1 1 SIMULATION OF POLYMER FLOODING APPLIED FOR OIL FIELD IN 2 PHITSANULOK BASIN 3 Jutikarn Kanarak* and Kriangkri Trisarn 4 Running head: Simulation of Polymer Flooding in Phitsanulok Basin 5 Abstract 6 This paper examines two questions: (1) study and compare of oil recovery 7 efficiency between the best case of waterflooding and polymer flooding by using 8 reservoir simulation technique and, (2) apply the discount cash flow to optimize 9 the polymer flooding selection from each scenario under current Dubai oil 10 prices. Three sizes of oil fields are modeled in anticline reservoir structure with 11 the original oil in place (OOIP) of 100, 30 and 5 million barrels respectively. 12 Each oil field has many production methods by using different polymer 13 concentrations and injection periods. The large size reservoir of model A100, oil 14 recovery has increased from waterflooding of 3.86-7.24% OOIP. The polymer 15 flooding has IRR range from 28.40-43.76% and PIR of 0.37-0.51, and the best 16 case is the scenario that used polymer concentration of 1,000 ppm and injection 17 period of 3rd-11thyear, that has net present value (NPV) of 170 MMUS$. The 18 medium size reservoir of model A30, oil recovery has increased from 19 waterflooding of 2.42-5.48% OOIP. The polymer flooding has IRR range from 20 53.91-56.76% and PIR of 0.36-0.40, and the best case is the scenario that used 21 polymer concentration of 1,000 ppm and injection period of 3rd-10thyear, that has * School of Geotechnology, Institute of Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand. E-mail: [email protected] * Corresponding Author 2 22 NPV of 53 MMUS$. The small size reservoir of model A05, oil recovery has 23 increased from waterflooding of 4.39-4.62% OOIP. The polymer flooding has 24 IRR range from 20.95-21.73% and PIR of 0.66-0.76, and the best case is the 25 scenario that used polymer concentration of 600 ppm and injection period of 4th- 26 20thyear, that has NPV of 15 MMUS$. 27 28 Keywords: Recovery efficiency, Polymer flooding, Waterflooding, Reservoir 29 simulation 30 31 Introduction 32 The oil field in Phitsanulok Basin, located in the central part of Thailand. This 33 study focused on Sirikit oil field where it is a part of the Phitsanulok Basin. The 34 Sirikit oil field has been produced by primary and secondary oil recoveries together 35 with the production of 22978 bbl/d (Department of Mineral Fuels., 2009). 36 secondary recovery, water injection has been applied to maintain reservoir pressure 37 with some successes; it is still water breakthrough due to high mobility ratio and 38 heterogeneity of geology that has actually occurred as high water cut stage. It causes 39 poor performance of waterflooding. In order to improve the oil recovery, the polymer 40 flooding is an attractive alternative to conventional waterflooding. 41 modifications need to be made to a waterflooding to enable polymer injection and 42 recovery of additional oil. Additional polymers with flood water can increase the 43 viscosity of the displacing phase (aqueous phase). The increased viscosity of water 44 during polymer flooding causes the change of water-oil fractional flow and the 45 improvement in vertical and areal sweep efficiency. Thus more oil is recovered. For Minor 3 46 Characteristics of Petroleum Reservoirs 47 The Sirikit field is a main oil field in the Phitsanulok Basin that is the area of 48 this study. The basin is an extensional Oligocene structure. The main reservoir 49 intervals lie within the Oligocene-Miocene fluvio-lacustrine Lan Krabu Formation 50 (Figure 1). The major reservoir facies are interpreted to be lacustrine mouth bars and 51 fluvial distributary channels. The central area of the field is intensely faulted, whereas 52 the western and eastern flanks are relatively undeformed. The field has an estimated 53 STOIIP (stock tank oil initially in place) of some 800 MMbbl (million barrels). The 54 main reservoirs contain undersaturated, light oil (39.4°API), and the initial reservoir 55 pressure of 3500 psi at depth of 3850 m. The bubble point is lower 1800 psi (Trisarn, 56 2006). Production started during 1982, and reservoir pressure quickly dropped to 57 below bubble point, which resulted in higher producing gas/oil ratios (GOR) and 58 lower oil rates. The reservoir drive energy was determined to be limited to solution 59 gas expansion, which is aided by gas-cap expansion in some reservoirs. To preserve 60 this energy and to optimize oil recovery, GOR limitations were set for the different 61 reservoirs. As early as 1982, a water injection scheme was suggested for the Sirikit 62 oil field. Consequently, in 1995 full-scale water injection commenced on the eastern, 63 unfaulted flank of the field (Bruce et al., 1999). This study was the field development 64 that investigated into optimizing recovery and identifying unswept oil volumes are 65 considered. 66 67 Enhanced Oil Recovery 68 The increase oil recovery efficiency by polymer flooding is proven workable a 69 widespread distribution, especially in the North America and China. In China, the 4 70 study on enhanced oil recovery by chemical flooding has been carried out for more 71 than 20 years (Han et al., 1999) and used both types of polymer which are 72 Polyacrylamide (PAM) and Polysaccharide (Biopolymer or Xanthan Gum). 73 results from China oil field can be proven that the polymer flooding technique can 74 increase the oil recovery of the various reservoir types. This study used the Xanthan 75 Gum for polymer flooding method, which has good performance more than the 76 Polyacrylamide for high temperature in the reservoir. The 77 The objective of polymer flooding is to reduce mobility ratio based on 78 increasing the water viscosity. In some cases, the polymer solution reduces the 79 permeability of the reservoir rock to water. The mobility ratio between the displacing 80 phase (polymer solution) and the displaced phase (oil) will be decreased, therefore, 81 the oil water contact will move steady in the formation from injection well to 82 production well. 83 The polymer flooding into reservoir for control the mobility of injected phase 84 can be shown in Figure 2. The figure show a schematic of a typical polymer flood 85 injection sequence: a preflush is usually consisting of low salinity brine; an oil bank is 86 injected by polymer; a fresh water buffer to protect the polymer solution from 87 backside dilution; and the last are drive water. 88 89 Reservoir Simulation Model design 90 The performance prediction of water and polymer injection for the fields was 91 built from the ECLIPSE OFFICE simulator model which confined well pattern. 92 Three sizes of oil fields are modeled with the oil in place of 100, 30 and 5 million 93 barrels respectively. Model sizes and dimensions are shown Table 1. Each oil field 5 94 has many production methods that use different polymer concentrations and various 95 times interval for injection. The properties of the reservoir are summarized in Table 96 2. The simulation pertained to a confined well pattern, the symmetry element being 97 represented by grid block of, 25 x 25 x 8 blocks (5000 cells) for all models, which are 98 shown in Figure 3. Polymer flooding pattern design for a comprehensive of the 99 flooding simulation which relies on the reservoir structure, drainage area, number of 100 well, production and injection activity. The summary of water and polymer injection 101 rate for each scenario is illustrated in Table 3. 102 The structural of model A100 shows peripheral flood injection pattern. There 103 are 17 production wells and 8 injection wells located in and around the reservoir 104 boundary, respectively. The appropriate spacing of each well is approximately 1000 105 ft. Model A30 shows peripheral flood injection pattern. There are 5 production wells 106 and 4 injection wells located in and around the reservoir boundary, respectively. The 107 appropriate spacing of each well is approximately 945 ft. Model A05 shows inverted 108 three-spot flood injection pattern. There are a production well and 2 injection wells 109 located at reservoir crest and down dip of the reservoir boundary, respectively. The 110 appropriate spacing of each well is approximately 350 ft. 111 The production and injection wells are located in the updip and downdip 112 structure, respectively. The appropriate numbers of well are considered to optimum 113 oil recovery, injection of polymer slug, polymer concentration and economic 114 evaluation. 115 The structure model for the Sirikit oil field is very important for maximal 116 improvement oil recovery. The field is geologically complex, being very faulted in a 117 lacustrine environment and heterogeneity of the various reservoirs. Trisarn (2006) found 6 118 vertical heterogeneity of porosity and permeability of the Sirikit L sand as shown in 119 Figure 4. 120 121 Results and Discussion of Polymer Flooding Simulation 122 The base case from the waterflooding of each model was tested which need to 123 found the best case as well as the highest oil recovery from the waterflooding. The 124 results found, all models of the waterflooding that have highest oil recovery can be 125 started within a reasonable time on 3rd year and water flood must be injected into the 126 reservoir until the end of project life, for reservoir pressure support. 127 The results of analysis obtained from the best scenario of the waterflooding 128 (base case) and the application of the polymer flooding technique in the three reserved 129 sizes of oil field with different polymer concentrations and various times interval for 130 injection are shown in Table 4. 131 There shows the scenarios of polymer injection that could have high 132 performance oil recovery efficiency when compared to the best case of water 133 injection. All scenarios have more incremental of oil from the polymer injection than 134 that would be gained from the water injection alone. For Model A100, oil recovery 135 has increased 5.25, 4.60, 3.86, 6.37, 5.73, 4.98, 7.24, 6.58 and 5.83% of OOIP in 136 scenario 2 to 10 respectively. Model A30, oil recovery has increased 4.25, 3.42, 2.42, 137 4.96, 4.01, 2.87, 5.48, 4.33 and 3.13% of OOIP in scenario 2 to 10 respectively. 138 Model A05, oil recovery has increased 4.40, 4.48, 4.39, 4.56, 4.39, 4.57, 4.52 and 139 4.62% of OOIP in scenario 2 to 9 respectively. 140 The results show that the polymer flooding can improve the water swept 141 coefficient and the volumetric sweep efficiency, consequently, water cut in reservoir 7 142 decreased. As a result, the polymer flooding method can successfully adjust the 143 mobility ratio between polymer solution and oil phase in the reservoir that is 144 effectively prompt of oil recovery efficiency, which are shown Figure 5-7. 145 The effects of reducing the water cut and increasing the oil production rate are 146 observed at all scenarios in each model. For example, model A100 with polymer 147 concentration of 1,000 ppm and a time interval injection of 3rd-11th year, the oil 148 production rate increases after injection of polymer solution on June 6th year, and at 149 the end of polymer flooding on 11th year, the water cut of that reservoir decreases 150 from 25.5% to 3.4% with a production rate increases from 2849 to 3667 bbl/day and 151 the polymer flooding can maintains oil production rate more than receives from the 152 waterflooding until June 21th year. 153 Comparison between the waterflooding and polymer flooding from model 154 A100, the oil saturation distribution after polymer flooding by injection polymer 155 concentration of 1000 ppm with injection slug size of 0.12 pore volume (PV) has been 156 selected to compare with the waterflooding (Figure 8-9). Before polymer flooding, 157 the oil saturation in all layers has been still very high. From the waterflooding, the oil 158 saturation has been decreased in small area around the wells only. After polymer 159 flooding, in the most area where is oil in placed can be controlled by the injection 160 wells and the production wells, the reservoir oil saturation has been decreased to the 161 residual oil saturation, that is more oil has been produced. 162 The comparison shows that oil saturation from polymer flooding has been 163 apparently decreased, especially in the upper six layers. The polymer flooding has 164 taken clearly effect on improving volumetric driving efficiency. On the other hand, 165 the two lower layers have not effectiveness by polymer flooding because a reservoir 8 166 with the aquifer may become difficult to be flooded, due to the flow of polymer 167 solution in the reservoir could not be regulated and that is difficult respect to control 168 of chemical loss. 169 The increasing of polymer concentration can increase the oil recovery, 170 however, the concentration of polymer need to be adjusted to the suitable injection 171 rate to prevent the extreme adsorption mechanism on the rock surface and undesired 172 blocking zones. If polymer slug size is very small, that is almost no enhanced oil 173 recovery. Most of polymer has been adsorbed on the pore surface of the rock. In 174 addition, the polymer injection with too high concentration more than appropriate 175 concentration will make the larger particle size which plug in pore spaces. The oil 176 recovery will be decrease due to the inaccessible pore volume that solid particle of 177 polymer cannot flow through. 178 The polymer injection within a reasonable time will make the highest oil 179 recovery. The main important to improvement oil recovery is to maintain pressure in 180 the reservoir for the stable pressure drop which control the oil optimum flow rate base 181 on the Darcy’s Law. Therefore, the polymer injection in the early stage of a water 182 flood is important as mention above and the simulation also provide the suitable time 183 period to start polymer injection. 184 The small reservoir geometry that has only a small oil bearing zone, such as 185 model A05, the economic design of a flooding may be not possible. Due to it is very 186 difficult to be flooded with respect to the control of chemical loss. Thus model A05 187 need to be used to the lower polymer concentration injection with a long period of 188 time, to prevent an adsorption and undesired blocking zone. The effect of polymer 189 injection with incremental of oil recovery are shown in Figure 10. 9 190 191 Economic Evaluation Economic evaluation is the final step in this study on the application of 192 polymer flooding for the enhanced oil recovery. The objective of economic 193 evaluation is the commerciality of each model project as the result from the reservoir 194 simulation. Table 5 lists the economic evaluation parameters used in this study. 195 From the result of polymer flooding in each model is compared to the best 196 case of the waterflooding which is used the same water/polymer solution injection 197 rate (displacing phase). The results of economic evaluation are shown in Table 6. 198 This table contains for net present value (NPV), internal rate of return (IRR) and 199 profit to investment ratio (PIR). For model A100, scenario of water injection has the 200 IRR after tax and 8% discounted of 33.49% and PIR of 0.46, while scenarios of 201 polymer injection have the IRR after tax and 8% discounted range from 28.40-43.76% 202 and PIR of 0.37-0.51. Accordingly, the best operation case for model A100 is the 203 scenario that used the polymer concentration of 1000 ppm and the time interval of 204 injection 3rd-11th year, that has the best NPV of 170 MMUS$. 205 Model A30, scenario of water injection has the IRR after tax and 8% 206 discounted of 55.43% and PIR of 0.39, while scenarios of polymer injection have the 207 IRR after tax and 8% discounted range from 53.91-56.76% and PIR of 0.36-0.40. 208 Accordingly, the best case for model A30 is the scenario that used the polymer 209 concentration of 1,000 ppm and the time interval of injection 3rd-10th year, that has the 210 best NPV of 53 MMUS$. 211 Model A05, scenario of water injection has the IRR after tax and 8% 212 discounted of 21.72% and PIR of 0.83, while scenarios of polymer injection have the 213 IRR after tax and 8% discounted range from 20.95-21.73% and PIR of 0.66-0.76. 10 214 Accordingly, the best operation case for model A05 is the scenario used the polymer 215 concentration of 600 ppm and the time interval of injection 4th-20th year, that has the 216 best NPV of 15 MMUS$. 217 218 Conclusions and Recommendations 219 The heterogeneity of the geological conditions in the reservoirs causes the oil 220 fields to have a high water cut stage, and low oil recovery efficiency using the 221 waterflooding method. 222 different size of oil fields with the various polymer concentrations by the reservoir 223 simulation, the results found the polymer flooding can increase the oil recovery more 224 than using the traditional waterflooding method only, due to the polymer solution can 225 improve the water swept coefficient and the volumetric sweep efficiency. Finally, 226 those have reduced the water cut in the oil reservoirs of heterogeneous geological 227 condition. The “Xanthan Gum” polymer solution is used in these oil fields 228 simulation. The reservoir with quite high temperature assures that this polymer 229 solution can increase the water viscosity. 230 polymer solutions and oil will be decreased. The application of the polymer flooding method in the Therefore, the mobility ratio between 231 Consequently, Model A100 with the 1000 ppm polymer solution injection and 232 inject period of 3rd-11th year, there is an increased profit of 1370 barrel of oil 233 production per ton of polymer injected, and the oil recovery efficiency will be 234 increased 5.25% OOIP more than the waterflooding. For Model A30, with the 1000 235 ppm polymer solution injection and injection period of 3rd-10th year, there is an 236 increased profit of 1450 barrel of oil production per ton of polymer injected, and the 237 oil recovery efficiency will be increased 4.25% OOIP more than the waterflooding. 11 238 For Model A05, with the 600 ppm polymer solution injection and injection period of 239 4th-20th year, there is an increased profit of 820 barrel of oil production per ton of 240 polymer injected, and the oil recovery efficiency will be increased 4.48% OOIP more 241 than the waterflooding. 242 The polymer flooding would not economic efficiency when the field used 243 excess concentration of polymer, due to the big consumed amount of polymer. Thus 244 the polymer flooding will make not profitable as well as the higher cost than the 245 waterflooding. 246 The heterogeneity effect of porosity and absolute permeability variation need 247 to apply and test for individual productive reservoir to make a reliable result of the 248 simulation result. 249 The simulation models used in this study appear to be conceptual model not 250 the real performance of oil field in the Phitsanulok Basin. 251 Acknowledgement 252 The authors wish to special thank to Asst. Prof. Thara Lekuthai who gave the valuable 253 suggestion for this research. Also, we would like to acknowledge the School of 254 Geotechnology, Suranaree University of Technology for all supports. 255 256 References 257 Bruce, A.R., Sanlug, M., and Duivenvoorden, S. (1999). Correlation techniques, 258 perforation strategies, and recovery factors: an integrated 3-D reservoir 259 modeling study, Sirikit field, Thailand. AAPG Bulletin, 83(10): 1535-1551. 260 Department of Mineral Fuels, Ministry of Energy, Thailand. [DMF]. (2009). Annual 261 Report 2009 [On-line]. Available from: www.dmf.go.th. Accessed date: Aug 20, 12 262 263 264 2010. Gharbi, R.B.C. (2004). Use of reservoir simulation for optimizing recovery performance. Journal of Petroleum Science and Engineering 42(2-4):183-194. 265 Han, D.K., Yang, C.Z., Zhang, Z.Q., Lou, Z.H., and Chang, Y.I. (1999). Recent 266 development of enhanced oil recovery in china. Journal of Petroleum Science 267 and Engineering 22(1):181-188. 268 269 Lake, W.L. (1989). Enhanced Oil Recovery. New Jersey: Prentice-Hall, Eaglewood Cliffs. 550 pp. 270 Li, X.P., Yu, L., Ji, Y.Q., Wu, B., Li, G.Z., Zheng, L.Q. (2009). New type flooding 271 systems in enhanced oil recovery. Chinese Chemical Letters 20(10): 1251-1254. 272 McCoy, S.T. and Rubin, E.S. (2008). The effect of high oil prices on EOR project 273 economics. Department of Engineering and Public Policy, Carnegie Mellon 274 University, Pittsburgh, USA. Available from: www.sciencedirect.com. Accessed 275 date: Jan 15, 2010. 276 Morley, C.K., Lonnikoff, L., Pinyochon, N., and Seusutthiya, K. (2007). Degradation 277 of a footwall fault block with hanging-wall fault propagation in a continental- 278 lacustrine setting: How a new structural model impacted field development 279 plans, the Sirikit field, Thailand. AAPG Bulletin 91(11):1637-1661 280 Thang, P.D. (2005). Enhanced oil recovery in basement rock of the White Tiger Field 281 in offshore Southern Vietnam, [MEng. thesis]. School of Civil Engineering, 282 Asian Institute of Technology. Pathumthani, Thailand, 133p. 283 Trisarn, K. (2006). Improvement oil recovery by water flooding in Thailand tertiary oil 284 field, [Research report]. School of Geotechnology, Institute of Engineering, 285 Suranaree University of Technology. 13 Figure 1. Schematic general stratigraphy of the Phitsanulok Basin and the Sirikit field. The strata of interest are the Oligocene-Miocene lacustrine deltaics of the Lan Krabu Formation (Bruce, et.al., 1999). 14 Figure 2. Schematic illustration of polymer flooding sequence, (Lake, 1989). 15 Figure 3. The model structure and confined well pattern of three reserve sizes. 16 Figure 4. The reservoir sections show the vertical heterogeneities of reservoir. 17 Figure 5. Production performance, Model A100-polymer 1,000 ppm-injected 3rd11th year. 18 Figure 6. Production performance, Model A30-polymer 1,000 ppm-injected 3rd10th year. 19 Figure 7. Production performance, Model A05-polymer 600 ppm-injected 4 th20th year. 20 Figure 8. Oil saturation distribution after waterflooding@the end of project life, Model A100-no polymer injection. 21 Figure 9. Oil saturation distribution after polymer flooding@the end of project life, Model A100-polymer 1,000 ppm-injection 3rd-11th year. 22 Figure 10. Effect of polymer injection (barrel oil/ton of polymer). 23 Table 1. Model sizes and dimensions Model Dimension (ft) Area (acres) Thickness (ft) 6,250 x 6,250 Horizontal grid dimension (ft) 250 A100 896.75 100 A30 3,375 x 3,375 135 261.49 160 A05 1,250 x 1,250 50 35.87 56 24 Table 2. Summary of reservoir and fluid properties Parameter Properties Depth 3,850 ft Temperature 203°F Rock type Consolidated Sandstone Porosity 19-26% Oil gravity 39.4°API Oil viscosity 2.1 cp Permeability 9.2-586 md Average kv/ kh 0.10 Datum depth 3,850 ft Initial static reservoir pressure 3,500 psi Oil formation volume factor 1.055-1.286 bbl/STB Dissolved gas specific gravity 0.8 Bubble point pressure 1,800 psi Water-oil contact depth 3,915 ft 25 Table 3. Injection rate of scenarios test Model A100 A30 A05 Injection scenarios Waterflooding Preflush by water Polymer injection Driving water Waterflooding Preflush by water Polymer injection Driving water Waterflooding Preflush by water Polymer injection Driving water Water injection (BWPD/well) 1,000 500 200 Polymer/water Injection (BWPD/well) 1,000 1,000 1,000 500 500 500 200 200 - 26 Table 4. Basic data of polymer flooding Model Pattern A100 A30 Peripheral flood Peripheral flood Injector/ Distance Scenario Producer between No. injector and producer (ft) 8/17 1,000 1 4/5 945 Polymer concentration (ppm) Date of water/ polymer injection Quantity of injected polymer (ton x pv) Incremental oil recovery (%OOIP) 3rd-25th - - 2 Water inj. (no-polymer) 1,000 3rd-11th 4,181x0.14 5.25 3 1,000 4th -12th 4,181x0.14 4.60 4 1,000 5th -13th 4,181x0.14 3.86 5 1,500 3rd-11th 6,272x0.14 6.37 6 1,500 4th -12th 6,272x0.14 5.73 7 1,500 5th -13th 6,272x0.14 4.98 8 2,000 3rd-11th 8,365x0.14 7.24 9 2,000 4th -12th 8,365x0.14 6.58 10 2,000 5th -13th 8,365x0.14 5.83 1 Water inj. (no- polymer) 1,000 3rd-25th - - 3rd-10th 929x0.12 4.25 3 1,000 4th -11th 929x0.12 3.42 4 1,000 5th -12th 929x0.12 2.42 5 1,500 3rd-10th 1,394x0.12 4.96 6 1,500 4th -11th 1,394x0.12 4.01 7 1,500 5th -12th 1,394x0.12 2.87 8 2,000 3rd-10th 1,858x0.12 5.48 9 2,000 4th -11th 1,858x0.12 4.33 10 2,000 5th -12th 1,858x0.12 3.13 1 3rd-20th - - 2 Water inj. (no-polymer) 600 3rd-20th 296x0.34 4.40 3 600 4th -20th 279x0.34 4.48 4 800 3rd-20th 395x0.34 4.39 5 800 4th -20th 372x0.34 4.56 6 1,000 3rd-20th 494x0.34 4.39 7 1,000 4th -20th 465x0.34 4.57 8 1,200 3rd-20th 592x0.34 4.52 9 1,200 4th -20th 557x0.34 4.62 2 A05 Inverted three-spot 2/1 350 27 Table 5. Economic evaluation parameter Project parameters A100 A30 A05 Dubai oil price (US$/bbl) 80 80 80 Income tax (%) 50 50 50 Inflation rate (%) 2 2 2 Real discount rate (%) 8 8 8 0-2,000 5 5 5 2,000-5,000 6.25 6.25 6.25 5,000-10,000 10 10 10 10,000-20,000 12.5 12.5 12.5 >20,000 15 15 15 Concession (MMUS$)* 3.75 2.50 0.50 Geological and geophysical survey (MMUS$) 5 4 1 Production facility (MMUS$) 250 100 10 Drilling exploration & appraisal well (MMUS$) 10.5 6 1 Drilling and completion production well (MMUS$/well) 1.5 1.5 1.5 Facility cost of water injection well (US$/well) 60,000 60,000 60,000 Facility cost of polymer injection well (US$/well) 62,000 62,000 62,000 Maintenance cost of water injection well (US$/year) 80,000 60,000 40,000 Maintenance cost of polymer injection well (US$/year) 80,000 60,000 40,000 Abandonment cost (US$/well) 12,500 12,500 12,500 Operating cost of production well (US$/bbl) 30 25 20 Operating cost of water injection (US$/bbl) 0.5 0.5 0.5 Operating cost of polymer injection (US$/bbl) 1.0 1.0 1.0 Polymer purchasing price including transportation (US$/kg) 7 7 7 Sliding scale royalty (%) Production level (bbl/day) *MMUS$ = Million US Dollar 28 Table 6. Economic evaluation results summary Model Scenario No. A100 A30 A05 Amount of polymer (ton) Capital cost (MMUS$) NPV with8% discounted (MMUS$) IRR with8% discounted (%) PIR with8% discounted (Fraction) 1 Time of water/ polymer injection (year) 23 - 307.33 141.94 33.49 0.46 2 9 4,181 337.10 170.31 43.76 0.51 3 9 4,181 337.10 150.83 33.28 0.45 4 9 4,181 337.10 135.62 28.84 0.40 5 9 6,272 351.74 169.31 43.38 0.48 6 9 6,272 351.73 150.25 33.08 0.43 7 9 6,272 351.73 134.90 28.62 0.38 8 9 8,365 366.38 167.37 43.00 0.46 9 9 8,365 366.37 149.21 32.81 0.41 10 9 8,365 366.37 133.86 28.40 0.37 1 23 - 126.54 49.60 55.43 0.39 2 8 929 133.04 53.05 54.33 0.40 3 8 929 133.04 50.83 55.31 0.38 4 8 929 133.04 52.53 56.76 0.39 5 8 1,394 136.29 52.99 54.91 0.39 6 8 1,394 136.29 50.51 55.21 0.37 7 8 1,394 136.29 52.22 56.72 0.38 8 8 1,858 139.55 52.24 53.91 0.37 9 8 1,858 139.55 49.75 55.08 0.36 10 8 1,858 139.55 51.75 56.68 0.37 1 18 - 17.15 14.26 21.72 0.83 2 18 296 19.34 14.49 21.21 0.75 3 17 279 19.22 14.69 21.73 0.76 4 18 395 20.03 14.38 21.12 0.72 5 17 372 19.87 14.61 21.67 0.74 6 18 494 20.72 14.27 21.03 0.69 7 17 465 20.52 14.51 21.61 0.71 8 18 592 21.42 14.18 20.95 0.66 9 17 557 21.17 14.42 21.54 0.68
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