Simulation and Experimental Investigation of Low Salinity Water Flooding in Sandstone Reservoirs

The effect of water chemistry on water-rock interactions and wettability modification during (low ionic strength) low salinity (LS) waterflooding of sandstone cores containing heavy and light oil was investigated. Results are reported from both coreflooding experiments and through simulation with CrunchFlow Multicomponent Reactive Flow and Transport oftware. For core saturated with high viscosity oil (Core2), flooding with HS water at 25°C resulted in an ultimate oil recovery (UOR) of 48% OOIP, and flooding low viscosity oil core (Core1) with HS water resulted in a similar UOR of 50% OOIP. Upon switching to LS water, the additional incremental UOR was 6% and 4% OOIP at 25°C for high and low oil viscosity, respectively. Flooding the cores with HS water followed by LS at other temperatures (70, 90, and 120°C) generally resulted in an increased incremental UOR due to LS of 2 to 4%. In all of the LS flooding cases, the effluent experienced a jump in pH over just the use of HS water. The LS effluent pH jump in light oil was high, but not as high as that in heavy oil at 120°C, meaning that the heavy oil resulted in more ion exchange. Core3 was allocated for surface reactivity test, the Ca2+ effluent was used for matching the Crunch Flow code. This experiment involved simultaneous processes including cation exchange, sorption, desorption, precipitation, and dissolution. To identify the processes, the experimental data were analyzed using the CrunchFlow reactive transport model that considers all these processes simultaneously. The simulation work was also presented in this work. We also studied the optimum pH, temperature, and Ca2+ desorption for sandstone. Desorption of Ca2+ associated with pH jump seems to have a large impact on LS water enhanced oil recovery