On the Dependence of Capillary Entry Pressure with Subsurface Depth in Geological CO2 Storage

Abstract

nder arbitrary uniformly-wet conditions with the use of an novel semi-analytical model. The interfacial tension between brine and CO2 is obtained as a function of the phases density difference, and the contact angle is evaluated based on the Frumkin–Derjaguin equation with the application of the DLVO theory to compute disjoining pressures isotherm curves under various storage formation conditions. Based on the developed model, the CO2 entry pressure can be computed in realistic cap-rock pore spaces extracted from 2D rock images from core samples located at various storage depths and under the appropriate pressure, temperature and brine ionic strength conditions. The dependency of brine/CO2 interfacial tension, contact angle and capillary entry pressure on CO2 storage depth and brine ionic strength is also investigated. The proposed workflow for entry pressure estimation and the relationship between capillary entry pressure and depth could enhance our understanding and improve the safety of CO2 storage. The simulated depth-dependent capillary entry pressure curves could also be incorporated into a reservoir simulation model to predict CO2 migration in the storage unit.