Research progress and prospect of CO2-water-rock interaction on petrophysical properties of CO2 geological sequestration

The CO2-water-rock interaction is the core issue of CO2 geological sequestration. The injection of CO2 disrupts the chemical balance of rock-formation water， and the changes in the chemical properties of formation water， primary mineral dissolution， and secondary mineral precipitation will lead to changes in the physical properties of reservoir and caprock， such as porosity， wettability， and mechanical properties and thus directly affect the CO2 injection capacity， sequestration efficiency， and sequestration security and stability. Based on the mechanism of CO2-water-rock interaction， this paper systematically expounds on the research progress of the effects of CO2-water-rock interaction on porosity， permeability， wettability， and mechanical properties of formation rocks. The results show that the change in rock porosity and permeability caused by CO2-water-rock interaction is closely related to its initial porosity and permeability characteristics and mineral composition， and the change of rock porosity and permeability characteristics directly affects the injection capacity and sequestration potential of the reservoir and the sealing capacity of the caprock. The change in wettability is related to the initial hydrophilic and oil-philic characteristics. The CO2-water-rock interaction usually weakens the water wettability of the hydrophilic rocks and enhances that of the oil-philic rocks， thus affecting the microscopic distribution and seepage characteristics of the multiphase fluids in the pores of the rocks. Due to the dissolution of cement and the formation of dissolution holes， the CO2-water-rock interaction will cause rock damage， and the mechanical parameters such as compressive strength， tensile strength， and elastic modulus will decrease. To a certain extent， the security of sequestration is affected. Under the setting of carbon neutrality， the CO2-water-rock interaction and rock physical property response under the scenarios of micro-nano-scale pore， deep microbial mediation， impure CO2 or industrial tail gas injection， and full sequestration cycle still need to be further studied.