Experimental investigation into salt precipitation during CO2 injection in saline aquifers

Abstract

Carbon Capture and Storage (CCS) is recognised as one of the most effective technologies for reducing CO2 emissions in the short to medium term. From a capacity point of view, deep saline aquifers offer the greatest potential. As supercritical CO2 is injected in the aquifer, a variety of strongly coupled physical and chemical processes occur. Among these various mechanisms, vaporisation of water requires particular attention as it can cause salt precipitation, which reduces the porosity and the permeability of the reservoir in the vicinity of the wellbore. This can lead to significant reduction in injectivity. Research described in this paper aims to provide a relationship between porosity changes and resulting permeability variations representing the effect of salt precipitation due to vaporisation. Supercritical CO2 core flooding experiments were conducted on a St. Bees sandstone core with fully saturated saline water obtaining several levels of alteration due to halite scaling. Porosity reduction ranged from around 4 to 29% of the initial value. Permeability impairments ranged from 30 to 86%. Results were used to calibrate a Verma-Pruess “tube-in-series” model which can be used to obtain more accurate results from numerical simulations.