Rock Dry-Out and Fines Migration During CO2 Storage: Laboratory and Mathematical Modelling

Abstract

The work comprises the set of lab corefloods of the displacement of water by CO2 from sandstone cores. Previous experimental studies investigated the effects of water evaporation, Rock Dry-out, viscous fingering and Fines Migration with respect to permeability damage during CO2 injection. However, the synergy of those physics mechanisms, their simultaneous occurrence and mutual interactions haven't been studied in necessary details. We performed 8 corefloods in 5 Berea cores, creating secondary and tertiary core re-saturations by brine after complete drying during CO2 flood. To study detachment of fines during different stages of rock drying, we modelled forces and torques exerting the attached clay particles by the by-passing CO2 flow. It allows formulating the mobilisation criteria for attached clays. The main phenomena observed encompass intensive viscous fingering, rock sweep by isolated fingers under high water saturation, uniform timely drying of the rock by injected CO2 during hundreds of thousands of PVI, abrupt rock permeability increase under joining the isolated viscous fingers into a united gas-conductive network, and fines production during the overall drying period. The micro-scale mechanical-equilibrium modelling of fines detachment accords to the fact of fines production during the total displacement period.