the ptential thermal energy stred in deep subsurface (3-5 km depth) frm the Engineered Gethermal System (EGS) sedimentary resurces in Suthwestern Ontari and identify a prspective prductin area fr gethermal energy explitatin. The industrial thermal data frm the bttm-hle temperature resurces f the il sand regins f Michigan Basin was applied in rder t prvide a first rder assessment f deep gethermal ptential fr electricity and heat generatin. A technical and an ecnmical resurce assessment were perfrmed based n the USGS vlumetric estimatin methd t imprve current Canada gethermal resurces base estimates fr innvative applicatins. It is cncluded that lw-temperature between (80 C 120 C) EGS resurces in Suthwestern f Ontari cntain apprximately 175 millin MWh f heat-in-place and expected that within the crdinate ranges f ( )W and ( )N, there exist an area f interest within the regin fr gethermal energy explitatin. 1. INTRODUCTION 1.1. Backgrund Gethermal energy plays a key rle in realizing targets in energy security, ecnmic develpment and mitigating climate change. Thrugh harnessing the stred thermal energy trapped within rcks, this resurce can be utilized in generating electricity and in direct applicatins. Hwever, befre the energy can be extracted frm depths within the Earth, explratry methds are crucial in lcating and prspecting the ptential f a gethermal system (Sanyal, 2010). Canadian resurces include all types f gethermal energy frm high t lw temperature. Gethermal energy plays a small rle in the Canadian energy market - nly thrugh direct-use heating applicatins. Currently there are n gethermal pwer plants in Canada despite the presence f high temperature resurces assciated with the Pacific Ring f Fire (Grasby et al., 2012). The majrity f hightemperature gethermal sites are lcated in the western part f Canada, (British Clumbia and Yukn) (Jessp et al., 1991). The first attempts t extract gethermal energy in Canada g back t 1973 fllwing the first majr il crisis. But as il prices stabilized in the early 1980s essentially all gethermal explratin activities stpped in Clearly, gethermal pwer generatin des nt yet make even a small cntributin t the Canadian energy market despite the presence f high temperature resurces in the west. Hwever, in recent years, increasing energy prices and rising effrts t reduce greenhuse gas emissins may be turning the tide back t this resurce. The apprach f the paper is t prduce a resurce assessment f the thermal cnditins in the crust beneath Suthwestern regin f Ontari, in search f a gethermal prspect and an estimate f the energy ptential accessible by EGS technique. Fr this purpse, we have analyzed the nn-gethermal resurces identified in previus studies frm Michigan Basin int a single assessment f deep (3-5 km), lw-temperature ( C) gethermal resurce ptential within the regin. Insufficient data acrss many regins f Canada renders categrizing gethermal resurces a difficult task. As a result, cmputer mdeling cupled with labratry investigatins t fill data gaps are being encuraged under the Executive Summary, Research Needs f the Gelgical Survey f Canada Open File 6914 (Grasby et al., 2012). Suthwestern Ontari has been f prime interest fr gethermal explitatin lcated in the east f the Michigan Basin. The paper presents a preliminary thermal investigatin int this area and highlights a ptential prductin field regin. Figure 1.1 indicates the lcatin f the study t perfrm these investigatins. 1

2 Figure 1.1: Ontari Regins Map-Zne 1, 2 and 3 f Suthwestern Ontari (derived frm MROO) 1.2. Area f Study The sedimentary basin f Suthwestern Ontari cnsists f many aquifers cvering apprximately 37,000 km 2 land. It is surrunded by Canadian Shield t the nrth and east, and Great Lakes t the suth and n the west by the Detrit River, Lake St. Clair, the St. Clair River and Lake Hurn. The Canadian Shield stands ut as a lw heat flw area (Blackwell and Richards, 2004; Jaupart and Mareschal, 2008), with heat flux values within 30 t 50 mw/m 2 range in cntrast t values that ften exceed 80 mw/m 2 in the active regins f Western Nrth America. In Eastern Canada (Figure1.2), the average gethermal heat flux is much lwer than in Western Canada (Majrwicz and Grasby, 2010). This is because a large part f Eastern Canada, including the prvince f Ontari (East-central), is lcated in the gethermal cld Canadian Shield, while sme areas are lcated in a htter sedimentary platfrm related t the Appalachian basins. The first gethermal assessments by (Jessp et al., 1991) indicate the ptential fr the Eastern Prvinces t prduce pwer using ht dry rck technlgy. The chice f the heat extractin technique depends n gelgical factrs (sedimentary vs. crystalline rcks) and the thermal ptential f the available heat. In the case f deep dry ht rcks, artificially created Enhanced Gethermal Systems (EGS) (Tester et al., 2006) may be the nly way t tap int the high temperature heat >120 C available in the crystalline basement rcks. T achieve this, a thermal carrier fluid (water, etc.) needs t be pumped int a clsed lp system thrugh the undergrund reservir t extract the gethermal heat and thrugh the pwer plant biler, prir t being re-injected in the grund. 2

3 Figure 1.2.: Heat flw cntur map fr Eastern Canada based n IHFC (Internatinal Heat Flw Cmmissin) heat flw density data base. 2. GEOLOGICAL HISTORY OF SOUTHERN ONTARIO The Palezic rcks in suthern Ontari are principally shales, limestnes, dlmites and sandstnes. A large number f Palezic grups, frmatins, and members f Cambrian, Ordvician, Silurian, and Devnian age have been identified in suthern Ontari. Many il and gas explratin wells were drilled there in the past and il and gas reservirs in Ontari are fund at a variety f depths and in different rck types. Cmmn reservirs include Cambrian sandstnes (at depths f 800 t 1200 m), Ordvician carbnates (800 t 900 m), Silurian carbnates (500 t 700 m and 350 t 450 m), and Devnian carbnates (110 t 140 m) all f which ccur in suthwestern Ontari. With this prepnderance f wells in the area, there is an pprtunity t gain useful infrmatin fr gethermal purpses by analyzing the recrded brehle lgs f the wells. Hwever the well data is nt available fr all these wells. Fur majr sedimentary basins ccur within Ontari. The sedimentary basins cver apprximately 320,000 km 2, which is almst ne third f the ttal surface area f the prvince. It includes nrthern Ontari and Hudsn Bay and the entire area f suthern Ontari (Figure, 2.1). 3

4 Figure 2.1: Area f Sedimentary Basins in Ontari (mdified frm Jhnsn et al.) In suthern Ontari, thick accumulatins f sedimentary rcks are present between the Michigan and Appalachian basins (Figure, 3.2). Extensive develpment f prsity and permeability is evidenced by the presence f il and gas reservirs and reginal saline water aquifers in these basins. The sedimentary rcks within the Michigan and Appalachian basins are distinguished by gelgic age and further subdivided int frmatins that can be mapped in the subsurface. The ldest and lwer mst rcks are f Cambrian age and cnsist mainly f sandstnes. Yunger sandstne, shale, and limestne rcks f Ordvician, Silurian, and Devnian age verlie the Cambrian rcks. Figure 2.2: Majr rck types and sedimentary basins ccur within Ontari 4

5 3. LITERATURE REVIEW 3.1. Gethermal Lw-Temperature EGS systems Gethermal resurces can be categrized int tw mdels: hydrthermal and EGS. Each categry is then subdivided int multiple system types. A hydrthermal system is a reservir with the fllwing characteristics: Prsity and/r permeability levels permitting the flw f water, Higher than average reginal thermal gradients, A surce and recharge system f flwing water. In cntrast t hydrthermal systems, EGS systems are gelgic systems that wuld require additinal stimulatin and enhanced recvery methds fr extractin f the available heat cntent. This categry includes tw primary subtypes: Sedimentary basins differ frm hydrthermal sedimentary systems in that they may lack water and/r permeability. Lw cnductivity, ht dry rck (HDR) ht rck that lacks ne r mre f the abve stated characteristics; in thery, may be accessed in any lcatin given sufficient depth and reservir stimulatin. (Breede et al., 2013), (Olasl et al., 2016), and (Dipipp, 2012) prvided cmprehensive reviews f existing enhanced gethermal systems including reservir stimulatin techniques that have been applied Vlumetric Heat in Place Assessments Saring prices f fssil fuels caused by the il-crises f 1973 and 1979 stimulated research t quantify the ptential f alternative energy surces including gethermal energy. At early stages f gethermal develpment, the size r ptential megawatt utput f a gethermal resurce can be estimated by different methds with relatively little data available. A theretical maximum ptential utput can be determined by the vlumetric heat-in-place methd develped by the U. S. Gelgical Survey (USGS) decades ag. In this methd, the amunt f heat in a blck f earth is largely assumed with cmmnly used factrs. Fr this methd, the area r regin belw the Earth's surface is divided int separate vlumes. Fr each vlume, the thermal energy in place (heat in place) is estimated based n measured r mdeled subsurface temperatures. Estimating the heat in place is straightfrward, but it is mre difficult t delimit the share that is technically prducible. T direct this issue, it is cmmn t apply an average value fr the recvery factr t btain the technical ptential. Hwever, little data is available n actual recvery factrs, making it hard t assess whether a chsen recvery factr is realistic and apprpriate fr resurce assessments f individual basins r entire regins. Mre realistic recvery factrs are used when data n lcatin-specific aquifer permeability and temperature are available. Fr areas withut any prir infrmatin r fr glbal-scale assessments, a lw recvery factr is mre apprpriate. One f the main challenges fr all resurce assessments is uncertainty quantificatin, especially when dealing with gelgical data. Vlumetric resurce assessments are therefre ften cmbined with prbabilistic methds like the Mnte-Carl methd. Multiple mdel runs yield a prbability distributin f the ptential, by allwing variatin in parameters. Uncertainty quantificatin fr a gethermal resurce assessment is challenging because it requires assumptins n suitable ranges fr parameters that can shw a strng spatial variatin and that depend n lcal unknwn gelgical cnditins. 4. TECHNICAL AND ECONOMICAL RESOURCE ASSESSMENT This sectin is used t describe the methd we use fr ur resurce assessment and t present the results Methdlgy In rder t assess the ptential amunt f heat that culd be extracted frm deep gethermal reservirs, the fllwing assumptins have been made: (i) tw temperature limits, i.e. minimum f 90 C and maximum f 110 C, are taken as examples fr the extreme gethermal cnditins available (see figure 4.1 fr the predicted depths t reach 120 C); (ii) the rejectin temperature is taken t be 40 C; a typical standard value fr the cndenser temperature (Tester et al., 2006); (iii) an average thermal gradient f 30 C/Km; (iv) a minimum recvery factr f was chsen accrding t Srey et al., (1982); and (v) an efficiency f 10% after passing the fluid thrugh a binary Organic Rankin Cycle. We defined a set f bth rck and fluid parameters fr describing and quantifying as listed in Table 1. 5

6 Figure 4.1: New cntur map f predicted drilling depths t ptentially reach 120 C in Eastern Canada, including the prvince f Ontari, and part f the United States. Table 1: Input variables with assciated units and default values. Parameters Range Unit Area km 2 Thickness (Interval) 500 m Rck Density (the average fr sediment and sandstne) 2.30E 12 kg/km 3 Prsity 0.1 Thermal Recvery Factr Rck Specific Heat (typical dlmite rck and sandstne) 0.92 kj/kg C Reservir Temperature (90-110) C Fluid Specific Heat 4.18 kj/kg C Fluid Density 1E 12 kg/m 3 Re-injectin Temperature 40 C Cnversin Efficiency 0.10 Plant Life 30 Plant Capacity Factr (%) 90% It is difficult t predict the actual temperature and pressure gradients fr sme selected areas due t the absence f necessary field data related t subsurface temperatures and pressures and the drilling depth required t reach the temperatures needed fr pwer r heat prductin. Frm Bttm Hle Temperature (BHT) datasets, and thrugh different methdlgies, the thermal prfile f sedimentary 6

7 frmatins can be estimated. The fllwing equatin results f a linear regressin f 405 BHT vs. assciated depths frm Michigan s Peninsula prvided by (Raymnd Vugrinvich, 1989): BHT ( C) = depth (m), is used t determine the subsurface temperatures Resurce estimatin Fr ur assessment the available heat in place is estimated based n equatin, as used by Brk et al. (1978): Q = ρ Cp V ΔT [kj] (1) in which ρ is the density f the rck, Cp is the heat capacity f the rck, V is the vlume f the rck, and ΔT is the change in temperature, respectively. The assumed interplated hrizntal surface areas frm the 90 C+, 100 C+, and 110 C+ intervals were multiplied with the 0.5 kilmeter (km) thicknesses, yields the ttal effective vlume. Table 2: Parameters and available heat in place fr the meter depth interval Area Vlume Average ΔT Q (J) Recverable MWt Interval (km 2 ) (km 3 ) ( C) (J) 90 C , C 36.9 C 14, , , C C 36.9 C C C 36.9 C MWh= J Table 3: Parameters and available heat in place fr the meter depth interval Area Vlume Average ΔT Q (J) Recverable MWt Interval (km 2 ) (km 3 ) (J) ( C) 90 C , C 46.5 C 8, , , C C 46.5 C 7, , , C C 46.5 C , Table 4: Parameters and available heat in place fr the meter depth interval Area Vlume Average ΔT Q (J) Recverable MWt Interval (km 2 ) (km 3 ) (J) ( C) 90 C , C 56.1 C 5, , , C , C 56.1 C 10, , , C C 56.1 C ,

8 Table 5: Parameters and available heat in place fr the meter depth interval Area Vlume Average ΔT Q (J) Recverable MWt Interval (km 2 ) (km 3 ) (J) ( C) 90 C , C 65.7 C 4, , , C C 65.7 C 8, , , C C 65.7 C , Table 6: Final estimate f energy in place, after recvery factr and taking pwer plant efficiency int accunt Range ( C) Recverable (J) MWt After Efficiency f (10%) (MWt) 90 33, , , The heat in place that can be realistically explited is limited by technical and ecnmic cnditins. These include surface and subsurface limitatins, such as plant facilities and drilling technlgies. Fllwing recmmendatins frm the review paper by (Grant, 2014), and (Srey et al., 1982) the technical ptential is calculated as a fractin f the heat in place using a recvery factr f By assuming a pwer plant lifetime f 30 years and capacity factr f 90%, there is the pssibility t develp a pwer plant with a capacity f 600 MWe ver the prductin perid. 5. RESULTS & CONCLUSIONS The Suthwestern Ontari basin has temperatures ver 90 C belw a depth f 3000 meters. An analysis fr meter depth interval was carried ut. The available energy in place fr each depth interval is listed in Tables 2 t 5. Althugh the Suthwestern Ontari has limited ptential fr large-scale pwer prductin, the subsurface findings clearly pint twards a ptential prductin field within the crdinate ranges f ( )W and ( )N displaying knwn temperature between (80 C-120 C). It is expected that lw temperature gethermal electricity generatin and direct use may still be viable with the develpment f deep EGS sedimentary resurces and by means f a binary cycle pwer plant. The energy summary, alng with the estimate after passing the fluid thrugh a binary Organic Rankin Cycle with an efficiency f 10% can be fund in Table 6. Accrdingly the ttal accessible resurce base in this assessment was fund t be arund 175 millin MWt. Hwever given physical and technical limitatins, the prtin f this resurce that can be extracted culd be significantly less. REFERENCES Blackwell, D. and M. Richards, Gethermal map f Nrth America., American Assciatin f Petrleum Gelgists (AAPG). 1 sheet, scale 1:6,500,000. Breede K, Dzebisashvili K, Liu X, Falcne G. A systematic review f enhanced (r engineered) gethermal systems: past, present and future, Gethermal Energy 1 (2013) Brk, C. A., Mariner, R. H., Mabey, D. R., Swansn, J. R., Guffanti, M., and L. J. P. Muffler, (1978). Hydrthermal Cnvectin Systems with Reservir Temperatures 90 C, in Assessment f Gethermal Resurces f the United States 1978, United States Gelgical Survey Circular 790, p

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