A 12-year cavern abandonment test

Abstract

In 1997-1998, an abandonment test was performed in a 950-m deep, 8000-m3 salt cavern operated by GDF SUEZ at Etrez, France. In this relatively small brine-filled cavern, which had been kept idle for 15 years before the test, thermal equilibrium was reached. A special system was designed to monitor leaks, which proved to be exceedingly small. In these conditions, brine permeation and cavern creep closure are the only factors to play significant roles in pressure evolution. This test strongly suggested that obtaining an equilibrium pressure such that the effects of these two factors were exactly equal would be reached in the long term. Four years later, pressure monitoring in the closed cavern resumed. Pressure evolution during the 2002-2009 period confirmed that cavern brine pressure will remain constant and significantly smaller than geostatic pressure in the long term, precluding any risk of fracturing and brine seepage to the overburden layers.