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Determining suitable operating pressures is important when developing deep storage cavities in salt formations due to continuous reduction in the cavern storage capacity caused by creep of the surrounding rock mass. Optimisation for long-term cavern performance typically requires numerical modelling to evaluate different geometries, operating pressures, account for variations in stratigraphy and material properties, and to develop closure predictions over relatively long periods. Commercially available numerical models offer different interface environments and solution methods resulting in varying levels of effort required for model set-up and execution. Models employing a simple graphical user interface and stable fast-execution algorithms are often preferred in the early stages of cavern design.
This paper discusses the implementation and numerical performance of creep algorithms using the finite element model (FEM) code PLAXIS. Constitutive models were implemented to evaluate salt cavern closure at a proposed gas storage facility in southern Arizona, USA. The PLAXIS results were verified against one-dimensional analytical solutions and compared to the finite difference code FLAC™ for a three-dimensional case scenario considering axisymmetric cavern closure.
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