Study on the Effect of Cyclic Loading on the Geomechanics of Sandstone Reservoirs in Gas Storage

In the implementation process of carbon capture and storage (CCS), the geomechanical problems arising from the cyclic injection of carbon dioxide into the formation cannot be ignored. To clarify the influence of cyclic loading on the geomechanics properties of reservoir rocks, cyclic loading tests were carried out on rocks in sandstone reservoirs with the RTR-2000 Rock Mechanics Test System, and the evolution of compressive strength, elastic modulus, and Poisson’s ratio parameters was analyzed, which revealed the law of the geomechanical deterioration and damage evolution of sandstone reservoirs under cyclic loading. The results show that under the same cyclic load, when the number of cycles is increased to a certain degree, the influence on the peak strength is small. As the number of cycles increases, the modulus of elasticity of rock appears to be increasing and then decreasing, whereas a rapid increase in Poisson’s ratio and a slow increase in Poisson’s ratio occur with the increase in the number of cycles. Under the same number of cycles, the peak strength of the core gradually decreased with the increase of the maximum cyclic stress. When the cyclic load was smaller than the yield stress of the core, the effect of cyclic loading on the strength of the core was small, and when the cyclic load was larger than the yield stress, the effect of cyclic loading on the strength increased significantly. With the increase of cyclic load, the modulus of elasticity showed a tendency to increase and then decrease, and Poisson’s ratio had a tendency of decreasing and the overall degree of change was small.