A Numerical Simulation Study of Temperature and Pressure Effects on the Breakthrough Pressure of CO2 in Unsaturated Low-permeability Rock Core

Gas breakthrough pressure is a key parameter to evaluate the sealing capacity of caprock,and it also plays important roles in safety and capacity of CO2 geological storage.Based on the published experimental results,we present numerical simulations on CO2 breakthrough pressure in unsaturated low-permeability rock under 9 multiple P-T conditions(which can keep CO2 in gaseous,liquid and supercritical states)and thus,a numerical method which can be used to accurately predict CO2 breakthrough pressure on rock-core scale is proposed.The simulation results show that CO2 breakthrough pressure and breakthrough time are exponential correlated with P-T conditions.Meanwhile,pressure has stronger effects on experimental results than that of temperature.Moreover,we performed sensitivity studies on the pore distribution index λ(0.6,0.7,0.8,and 0.9)in van Genuchten-Muale model.Results show that with the increase of λ,CO2 breakthrough pressure and breakthrough time both show decreasing trends.In other words,the larger the value of λ is,the better the permeability of the caprock is,and the worse the CO2 sealing capacity is.The numerical method established in this study can provide an important reference for the prediction of gas breakthrough pressure on rock-core scale and for related numerical studies.