Experimental investigation on the long-term interactions of anhydrite rock, crude oil, and water in a mine-out space for crude-oil storage

Abstract

To evaluate the effectiveness of the usage of anhydrite mine-out spaces for crude-oil storage, this study conducted a long-term experimental investigation on the interaction of anhydrite rock with crude oil and water with varying pressure using pressurized reactors designed in this work. The physical and mechanical properties of anhydrite-rock samples for different test periods were studied to evaluate the effect of crude oil and water on the anhydrite-rock properties and reveal the action mechanism. The crude-oil property was tested after the experiments were completed to evaluate the effect of anhydrite on the crude oil. The results demonstrated that under long-term contact with varying pressure, the crude oil did not affect the physical and mechanical properties of anhydrite, and the anhydrite did not affect the crude-oil properties. However, the dissolution and recrystallization effects of water on the anhydrite induced reduction in the strength and stiffness of the anhydrite rock to a certain extent. Thus, water can potentially reduce the stability of an anhydrite mine-out space, which should be focused on when an anhydrite mine-out space is used for underground crude-oil storage.