The authors provide a process to evaluate and plan the injection of low salinity water to enhance oil recovery on Central-Khoreiver Uplift (CKU) fields with relatively high oil viscosity (6-7 mPa∙s). Use of chemicals for oil displacement in such conditions is complicated due to high formation water salinity (up to 210 kg/m3)and high formation temperature (70 °С).
Several scenarios are described for application of low salinity or engineered salinity water to improve oil recovery from carbonate formations, but there is no established and integrated mechanism to characterize the mechanism of oil mobilization. As a result of coreflooding experiments on cores from CKU producing formations it is shown that incremental oil recovery from injection of low salinity water ranges from 1 to 10% in comparison with formation water. Linear hydrodynamic models were tuned to laboratory data, and then sector models were built to predict the technological efficiency. Joint application of low salinity water and polymeric chemicals was evaluated, coreflooding experiments were used to find the incremental recovery factors due to combined use of polymer and water with different salinity. It was shown that joint use of polymers and low salinity water can yield an increased oil recovery up to 15% in zones fully swept by injected agent.
In December 2020 the low salinity water injection pilot was started on Visovoye oilfield. Low salinity water (8-9 kg/m3) from the Jurassic horizon replaced treated produced water (180-210 kg/m3). During the long-term injection salinity of produced water in some wells dropped by 20-40%, it allowed to evaluate the swept zones of the formation and improve the forecasting ability of hydrodynamic model. The expected technological efficiency of low salinity water injection on Visovoye field involves the improvement of recovery factor by 1% (to 2033). Potential combined injection of mobility control agent (polymer) and low salinity water can lead to incremental oil recovery from 22 to 44 tons of oil per 1 ton of polymer injected.
References
1. Kornilov A., Zhirov A., Petrakov A. et al., Selection of effective surfactant composition to improve oil displacement efficiency in carbonate reservoirs with high salinity formation water, SPE-196772-MS, 2019, DOI: 10.2118/196772-MS
2. Kruglov D.S., Smirnov A.E., Tkachev I.V. et al., Design of pilot test to evaluating the efficiency of surfactant-polymer flooding in field conditions using single well chemical tracer test (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2021, no. 12, pp. 102–106, DOI: 10.24887/0028-2448-2021-12-102-106
3. Fathi S.J., Austad T., Strand S., Water-based enhanced oil recovery (EOR) by “Smart Water” in carbonate reservoirs, SPE-154570-MS, 2012, DOI: 10.2118/154570-MS
4. Fathi S.J., Austad T., Strand S., Water-based enhanced oil recovery (EOR) by «Smart Water»: Optimal ionic composition for EOR in carbonates, Energy & Fuels, 2011, V. 25(11), pp. 5173-5179, DOI: 10.1021/ef201019k
5. Zhang P., Austad T., Wettability and oil recovery from carbonates: Effects of temperature and potential determining ions, Colloids and Surfaces A: Physicochem. Eng. Aspects, 2006, V. 279, pp. 179-187, DOI: 10.1016/j.colsurfa.2006.01.009
6. Shariatpanahi S.F., Strand S., Austad T., Evaluation of water-based enhanced oil recovery (EOR) by wettability alteration in a low-permeable fractured limestone oil reservoir, Energy & Fuels, 2010, V. 24(11), pp. 5997–6008, DOI: 10.1021/ef100837v
7. Yousef A.A., Liu J.S., Blanchard G.W. et al., Smart waterflooding: Industry’s first field test in carbonate reservoirs, SPE-159526-MS, 2012, DOI: 10.2118/159526-MS
8. Keller Yu.A., Uskov A.A., Krivoguz A.N. et al., The application of SWCTT for evaluating the efficiency of low-salinity water flooding at the carbonate reservoir of the Kharyaginskoye oil field (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2020, no. 7, pp. 109-113, DOI: 10.24887/0028-2448-2020-7-109-113
9. Chorniy A., Khodakov I., Popov D. et al., Practical application of flow diversion techniques for development of fractured carbonate reservoirs, SPE-196855-MS, 2019, DOI: 10.2118/196855-MS
10. Kornilov A.V., Tkachev I.V., Fomkin A.V. et al., Injection of low-salinity water as an integral part of enhanced oil recovery programmes for carbonate formations of the Central-Khoreiver Uplift oilfields, SPE-206433-MS, 2021, DOI: 10.2118/206433-MS
11. Shakeel M., Pourafshary P., Hashmet M.R., Hybrid engineered water-polymer flooding in carbonates: A review of mechanisms and case studies, App. Sci., 2020, no. 10 (6087), DOI: 10.3390/app10176087
