Mechanical stability of salt caverns under intensive gas storage conditions using LOCAS and DISROC

Abstract

International audienceIn gas storage operations, injection and withdrawal rates can reach high levels to meet increasing demand. Salt caverns intensive exploitation methods introduce significant mechanical challenges, particularly wall spalling. Spalling involves the detachment of plates or blocks from the cavern walls or roof, occurring with minimal volume loss, unlike progressive closure through creep. This study focuses on the detachment of overhanging blocks within specific salt caverns. Wall spalling is of particular concern because it can compromise the structural stability of the caverns, damaging well tubing posing risks to both the safety and the efficiency of storage operations. This article explores the mechanical stability of salt caverns using two finite element software. LOCAS software identifies potential failure zones in continuous media. It helps to examine damage initiation due to salt dilation and the onset of effective tensile stresses at the cavern wall. Dilatancy refers to the volume increase accompanying material deformation under stress, leading to microcracks formation. DISROC software simulates crack initiation and propagation for detailed failure analysis. It employs joint element model to visualize failure mechanisms in the selected cavern blocks. Simulating crack formation and propagation at the joints between blocks, offers a detailed perspective on how failure develop and extend within the cavern structure. These two methods are compared to assess the onset of damage and associated mechanisms in salt caverns under intensive gas storage conditions