Assessment of the water-sealed safety of underground crude oil storage based on a three-dimensional refined numerical model

Abstract

Objective The principle of a "gap storage water seal" is used to realize large-scale underground storage of crude oil, in which water-sealed safety is an important prerequisite for the safe and economical operation of underground oil storage. Methods To evaluate the water-sealed safety of underground oil storage, based on a refined engineering geological survey, the permeability coefficients of cavern surrounding rock, fault zones, dense joint fracture zones, and broken zones are obtained accurately, and the spatial variation of the permeability coefficient within the reservoir area is comprehensively analysed. Combined with multi-source high-precision survey information, a three-dimensional refined seepage numerical simulation model is constructed. After comparing and analysing both advantages and disadvantages of the three-dimensional refined model and corresponding homogeneous medium model, a numerical simulation is carried out to compare and analyse the reliability of cave storage with or without a water seal, and the water inflow of cavern during construction and operation is also predicted. Results Results show that the three-dimensional refined model can accurately reflect the influence of geological structures on the groundwater level and water pressure, making analysis more in line with the real situation.The water curtain system can effectively improve the water-sealed safety of underground oil storage. Specifically, when the cavern is excavated without water curtain, the groundwater level drops significantly, and drainage area exists above some caverns. When the cavern is excavated under water curtain, the groundwater level does not drop significantly, and thick aquifer exists above the cavern, ensuring the water-sealed safety of underground oil storage; at the same time, the water inflow of cavern is under control. Conclusion Assessment of the water-sealed safety of underground crude oil storage provided in this article can be used as a reference for other similar projects.

Keywords

• underground water-sealed oil storage
• assessment of the water-sealed safety
• three-dimensional refined model
• numerical simulation