Experimental and theoretical research on the feasibility of oil storage in sediment voids for salt cavern oil storage (SCOS)

Large-scale underground oil storage is crucial for national development. One effective method, underground salt cavern oil storage (SCOS), is utilized in the US, France, Canada, and Germany, but China currently lacks SCOS facilities. The significant difference between China's lacustrine salt rock and the marine salt rock found elsewhere leads to substantial sediment particles accumulation at the bottom of the caverns, wasting valuable underground storage space. To address this, a new method called sediment void oil storage (SVOS) is proposed. To assess SVOS's feasibility, custom equipment was created and a series of experiments (including oil loss, sediment structure, and component tests) were conducted. An oil loss theoretical model was developed, and the engineering potential of SVOS was analyzed. Results indicate that sediment voids can effectively store oil, with capacity influenced by sediment grain composition and lithology. Three oil loss modes—oil absorption, adhesion, and siltation—affect SVOS's operation, which is also related to sediment pore structure and granular characteristics (such as surface texture, sphericity, and roundness). The maximum oil recovery rates for oil-immersed mudstone and gypsum sediments reached 99.97 % and 99.93 %, respectively. The research contributes valuable insights for advancing underground salt cavern oil storage.