Analysis of pillar stability of mined gas storage caverns in shale formations

The observed failure of mined storage caverns in shale formations indicates that one of the major causes of pillar failure is the effect of jointing, fracturing, and deterioration of the shale in the outer portions of the pillar due to a combination of stress slabbing and slaking. The effect of width/height ratio on pillar capacity is also apparent. After the collapse of the Lick Creek, Illinois, room and pillar cavern in 1973, a design approach has been developed for pillar size and loading that takes into account rock and geometric conditions that influence stability, including the conditions that led to the failure at Lick Creek. This paper presents a design criterion for evaluating the overall stability of the pillars in mined gas storage caverns in shale formations. The study includes the closed form pillar stability calculations as well as three-dimensional numerical analyses to verify the analysis method.