Distribution, formation and evolution of sand ridges on the East China Sea shelf

Influence of CO2 corrosion on reservoir mineralogical composition, pore structure and their mechanical characteristics was studied using XRD, SEM, rock tri-axial machine and core flow experimental equipment. It was found that the corrosion effect was mainly attributed to rock texture and structure, fluid composition and external dynamical conditions in the experimental conditions. For cores with bedding structures, their bedding surfaces were the preferential corrosion regions, because micro-cracks would evolve at these surfaces in the pressure-releasing process. However, for cores with massive structures controlled by stable water environment, the CO2 corrosion would result in pore enlargement and secondary pore formation. The gas velocity from outlet showed sharp increase in the injection process of CO2-H2O solution. This could be explained by two changes caused by corrosion. One was the opening and closure of micro-cracks. The other was particle migration. As the corrosion time increased, both tensile strength and compressive strength decreased, which confirmed decrease of cementation strength. It should also be noted that permeability increase and micro-cracks generation would pose damage to the capacity of CO2 geological storage.