Influence of high horizontal stress regime on the shape of LPG caverns - A case study

Incoherent results of in-situ stress measurements and their implications in designing a crude oil storage caverns project are presented in this paper. Core-discing at depths corresponding to abnormally higher stress magnitude values were observed at the project site. It is brought to the notice that an optimistic assessment of in-situ stresses may result into costly design surprises during the excavation stage. Consideration of incoherency in the computed in-situ stress magnitudes and orientation resulted into lowering of the caverns level farther 5 m from the surface than the design requirements as per the storage pressure. The paper also briefly outlines the project settings, fundamentals of crude oil storage projects in unlined mined caverns and in-situ stress measurements using hydro-frac technique. Impacts of in-situ stress regime on the caverns design is evaluated by using numerical modeling for which plain strain numerical models are prepared using a general purpose finite difference code, FLAC3D.