A study to evaluate the impact of operational pressure cycles on the long-term stability of underground hydrocarbon storage caverns in Singapore was performed. As the stored products are withdrawn for consumption and subsequently replenished during operations, frequent storage pressure variations inside the caverns are anticipated. This study evaluated whether such storage pressure fluctuations, which tend to affect rock mass strength and support strength with the passage of time, will have a significantly negative effect on the overall stability and operational life of the caverns. The study assessed the impact of pressurization and depressurization cycles on the global stability of the storage caverns using numerical models, while assuming progressive weakening of the rock mass and rock support. A sensitivity analysis was also performed to evaluate the response of the cavern rock mass to variations in a set of critical input parameters. The results of the sensitivity analysis were also used to identify an appropriate minimum operating pressure (mOP) criterion.
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