PNNL

Abstract

In 2013, Pacific Northwest National Laboratory led a geologic carbon sequestration field demonstration where ~1000 Mt of CO2 was injected into several deep Columbia River Basalt zones near Wallula, Washington. Rock core samples extracted from the injection zone two years after CO2 injection revealed nascent carbonate mineralization, consistent with laboratory experiments and reactive transport modeling. Here, we report on a new numerical model analysis of the 2012 preinjection and 2015 post injection hydrologic tests that capitalize on the difference in fluid properties between scCO2 and water for assessing changes in near field, wellbore/reservoir conditions, and the fate of CO2 in the injection zones approximately two years following termination of injection. This comparative analysis provides a means for quantitatively estimating how much of the injected CO2 was mineralized, without relying solely on reactive transport simulation predictions that are parametrized by an amalgam of mineral dissolution rates. Our numerical modeling of hydrologic test results indicates that 65% of the injected CO2 was sequestered via mineralization, with the resulting carbonates occupying 4.3% of the available reservoir pore space. This new approach for determining the fate of subsurface CO2 in reactive formations is also likely applicable for long term (~50 years) monitoring and verification of subsurface carbon storage reservoirs.