Abstract

Hydraulic containment type underground LPG storage caverns preserve liquid petroleum gas productions with the relative high storage pressure than conventional underground crude storage caverns. Therefore despite of the conventional evaluation on rock mechanical stability, the air-tightness evaluation is essential for the risk assessment on the underground LPG storage cavern. However, the conventional air-tightness evaluation methods apply the groundwater simulation and rock mechanical analysis respectively and have difficulty to represent the pore-pressure and gas pressure while fracture occurred at the cavern vicinity. In this study, the authors have developed a new hydro-mechanical coupling analysis method to evaluate both the rock mechanical stability and air-tightness of underground LPG storage caverns by the bonded-particle model. For air-tightness assessment on underground LPG storage caverns, the authors have concerned the capillary pressure in the gas-water dual phase flow and attempted to encode it into the analysis method for discussing the condition of gas leakage. Further, consideration the fractures in the cavern vicinity are the primary leakage path, the authors have discussed the relationship between capillary pressure with rock permeability and fracture density and achieved to define the capillary pressure theoretically.

For verification, the authors have conducted an in-field air-tightness test to compress an air-chamber to 1.0MPaG, meanwhile the authors have applied the develop hydro-mechanical coupling analysis method to evaluate the air-tightness of the air-chamber. As the result, the leakage was detected while the air-chamber was compressed to 0.778MPaG. For the evaluation results, the developed method achieved to represent the gas leakage and distributions of unsaturated zone, meanwhile, the represented pore pressure characteristics also verified the applicability of developed hydro-mechanical coupling analysis method.

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