A Caprock Evaluation Methodology for Underground Gas Storage in a Deep Depleted Gas Reservoir: A Case Study for the X9 Lithologic Trap of Langgu Sag, Bohai Bay Basin, China

The evaluation of caprocks’ sealing capacity is exceedingly important for depleted gas reservoirs to be reconstructed into storage. In this paper, based on the physical mechanism caprock, four aspects ten indexes caprock quality were firstly selected, and related classification standards established. Secondly, rock mechanical mechanism, elastic plastic selected characterize brittleness a method complete stress-strain curves was Then, systematic comprehensive model (including 5 12 indexes) storage proposed, analytic hierarchy process (AHP) used determine weight in model, formula calculating suitability Finally, geological data, laboratory, field test including X-ray diffraction, poro-permeability test, displacement pressure, tri-axial compression X9 reservoir, result from showed that suitable underground