Numerical Modeling Investigations on Waste Disposal Salt Caverns

Abstract

Over the past decades, the increased volume of oil-field waste disposal and the recognition of the environment and health impacts from conventional and traditional disposal approaches have led to an increased demand for solution-mined salt caverns as an effective method for permanent abandonment of oil field solid waste. The favourable geomechanical properties of the rock salt including very low permeability and high ductility behavior ensure the underground solution mined salt caverns provide secure containment facilities for petroleum industry products, with much higher storage volumes and decreased surface land requirements and correspondingly lower costs. The post-closure geomechanical behavior during long-term abandonment are of primary importance in the assessing the feasibility of disposal salt caverns for oil field waste, as well as the multiple-cavern configurations around the same site. This thesis focuses on significant numerical modeling investigations of the structural stability and integrity of the salt caverns, the likelihood of nonsalt caprock failure, the induced surface subsidence and theoretical casing behavior, the closure behavior of the salt caverns, and the interactions between adjacent caverns during operation and permanent abandonment under various cavern configurations and internal pressure conditions. The analysis of field core logging results and laboratory testing studies assisted the above-mentioned numerical studies. It was shown that for all simulated cavern configurations, the disposal of oil field solid waste into the salt caverns would significantly increase the stability and structural integrity of the caverns and mitigate the induced deformations and cavern storage volume loss remarkably. Multiple-cavern configurations at a site could be considered if they are designed well and operated and abandoned appropriately with injected dense waste.