Performance of a Polymer Flood with Shear-Thinning Fluid in Heterogeneous Layered Systems with Crossflow

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1 Energies 211,, ; doi:1.339/en1112 OPEN ACCESS energies ISSN Article Performance of a Polymer Flood with Shear-Thinning Fluid in Heterogeneous Layered Systems with Crossflow Kun Sang Lee Department of Natural Resources and Enironmental Engineering, Hanyang Uniersity, Seoul , Korea; kunslee@hanyang.ac.kr; Tel.: ; Fax: Receied: 13 May 211; in reised form: 23 June 211 / Accepted: 27 July 211 / Published: 2 August 211 Abstract: Assessment of the potential of a polymer flood for mobility control requires an accurate model on the iscosities of displacement fluids inoled in the process. Because most polymers used in EOR exhibit shear-thinning behaior, the effectie iscosity of a polymer solution is a highly nonlinear function of shear rate. A reseroir simulator including the model for the shear-rate dependence of iscosity was used to inestigate shear-thinning effects of polymer solution on the performance of the layered reseroir in a fie-spot pattern operating under polymer flood followed by waterflood. The model can be used as a quantitatie tool to ealuate the comparatie studies of different polymer flooding scenarios with respect to shear-rate dependence of fluids iscosities. Results of cumulatie oil recoery and water-oil ratio are presented for parameters of shear-rate dependencies, permeability heterogeneity, and crossflow. The results of this work hae proen the importance of taking non-newtonian behaior of polymer solution into account for the successful ealuation of polymer flood processes. Horizontal and ertical permeabilities of each layer are shown to impact the predicted performance substantially. In reseroirs with a seere permeability contrast between horizontal layers, decrease in oil recoery and sudden increase in WOR are obtained by the low sweep efficiency and early water breakthrough through highly permeable layer, especially for shear-thinning fluids. An increase in the degree of crossflow resulting from sufficient ertical permeability is responsible for the enhanced sweep of the low permeability layers, which results in increased oil recoery. It was obsered that a thinning fluid coefficient would increase injectiity significantly from simulations with arious injection rates. A thorough understanding of polymer rheology in the reseroir and accurate numerical modeling are of fundamental importance for the exact estimation on the performance of polymer flood.

2 Energies 211, 1113 Keywords: polymer flood; iscosity; shear-thinning fluid; crossflow; simulation 1. Introduction Among arious enhanced oil recoery (EOR) methods, polymer flooding has been considered as an attractie alternatie to conentional waterflooding for many reseroirs [1 3]. It is also one of the most mature EOR techniques because relatiely minor modifications need be made to a waterflood to enable polymer injection and recoery of additional oil. Polymers proide mobility control to yield a more stable displacement and a sharper front by increasing the iscosity of the injected aqueous phase. The economic success of polymer flooding is particularly susceptible to injection rate or injectiity, which is directly related in turn to the iscosity of the injection fluids []. The iscosity can be affected by a number of factors such as polymer concentration, temperature, and salinity [5,6]. In addition, polymers are of interest in EOR applications because of their rheological properties in dilute solutions. Polymeric addities usually make the displacement fluids exhibit non-newtonian rheological behaior. Normally, polymer solutions used in EOR processes are shear-thinning or pesudoplastic fluids in a iscometer, whose apparent iscosity decreases in a reseroir with increasing shear rate. Some polymer solutions may exhibit pseudodilatant behaior in porous media [7,]. The shear-thinning behaior is beneficial from the standpoint of injectiity, because the iscosity near the injection well is lower due to higher shear rate, which proides more faorable injectiity. Once the polymer moes far into the reseroir, shear rates decline and the iscosity increases, which proides the desired mobility control. Howeer, shear-thinning may be undesirable in terms of sweep efficiency and resulting oil recoery, especially in heterogeneous reseroirs. The rheological properties of polymer systems under reseroir conditions hae been recognized as one of the most important factors goerning the success of a polymer flood. Shear-thinning behaior may impair sweep and oil recoery by inducing instability and/or exacerbating elocity contrast [3]. Howeer, Seright [9] suggested that the ertical sweep efficiency using shear-thinning fluids is not expected to be dramatically different from that for Newtonian or shear-thickening fluids for practical conditions during polymer floods. In spite of possible sweep impairment, effects of shear-thinning behaior on the oil recoery hae not been inestigated in detail. When polymer flooding is considered, it is required to ealuate rheological properties of the polymer solution and their effects on the performance of the process. Although fluid iscosity is a critical property in many polymer applications, there is relatiely little published information regarding multi-phase shear-thinning fluid flow in the reseroir or numerical modeling for such analyses [3,1]. Accurate assessment of the potential for polymer flooding projects requires a detailed model on the iscosity of polymer solution as a function of shear rates. The objectie of this work was to ealuate polymer flood processes associated with polymer solutions by adopting a shear-thinning iscosity model for use in reseroir simulation. From simulations using Newtonian and non-newtonian models, the changes in oil recoery are inestigated for multi-layered heterogeneous reseroirs. Parameters considered in this study include coefficients of a shear-thinning iscosity model, heterogeneities of permeability, and the degree of crossflow among

3 Energies 211, 111 layers which are expected to induce different shear rates and affect polymer injection and flood performance in result. 2. Mathematical Theory 2.1. Flow and Viscosity Model Among the most adanced chemical EOR simulators, a general simulator named UTCHEM has proen to be particularly useful for modeling multicomponent and multiphase transport processes [11]. UTCHEM has been extensiely erified by comparing to analytical solutions of simple problems such as Buckley-Leerett flow and tracer transport in the quarter of a 5-spot and experimental measurements for its ability to predict the flow of fluids through the reseroir. Thus, UTCHEM will be used in this study to inestigate shear-thinning effects in arious reseroir models during the simulation of multi-dimensional polymer flood processes for enhanced recoery of remaining oil. The basic mass conseration equation for components can be written as follows [12]: n p ( ϕc κρκ) + ρκ ( Cκlul Dκl) = Rκ (1) t l= 1 where κ is component index, l is phase index including water ( l = 1) and oil ( l = 2 ) phases, φ is porosity, C ~ κ is oerall concentration of component κ (olume fraction), ρ κ is density of component κ (ML 3 ), n p is number of phases, C κ l is concentration of component κ in phase l (olume fraction), u l is Darcy flux of phase l (Lt 1 ), S l is saturation of phase l, R κ is total source/sink term for component κ (olume of component κ per unit olume of porous media per unit time), D κl is dispersion tensor. The oerall concentration ( C ~ κ ) denotes the olume of component κ summed oer all phases. The phase flux from Darcy s law is: kkrl u l = ( pl γ l h) μ (2) l where k is the intrinsic permeability tensor, h the ertical depth, k rl the relatie permeability, μ l the iscosity, and γ l the specific weight for phase l. Relatie permeabilities are modeled based on Corey o functions with parameters of endpoint ( k rl ), exponent ( n l ), and residual saturation ( S lr ). Liquid phase iscosities are important parameters to determine phase fluxes gien by Equation (2). The iscosity of polymer solutions at zero shear rate, μ p, depends on the effectie salinity and polymer concentration and has traditionally been modeled by the Flory-Huggins equation: ( ) 2 3 S p μp = μ w 1 Ap C Ap C Ap C C SEP (3) where C 1 is the polymer concentration in aqueous phase and μ w is the brine iscosity, A pi s are μ p μw constants, C SEP is the effectie salinity, and S p is the slope of μw following equations should be used to calculate the effectie salinity: s. C SEP on a log-log plot. The

4 Energies 211, 1115 C SEP ( β p 1) C51 + C61 = () C 11 where C 51 and C 61 are anion and dialent cation concentration in the aqueous phase and β p is a parameter magnifying the strength of dialent cation concentration. The apparent iscosity decreases with increased shear rate because the polymer molecules are able to align themseles with the shear field to reduce internal friction. An appreciation of the shear-thinning properties of polymer solutions and the calculation of shear rate for each phase leads to apparent iscosity for the solution in the gien reseroir conditions. Meter model is used to account the reduction in the apparent iscosity of shear-thinning fluids as a function of shear rate (γ ): μ μ μ p w p = μw + P 1 γ 1+ γ1/2 where P is an empirical coefficient, and γ 1/ 2 is the alue of shear rate where polymer iscosity is reduced by half. Two primary parameters in Meter s equation are P and γ 1/ 2. The shear rate for phase l is modeled by: γ c ul γ = (6) kk ϕs where γ c is the empirical shear rate coefficient and k is the appropriate aerage permeability. The injectiity of a well, I, is defined as: rl l (5) q inj I = (7) Δ p where q inj is the olumetric injection rate into the well and Δ p is pressure drop between the bottom-hole flowing pressure and reference pressure []. In this study, Δ p is considered as a pressure drop at the well block Sweep Impairment According to AlSofi et al. [3], shear thinning affects sweep mainly by exacerbating the elocity contrast and/or inducing instability. Velocity contrast can be regarded as an additional preferential penetration of shear-thinning fluids in comparison to a Newtonian fluid. A shear-thinning fluid has higher tendency to flow in the high permeability layer due to lower iscosity at higher shear. Some of the preious work deals with an experiment on the core where the effects of shear-thinning behaior are included [9,13]. These studies hae shown that understanding and modeling of polymer rheology in porous media are also important for successful implementation of polymer flood though iscosity of the polymer solution is of far greater releance to sweep. This study has tried to capture the effects of non-newtonian fluid on the sweep, oil recoery, and injectiity in the heterogeneous multilayered reseroir.

5 Energies 211, Modeling While many experimental studies hae examined the rheological stability of EOR polymers, ery few of the data hae been employed for a quantitatie inestigation of the effects of shear-rate dependence on polymer transport in a reseroir and on the performance of polymer EOR processes. The simulation scheme of UTCHEM, together with the apparent iscosity calculation equation allows a more quantitatie prediction of the shear-rate effects. The problem concerns the performance of a polymer flooding process in a three-dimensional oil reseroir that includes the reseroir height, i.e., graity and capillary forces are simultaneously considered. The computational domain consists of a hypothetical site of one-quarter of an injection-well-centered fie-spot. The modeled system used in this study is a square reseroir with a horizontal area of 5 5 ft 2 and a ertical thickness of 25 ft. Vertically, the simulation domain consists of fie layers; and each layer is discretized into grid blocks. Each grid block has dimensions of 3, 3, and 5 ft for x, y, and z directions, respectiely. The outer boundary is represented as a noflow and adiabatic boundary to simulate symmetry in an array. The model assumes that the reseroir is originally saturated with oil and water. Initial saturations of water and oil were assumed constant eerywhere in the reseroir at.3 and.62, respectiely. The iscosities of brine and oil are.73 cp and cp at reseroir condition, respectiely. Permeability heterogeneity is one of the most important factors that leads to low sweep efficiency in oil recoery from petroleum reseroirs. The largest changes in reseroir permeability typically occur in the ertical direction. Simulation studies were performed for simplified fie-layer reseroir model. Horizontal permeabilities are gien in Table 1 from the top to the bottom-layers. The aerage permeability is 1 md. The permeability contrast in ertical to horizontal direction ( k / kh ) is set to be. to 1. to examine the effects of crossflow between layers. Table 1. Permeability of layers. Cases Horizontal Permeabilities (md) σ(lnk) uniform 1, 1, 1, 1, 1 low contrast 19, 122, 1, 2, medium contrast 272, 165, 1, 61, high contrast 739, 272, 1, 37, Water or polymer solution is pumped into the injection well at constant flow rates q inj = 1 ft 3 /day and continued oer a simulation period of 125 days. The reseroir fluids are recoered from the production well constrained with pressure at 1 psia, the same pressure as the initial reseroir pressure. In order to clarify the effects of shear-rate dependence during the flow of polymer solution through the reseroir, comparisons were made among results from simulations under different fluid and reseroir models of polymer flood. Input parameters for the simulations are mainly obtained from an earlier simulation study presented in the reference [1] and define the physical properties of reseroir, fluid properties, and chemical properties, as gien in Table 2.

6 Energies 211, 1117 Table 2. Input parameters for simulation. (a) properties of reseroir rock and fluids; (b) polymer properties. Rock Relatie permeability Fluids Viscosity (a) porosity (φ).2 depth 2 ft permeability (k) horizontal ( k h ) 1 md ratio (k /k h ). 1. compressibility (c r ) psi 1 o water ( k o rw ).2 endpoint ( k rl ) oil ( k ) 1. exponent ( n l ) residual saturation ( S lr ) iscosity (μ) density (ρ) compressibility parameters for zero shear iscosity parameters for effectie salinity parameters for shear rate dependence (b) o ro water ( n w ) 1.5 oil ( n o ) 2. water ( S lw ).2 oil ( S lo ).2 water (μ w ).73 cp oil (μ o ) cp water (ρ w ).3353 psi/ft oil (ρ o ).3539 psi/ft water (c w ) psi 1 oil (c o ) psi 1 A p1 3.7 wt% 1 A p2 16 wt% 2 A p3 wt% 3 β p for C SEP 2 C SEP, min.1 meq/ml slope of μ p s. C SEP.3 γ c 13 γ 1/ 2 2 s 1 P day( darcy) 1 2 ft s. Results and Discussion The model ealuated the flow of brine associated with polymer and oil through a reseroir during the process. In the runs, oil of cp was displaced with brine or brine with polymer injected at constant rate. Polymer concentration changes from.1 to.%, being graded in the chase water. The salinities of reseroir connate water and injected water are same. Figure 1 shows concentration data used in the simulations. To understand the effects of arious parameters on the oil recoery, simulation was performed with the injection sequence of polymer flooding followed by waterflooding.

7 Energies 211, 111 Figure 1. History of polymer concentration in the injecting water..12 Polymer Concentration (wt%) P Dependency The simulation results obtained from the highly heterogeneous case with P = 1. and 2.6 are compared. Figures 2 and 3 shows the saturation of oil phase and iscosity in the aqueous phase for layers 1, 3 and 5 at 123 days or.957 pore olume injected. Due to permeability heterogeneity, a clear elocity contrast exists between layers. Therefore, shear-thinning property of polymer solution affects front location and production performance. For the case of P = 2. 6, a greater distance separates the fronts between the most and least permeable layers. Comparisons of aqueous phase iscosities in layers 1, 3, and 5 predicted from the simulations are gien in Figure 3. Due to permeability of each layer, the fronts were at arious distances from the injection well. Injection of shear-thinning fluid leads to significantly lower iscosity near the injection well where shear rate is higher. The iscosity decreases gradually behind the front due to higher shear rate near the injection well irrespectie of almost same polymer concentration. Howeer, the iscosity of Newtonian fluid is directly proportional to the polymer concentration in aqueous phase. Figure 2. Oil phase saturation of layers 1, 3, and 5 at 1,23 days for k / = and ( ln k) = σ with different P : (a) P = 1. ; (b) P = (a) k h

8 Energies 211, 1119 Figure 2. Cont (b)

9 Energies 211, 112 Figure 3. Water phase iscosity of layers 1, 3, and 5 at 1,23 days for k / = and ( ln k) = σ with different P. (a) P = 1. ; (b) P = (a) k h (b)

10 Energies 211, 1121 Figure 3. Cont Figure compares estimated polymer concentrations in layer 5 for Newtonian and shear-thinning solutions. At later time, the concentration at the front located far from the injection well is equal to or less than the injection concentration due to dispersion inside the reseroir. Howeer, the iscosity increases due to lower shear rate as the front of shear-thinning fluid has a certain distance from the injection well and moes at much lower elocity to the production well. A comparison of the two iscosity distribution indicates a clear difference between the floods with the Newtonian and shear-thinning fluids. Seeral cases were studied in which the sensitiity of oil recoery and water-oil ratio to the consideration of P in ealuating fluid iscosity μ κ and heterogeneity of layered reseroir was determined. Differences in oil recoery and water-oil ratio were compared oer production period. Simulation studies on the performance of polymer flood hae been carried out with the dependency of fluid iscosities on the P parameter in the reseroir without crossflow. Four cases were considered in which the P parameters were aried from 1. (Newtonian) to 2.6. Figure. Polymer concentration in water phase of layer 5 at 1,23 days for k / = and ( ln k) = σ with different P. (a) P = 1.. (b) P = k h (a) (b)

11 Energies 211, 1122 Figures 5a d show oil recoery and water-oil ratio in ft 3 /ft 3 of polymer flood predicted from simulations for constant flow rate. As can be seen, oil recoery decreases less than 3% by non-newtonian behaior in homogeneous reseroir. Figure 5. History of production wells obtained from simulations for k / k h = with different P and permeability heterogeneity. (a) σ ( ln k) = ; (b) σ ( ln k) = ; (c) σ ( ln k) =. 72 ; (d) ( ln k ) = σ. (a). 16 Cummulatie Oil Recoery.6..2 P Parameter Water-Oil Ratio 12 P Parameter (b). 12 Cummulatie Oil Recoery.6..2 P Parameter Water-Oil Ratio P Parameter

12 Energies 211, 1123 Figure 5. Cont. (c). 2 Cummulatie Oil Recoery.6..2 P Parameter Water-Oil Ratio P Parameter (d). 1 Cummulatie Oil Recoery.6..2 P Parameter Water-Oil Ratio 6 2 P Parameter The results become a lot more sensitie to change in σ ln k become larger. Reseroir heterogeneity seems to hae a pronounced effect on the tertiary oil recoery efficiency. For the case of σ ( ln k) =. 3156, the cumulatie oil recoery decreases more than 22% from.5699 to.379. For highly heterogeneous reseroir, the recoery decreases more than 3%. Shear-thinning properties also increase water-oil ratio. This obseration results from the fact that rapid increase in WOR occurs due to polymer solution s preferential penetration into high permeability layer due to lower iscosity near the injection well. Therefore, a larger decrease in oil recoery is obsered for shear-thinning fluid injected into highly-heterogeneous reseroirs..2. Crossflow P alues as ( ) In attempts to inestigate effects of crossflow, four cases of polymer flooding were run in which the ratio of ertical to horizontal permeability was aried from. to 1.. Figures 5a,b show results of

13 Energies 211, 112 polymer flood k / kh for a highly heterogeneous reseroir of σ ( ln k) = in which the relatie difference among results are largest. As shown in Figure 6, lower oil recoery and rapid increase in WOR are obtained with smaller k / k h alue. When polymer solution is injected into a stratified reseroir with layers of widely differing permeability, the oil recoery is dominated by crossflow due to combined effects of iscosity-deried pressure gradients and graity. Sufficient ertical permeability allows injected fluid to induce crossflow in reseroir. As the ertical permeability increases, oil migrates to other layers more easily, where it is swept by the displacing water to the producing well. An increased oil recoery and decreased WOR is obtained due to an increase in the degree of crossflow. Figure 6. History of production wells obtained from simulations for heterogeneous reseroir of σ ( ln k) = with different P and k / kh. (a) P = 1. (Newtonian fluid); (b) P = (a).5 3 Cummulatie Oil Recoery..3.2 k /k h Water-Oil Ratio 2 1 k /k h (b) Cummulatie Oil Recoery..3.2 k /k h Water-Oil Ratio 6 k /k h

14 Energies 211, 1125 The larger P is, the clearer this trend becomes. A comparison of oil recoery indicates that the higher alue of k / kh results in increasing recoery more than 5% from.335 to.7 for Newtonian fluid and more than twice from.2321 to.793 for P = Howeer, the changes in cumulatie oil recoery and WOR become smaller if k / kh is larger than.1. These results again demonstrate that the parameters of a iscosity model must be taken into account when estimating the performance of polymer floods..3. Injection Rate The iscosity behaior of polymer solution in the reseroir was also studied at different injection rates. The aim of this simulation was to ealuate the oil recoery and injection pressure gien P alues with different injection or production flow rates. The calculations were performed for well and reseroir configuration which is the same as the base case (uniform permeability). The flow rates are changed to 5, 15, and 3 ft 3 /day, which correspond to.15,.5, and.9 pore olume injected during the simulation period, respectiely. Figures 7a,b compare oil recoery and injectiity from the numerical calculations for P = 1.5 and 2.6. For the case of P = 1. 5 which is close to Newtonian polymer solution, the range in injection pressure is proportionally increased with increased injection rate as expected from Darcy s law and the injectiity remains almost same. The larger the P alue is, the lower the injectiity is. The aerage injection pressure increased by 6.3 times from 571 psi to 35,999 psi for P = 1. 5 and only 3.3 times from 6516 psi to 21, psi for P = 2. 6 during initial 2.5 years of polymer injection. Therefore, considerable differences in injectiity are obtained with arious flow rates for P = If maximum injection pressure constraint is imposed on the injection well to aoid fracturing, the oil recoery will be lower in the case of injecting Newtonian fluid. Figure 7. History of injection and production wells obtained from simulations for homogeneous reseroir with different P. (a) P = 1. 5 ; (b) P = (a).5.6 Cummulatie Oil Recoery Injection Rate(ft 3 /day) Injectity (ft 3 /day/psi)..2 Injection Rate(ft 3 /day)

15 Energies 211, 1126 Figure 7. Cont. (b).5.6 Cummulatie Oil Recoery Injection Rate(ft 3 /day) Injectiity (ft 3 /day/psi)..2 Injection Rate(ft 3 /day) The results suggest that, eerything else being the same, the use of polymer solution with large P (i.e., high shear-thinning) is a promising flow condition due to relatiely improed injectiity. This obseration emphasizes the importance of ensuring that the adequate iscosity model is used, taking into account the shear-thinning effects at high flow rate. 5. Conclusions Though iscosity of the polymer solution is of far more importance to sweep, the understanding and modeling of rheology of polymer solutions are also important for an accurate prediction of polymer flood in a heterogeneous multilayered reseroir. Through extensie simulations in a hypothetical 5-point pattern reseroir with a iscosity model including shear-thinning effects, the effects of arious parameters of iscosity model, reseroir, and operation on the performance of polymer flood are examined. From a series of polymer flooding simulations carried out in this work in order to ealuate the oil recoery efficiency of a polymer flooding process in a reseroir, the following conclusions were deried through numerical ealuation of the results. The simulation scheme with the iscosity reduction at higher shear rate allows a more quantitatie prediction of reseroir performance. Shear-thinning behaior does not affect the oil recoery significantly for homogeneous reseroir. Howeer, oil recoery decreases a lot for larger P alues due to elocity contrast among layers as reseroir heterogeneity becomes larger. With an increase in the degree of crossflow, oil migrates to other layers more easily due to higher sweep by the displacing fluid. This trend becomes clearer by considering shear-thinning behaior of polymer solution. Non-Newtonian fluid rheology also affects the injectiity directly because different pressure gradient alter the apparent iscosity of displacing fluid due to change in flow rate and shear rate. From numerical study carried out with arious injection rates, it was obsered that a shear-thinning fluid with large P coefficient would increase injectiity significantly, though at low flow rates, shear-thinning impact is limited. The results from extensie simulations demonstrate that the

16 Energies 211, 1127 parameters of a iscosity model must be taken into account when estimating the performance of polymer floods. Acknowledgements This work was supported by the Energy Efficiency & Resources of the Korea Institute of Energy Technology Ealuation and Planning (KETEP) grant funded by the Korea Goernment Ministry of Knowledge Economy. References 1. Needham, R.B.; Doe, P.H. Polymer flooding reiew. J. Pet. Technol. 197, 39, Taylor, K.C.; Nasr-El-Din, H.A. Water-soluble hydrophobically associating polymers for improed oil recoery: A literature reiew. J. Pet. Sci. Eng. 199, 19, AlSofi, A.M.; LaForce, T.C.; Blunt, M.J. Sweep Impairment Due to Polymers Shear Thinning. In Proceedings of the SPE Middle East Oil and Gas Show and Conference, Bahrain, Bahrain, 15 1 March 29; Paper Number SPE MS.. Lake, L.W. Enhanced Oil Recoery; Prentice Hall: Englewood Cliffs, NJ, USA, Clifford, P.J.; Sorbie, K.S. The Effects of Chemical Degradation on Polymer Flooding. In Proceedings of the SPE Oilfield and Geothermal Chemistry Symposium, Phoenix, AZ, USA, 9 11 March 195; Paper Number SPE 1356-MS. 6. Dong, H.Z.; Fang, S.F.; Wang, D.M.; Wang, J.Y.; Liu, Z.; Hong, W.H. Reiew of Practical Experience & Management by Polymer Flooding at Daqing. In Proceedings of SPE/DOE Symposium on Improed Oil Recoery, Tulsa, OK, USA, 2 23 April 2; Paper Number SPE 1132-MS. 7. Seright, R.S.; Seheult, J.M.; Talashek, T. Injectiity characteristics of EOR polymers. SPE Reser. Eal. Eng. 29, 12, Seright, R.S.; Fan, T.; Warik, K.; Balaban, R.C. New insights into polymer rheology in porous media. SPE J. 211, 16, Seright, R.S. Potential for polymer flooding reseroirs with iscous oils. SPE Reser. Eal. Eng. 21, 13, Gleasure, R.W.; Phillips, C.R. An experimental study of non-newtonian polymer rheology effects on oil recoery and injectiity. SPE Reser. Eng. 199, 5, Reseroir Engineering Research Program, Center for Petroleum and Geosystems Engineering. UTCHEM-9. A Three-Dimensional Chemical Flood Simulator; Uniersity of Texas at Austin: Austin, TX, USA, Delshad, M.; Pope, G.A.; Sepehrnoori, K. A compositional simulator for modeling surfactant enhanced aquifer remediation, 1 fomulation. J. Contam. Hydrol. 1996, 23, Delshad, M.; Kim, D.H.; Magbagbeola, O.A.; Huh, C.; Pope, G.A.; Tarahhom, F. Mechanistic Interpretation and Utilization of Viscoelastic Behaior of Polymer Solutions for Improed Polymer-Flood Efficiency. In Proceedings of SPE/DOE Symposium on Improed Oil Recoery, Tulsa, OK, USA, 2 23 April 2; Paper Number SPE 1356-MS.

17 Energies 211, Anderson, G.A. Simulation of Chemical Flood Enhanced Oil Recoery Process Including the Effects of Reseroir Wettability. Master Thesis, Uniersity of Texas at Austin, Austin, TX, USA, by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creatie Commons Attribution license (