Simulation of Low-Salinity Water-Alternating Impure CO 2 Process for Enhanced Oil Recovery and CO 2 Sequestration in Carbonate Reservoirs

Kwangduk Seo, Bomi Kim, Qingquan Liu and Kun Sang Lee ()
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Kwangduk Seo: Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul 04763, Republic of Korea
Bomi Kim: Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul 04763, Republic of Korea
Qingquan Liu: School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China
Kun Sang Lee: Department of Earth Resources and Environmental Engineering, Hanyang University, Seoul 04763, Republic of Korea

Energies, 2025, vol. 18, issue 5, 1-20

Abstract: This study investigates the combined effects of impurities in CO 2 stream, geochemistry, water salinity, and wettability alteration on oil recovery and CO 2 storage in carbonate reservoirs and optimizes injection strategy to maximize oil recovery and CO 2 storage ratio. Specifically, it compares the performance of pure CO 2 water-alternating gas (WAG), impure CO 2 -WAG, pure CO 2 low-salinity water-alternating gas (LSWAG), and impure CO 2 -LSWAG injection methods from perspectives of enhanced oil recovery (EOR) and CO 2 sequestration. CO 2 -enhanced oil recovery (CO 2 -EOR) is an effective way to extract residual oil. CO 2 injection and WAG methods can improve displacement efficiency and sweep efficiency. However, CO 2 -EOR has less impact on the carbonate reservoir because of the complex pore structure and oil-wet surface. Low-salinity water injection (LSWI) and CO 2 injection can affect the complex pore structure by geochemical reaction and wettability by a relative permeability curve shift from oil-wet to water-wet. The results from extensive compositional simulations show that CO 2 injection into carbonate reservoirs increases the recovery factor compared with waterflooding, with pure CO 2 -WAG injection yielding higher recovery factor than impure CO 2 -WAG injection. Impurities in CO 2 gas decrease the efficiency of CO 2 -EOR, reducing oil viscosity less and increasing interfacial tension (IFT) compared to pure CO 2 injection, leading to gas channeling and reduced sweep efficiency. This results in lower oil recovery and lower storage efficiency compared to pure CO 2 . CO 2 -LSWAG results in the highest oil-recovery factor as surface changes. Geochemical reactions during CO 2 injection also increase CO 2 storage capacity and alter trapping mechanisms. This study demonstrates that the use of impure CO 2 -LSWAG injection leads to improved oil recovery and CO 2 storage compared to pure CO 2 -WAG injection. It reveals that wettability alteration plays a more significant role for oil recovery and geochemical reaction plays crucial role in CO 2 storage than CO 2 purity. According to optimization, the greater the injection of gas and water, the higher the oil recovery, while the less gas and water injected, the higher the storage ratio, leading to improved storage efficiency. This research provides valuable insights into parameters and injection scenarios affecting enhanced oil recovery and CO 2 storage in carbonate reservoirs.

Keywords: impure CO 2; water-alternating gas (WAG); enhanced oil recovery (EOR); low-salinity water; geochemistry; carbonate reservoir; carbon capture; utilization and storage (CCUS) (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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