Estimation of Local Capillary Trapping Capacity from Geologic Models

Abstract

Local capillary trapping, which is accumulation of CO2 under local capillary barriers, occurs during buoyancy-driven flow through rocks with fine-scale heterogeneity. However, fine-scale flow simulations that resolve the local heterogeneity and show the local capillary trapping have very large and impractical run times. In this work, we find a fast method to estimate these structures from the geologic model assuming a critical capillary entry pressure for the domain. The algorithm uses the capillary entry pressure field and the critical entry pressure as inputs and finds the potential barriers inside the domain and calculates the holes surrounded by clusters of potential barriers. The holes correspond to local capillary traps and will give us an estimate of the local capillary trapping capacity in the domain. This estimate should be an upper bound, since we cannot judge a priori whether CO2 will find its way into these holes.