COMPUTER MODELLING OF THE SOUTHERN NEGROS GEOTHERMAL FIELD, PHILIPPINES. F.X.M.STA.ANA and MJ.O'SULLIVAN

Transcription

1 85 Proc. 10th New Zealand Geothermal Workshop 1988 COMPUTER MODELLING OF THE SOUTHERN NEGROS GEOTHERMAL FIELD, PHILIPPINES F.X.M.STA.ANA and MJ.O'SULLIVAN Theoretical and Applied Mechanics, University of Auckland ABSTRACT The main features of the Palinpinon reservoir in Southern Negros are described and used to establish a conceptual model. This conceptual model forms the basis of a computer model of the reservoir which is used to match the pre-exploitation natural state and data from the five years of exploitation history of Palinpinon I (112.5 MWe power station) in Puhagan. Because of the complexity of the flow patterns in the reservoir, several preliminary versions of the computed model were tested and rejected. The computer model is still being improved, particularly to allow a more detailed representation of the production and injection areas. structural map of the Palinpinon field. Structures which serves as major channels for geothermal fluid are the Ticala fault and its splays, Lagunao fault, Puhagan fault and its splays in the Puhagan sector; Nasulo, Nasuji, Okoy and Sogongon faults in the Nasuji-Sogongon sector. 1.0 INTRODUCTION General Information The Palinpinon geothermal field (consisting of the Puhagan, Nasuji and Sogongon sectors) is situated in the southern part of the Negros Island, Philippines. Another geothermal prospect, the Baslay-Dauin area, is situated to the south of the Cuernos Volcano. Interpretation of data from deeper penetrating resistivity methods show that the fluid from the Baslay-Dauin area appears to be related or connected to those produced in the Puhagan and Nasuji-Sogongon area (Bromley and Espanola, 1982). A MWe variable-load power plant commissioned in 1983 is now being fed by wells from the Puhagan area. Likewise, a 1.5 MWe pilot plant is in operation using the steam produced from Okoy 5 (OK5), a well situated between Puhagan and Nasuji. A similar 1.5 MWe pilot plant located in Puhagan and powered by steam from OK7, serves as a start-up unit for the large power plant. At present, only about 60% of the total capacity of the plant is being utilised because of the low demand. There are 56 wells in the geothermal project. Thirty-one of these are connected to the Palinpinon geothermal power station (i.e. the MWe PAL-I plant), 10 of which are used as reinjection wells to dispose of the separated waste water. Wells in the Nasuji-Sogongon area are intended for the proposed Palinpinon II power development. At present, existing wells in the Nasuji-Sogongon area have a power potential of 67 MWe. Geology Cuernos Volcanics consisting of generally weakly altered andesite/dacite is the youngest formation found in the region. This is underlain by andesitic breccias and andesite of the Southern Negros Formation (SNF). Below the SNF is the Okoy Sedimentary Formation (OSF), a dominantly sediment sequence of calcisiltite, chloritised andesitic breccias and andesitic volcanics. In the Nasuji-Sogongon sector, the Okoy Formation is replaced by quartz monzodiorite which forms the Nasuji Pluton. The absence of the Okoy Formation in that sector was believed to be due to thinning of the formation towards this sector. The pluton accounts for a large portion of the total energy available in the area. It remains to be seen how wells drilled in the monzodiorite will perform during large scale production. Many of the mapped structures are faults and joints which generally control the drainage pattern of the region. The faults are mostly gravity faults and have dips from 70 to 90. Figure 1 shows the FIGURE 1. Structural Map of Palinpinon Thermal Manifestations It was the thermal springs in the Okoy River Valley which first showed indications of a high temperature geothermal system existing in the region. These neutral ph springs mostly have boiling temperatures and contain a high (>3000 mg/1) concentration of chloride which is comparable to what was later measured in the reservoir. Silica temperatures confirm the presence of high temperature fluids (>230) (Glover, 1975). At higher elevations, thermal springs become more acidic and exhibit high SO4 content and lower chloride concentrations (1500 mg/1). Temperatures are warm which indicate mixing with groundwater. Closer to the peak of Cuernos de Negros is a large area of altered grounds with some cold acid springs. These kaipohans, which is also the name of the place, occur in a region devoid of vegetation due to acidic leaching caused by the migration of H2S and CO2 from below. A similar pattern of thermal spring demarcation along with fumarolic activities can be observed in the Baslay-Dauin area, south of the Cuernos peak. The pattern of decreasing ph and chloride with increasing sulphate content from lower elevation to higher elevation would indicate a geothermal system typical of those found in mountainous terrains (Hochstein, 1985). As well as the chloride and sulphate content, the ph and other geochemical data, also drilling data and geophysical results provide evidence of a high temperature fluid system located underneath the dormant Cuernos Volcano.

2 86 Geophysics Because high elevations and the effect of fresh volcanics mask the electrical response, Schlumberger surveys were not able to provide information on the boundaries of the deep high temperature region. However, they were able to identify the long narrow anomalous zone in the Okoy River Valley, the anomalies in the Nasuji-Sogongon, and areas south of Cuernos de Negros peak. The dipole-dipole, on the other hand, because of its capability to penetrate deeper, was able to detect a conductive anomaly which extends from the Okoy Valley anomaly towards the Baslay-Dauin anomaly. These results suggest that the anomalies in the Okoy Valley and Baslay-Dauin are connected to one system (Bromley and Espanola, 1982). Geochemistry than in Puhagan, it is premature to finally decide on the extent of the productive region. c) Troughs and bumps seen on both kh and injectivity contours can be related to geological structures. Structures superimposed over these contours reveal that the major faults which have been mapped significantly control the flow direction of the fluid from the upflow area. d) Of the wells completed in central Puhagan.awo were nonproductive or non-commercial (OK4 and PN25D). Both have high temperatures and encountered formations penetrated by other wells. However, both failed to exhibit the high permeability which exists in nearby wells. One reason is that both may not have encountered structures with proven permeability (e.g. Ticala fault, Lagunao fault). All geothermometers, and the concentrations of chloride and other geochemical components have indicated that fluid with the highest temperature and highest salinity originates in the postulated upflow region southwest of the Puhagan sector and extends to a depth greater than 3 kilometers. Fluids from the upflow zone contain about 4200 ppm of chloride and geothermometers indicate temperatures as high as 328 C (Jordan, 1983), which agrees with the measured maximum temperature of 330 C. The fluid composition is fairly similar throughout the field. It is neutral to slightly alkaline with significant amount of chloride, alkali metals, boron and silica. However, some bores exhibit different chemistry. Wells targeted south and southeast of the Nasuji sector (i.e. OKI ID, NJ1D, NJ2D) and also wells drilled in the Dauin area discharge acid fluid with high H2S and SO4 concentration. 4- Non-condensable gases average approximately 2 to 2.5 weight percent in the steam phase, of which carbon dioxide is the major component (92 to 94 mole percent of the total gas). Other gases are H2S, NH3, H2, N2 and CH4 (0.3 to 3 mole percent). Field chemistry has also shown that two or more feed zones are tapped by the wells and that the chemical compositions of these production zones vary. The chemical difference with depth, between zones and also the difference noted between wells of close proximity suggest that fluid flow is controlled in a complex manner, i.e. through faults or fractures. Temperature contours developed from geothermometer temperatures exhibit similar trends. There are decreasing temperatures in all directions from the southeast of Puhagan with a much narrower protrusion in the northeast direction toward the Okoy Valley, which can be related to structural control by faults with the same bearing. The broader band in the west (Nasuji-Sogongon area) suggests dilution with less mineralised water. Jordan (1983) however, believes that this may merely be due to smaller amount of data in the sector. FIGURE 2. Transmissivity (kh) Contour Map of Palinpinon 4- Similar patterns can be found with the various chemical isographs, e.g. chloride, the chemical ratios and gas ratios. Details of the field chemistry are given in Jordan (1983). Permeability Distribution H^D ' / \ Figure 2 and 3 show the distribution of kh and injectivity across the field. The locations of permeable zones in the wells were deduced from interpretation of downhole temperature logs, drilling breaks and circulation losses. From Figure 4, which shows the distribution of permeable horizons, no definite correlation of the occurence of permeable zones in individual rock units can be made. Permeability appears to be randomly distributed. Moreover, the locations of major permeable zones in neighboring wells do not seem to correlate. However, some generalisation and observations can be obtained from the given data as follows. a) Wells drilled in the periphery or northeastern outflow zone (Nl, N2, N3, OK3) appear to have poorer permeability than wells drilled in central Puhagan. This may be due to the smaller depths reached and the relatively low temperatures, or both. b) A region of high permeability is observed in the central Nasuji- Sogongon sector. However, because there are fewer wells in the area FIGURE 3. Injectivity Contour Map of Palinpinon e) Bores drilled toward the south-southeast of the Nasuji sector have relatively low permeability. OKI ID for one, did not discharge despite attempted steam-injection stimulation. NJ1D and NJ2D have low discharge outputs. Furthermore, both wells produced low ph fluid, which was believed to have come from an acid sulphate aquifer below the main Kaipohan area and to have flowed down through some preferential flowpath to the contact zone of the pluton intersected by the wells (Seastres, 1985). f) OK8 which was drilled towards the northwest is relatively impermeable. The same can be said of the directionally redrilled OK8RD, which was designed to test the low resistivity anomaly in the north. This indicates poor permeability in the immediate north of the field.

3 87 4- FIGURE 6. Isotherms at -1400m MSL FIGURE 4. Permeable Zone Locations of Puhagan and Nasuji- Sogongon wells Temperature Distribution Figure 5 to 7 show the temperature distribution across the field at different elevations. These were obtained from stable formation temperature profiles derived from downhole surveys. The pattern of temperatures in all the layers is generally similar and exhibits a lowering of temperatures outwards in all direction (contours were left open towards the southeast due to absence of data in the area). There are, however, some variations. To the east and northeast, the isotherms show a very pronounced elongation towards the direction of low elevations. It can be seen from the structural map that this follows the orientation of the Ticala Fault and associated parallel faults. The temperature gradient appear to be more uniform in the northwest and western direction. This may be a spurious result produced by extrapolation of sparse data from the smaller number of wells which define the area. It could also be related to a more dominant horizontal aquifer, possibly a contact zone where fluid flows (Maunder, et.al., 1982, McNitt et.al., 1982). FIGURE 7. Isotherms at -2100m MSL 4- Pressure Distribution lomid KA1POHAN A useful parameter that can be obtained from the pressure profiles is the pressure pivot point, where pressure does not vary during warming up of the well, and therefore reflects the formation pressure in the region surrounding the well. A plot of the pressures calculated at the pivot points of all the wells taken from various depths gives the reservoir pressure gradient. Figure 8 shows the different gradient profiles for different sectors. An average gradient of 0.78 MPa/lOOm is computed based on the average slope. This is above hydrostatic gradient (about 0.7 MPa/lOOm). A gradient of about 0.8 MPa/lOOm is measured in the upflow region. This high gradient is the mechanism which causes the fluid to rise, and is consistent with the higher temperatures found in that region. The slightly higher pressure gradient in the Puhagan reinjection sector may be due to overpressuring caused by the injected waste water (produced by discharge testing of the production bores). Most of the reinjection wells, particularly those drilled later (i.e. PN3RD to PN9RD) have shown overpressuring due to injection of waste brine in 0K12RD and PN1RD (which were used to dispose of the waste water from the test separators from the production sector). FIGURE 5. Isotherms at -600m MSL Figure 9 shows the pressure distribution across the field. This follows a similar trend exhibited by the isothermal contours.

4 FIGURE 9. Pressure Distribution in Palinpinon Field FIGURE 8 Pressure gradient profiles of the different sectors of the field Bore Output Measurements Except for the recent wells (i.e. PN27D to PN31D) the majority of the wells have been subjected to short to medium term discharge testing which lasted for times ranging from a couple of months up to a much longer period (prior to commissioning of the MWe plant in Puhagan). Most of the wells exhibited declining massflow and enthalpy. Most of the flowing surveys conducted during this period indicate flashing in the wellbore usually above the casing shoe, which indicates all-liquid flow from the reservoir. Depending on the permeability around the well, fully open massflow rates range from as low as 9 kg/s to about 100 kg/s. Discharge enthalpy is dictated by the mixing of fluid from 2 or more producing zones in each well. Preexploitation average field enthalpy is about 1280 kj/kg. Separation of fluid at the surface has shown the dryness to be about 25 to 30% (at 0.7 MPa separator pressure) and an average output of 6 to 7 MWe per well (based on a 2.82 kg/s of steam per MWe conversion). * \OKIIO KAIPOHAN FIGURE 10. Total massflow distribution across Palinpinon Field be made when this sector is developed and more data become available. Entry of cooler fluid into reservoir is shown by the temperature reversals experienced in the wells. Figure 10 shows the distribution of the maximum discharge rates of the wells across the field. These were found to show similar pattern displayed by the permeability contours. Conceptual Model The hydrological model derived from the analyses of data from the different disciplines is shown in Figure 11. This model is basically the same as that presented by Hochstein (1985) to describe geothermal systems in mountainous terrains. Fluid is believed to upflow from south-southwest of Puhagan and outflows in the northeast and northwest directions via preferential flow channels with flow tongues developing as it goes up. To the northeast, the Ticala fault is the major structure directing the flow toward the Okoy River Valley. A much wider region of upflow can be observed in the northwest direction toward the Nasuji-Sogongon sector. Contribution of fault structures to the flow pattern in this direction is less defined. This may be a genuine physical phenomenon or it may represent a lack of accuracy produced by the smaller number of data available in this part of the field. Further refinement to the model can FIGURE 11. Conceptual Model of Palinpinon Reservoir

5 COMPUTER MODELLING OF PALINPINON The first reservoir simulation of the Southern Negros was carried out by McNitt et.al. (1982) using a lumped-parameter model to represent the reservoir. The pressure decline was computed to determine the performance of the field during the proposed 25 year exploitation period. Since the data available then were not complete and a definite development strategy had not been determined, the results were considered preliminary only. Batayola (1983) and KRTA (1985) carried out 3-D reservoir modellings of Palinpinon using production data of the completed wells at that time. However, the results were not satisfactory as they did not match the field data. w30000 ( o 8 s S / /nihcala /\ Q /T. / X xf 8 X v '\j / /--!!i x/ / X The natural state simulation described in the present work was carried out in various stages and several models were tested in trying to obtain a good representation of the hydrological flow pattern of the field. As illustrated in the conceptual model, as well as in the different isographs, the flow pattern of the field through the reservoir is quite complicated. Geological structures have caused preferential channeling of the upflow fluid and the intrusion/mixing of cooler meteoric waters. It is this complex flow movement of upflow and cold fluid mixing which the steady-state model attempts to reproduce t- Preliminary Modelling Simple 1-D and 2-D models were initially set-up in an attempt to establish the probable upflow values to be used in the later larger model, and to model the outflow tongues which are the predominant feature of the hydrological flow pattern. It was demonstrated, using a one-dimensional vertical column (surface to -2400m MSL), that in order to reproduce in the model the observed pressure gradient in the upflow region of the reservoir, which is above hydrostatic, some fluid must be injected at the bottom. About 20 kg/s of throughflow is injected at the bottom of the 1-D column to match the pressure profile in the reservoir. Removal of the injected flow causes the pressure in the reservoir model to drop (more than 10 bars drop at the bottom block). To replicate the flow elongation towards the northeast and the uniform protrusion to the west of the upflow, a two-dimensional 34-block model was set-up by taking the section of the field where the outflow tongues are observed. However, this was later discontinued after several runs as it was thought that lateral movement and mixing of cooler fluid is necessary to reproduce the lower temperature beneath the outflow tongues, particularly towards the northeast. Threedimensional modelling was therefore adapted. 3.0 THREE DIMENSIONAL NATURAL STATE MODELLING FIGURE 12. Configuration of first model - model 1 Discussion of Results (Model 1) Several simulations were carried out in attempting to match the observed data (temperatures and pressures) with those of the model. However, none of the results were satsifactory. It was decided that the model did not cover a large enough area and therefore cold recharge could not be represented. A new model was then formulated which incorporated larger volumes of rock for the upflow and lateral recharge. Model 2 - Description Figure 13 illustrates the next model used in the succeeding simulation attempts. In this 85-block model, the same layering (i.e. 4 layers) as in Model 1 was utilised. Also, in this model, uniform block volumes were used for easier setting up of the input data and better computation efficiency. The area covered by the model is much larger. It was extended to the southeast to include the Cuernos de Negros peak and Lake Belendepaldo (which are inferred sources of recharge for the system). To the northwest, west and southwest, the high country which encircles the Okoy valley was included in the model. The Okoy valley area was extended further to the northeast to include the shallow exploratory wells Nl and OKI, and Magaso area. Again, the thickness of the topmost layer blocks were varied following approximately the contours of the elevation of the groundwater surface, which were estimated based on the water level in the wells. Model 1 - Description Figure 12 shows the first 3-D model set-up used for the natural state simulation. The configuration and orientation more or less conform to the flow pattern indicated by the different contours (particularly the isotherms). It is basically a sideward expansion of the 2-D model earlier tried. The outermost wells, i.e. N3, 0K8RD, OK10D, PN5RD, NJ3D and SG3D, were used to define the boundaries of the reservoir model. The model was divided into four layers according to the distribution of the permeable zones among the wells. The feed zones can be lumped into four groups, namely: a) surface to -200m MSL, b) -200m to -1000m MSL, c) -1000m to -1800m MSL, d) m to -2400m MSL intervals, with the topmost layer having varying thickness to represent the changing topography of the water table. The block division for each layer was chosen such that production and reinjection sectors (particularly in Puhagan) are separated. This is with the exception of PN17D which, because of the proximity of the bottomhole with those of the reinjection wells, was included with the reinjection block. For the Nasuji-Sogongon sector, since development of that part of the field has not commenced, the division of the region was done according to the proposed designation of the wells and wellpads into production and reinjection as suggested in the feasibility/resource assessment study independently conducted by the authors. FIGURE 13. Configuration of second model - model 2

6 90 Discussion of Results (Model 2) The temperature inversion to the northeast (i.e. higher temperatures at the upper middle layer than at the lower middle layer) proved to be the difficult feature to reproduce in the model. Figure 14 shows the best results obtained chosen from among the several simulation runs. The temperature in layer CCC in the Puhagan reinjection area (block 10) are much higher than those measured. Because of the large areal distance encompassed by each block (each block covers 2km x 2km of area), the fine structure of the movement of cold and hot fronts shown in the isotherms could not be matched in detail. The temperature in the central part of the model (block 9) is the result of mixing of fluid going through its interface from adjacent blocks. Thus, in order for the fluid going to the outflow blocks (block 10, 11) to still be hot enough to match the observed temperatures, a higher temperature is required in the central block (block 9). Unfortunately, much higher than that which is observed. The problem was partially solved by subdividing blocks 9, 10 and 11 in each layer into two (Figure 15). However, the results were still not good. Further runs using this model was discontinued and an improved model was set up. Model 3 - Description The aim of this model was to match the block structure in the production region to the conjectured flowpaths and to include a large are so that cold recharge on the outskirts of the field could be modelled. Because of the complexity of the flowpaths a complex model shape was selected as shown in Figure 16. Discussion of Results (Model 3) This model (3A) initially used a triangular shape for block 3. However, because of difficulty in obtaining a lower temperature in this block, especially at the top layers (AAA and BBB), this was replaced by a trapezoid (see Figure 16) to connect the large recharge block 16, to induce cooler fluid to flow into block 3. Blocks 16 and 36 are sources of low temperature fluid which enter the reservoir from the north as exhibited by the isotherms at shallow depths (refer to Figure 5). Several runs were made before a satisfactory match to observed temperature and pressure was obtained (Figure 17). A total of 21 rock types were used, and the permeabilities range from 0.2 to 10 md with the highest permeability value used in the outflow region of Puhagan (where Pal-I reinjection wells are situated). Model 3A was later improved by subdividing some of the large blocks in the production region (see Figure 18) to allow more accurate modelling of the the interaction of production and reinjection wells. Work is still ongoing on these models. 4.0 PRODUCTION HISTORY MATCHING The best natural state model derived (model 3A) was used for exploitation history matching to validate the permeability parameters used in the steady-state runs. The porosity values were based on the laboratory results obtained by de Leon (1984) on the porosities of cores from the wells. The production history covers a period of five years starting from the commissioning of Palinpinon-I in The load has been variable, although production has since risen due to increasing demand. Present load averages 50 MWe with a peak of 60 MWe. The average field enthalpy has risen to about 1500 kj/kg by the end of Because of the variable nature of the steam supply, utilisation of the wells has also been variable. This has steadied recently though, with the decreased utilisation of wells found to receive large amounts of reinjection returns. Tracer tests conducted have established that the majority of the production wells in Puhagan communicate with the reinjection sector, with fluid returning as early as 40 hours after injection (Urbino, et.al., 1986). Production from the reservoir was estimated on a well-by-well basis. The wells in the geothermal field show a large variation in the level of production. For example, OK7 has its major feed zone from the bottom layer. On the other hand, PN26, which is only about 100m away, produces mostly from a shallower zone. Furthermore, because the majority of the wells are deviated, the permeable zones do not lie in the same column in the natural state (computer) model. For each well, the distribution of flow between feed zones was calculated using the mass and energy balances computed from the total flow and discharge enthalpy for each different feed zones. The flow in each block was determined by adding the contribution from each feed zone in that layer. Satisfactory matches for the pressure and enthalpy trends were obtained for model 3A (Figure 19). The more detailed model is being used to produce a more accurate steady state and has the potential for a more accurate representation of the behaviour of the reservoir during exploitation. However, the results for the natural state and history matching from model 3A are encouraging enough to merit its use for predicting the future behaviour of Palinpinon. 5.0 SUMMARY AND CONCLUSIONS Based on the given geoscientific and well data, a conceptual model of the Palinpinon field was derived. This was then used to develop a natural state model, which was validated by a production history match The next step is for prediction runs to be performed to determine the performance of the field during long term and largescale production. REFERENCES BATAYOLA, GJ. (1983) A Simulation Study of the Puhagan Section of the Southern Negros Geothermal Reservoir, Philippines. Geotherm Project Paper, Geothermal Institute, University of Auckland, N.Z. BROMLEY, CJ. and ESPANOLA, O.S. (1982) Resistivity Methods Applied to Geothermal Exploration in the Philippines. Proceedings of the Pacific Geothermal Conference/4th N.Z. Geothermal Workshop, pp DE LEON, M.M. (1984). Porosity Calculations for some of the cores of Southern Negros wells. PNOC-EDC Internal Report. GLOVER, R.B. (1975) Chemical Analysis of Waters from Negros Oriental, Philippines and their Significance. DSIR, Chemistry Division, N.Z. HOCHSTEIN, M.F. (1985) Geothermal Diploma Notes. Geothermal Institute, University of Auckland, N.Z. JORDAN, O.T. (1983) Interpretation of the Reservoir Geochemistry, Southern Negros Geothermal Field. PNOC-EDC Internal Report. KRTA (1985) Puhagan Reservoir Simulation Part3 Description of Model and Input Data and Results of Long Term Operation at 40 and 120 MWe. KRTA Ltd., Auckland, N.Z. MAUNDER, B.R., BRODIE, AJ. and TOLENTINO, B.S. (1982) The Palinpinon Geothermal Resource, Negros, Republic of the Philippines - An Exploration Case History. Proceedings of the Pacific Geothermal Conference/4th N.Z. Geothermal Workshop, pp McNITT, J.R., SANYAL, S.K., KLEIN, C.W. and CHE, M. (1982). An Evaluation of the Geothermal Reservoir at Palinpinon, Negros Oriental, The Philippines, Vol. 1 and 2. Geothermex, Inc., Berkeley Ca. SEASTRES, J.S. (1985) Hydrothermal Alteration and Related Chemistry of Sulphate Rich Wells in the Nasuji-Sogongon and Baslay-Dauin Sectors, Southern Negros Geothermal Field, Philippines. PNOC-EDC Internal Report. URBINO, M.E.G., ZAIDE, M.C., MALATE, R.C.M. and BUEZA, E.L. (1986). Structural Flowpaths of Reinjected Fluids from Tracer Tests - Palinpinon I, Philippines. Proceedings, 8th N.Z. Geothermal Workshop, pp

7 FIGURE 14 Temperature ( C) and Pressure (MPa) match of Model 2 91 FIGURE 15. Temperature ( C) and Pressure (MPa) match of Model 2 with blocks 9,10,11 subdivided / ,,o S 1SB/1.8 20O Z15/ M1/1.H /1.5 LAYER AAA (0 m MSL) LAYER OAA (0 m HSL) IX ACTUAL 169/ COMPUTED ACTUAL 1B7/1.2 - COMPUTED ese/b.9 SB1/7.1 Z4O 2S3/B.7 271/6.9 2=O 2S0 2B7/7.S / /B /7.0 LAYER BBB (-600 m MSL) LAYER BBB <-600 m MSL) /13.S 293/ / / / «!?S, Z1S/J3.6-23B 213/ /13.5 LAYER CCC <-14OO m MSI.) LAYER CCC (- 400 m MSL) 1 3O3 Z33/13.1 zao EG7/ /13.0 2B0 266/ /1B /13.5 LAYEH DDD ( m MSL) LAYER DDD <-2100 m MSL) IX

8 92 FIGURE 16. Configuration of third model - model 3 A FIGURE 18. Configuration of model 3B FIGURE 17. Temperature (OQ and Pressure (MPa) match of Model 3A LfiYEH BBB (-600 m MSL) 13S 128/1.6 _ /13 ISO 173/1.7 -IBO 176/1.5 CCC (-1400 n MSLI

9 93 PRESSURE TREND IN B2 BLOCX PRESSURE TREND IN C2 BLOCK A OX1BD PRESSURE TREND(-623.9n) 0 W27D PRESSURE IREND(-643.8n> L PN23D PRESSURE IREND( ) i?h?,& PRESSURE IRENIK-12S4.3nt i PN13D PRESSURE TREND (682,Bn) j 0X9D PRESSURE TREND ( M) 0 PN15D PRESSURE IREND (834.2) $ PN26 PRESSURE TREND (-884.8n> SlUULfllED PRESSURE 0 PN30D PRESSURE TREND(-947.0n> 1 PN20D PRESSURE IREND( ) 4 PH21D PRESSURE IREND(-1281 n) 0 p N14 PRESSURE TREND (-1789 n) SinULftTED PRESSURE H A. -5._ 12B0 14B BBD 1 PRESSURE TREND IN D2 BLOCK PRESSURE IRE IN D3 SLOCK A FN14 PRESSURE TRENIi(-1789.n) k PN1GB PRESSURE TREND( ) A PN14 PRESSURE TREND(-1789.n) A PN2STI PRESSURE TREND( ) PN24D PRESSURE TREND( ) SIHULflTED PRESSURE SIHULflTED PRESSURE (PGEX9) i sfia 4ig 6ia saa lo'aa 1200 TIME, days PRESSURE TROTO IN B18 BLOCK PflLlNPINON I ENTHMJV TREND A NJfD PRESSURE TREND (-592.«n> A NJ5D PRESSURE IREND (-853.9n) SIHULflTED PRESSURE (PGEX9) Q NJ75 PRESSURE TREN5( n> I NJ1D PRESSURE TREND(-884, n) L OBSERVED ENTHflLPV SIMULfllED ENTHALPY (PGEX9) ^ 35^ TII1E, MONTHS FIGURE 19. Pressure and Enthalpy results for Production History Match