Permeability alteration in heterogeneous carbonate caprock induced by geochemical reaction

Abstract

Carbon Capture and Storage (CCS) has the potential to help reduce CO2 emissions to the atmosphere and so mitigate climate change. CCS schemes are only successful if the CO2 remains successfully sequestered underground for many hundreds of years. One possible problem for CCS systems is the dissolution of reactive minerals within caprock fractures,induced by acidified brine flow. This increases fracture permeability and acts as a potential leakage pathway for CO2. This work investigated the impact of changes to fracture permeability and consequently leakage risk in fracture systems consisting of both reactive and unreactive species. Focus was given to comparing homogeneous reactive calcite caprock formations and heterogeneous calcite/dolomite/unreactive species formations. It was found that unreactive species limit the changes to total fracture permeability and so will reduce leakage risk compared to a homogenous reactive formation.