Gradual or Instantaneous Wettability Alteration During Simulation of Low-Salinity Water Flooding in Carbonate Reservoirs

Injection of low-salinity water into carbonate reservoirs has gained attention as a viable and efficient enhanced oil recovery approach through wettability alteration as prevailing mechanism. However, modeling and implementation of wettability alteration during simulation of low-salinity water injection are challenging because of the complex ion interactions and chemical reactions in the brine and oil mixture as well as on the rock surface. It is noteworthy that wettability alteration is usually considered instantaneous in black oil simulation. The main purpose of this work was to put this assumption into perspective; thus, it aims at discerning under what circumstances the instantaneous wettability alteration approach is plausible during simulation of low-salinity water flooding. To answer this question, an approach was proposed to consider gradual wettability alteration during simulation of low-salinity water flooding and the results were compared with instantaneous wettability alteration method. The results show that the impacts of simultaneous increase in SO42-, Ca2+ concentrations and temperature cause the difference between gradual and instantaneous wettability alteration to be more noticeable at the early times of injection. Therefore, the results highlight that the impact of gradual consideration would be important at the early time of low-salinity water flooding process.