Bulk and Surface Aqueous Speciation of Calcite: Implications for Low-Salinity Waterflooding of Carbonate Reservoirs
- Maxim P. Yutkin (King Abdullah University of Science and Technology) | Himanshu Mishra (King Abdullah University of Science and Technology) | Tadeusz W. Patzek (King Abdullah University of Science and Technology) | John Lee (University of California) | Clayton J. Radke (University of California)
- Document ID
- Society of Petroleum Engineers
- SPE Journal
- Publication Date
- February 2018
- Document Type
- Journal Paper
- 84 - 101
- 2018.Society of Petroleum Engineers
- Carbonates, Surface, Calcite, Waterflood, Equilibrium
- 2 in the last 30 days
- 442 since 2007
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Low-salinity waterflooding (LSW) is ineffective when reservoir rock is strongly water-wet or when crude oil is not asphaltenic. Success of LSW relies heavily on the ability of injected brine to alter surface chemistry of reservoir crude-oil brine/rock (COBR) interfaces. Implementation of LSW in carbonate reservoirs is especially challenging because of high reservoir-brine salinity and, more importantly, because of high reactivity of the rock minerals. Both features complicate understanding of the COBR surface chemistries pertinent to successful LSW. Here, we tackle the complex physicochemical processes in chemically active carbonates flooded with diluted brine that is saturated with atmospheric carbon dioxide (CO2) and possibly supplemented with additional ionic species, such as sulfates or phosphates.
When waterflooding carbonate reservoirs, rock equilibrates with the injected brine over short distances. Injected-brine ion speciation is shifted substantially in the presence of reactive carbonate rock. Our new calculations demonstrate that rock-equilibrated aqueous pH is slightly alkaline quite independent of injected-brine pH. We establish, for the first time, that CO2 content of a carbonate reservoir, originating from CO2-rich crude oil and gas, plays a dominant role in setting aqueous pH and rock-surface speciation.
A simple ion-complexing model predicts the calcite-surface charge as a function of composition of reservoir brine. The surface charge of calcite may be positive or negative, depending on speciation of reservoir brine in contact with the calcite. There is no single point of zero charge; all dissolved aqueous species are charge determining. Rock-equilibrated aqueous composition controls the calcite-surface ion-exchange behavior, not the injected-brine composition. At high ionic strength, the electrical double layer collapses and is no longer diffuse. All surface charges are located directly in the inner and outer Helmholtz planes.
Our evaluation of calcite bulk and surface equilibria draws several important inferences about the proposed LSW oil-recovery mechanisms. Diffuse double-layer expansion (DLE) is impossible for brine ionic strength greater than 0.1 molar. Because of rapid rock/brine equilibration, the dissolution mechanism for releasing adhered oil is eliminated. Also, fines mobilization and concomitant oil release cannot occur because there are few loose fines and clays in a majority of carbonates. LSW cannot be a low-interfacial-tension alkaline flood because carbonate dissolution exhausts all injected base near the wellbore and lowers pH to that set by the rock and by formation CO2. In spite of diffuse double-layer collapse in carbonate reservoirs, surface ion-exchange oil release remains feasible, but unproved.
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Al-Shalabi, E. W., Sepehrnoori, K., and Pope, G. 2014. Geochemical Interpretation of Low Salinity Water Injection in Carbonate Oil Reservoirs. Presented at the SPE Improved Oil Recovery Symposium, Tulsa, 12–16 April. SPE-169101-MS. https://doi.org/10.2118/169101-MS.
Alotaibi, M. B. and Yousef, A. A. 2015. The Impact of Dissolved Species on the Reservoir Fluids and Rock Interactions in Carbonates. Presented at the SPE Saudi Arabia Section Annual Technical Symposium and Exhibition, Al-Khobar, Saudi Arabia, 21–23 April. SPE-177983-MS. https://doi.org/10.2118/177983-MS.
Alotaibi, M. B., Nasr-El-Din, H. A., and Fletcher, J. 2011. Electrokinetics of Limestone and Dolomite Rock Particles. SPE Res Eval & Eng 14 (5): 594–603. SPE-148701-PA. https://doi.org/10.2118/148701-PA.
Alshakhs, M. J. and Kovscek, A. R. 2015. An Experimental Study of the Impact of Injection Water Composition on Oil Recovery from Carbonate Rocks. Presented at SPE Annual Technical Conference and Exhibition, Houston, 28–30 September. SPE-175147-MS. https://doi.org/10.2118/175147-MS.
Arvidson, R. S., Ertan, I. E., Amonette, J. E. et al. 2003. Variation in Calcite Dissolution Rates: A Fundamental Problem? Geochim. Cosmochim. Ac. 67 (9):1623–1634, 2003. https://doi.org/10.1016/S0016-7037(02)01177-8.
Austad, T., Shariatpanahi, S. F., Strand, S. et al. 2015. Low Salinity EOR Effects in Limestone Reservoir Cores Containing Anhydrite: A Discussion of the Chemical Mechanism. Energ. Fuel. 29 (11): 6903–6911. https://doi.org/10.1021/acs.energyfuels.5b01099.
Berg, J. C. 2010. An Introduction to Interfaces & Colloids: The Bridge to Nanoscience. Singapore: World Scientific.
Bird, R. B., Stewart, W. E., and Lightfoot, E. N. 2007. Transport Phenomena, second edition. New York City: Wiley.
Brady, P. V., Morrow, N. R., Fogden, A. et al. 2015. Electrostatics and the Low Salinity Effect in Sandstone Reservoirs. Energ. Fuel. 29 (2): 666–677. https://doi.org/10.1021/ef502474a.
Buckley, J. S. and Morrow, N. R. 2010. Improved Oil Recovery by Low Salinity Waterflooding: A Mechanistic Review. Oral presentation given at the 11th International Symposium on Evaluation of Wettability and Its Effect on Oil Recovery, Calgary, 6–9 September.
Chandrasekhar, S. and Mohanty, K. K. 2013. Wettability Alteration with Brine Composition in High Temperature Carbonate Reservoirs. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, 30 September–2 October. SPE-166280-MS. https://doi.org/10.2118/166280-MS.
Charlton, S. R. and Parkhurst, D. L. 2011. Modules Based On the Geochemical Model PHREEQC for Use in Scripting and Programming Languages. Comput. Geosci. 37 (10): 1653–1663. https://doi.org/10.1016/j.cageo.2011.02.005.
Chou, L., Garrels, R. M., and Wollast, R. 1989. Comparative Study of the Kinetics and Mechanisms of Dissolution of Carbonate Minerals. Chem. Geol. 78 (3–4): 269–282. https://doi.org/10.1016/0009-2541(89)90063-6.
Cubillas, P., Köhler, S., Prieto, M. et al. 2005. Experimental Determination of the Dissolution Rates of Calcite, Aragonite, and Bivalves. Chem. Geol. 216 (1–2): 59–77. https://doi.org/10.1016/j.chemgeo.2004.11.009.
Davies, C. W. 1962. Ion Association. Oxford, UK: Butterworths.
Davis, J., James, R., and Leckie, J. 1978. Surface Ionization and Complexation at the Oxide/Water Interface: I. Computation of Electrical Double Layer Properties in Simple Electrolytes. J. Colloid Interf. Sci. 63 (3): 480–499. https://doi.org/10.1016/S0021-9797(78)80009-5.
Davis, J. A. and Kent, D. B. 1990. Surface Complexation Modeling in Aqueous Geochemistry. Rev. Mineral. Geochem. 23 (1): 177–260.
Dzombak, D. A. and Morel, F. M. M. 1990. Surface Complexation Modeling: Hydrous Ferric Oxide. Hoboken, New Jersey: John Wiley & Sons.
Eisenlohr, L., Meteva, K., Gabrovšek, F. et al. 1999. The Inhibiting Action of Intrinsic Impurities in Natural Calcium Carbonate Minerals to Their Dissolution Kinetics in Aqueous H2OCO2 Solutions. Geochim. Cosmochim. Ac. 63 (78): 989–1001. https://doi.org/10.1016/S0016-7037(98)00301-9.
Fathi, S. J., Austad, T., and Strand, S. 2010. “Smart Water” as a Wettability Modifier in Chalk: The Effect of Salinity and Ionic Composition. Energ. Fuel. 24 (4): 2514–2519. https://doi.org/10.1021/ef901304m.
Felder, R. M., Rousseau, R. W., and Bullard, L. G. 2015. Elementary Principles of Chemical Processes, fourth edition. New York City: Wiley.
Fenter, P., Geissbühler, P., Dimasi, E. et al. 2000. Surface Speciation of Calcite Observed In Situ by High-Resolution X-Ray Reflectivity. Geochim. Cosmochim. Ac. 64 (7): 1221–1228. https://doi.org/10.1016/S0016-7037(99)00403-2.
Folk, R. L. 1959. Practical Petrographic Classification of Limestones. AAPG Bull. 43 (1): 1–38. https://doi.org/10.1306/0BDA5C36-16BD-11D7-8645000102C1865D.
Folk, R. L. 1962. Spectral Subdivision of Limestone Types. In Memoir 1: Classification of Carbonate Rocks – A Symposium, AAPG Special Volumes, ed. W. E. Ham, 62–84. Tulsa: American Association of Petroleum Geologists.
Geissbühler, P., Fenter, P., DiMasi, E. et al. 2004. Three-Dimensional Structure of the Calcite-Water Interface by Surface X-Ray Scattering. Surf. Sci. 573 (2): 191–203. https://doi.org/10.1016/j.susc.2004.09.036.
Grahame, D. C. 1947. The Electrical Double Layer and the Theory of Electrocapillarity. Chem. Rev. 41 (3): 441–501. https://doi.org/10.1021/cr60130a002.
Heberling, F., Trainor, T. P., Lützenkirchen, J. et al. 2011. Structure and Reactivity of the Calcite-Water Interface. J. Colloid Interf. Sci. 354 (2): 843–857. https://doi.org/10.1016/j.jcis.2010.10.047.
Hiemstra, T. and Riemsdijk, W. H. 1996. A Surface Structural Approach to Ion Adsorption: The Charge Distribution (CD) Model. J. Colloid Interf. Sci. 179 (2): 488–508. https://doi.org/10.1006/jcis.1996.0242.
Hiorth, A., Cathles, L. M., and Madland, M. V. 2010. The Impact of Pore Water Chemistry on Carbonate Surface Charge and Oil Wettability. Transport Porous Med. 85 (1): 1–21. https://doi.org/10.1007/s11242-010-9543-6.
Jadhunandan, P. P. and Morrow, N. R. 1995. Effect of Wettability on Waterflood Recovery for Crude-Oil/Brine/Rock Systems. SPE Res Eval & Eng 10 (1): 40–46. SPE-22597-PA. https://doi.org/10.2118/22597-PA.
Kerisit, S. and Parker, S. C. 2004. Free Energy of Adsorption of Water and Calcium on the  Calcite Surface. Chem. Commun. 1: 52–53. https://doi.org/10.1039/b311928a.
Kim, S. and Santamarina, J. C. 2016. Geometry-Coupled Reactive Fluid Transport at the Fracture Scale: Application to CO2 Geologic Storage. Geofluids 16 (2): 329–341. https://doi.org/10.1111/gfl.12152.
Lager, A., Webb, K. J., and Black, C. J. J. 2007. Impact of Brine Chemistry on Oil Recovery Experiments. Oral presentation given at IOR 2007 – the 14th European Symposium on Improved Oil Recovery, Cairo, 2–224 April.
Lager, A., Webb, K. J., Black, C. J. J. et al. 2006. Low Salinity Oil Recovery – An Experimental Investigation. Oral presentation of paper SCA2006-36 given at the International Symposium of the Society of Core Analysts, Trondheim, Norway, 12–16 September.
Lager, A., Webb, K. J., Black, C. J. J. et al. 2008a. Low Salinity Oil Recovery - An Experimental Investigation. Petrophysics 49 (1): 28–35. SPWLA-2008-v49n1a2.
Lager, A., Webb, K. J., Collins, R. I. et al. 2008b. LoSal Enhanced Oil Recovery: Evidence of Enhanced Oil Recovery at the Reservoir Scale. Presented at the SPE Symposium on Improved Oil Recovery, Tulsa, 19–23 April. SPE-113976-MS. https://doi.org/10.2118/113976-MS.
Lasaga, A. C. and Luttge, A. 2001. Variation of Crystal Dissolution Rate Based on a Dissolution Stepwave Model. Science 291 (5512): 2400–2404. https://doi.org/10.1126/science.1058173.
Lasaga, A. C., Soler, J. M., Ganor, J. et al. 1994. Chemical Weathering Rate Laws and Global Geochemical Cycles. Geochim. Cosmochim. Ac. 58 (10): 2361–2386. https://doi.org/10.1016/0016-7037(94)90016-7.
Lashkarbolooki, M., Riazi, M., Hajibagheri, F. et al. 2016. Low Salinity Injection into Asphaltenic-Carbonate Oil Reservoir, Mechanistical Study. J. Mol. Liq. 216 (April): 377–386. https://doi.org/10.1016/j.molliq.2016.01.051.
Levine, S., Mingins, J., and Bell, G. M. 1967. The Discrete-Ion Effect in Ionic Double-Layer Theory. J. Electroanal. Chem. 13 (3): 280–329. https://doi.org/10.1016/0022-0728(67)80125-6.
Lu, P., Wang, Q., Chen, T. et al. 2016. A New Approach for Modeling Scale Formation during Water Injection into Carbonate Reservoirs. Presented at the SPE Kingdom of Saudi Arabia Annual Technical Symposium and Exhibition, Dammam, Saudi Arabia, 25–28 April. SPE-182762-MS. https://doi.org/10.2118/182762-MS.
Lucia, F. J. 2007. Carbonate Reservoir Characterization: An Integrated Approach, second edition. Berlin: Springer Berlin Heidelberg
MATLAB, version 8.6 (R2015b). 2015. Natick, Massachusetts: The MathWorks, Inc.
Möller, P. and Sastri, C. S. 1974. Estimation of the Number of Surface Layers of Calcite Involved in Ca-45Ca Isotopic Exchange with Solution. Int. J. Res. Phys. Chem. Chem. Phys. 89 (1–4):80–87. https://doi.org/10.1524/zpch.1974.89.1-4.080.
Möller, P. and Werr, G. 1972. Influence of Anions on Ca2+ – Mg2+ Surface Exchange Process on Calcite in Artificial Sea Water. Radiochim. Ac. 18 (3): 144–147. https://doi.org/10.1524/ract.19126.96.36.199.
Morrow, N. R. and Buckley, J. 2013. Improved Oil Recovery by Low-Salinity Waterflooding. J Pet Technol 63 (5): 106–112. SPE-129421-JPT. https://doi.org/10.2118/129421-JPT.
Morse, J. W. and Arvidson, R. S. 2002. The Dissolution Kinetics of Major Sedimentary Carbonate Minerals. Earth Sci. Rev. 58 (1–2): 51–84. https://doi.org/10.1016/S0012-8252(01)00083-6.
Mugele, F., Siretanu, I., Kumar, N. et al. 2016. Insights From Ion Adsorption and Contact-Angle Alteration at Mineral Surfaces for Low-Salinity Waterflooding. SPE J. 21 (4): 1204–1213. SPE-169143-PA. https://doi.org/10.2118/169143-PA.
Myint, P. C. and Firoozabadi, A. 2015. Thin Liquid Films in Improved Oil Recovery from Low-Salinity Brine. Curr. Opin. Colloid Interf. Sci. 20 (2): 105–114. https://doi.org/10.1016/j.cocis.2015.03.002.
Nasralla, R. A. and Nasr-El-Din, H. A. 2012. Double-Layer Expansion: Is It a Primary Mechanism of Improved Oil Recovery by Low-Salinity Waterflooding? Presented at the SPE Improved Oil Recovery Symposium, Tulsa, 14–18 April. SPE-154334-MS. https://doi.org/10.2118/154334-MS.
Newman, J. and Thomas-Alyea, K. 2004. Electrochemical Systems, third edition. Hoboken, New Jersey: John Wiley & Sons.
Nystrom, R. 2001. The Influence of Na+, Ca2+, Ba2+, and La3+ on the ζ Potential and the Yield Stress of Calcite Dispersions. J. Colloid Interf. Sci. 242 (1): 259–263. https://doi.org/10.1006/jcis.2001.7766.
Palandri, J. L. and Kharaka, Y. K. 2004. A Compilation of Rate Parameters of Water-Mineral Interaction Kinetics for Application to Geochemical Modeling. US Geological Survey Open File Report of 2004-1068, National Energy Technology Laboratory, US Department of Energy, Menlo Park, California, March 2004.
Parkhurst, D. and Apello, C. 2014. Description of Input and Examples for Phreeqc Version 3: A Computer Program for Speciation, Batch-reaction, One-Dimensional Transport, and Inverse Geochemical Calculations. Createspace Independent Publishing Platform.
Peng, J., Tang, G.-Q., and Kovscek, A. 2009. Oil Chemistry and Its Impact on Heavy Oil Solution Gas Drive. J. Pet. Sci. Eng. 66 (1–2): 47–59. https://doi.org/10.1016/j.petrol.2009.01.005.
Pierre, A., Lamarche, J. M., Mercier, R. et al. 1990. Calcium as Potential Determining Ion in Aqueous Calcite Suspensions. J. Dispers. Sci. Technol. 11 (6): 611–635. https://doi.org/10.1080/01932699008943286.
Plummer, L. N., Wigley, T. M. L., and Parkhurst, D. L. 1978. The Kinetics of Calcite Dissolution in CO2-Water Systems at 5 degrees to 60 degrees C and 0.0 to 1.0 atm CO2. Am. J. Sci. 278 (2): 179–216. https://doi.org/10.2475/ajs.278.2.179.
Pokrovsky, O. S., Mielczarski, J. A., Barres, O. et al. 2000. Surface Speciation Models of Calcite and Dolomite/Aqueous Solution Interfaces and Their Spectroscopic Evaluation. Langmuir 16 (6): 2677–2688. https://doi.org/10.1021/la980905e.
Puntervold, T., Strand, S., Ellouz, R. et al. 2015. Modified Seawater as a Smart EOR Fluid in Chalk. J. Pet. Sci. Eng. 133 (September): 440–443. https://doi.org/10.1016/j.petrol.2015.06.034.
Qiao, C., Johns, R., and Li, L. 2016. Understanding the Chemical Mechanisms for Low Salinity Waterflooding. Presented at SPE Europec featured at the 78th EAGE Conference and Exhibition, Vienna, Austria, 30 May–2 June. SPE-180138-MS. https://doi.org/10.2118/180138-MS.
Qiao, C., Li, L., Johns, R. T. et al. 2014. A Mechanistic Model for Wettability Alteration by Chemically Tuned Water Flooding in Carbonate Reservoirs. Presented at the SPE Annual Technical Conference and Exhibition, Amsterdam, 27–29 October. SPE-170966-MS. https://doi.org/10.2118/170966-MS.
Rezaeidoust, A., Puntervold, T., Strand, S. et al. 2009. Smart Water as Wettability Modifier in Carbonate and Sandstone: A Discussion of Similarities/Differences in the Chemical Mechanisms. Energ. Fuel. 23 (9): 4479–4485. https://doi.org/10.1021/ef900185q.
Ricci, M., Spijker, P., Stellacci, F. et al. 2013. Direct Visualization of Single Ions in the Stern Layer of Calcite. Langmuir 29 (7): 2207–2216. https://doi.org/10.1021/la3044736.
Sakuma, H., Andersson, M. P., Bechgaard, K. et al. 2014. Surface Tension Alteration on Calcite, Induced by Ion Substitution. J. Phys. Chem. C 118 (6): 3078–3087. https://doi.org/10.1021/jp411151u.
Salem, M. R., Mangood, A. H., and Hamdona, S. K. 1994. Dissolution of Calcite Crystals in the Presence of Some Metal Ions. J. Mater. Sci. 29 (24): 6463–6467. https://doi.org/10.1007/BF00354005.
Setschenow, Z. 1899. Ueber die Constitution der Salzlösungen auf Grund ihres Verhaltens zur Kohlensäure. Z. Chem. Physik 4: 117–120.
Sheng, J. J. 2014. Critical Review of Low-Salinity Waterflooding. J. Pet. Sci. Eng. 120 (August): 216–224. https://doi.org/10.1016/j.petrol.2014.05.026.
Siffert, D. and Fimbel, P. 1984. Parameters Affecting the Sign and Magnitude of the Eletrokinetic Potential of Calcite. Colloid. Surface 11 (3–4): 377–389. https://doi.org/10.1016/0166-6622(84)80291-7.
Sjöblom, J., Simon, S., and Xu, Z. 2015. Model Molecules Mimicking Asphaltenes. Adv. Colloid Interf. 218 (April): 1–16. https://doi.org/10.1016/j.cis.2015.01.002.
Somasundaran, P. and Agar, G. E. 1967. The Zero Point of Charge of Calcite. J. Colloid Interf. Sci. 24 (4): 433–440. https://doi.org/10.1016/0021-9797(67)90241-X.
Sorbie, K. S. and Collins, I. R. 2010. A Proposed Pore-Scale Mechanism for How Low Salinity Waterflooding Works. Presented at the SPE Improved Oil Recovery Symposium, Tulsa, 24–28 April. SPE-129833-MS. https://doi.org/10.2118/129833-MS.
Sposito, G. 2008. The Chemistry of Soils. Oxford, UK: Oxford University Press.
Strand, S., Høgnesen, E. J., and Austad, T. 2006. Wettability Alteration of Carbonates—Effects of Potential Determining Ions (Ca2+ and SO2–4) and Temperature. Colloid. Surface. A 275 (1–3): 1–10. https://doi.org/10.1016/j.colsurfa.2005.10.061.
Stumm, W. and Morgan, J. J. 1996. Aquatic Chemistry: Chemical Equilibria and Rates in Natural Waters, third edition. Environmental Science and Technology. Hoboken, New Jersey: John Wiley & Sons.
Tang, G.-Q. and Morrow, N. R. 1997. Salinity, Temperature, Oil Composition, and Oil Recovery by Waterflooding. SPE Res Eval & Eng 12 (4): 269–276. SPE-36680-PA. https://doi.org/10.2118/36680-PA.
Tang, G.-Q. and Morrow, N. R. 1999. Influence of Brine Composition and Fines Migration on Crude Oil/Brine/Rock Interactions and Oil Recovery. J. Pet. Sci. Eng. 24 (2–4): 99–111. https://doi.org/10.1016/S0920-4105(99)00034-0.
Tang, G.-Q. and Morrow, N. R. 2002. Injection of Dilute Brine and Crude Oil/Brine/Rock Interactions. In Environmental Mechanics: Water, Mass and Energy Transfer in the Biosphere, Geophysical Monograph Series, Vol. 129, ed. P. A. C. Raats, D. Smiles, and A. W. Warrick, 171–179. https://doi.org/10.1029/129GM16.
Thompson, D. W. and Pownall, P. G. 1989. Surface Electrical Properties of Calcite. J. Colloid Interf. Sci. 131 (1): 74–82. https://doi.org/10.1016/0021-9797(89)90147-1.
Truesdell, A. H. and Jones, B. F. 1974. Wateq, a Computer Program for Calculating Chemical Equilibria of Natural Waters. J. Res. US Geol. Survey 2 (2): 233–274.
Van Cappellen, P., Charlet, L., Stumm, W. et al. 1993. A Surface Complexation Model of the Carbonate Mineral-Aqueous Solution Interface. Geochim. Cosmochim. Ac. 57 (15): 3505–3518. https://doi.org/10.1016/0016-7037(93)90135-J.
Verwey, E. J. W. and Overbeek, J. T. G. 1948. Theory of the Stability of Lyophobic Colloids: The Interaction of Sol Particles Having an Electric Double Layer. New York: Elsevier Publishing Company.
Webb, K., Black, C., and Al-Ajeel, H. 2004. Low Salinity Oil Recovery - Log-Inject-Log. Presented at SPE/DOE Symposium on Improved Oil Recovery, Tulsa, 17–21 April. SPE-89379-MS. https://doi.org/10.2118/89379-MS.
Wolthers, M., Charlet, L., and Van Cappellen, P. 2008. The Surface Chemistry of Divalent Metal Carbonate Minerals: A Critical Assessment of Surface Charge and Potential Data Using the Charge Distribution Multi-Site Ion Complexation Model. Am. J. Sci. 308 (8): 905–941. https://doi.org/10.2475/08.2008.02.
Yildiz, H. O. and Morrow, N. R. 1996. Effect of Brine Composition on Recovery of Moutray Crude Oil by Waterflooding. J. Pet. Sci. Eng. 14 (3–4): 159–168 https://doi.org/10.1016/0920-4105(95)00041-0.
Yousef, A. A., Al-Saleh, S., Al-Kaabi, A. et al. 2011. Laboratory Investigation of the Impact of Injection-Water Salinity and Ionic Content on Oil Recovery From Carbonate Reservoirs. SPE Res Eval & Eng 14 (5): 578–593. SPE-137634-PA. https://doi.org/10.2118/137634-PA.
Zahid, A., Shapiro, A. A., and Skauge, A. 2012. Experimental Studies of Low Salinity Water Flooding Carbonate: A New Promising Approach. Presented at the SPE EOR Conference at Oil and Gas West Asia, Muscat, Oman, 16–18 April. SPE-155625-MS. https://doi.org/10.2118/155625-MS.
Zhang, P. and Austad, T. 2006. Wettability and Oil Recovery from Carbonates: Effects of Temperature and Potential Determining Ions. Colloid. Surface. A 279 (1–3): 179–187. https://doi.org/10.1016/j.colsurfa.2006.01.009.
Zhang, P., Tweheyo, M. T., and Austad, T. 2007a. Wettability Alteration and Improved Oil Recovery by Spontaneous Imbibition of Seawater into Chalk: Impact of the Potential Determining Ions Ca2+, Mg2+, and SO2–4. Colloid. Surface. A 301 (1–3): 199–208. https://doi.org/10.1016/j.colsurfa.2006.12.058.
Zhang, Y., Xie, X., and Morrow, N. R. 2007b. Waterflood Performance by Injection of Brine With Different Salinity for Reservoir Cores. Presented at the SPE Annual Technical Conference and Exhibition, Anaheim, California, 11–14 November. SPE-109849-MS. https://doi.org/10.2523/109849-MS.
Zhang, Y. and Morrow, N. R. 2006. Comparison of Secondary and Tertiary Recovery With Change in Injection Brine Composition for Crude-Oil/Sandstone Combinations. Presented at SPE/DOE Symposium on Improved Oil Recovery, Tulsa, 22–26April. SPE-99757-MS. https://doi.org/10.2523/99757-MS.