Influence of supercritical CO2 on the physical property of tight sandstone

Abstract

In low-pressure gas reservoirs, water-based fracture fluid is difficult to flowback, which is unfavorable for several tight sandstone gas reservoirs in the Sichuan Basin with low pressure and high permeability geological characteristics. Supercritical CO2 possesses a number of remarkable physical and chemical features, including a density near to water, a viscosity close to gas, and high diffusion. Supercritical CO2 fracturing is a new type of non-aqueous fracturing method that is favorable to fracturing flowback in low-pressure tight sandstone and has a wide range of applications. To discuss on whether supercritical CO2 fracturing with low pressure tight sandstone is feasible. Tight sandstone cores from the Jinqiu gas field in the Sichuan Basin were used to study the influence of supercritical CO2 on the physical properties of sandstone reservoirs. Supercritical CO2 was used to interact with tight sandstone samples, and then the changes in porosity, permeability, and rock microstructure of tight sandstone were observed under various time, pressure, and temperature conditions. After the interaction between tight sandstone and supercritical CO2, new dissolution pores will appear, or the original pores will be increased, and the width of some natural fractures will also be increased, and the porosity will increase by 1.09%–8.85%, and the permeability will increase by 2.34%–21.26%, quantifying the influence of supercritical CO2 on physical properties of tight sandstone, and further improving the interaction mechanism between supercritical CO2 and tight sandstone. This study improves in the understanding of the tight sandstone-supercritical CO2 interaction mechanism, as well as providing an experimental foundation and technological guarantee for field testing and use of supercritical CO2 in low-pressure tight sandstone gas reservoirs.