Study on the effect of supercritical carbon dioxide on rock mechanical properties of carbonate reservoirs

Abstract Supercritical carbon dioxide to improve gas recovery technology has broad prospects for promotion, but its effect on the mechanical properties of carbonate reservoir rock is not clear, selected the Permian Maokou Formation carbonate reservoir rock samples in the Sichuan Basin, the the use of supercritical CO 2 to soak samples, and then carry out nanoindentation experiments, research on the samples of the supercritical CO 2 without the use of temperature and pressure immersion elasticity, hardness, creep performance and other micro-mechanical parameters of the change rule. The results show that the greater the supercritical CO 2 properties and other micromechanical parameters under supercritical CO 2 immersion without temperature and pressure. The results show that the greater the supercritical CO 2 immersion temperature and pressure, the longer the time, the greater the corresponding reduction in hardness and elastic modulus, of which the nanoindentation hardness and elastic modulus were reduced by 44.76% and 30.45% after the immersion treatment at 75°C and 20MPa. The creep of carbonate rock increases with the increase of soaking temperature and pressure and time, but the supercritical CO 2 stops “intruding” with the increase of soaking temperature and pressure and time. “intruding” with the increase of soaking time at the lower temperature and pressure (60°C, 10MPa), and the increase of driving pressure can further promote the supercritical CO 2 “intrusion”. Increasing the driving pressure can further promote the supercritical CO 2 “invasion”. The modulus of elasticity and hardness of carbonate rocks after supercritical CO2 immersion at the nanoscale are characterized by a concentration of values and an overall decrease in hardness, and the presence of CO 2 in the samples in the form of non-fluid dynamics has less influence on the strength properties of the samples at the pores and fissures, and has a greater influence on the strength of calcite on the surface of the samples. The paper reveals the effect of supercritical CO2 immersion on the mechanical properties of carbonate rock, which provides theoretical support for the geological sequestration of CO 2 in carbonate reservoirs.