Effects of Acid Corrosion on Deformation Evolution and Seepage Characteristics of Weakly Cemented Sandstones: Understanding Sensitive Reservoirs for CO₂ Geological Storage

Carbon dioxide (CO2) storage is an effective way to control carbon emissions and mitigate environmental problems, and the injection of CO2 depends on reservoir permeability, which is likely sensitive to the acidic CO2 solution. However, the acid corrosion effects on calcite-cemented sandstone under different stress conditions have rarely been studied. This study prepared a series of calcite-cemented sandstones with the same cementation content of 14% and investigated the effects of acid corrosion on their mechanical strength and permeability using a high-pressure core holder. The cementation weakening by acid corrosion decreases the mechanical yield and changes the failure modes, and the shrinkage factor of the yield envelope of cementation-weakened sandstones is found to be 0.82. The sandstone permeability with acid corrosion shows different evolution laws under three conditions of low, deviator, and high stresses and is particularly sensitive to the shear and compaction bands. In addition, the competition phenomenon of pore expansion and shrinkage is observed inside the cement-weakened sandstones using CT scanning. The results indicate that the permeability of the compaction band is 10 times lower than normal, and its prediction must consider the effect of grain breakage on the void ratio. This study reveals the comprehensive effects of effective stress and acid corrosion on weakly cemented sandstones, which is helpful to understand the deformation evolution and seepage characteristics of CO2 geological storage reservoirs.