Design and test aspects of a water curtain system for underground oil storage caverns in China

• Several issues on designing and testing the water curtain system for a pilot underground storage caverns were investigated.
• Design principles for water curtain systems were investigated.
• Testing procedure and results of the water curtain system for the caverns were introduced.
• The interconnectivity of the water curtain boreholes was analyzed.
• An improved testing procedure was proposed according to the practice for the pilot caverns.

A water curtain system consists of many boreholes arranged in a systematic manner. To maintain tight seals when storing substances (e.g., crude oil), water curtain systems are usually employed for underground storage in hard rock. With the aid of these systems, stable seepage fields develop around storage caverns, and hydrodynamic containment is achieved in the storage caverns. In this paper, several issues regarding the design and testing of a water curtain system in underground oil storage caverns in China were investigated. Regarding the design of these systems, natural and artificial containments were compared, and the role of hydrogeology in the selection of containment was explored. A literature review on the geometrical parameters of these systems used in storage caverns was performed and provided reference for the design of the proposed water curtain system. The influence of rock joint orientations on the arrangement of boreholes in the curtain system was addressed; it was concluded that the boreholes should be arranged perpendicularly to the dominant joints to obtain a system with good performance. Regarding the testing of these systems, a procedure used to evaluate the performance of the proposed water curtain system was developed. A method used to determine the interconnectivity of the system was also developed, and an improved test procedure was proposed based on the test results. A curtain system injection test was performed, and the groundwater flow rates into both the water curtain system and the storage caverns were measured. It was shown that the groundwater flow rates were dominated by the groundwater flow in the rock joints and the areas where high groundwater flow rates around the cavern surfaces coincided with those where high groundwater flow rates appeared at water curtain boreholes.