SwellingExtraction Test of a Small Sample Size for Phase Behavior Study

SPE 153383 A New Look at the Minimum Miscibility Pressure (MMP) Determination from Slimtube Measurements Abiodun Matthew Amao, SPE; Shameem Siddiqui, SPE; Habib Menouar, SPE, Bob L Herd Department of Petroleum Engineering, Texas Tech University Copyright 2012, Society of Petroleum Engineers This paper was prepared for presentation at the Eighteenth SPE Improved Oil Recovery Symposium held in Tulsa, Oklahoma, USA, 14–18 April 2012 This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s) Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s) The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied The abstract must contain conspicuous acknowledgment of SPE copyright Abstract Slimtube measurement is one of the standard experimental techniques used for determining the minimum miscibility pressure (MMP) of an oil and injection gas system prior to the initiation of an enhanced oil recovery (EOR) project It is preferred because it involves actual fluid displacement in a porous medium However, the specific criterion for determining the cut-off point during the measurement is not uniquely agreed upon in the literature Different criteria have been proposed by researchers and this has been one of the setbacks of using Slimtube measurements The most commonly used criterion is the 1.2 PV criterion, which uses the recovery after injecting 1.2 pore volumes of the displacing gas as the cut-off However, experimental observations show that even at supercritical condition, the volume of a gas is a strong function of the experimental pressure Therefore, there is a need to develop an alternative means of determining the MMP that is not subject to particular pore volumes injected during Slimtube measurements This work presents different means of determining the MMP, based entirely on recovery and the particular displacement phenomenon In this approach, two new parameters are defined – the instantaneous recovery rate (IRR) and the oil recovery rate (ORR) The maximum values for these parameters for each experiment are used as the cut-off value This new criteria was used in analyzing nine experimental data using oil from the Permian Basin The results were compared with MMP prediction based on maximum recovery from each of the runs and the results were found to be in agreement These new criteria will provide consistent cut-off point for experimental runs because Slimtube measurements take a long time to complete The new procedure ensures that adequate data have been gathered during each experimental run, sufficient for a consistent experimental analysis Introduction The measurement of the MMP is of immense interest in the petroleum industry, several experimental procedures, correlations, numerical routines and algorithms have been proposed in the literature Experimental methods include Slimtube measurement (Yellig et al., 1980), rising bubble technique (Christiansen et al., 1987), vanishing interfacial tension (Rao, 1997) Numerical methods include single and multiple cell models, 1-D Slimtube simulations (Metcalfe et al., 1973, Neau et al, 1996) Analytical methods are based on method of characteristics (Wang, 1998) Empirical methods are the different correlation based prediction methods as presented in the literature (Emera et al., 2005, Emera et al 2006, Huang et al 2003) However, of all these methods the Slimtube experimental method is the most standard procedure for predicting the MMP This is a dynamic experiment which is designed to mimic a one dimensional reservoir The Slimtube is a cylindrical tube, with a diameter of 0.25 inch with length ranging from 25 –75 ft It is packed with uniform sand or glass beads and it is housed in a temperature bath The tube is initially saturated with the reservoir oil above its bubble point pressure (i.e single phase oil) The oil is then displaced by the proposed injection gas from the tube at a fixed experimental pressure controlled by a back pressure regulator Miscibility conditions are determined by conducting the experiment at various pressures or injection gas enrichment levels and recording the oil recovery The recovery data is then plotted against the pressure and the curve is used in predicting the MMP Different criteria have been proposed in the literature for identifying the MMP from this experimental procedure 2 SPE 153383 Background and Theory Miscibility has become a very important concept in the design and operation of gas injection processes The attainment of miscibility in any miscible injection process is the optimal operational regime for the process Therefore, it is of special importance in miscible gas injection processes Thermodynamically, two or more fluids are termed miscible if a mixture of the fluids forms a single phase whenever the fluids are mixed in any proportion at a particular condition of pressure and temperature (or a particular thermodynamic state) Therefore, when two fluids attain miscibility, the interface between them vanishes, i.e the interfacial tension (IFT) equals zero Two or more fluids are said to be first contact miscible (FCM) if the resulting mixture is a single phase fluid whenever the fluids first come in contact and are mixed in any proportion Multi-contact miscible (MCM), this implies the two fluids become miscible after several contacts Therefore, a fundamental premise of MCM is that the fluids must contact each other numerous times and exchange components back and forth until miscibility is attained and a single phase system results Classically, MCM has been explained by two governing mechanisms, these are the vaporizing gas drive and the condensing gas drive mechanisms Vaporizing gas drive (VGD) mechanism occurs if miscibility between an injected lean gas and the reservoir oil is achieved by the enrichment of the injected lean gas with medium and intermediate hydrocarbon components from the reservoir oil The lean gas basically vaporizes (strips) these components off the oil, becomes richer, and due to several multiple contacts becomes miscible with the oil As the injected gas migrates through the reservoir, its composition changes gradually from the initial value to a critical composition, which is the point of miscibility with the reservoir oil The zone in which the composition of the injected gas gradually changes from its initial state to the reservoir fluid composition is called the transition zone (Rathmell et al., 1971) This is a complex thermodynamic phenomenon driven by the chemical potential of the two fluids and their composition Here, miscibility is controlled by the reservoir oil composition Condensing gas drive (CGD) mechanism occurs if miscibility is attained between an enriched injection gas and the reservoir oil through the condensation (loss) of the intermediate components of the gas to the reservoir oil The multiple contacts between the two fluids lead to the enriching of the reservoir oil until it attains a critical composition, at which point it becomes miscible with the injection gas Here, miscibility is controlled by the composition of the injected gas, which is also called its enrichment level MCM is achievable only when the compositional path goes through the critical state of the system The critical composition of a hydrocarbon system is unique MCM is a strong function of temperature, pressure and composition of the injected gas and reservoir fluid However, we assume hydrocarbon reservoirs to be isothermal without a significant variation in temperature (although this assumption may not be valid for compositionally grading reservoirs) This implies that the only variables that can be controlled by petroleum engineers are reservoir pressure and injection gas composition (since we cannot change the reservoir oil composition) This leads to two very important concepts in MCM, these are the minimum miscibility pressure (MCM) and the minimum miscibility enrichment (MME) The MMP is the lowest pressure at which the injected gas and the oil in place become multi-contact miscible At this pressure, the displacement process becomes very efficient The MME at a particular pressure is the lowest possible enrichment level of a given component or a group of components in the injection gas which results in multi-contact miscibility The MMP and the MME are conceptually the same They both define the same physical phenomenon but from two different angles The MMP defines it as a variation in pressure to achieve miscibility while the MME defines it as a variation in the injection gas composition to achieve miscibility Therefore, the accurate prediction of MMP/MME is of prime importance in the design and optimization of any miscible gas injection process Experimental Methodology The methodology employed for this experimental study is presented in this section Carbon Dioxide (CO2) was used as the injection gas in this experimental study The Slimtube apparatus used was manufactured by Ruska; however some modifications were made to the original design to accommodate the data acquisition system and a differential capillary tube in the flow stream Oil Sample The crude oil sample used for this study, hereafter referred to as oil sample, was obtained from G R Brown and Associates It is from a well in their Garza field, located in the Permian Basin and Garza County of West Texas The sample is a separator sample (stock tank), which implies that it was obtained at separator conditions The oil has a specific gravity of 0.849 at 60/60 oF, which corresponds to an API gravity of 35.16o Apparatus The experimental apparatus consists of the CO2 loading apparatus, the Slimtube experimental setup and the data acquisition system Figure is the schematic presentation of how CO2 was transferred from the CO2 cylinder to a floating piston accumulator (FPA) used in the setup Figure shows the schematic diagram of the Slimtube setup, as stated earlier, modifications were made to the original Ruska design to integrate the data acquisition system and a thin capillary tube The aim of the capillary tube was to further characterize the effluent property of the fluid being displaced from the Slimtube A Quizix pump was used for the fluid displacement The data acquisition system is based on the National Instruments LabVIEW software and their compact field point hardware The connection of the pressure transducers to the field point and ultimately to the SPE 153383 data acquisition computer is shown in figure The volume of the fluid effluent is recorded by connecting an electronic balance to the data acquisition Experimental Procedure The experimental procedure is presented in two parts, first the CO2 loading procedure and secondly the Slimtube experimental procedure The CO2 loading procedure was used to safely transfer CO2 from the supply bottle at a pressure of 800 psi to higher pressure in the FPAs needed for the experiments Figure shows this layout; vacuum was pulled on the CO2 supply line to evacuate any air from the two FPAs Both FPAs were then filled with CO2 from the CO2 cylinder, after which valve B was close and FPA-1 was used to load up FPA-2 Thus FPA-2 had a CO2 at higher pressure, the pressure was monitored using the data acquisition system The Slimtube experimental procedure is in three parts, the Slimtube pre-experimental clean-up and preparation, experimental run and post-experimental clean-up Prior to this the volume of the porous medium in the Slimtube had been determined The Slimtube was prepared for the experiment by cleaning it with Toluene, after which the heating system was turned on and allowed to equilibrate Kaydol 35 was used as the bath oil, its properties were found to be most suitable for the experimental conditions Nitrogen gas was then connected to the Slimtube and the system was blown-down, after this, vacuum was pulled on the porous medium to evacuate the Nitrogen gas The Slimtube was then filled with the sample oil, the fill-up was continued until a consistent sample was observed at the effluent The experimental set point was determined by the backpressure applied on the system as shown in figure The already loaded CO2 gas in the FPA was then connected to the Slimtube setup, the CO2 gas was then loaded into the resident FPA in the Slimtube apparatus Once the CO2 loading had been completed, the system was allowed to equilibrate, and the experiment was commenced After the experiment, the Slimtube was cleaned using Toluene, this was done to prevent any residual CO2 gas in the porous medium and to prevent the formation and deposition of Asphaltenes in the porous medium The same procedure outlined above was then followed to prepare the Slimtube for the next experimental run The experiments were conducted at a constant and flow rate of 0.25 cc/min, which corresponds to 15 cc/hr The injection of CO2 was continued until the incremental recovery recorded was zero, the experiment was deemed completed at this point Several experiments were conducted and the results are presented and analyzed in the next section Results and Analysis In this section the Slimtube data are presented The first set of data presented is the raw data acquired using the data acquisition system designed for the experiments The raw data have null recovery time; while the other set have only data during oil recovery active times The null recovery time is basically the time it took the system to build pressure up to and above the prevailing back pressure preset on the system The experiments were designed this way so that the whole history of system pressure buildup, to CO2 breakthrough and end of the experiment can be captured This approach helped in a holistic assessment and analysis of the data; also it prevented any surge in pressure or perturbations in the Slim tube during the experiments Experiments were conducted at nine pressure points, figure shows the injection pressure recorded during the experiments Figures through 12 show the injection and back pressures and the recovery volume for each experimental run Figure 13 is the recovery plot versus pore volume injected (PVI) for all the experimental run Data Analysis and MMP Prediction In this section, a detailed analysis of the data acquired in the course of the Slimtube experiments is presented Several derived plots were made to investigate the dynamics of the Slimtube experiments and improve on the measurement and evaluation criteria as it is practiced today The MMP was calculated using the standard methodology of plotting recovery vs pressure and drawing a line through the sloping part and the straight line part, the intersection of which gives the MMP In the literature, several criteria have been proposed for predicting the MMP from a Slimtube experiment Some of the criteria and definition of the MMP are; ̇ The pressure that causes 90% oil recovery at 1.2 P.V of gas injected (William et al., 1980) ̇ An oil recovery of 94% when the gas-oil ration reaches 40,000 scf/bbl (Holm and Josendal, 1974) Egwuenu, (2004) also listed the following criteria among others; ̇ Distinct point of maximum curvature when cumulative recovery of oil at 1.2 PV of gas injected is plotted vs pressure ̇ Distinct point of maximum curvature when recovery of oil at gas breakthrough is plotted vs pressure A critically look at these criteria reveals a fundamental non-uniqueness Also from the recovery curves of all the runs presented in figure 13, it is apparent that the 1.2 PV criteria cannot be a consistent one, considering that different pore volumes of the injection gas has to be injected for different experimental pressures A comparison was made to show the recoveries at these “known” pore volume criteria and a plot of each of these has been made, this is presented in Table and figure 14 It is obvious that the classic shape of the MMP curve is not apparent; hence the MMP cannot be determined from these plots The volume of a gas is still a strong function of pressure even at supercritical conditions, the critical pressure and temperature of C02 is 1070 psia and 88 oF respectively However a look at the plot of density vs pressure for different temperatures for CO2 presented in figure 15 shows that huge variability in the density with increase in pressure This explains why pore vo- SPE 153383 lumes are still immensely affected by the experimental pressures, even at supercritical conditions A critical look at the recovery plot in figure 13 shows that the point at which recovery plateaus is a function of the experimental pressure Also as the pressure decreases, more pore volume of the displacing gas has to be injected into the Slimtube This implies that fixing a cut-off point from which the recovery is gotten in predicting the MMP is not adequate A more consistent methodology is required, one that will be equally applicable irrespective of the operating pressure of the experiment In this work, new criteria are proposed; these criteria are based on an intrinsic property of the experimental procedure and recovery This new method is not affected by the “variable” pore volume injection criteria The most important factor in a Slimtube experiment is the oil recovery, and for any miscible EOR process, we want to maximize recovery from an asset In addition to the known injected pore volume cut offs, the maximum recovery from a Slimtube had also been proposed as a criteria for determining the MMP, as presented by Egwuenu (2004) This criterion was also used in choosing the points to plot on the classic recovery vs pressure plot for MMP determination This is presented in figure 25 and 26; table shows the pore volumes at which these maximum recoveries were observed for each of the runs None was below the 1.2 P.V criteria Also more limiting are the other criteria that stipulates particular recovery percentage This data shows that much more than 1.2 PV is required to get the maximum recovery for a pressure point during Slimtube experiments as indicated by the PVI @ maximum recovery column It can be understood that experiments cannot go on forever, however a representative recovery for each data point is essential for data analysis The plots made included the conventional MMP plot and new rates plots, two types of rates were investigated These rates are the instantaneous recovery rate (IRR) and oil recovery rate (ORR) These rate plots throw more light into understanding the acquired Slimtube data Also a new approach is presented on how to consistently analyze Slimtube data based on the newly proposed rate plots The first derived data presented is the oil recovery rate (ORR), cumulative rate is calculated using the expression stated in equation 1; (1) This is recovery over the time taken Figure 16 shows the plot of the calculated oil recovery rate with PVI The plot shows a unique inflection point on the data which has a sharp turn for the high pressure plots while the inflexion point is not has sharp for the low pressure data Interestingly, the maximum oil recovery rate does not have any unique physical significance based on analysis However, these plots reveal the following salient points; ̇ Oil recovery rate is faster (higher) at higher pressure compared to lower pressures ̇ For the same pore volume of injection gas, more recovery is gotten at high pressure compared to low pressure ̇ Once the maximum ORR is achieved, decline sets in the oil recovery rate, decline is more rapid at higher pressure than lower pressures The ORR for all the runs was presented earlier in figure 16, this curve shows a maximum point and a point of inflexion in the data This point is the first of the proposed new criteria; it is the maximum ORR of the data set A plot of the maximum ORR for each of the experimental run versus the experimental pressure shows a linear trend with a R2 value of 0.9745; this is presented in figure 17 This implies a significant correlation between pressure and ORR The second rate plot is the instantaneous recovery rate (IRR) The IRR is defined by the expression given in equation 2; (2) The time step is the time interval over which the data is acquired by the data acquisition system In this study, the time step used is 10 seconds The IRR for each of the experimental run is presented in figures 18 through 26 As can be seen from the figures, the unique point signifying maximum IRR is obvious in all the figures The only ones with a noisy IRR data are figures 19 and 20; however all the other figures have clear and distinctly observable maximum IRR This unique point and its corresponding recovery is the newly proposed IRR cut-off to be used in predicting the MMP ̇ ̇ ̇ ̇ Calculate oil recovery rate (ORR) and the instantaneous recovery rate (IRR) for all the recovery data acquired for each experimental run, using equation and respectively Determine the maximum ORR and IRR for each experimental run and record the corresponding recovery at these maximum points for each experiment Make plots of the recovery (either raw or percent) at these points vs pressure for each criterion, just as in the classic MMP plot Predict the MMP from any of these two plots SPE 153383 Figure 27shows the maximum recovery percentage vs experimental pressure The classic shape of the MMP curve is immediately apparent from looking at these figures From figure 28 and has shown on the plot, the MMP is determined to be about 1570 psi Figure 29 percent recovery at maximum ORR, the MMP is estimated to be 1565 psi from figure 30, which is reasonably close to that predicted using the maximum recovery plot Figure 31 is the percentage recovery plot at maximum IRR, the predicted MMP using the maximum IRR is 1550 psi These results show that the MMP can be predicted accurately within an acceptable tolerance while using the newly proposed maximum ORR and maximum IRR criteria These new criteria will eliminate doubts in whether sufficient pore volumes has been injected during an experiment, because once the maximum ORR or IRR is determined during an experiment, the experimentalist will be sure that sufficient volume of gas has been injected to predict the MMP for the oil system The maximum IRR is an inherent characteristic of each experimental run because it relates to the injection gas breakthrough time Conclusions and Recommendations Two new criteria have been presented and demonstrated as adequate in predicting the MMP These criteria has presented should further help in clarifying ambiguities inherent with MMP cut-offs based on pore volume injection These new criteria are based on recovery rates and their occurrence is an inherent function of the displacement process These same criteria are equally applicable to any MMP measurement irrespective of the injection gas used The success of CO2 miscible gas injection projects is greatly dependent on the reservoir pressure The MMP as the name implies is a minimum pressure at which miscibility can occur, however, for sufficient recovery, the MMP has to be exceeded It is apparent from the experiments that the displacement efficiency of CO2 is better at higher pressure because CO2 is highly compressible and as the pressure is increased, the density increases hence its displacement efficiency increases Acknowledgement The authors wish to acknowledge the financial support given by the Bob L Herd Department of Petroleum Engineering, Texas Tech University The authors also acknowledge Mr J McInerney for his support with the experiments References 10 11 12 13 14 15 16 Ahmadi, K and Johns, R.T 2008 Multiple Mixing-Cell Method for MMP Calculations Paper SPE 116823, presented at the SPE Annual Technical Conference and Exhibition held in Denver, Colorado, September 21st – 24th Christiansen, R.L and Haines, K.H 1987 Rapid Measurement for Minimum Miscibility Pressure with the Rising-Bubble Apparatus SPE Reservoir Engineering (4): 523-527 SPE 13114-PA Dadina N Rao.1997 A New Technique of Vanishing Interfacial Tension for Miscibility Determination Fluid Phase Equilibria, 139, 311-324 Elsevier Science Egwenu, A.M 2004 Improved Fluid Characterization for Miscible gas Floods Master’s thesis, University of Texas at Austin, Austin, Texas Emera, K.M and Sarma H.K 2006 A Reliable Correlation to Predict the Minimum Miscibility Pressure when CO2 is Diluted with other Gases SPE Reservoir Evaluation & Engineering, 366-377 Emera, K.M and Sarma, H.K 2005 Use of Genetic Algorithm to Estimate CO2-oil Minimum Miscibility Pressure-A key Parameter in Design of CO2 Miscible Flood Journal of Petroleum Science and Engineering 46, 37 -52 Holm L.W and Josendal V.A 1974 Mechanism of Oil Displacement by Carbon Dioxide Paper SPE 4736-PA Journal of Petroleum Technology, Volume 26,(12) 1427-1438 Huang, Y.F., Huang, G.H., Dong, M.Z and Feng, G.M 2003 Development of an Artificial Neural Network for Predicting Minimum Miscibility Pressure in CO2 Flooding Journal of Petroleum Science and Engineering 37, 83-95 Jarrell P.M., Fox C.E., Stein M.H and Webb S.L Practical Aspects of CO2 Flooding Monograph Series Volume 22, SPE, Richardson, TX Kechut, N.I., Zain, Z Md., Ahmad, N and DM Anwar, Raja DM Ibrahim 1999 New Experimental Approaches in Minimum Miscibility Pressure (MMP) Determination Paper SPE 57286 presented at the SPE Asia Pacific Improved Oil Recovery Conference held in Kuala Lumpur, Malaysia, 25th- 26th October Metcalfe, R.S., Fussel, D.D and Shelton, J.L 1973 A Multi-cell Equilibrium Separation Model for the Study of Multiple Contact Miscibility in Rich Gas Drive Paper SPE 3995 presented at SPE-AIME 47th Annual Fall Meeting, held in San Antonio Neau, E., Avaullee, L and Jaubert, J.N 1996 A New Algorithm for Enhanced Oil recovery Calculations Fluid Phase Equilibria 117, 265-272 Elsevier Science Rathmell, J.J, Stalkup, F.I and Hassinger, R.C 1971 A Laboratory Investigation of Miscible displacement by Carbon Dioxide Paper SPE 3483, presented at the 46th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, held at New Orleans, Louisiana, October 3rd -6th Wang, Y 1998 Analytical Calculation if Minimum Miscibility Pressure PhD dissertation, Stanford University, Stanford, California William, C A., Zana, E.N and Humphrys, G.E.1980 Use of the Peng-Robinson Equation of State to Predict Hydrocarbon Phase Behavior and Miscibility for Fluid Displacement Paper SPE 8817 presented at the first joint SPE/DOE Symposium on Enhanced Oil Recovery, Tulsa, Oklahoma Yellig W F and Metcalfe R.S 1980 Determination and Prediction of CO2 Minimum Miscibility Pressure Journal of Petroleum Technology, 160-168 SPE 153383 Pressure Gauge B C Micron Filter D E Relief Valve Vent A FPA-1 Vacuum Pump Floating Piston Accumulators (FPA) FPA-2 CO2 Cylinder Trap Quizix Pump F G H Water Reservoir Measuring Cylinder : Two-way Valve :Three-Way Valve Figure 1: Schematic Diagram of the CO2 Loading Procedure TC-120 Compact Fieldpoint AI-112 CO2 Oil cFP-2200 Pressure DeMod DeMod D Sight Glass DPT B C CO2 DPT A BPR Soltrol 170 Quizix Pump TC TC Electronic Balance DPT: Differential Pressure Transducer DeMod: Demodulator BPR: Back Pressure Regulator Oil Bath Figure 2: Schematic of the MMP Experimental Set-up Water Reservoir Water Collector Toluene SPE 153383 Figure 3: Injection Pressure vs PVI for all Runs Figure 4: Pressures and Recovery vs PVI @ 500 psia Figure 5: Pressures and Recovery vs PVI @ 750 psia Figure 6: Pressures and Recovery vs PVI @ 1000 psia Figure 7: Pressures and Recovery vs PVI @ 1250 psia Figure 8: Pressures and Recovery vs PVI @ 1500 psia SPE 153383 Figure 9: Pressures and Recovery vs PVI @ 1750 psia Figure 10: Pressures and Recovery vs PVI @ 2000 psia Figure 11: Pressures and Recovery vs PVI @ 2500 psia Figure 12: Pressures and Recovery vs PVI @ 3000 psia Figure 13: Recovery vs Pore Volume Injected (PVI) for all Runs SPE 153383 Table 1: Percent Recovery at Different Pore Volume Injected Pressure Recovery @ PV (%) Recovery @ 1.2 PV (%) Recovery @ 1.5 PV (%) 500 2.7514 3.6353 5.6665 750 3.5756 5.2877 8.7081 1000 6.0309 8.3690 12.9325 1250 5.1544 7.3515 11.7541 1500 12.8565 17.9117 30.0048 1750 21.9832 33.9096 80.3450 2000 11.1503 19.6013 54.9985 2500 34.3303 85.9567 87.4906 3000 57.9736 87.8251 88.0850 Recovery at Different Pore Volume Cut-offs 100 Percent Recovery (%) 90 80 Recovery @ 1.0 PV (%) 70 Recovery @ 1.2 PV (%) 60 Recovery @ 1.5 PV (%) 50 40 30 20 10 0 500 1000 1500 2000 2500 3000 3500 Pressure (psi) Figure 14: Plot of Recovery at Suggested Pore Volume for MMP Evaluation CO2 Density vs Pressure For Differerent Temperatures 60 Density @ 80 F Density @ 100 F 50 Density (lbs/ft3) Density @ 150 F Density @ 200 F 40 30 20 10 0 500 1000 1500 2000 Pressure (psi) 2500 Figure 15: Density vs Pressure Plot at Different Temperatures (Jarell et al., 2002) 3000 3500 10 Figure 16: Oil Recovery Rate (ORR) vs PVI for all Runs SPE 153383 Figure 17: Maximum Oil Recovery Rate (ORR) vs Pressure Figure 18: Oil Recovery and IRR vs PVI @ 500 psi Figure 19: Oil Recovery and IRR vs PVI @ 750 psi Figure 20: Oil Recovery and IRR vs PVI @ 1000 psi SPE 153383 Figure 21: Oil Recovery and IRR vs PVI @ 1250 psi Figure 23: Oil Recovery and IRR vs PVI @ 1750 psi Figure 25: Oil Recovery and IRR vs PVI @ 2500 psi 11 Figure 22: Oil Recovery and IRR vs PVI @ 1500 psi Figure 24: Oil Recovery and IRR vs PVI @ 2000 psi Figure 26: Oil Recovery and IRR vs PVI @ 3000 psi 12 SPE 153383 Table 2: Pore Volume Injected and Percent Recovery at Maximum Recovery Maximum Recovery Pressure Recovery Maximum Recovery (%) PVI @ Maximum Recovery 500 65.6098 39.97 3.04 750 72.0611 43.90 3.20 1000 80.3995 48.98 2.87 1250 93.1075 56.73 2.63 1500 131.1598 79.91 1.98 1750 137.9997 84.08 1.62 2000 141.4989 86.21 1.72 2500 143.6056 87.49 1.36 3000 144.5812 88.08 1.33 Figure 27: Recovery vs Pressure at Maximum Recovery Figure 28: MMP Predicted from Maximum Recovery Percentage Figure 29: Recovery at Maximum ORR vs Pressure Figure 30: MMP Predicted from Maximum ORR % Recovery SPE 153383 Figure 31: Recovery at Maximum IRR vs Pressure 13 Figure 32: MMP Predicted from Maximum IRR Percent Recovery ... Brown and Associates It is from a well in their Garza field, located in the Permian Basin and Garza County of West Texas The sample is a separator sample (stock tank), which implies that it was... accommodate the data acquisition system and a differential capillary tube in the flow stream Oil Sample The crude oil sample used for this study, hereafter referred to as oil sample, was obtained... obtained at separator conditions The oil has a specific gravity of 0.849 at 60/60 oF, which corresponds to an API gravity of 35.16o Apparatus The experimental apparatus consists of the CO2 loading