Experimental Study of Cement - Sandstone/Shale - Brine - CO 2Interactions

Abstract

Background: Reactive-transport simulation is a tool that is being used to estimate long-term trapping of CO 2, and wellbore and cap rock integrity for geologic CO 2storage. We reacted end member components of a heterolithic sandstone and shale unit that forms the upper section of the In Salah Gas Project carbon storage reservoir in Krechba, Algeria with supercritical CO 2, brine, and with/without cement at reservoir conditions to develop experimentally constrained geochemical models for use in reactive transport simulations.Results: We observe marked changes in solution composition when CO 2reacted with cement, sandstone, and shale components at reservoir conditions. The geochemical model for the reaction of sandstone and shale with CO 2and brine is a simple one in which albite, chlorite, illite and carbonate minerals partially dissolve and boehmite, smectite, and amorphous silica precipitate. The geochemical model for the wellbore environment is also fairly simple, in which alkaline cements and rock react with CO 2-rich brines to form an Fe containing calcite, amorphous silica, smectite and boehmite or amorphous Al(OH) 3.Conclusions: Our research shows that relatively simple geochemical models can describe the dominant reactions that are likely to occur when CO 2is stored in deep saline aquifers sealed with overlying shale cap rocks, as well as the dominant reactions for cement carbonation at the wellbore interface. © 2011 Carroll et al; licensee Chemistry Central Ltd.