Enhancing oil recovery of gas flooding by regulating rock surface wettability

Rock surface wettability plays a crucial role in gas flooding for oil recovery. Natural rock surfaces are usually oleophilic, resulting in high flooding resistance and low recovery in gas flooding. This study explores the regulation of the wettability of sandstone rock surfaces by modifying them with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane or its mixtures with hexyltrimethoxysilane to achieve oil contact angles ranging from 0° to 93.2°. Simulated gas flooding experiments, with N 2 as model gas, reveal that reducing the oleophilicity of rock surfaces improves gas flooding efficiency. Compared to the unmodified superoleophilic rocks, the final oil recoveries in the cores with neutral oil wettability significantly increases and the pressure differential for gas flooding significantly decreases. In cases of cores with permeability of 22 mD, 0.88 mD and 0.09 mD, the increases in oil recovery are from 28.5% to 37.5%, from 20.2 to 27.3% and from 9.1% to 15.4%, respectively; and the reductions of pressure differential for gas flooding are from 53 kPa to 41 kPa, from 323 kPa to 272 kPa, from 1054 kPa to 935 kPa, respectively. These results highlight the critical influence of wettability regulation on gas flooding efficiency, offering valuable insights for optimizing oil recovery strategies.