Mechanical properties of gypsum mine rock around a strategic petroleum reserve (SPR) cavern under the crude oil seepage condition

As China's demand for imported oil continues to grow, large-scale oil storage facilities have become increasingly important. Currently, China primarily uses underground salt cavern spaces and newly excavated underground water-sealed caverns for oil storage, which places high demands on the rock formations. China has abundant and widely distributed gypsum mineral resources, and utilizing abandoned gypsum mines for oil storage could not only turn waste into treasure by controlling underground space but also generate significant economic and social value. This article aims to systematically evaluate the mechanical properties of gypsum rock through long-term immersion tests in crude oil to assess the impact of crude oil immersion on the mechanical performance of gypsum rock and explore the feasibility of using gypsum mines as long-term stable oil storage caverns. The results show that oil immersion treatment reduces the uniaxial tensile strength of gypsum samples, but has little effect on their compressive strength and long-term strength. From a mechanical performance perspective, it is feasible to use gypsum mine voids for crude oil storage.