A reservoir rock wettability modifier for ultra-high temperature and high salinity environment

During drilling process, the water phase in drilling fluids infiltrates rock fractures through capillary action. The surface wettability of dolomite is governed by multiple factors, resulting in an unstable wetting state. Studies have shown that altering the surface wettability of reservoir rocks to an intermediate wetting state can effectively reduce the damage of drilling fluids to oil and gas reservoirs and improve oil and gas recovery. Therefore, it is necessary to develop a reservoir protectant to prevent the water phase in the drilling fluid from intruding into the oil and gas reservoirs. Given this, a modified polysiloxane was synthesized to alter the surface wettability of dolomite. Tetramethylcyclotetrasiloxane (D^H₄) and octamethylcyclotetrasiloxane (D₄) were ring-opened copolymerized to obtain the hydrogen-containing polysiloxane, which in turn reacted with unsaturated hydrocarbons to obtain the modified polysiloxane. The ability of reservoir protectants to regulate the surface wettability of dolomite under high-temperature and high-salinity conditions was tested. The experimental results show that the reservoir protectant is able to alter the wettability of the dolomite surface to an intermediate wetting state by adsorption on the rock surface even after 16 h of aging at 240 ℃ and 15% salt concentration.