Tightness of an underground energy storage salt cavern with adverse geological conditions

Abstract

A micro-permeable interlayer (MPI) has been found in a salt cavern construction area of the Jintan salt cavern underground gas storage district, Jiangsu, China. The MPI has caused sealing failures of several wells. Tightness is a prerequisite of salt caverns used for energy storage. To quantifiably evaluate the tightness of gas storage salt caverns constructed in formations including an MPI, permeability testing of MPI samples and numerical simulations are carried out. The MPI permeability ranges from 1.10 × 10−16 m2 to 2.12 × 10−14 m2 with an average of 8.16 × 10−15 m2, much larger than that of the rock salt and of other interlayers at the same formation. The effects of the MPI permeability, MPI thickness, width of pillars between caverns, and MPI location on the tightness of the cavern are investigated. The permeability and the location of the MPI are the key factors affecting the cavern tightness. It is suggested to seal the MPI rather than allow it to intersect the caverns untreated in the areas containing the MPI. A rock salt layer between the MPI and the cavern with a thickness of about 5 m is proposed to seal the MPI.