Study on the Influencing Factors of CO2 Storage in Low Porosity-Low Permeability Heterogeneous Saline Aquifer

The safety and long-term storage capacity of CO2 geological storage are necessary factors for project design and engineering development. Evaluating the influencing factors of CO2 storage and quantitatively analyzing the sensitivity of each parameter have an important guiding role in the design and development of storage projects. In this paper, the Liujiagou Formation in the northeast of the Ordos Basin is taken as an example. Based on the TOUGH/Petrasim simulation tool, the RZ2D geological storage model is established. Seven influencing factors, namely salinity, temperature, horizontal and vertical permeability ratio, pore geometry factor, residual gas saturation, liquid saturation and pore compression coefficient, were compared and analyzed to control the plume migration behavior, interlayer pressure accumulation and storage capacity of low porosity and low permeability heterogeneous reservoirs, and the sensitivity of each parameter to interlayer pressure and storage capacity was quantitatively analyzed. The simulation results show that the uncertain factors affect the safety of CO2 geological storage to a certain extent by affecting the speed of the residual storage and dissolution storage mechanism. High residual gas saturation and salinity will make CO2 mostly exist in the form of free state, which will adversely affect the safety and storage capacity of CO2 saline aquifer storage. High temperature and high vertical permeability ratio will lead to higher interlayer pressure accumulation, which is not conducive to the safety of the storage project but is beneficial to the storage capacity. Temperature, transverse and longitudinal permeability ratio and pore geometry factor control the propagation velocity of plume. The larger these factors are, the faster the plume velocity is. Higher liquid phase saturation is not better; higher liquid phase saturation leads to a large build-up of pressure in the reservoir and can have an adverse effect on the storage volume. The sensitivity analysis of all factors shows that the liquid saturation and temperature have the greatest influence on CO2 geological storage, and the pore compression coefficient has the least influence. The conclusions of this paper can provide a theoretical reference for the design and development of a CO2 saline aquifer storage project in a low porosity and low permeability reservoir area.