Numerical Simulations of the Thermal Impact of Supercritical CO2 Injection on Chemical Reactivity in a Carbonate Saline Reservoir

Abstract

International audienceGeological sequestration of CO2 offers a promising solution for reducing net emissions of greenhouse gases into the atmosphere. This emerging technology must make it possible to inject CO2 into deep saline aquifers or oil- and gas-depleted reservoirs in the supercritical state (P > 7.4MPa and T > 31.1◦C) to achieve a higher density and therefore occupy less volume underground. Previous experimental and numerical simulations have demonstrated that massive CO2 injection in saline reservoirs causes a major disequilibrium of the physical and geochemical characteristics of the host aquifer. The near-well injection zone seems to constitute an underground hydrogeological system particularly impacted by supercriticalCO2 injection and themost sensitive area, where chemical phenomena (e.g. mineral dissolution/precipitation) can have a major impact on the porosity and permeability. Furthermore, these phenomena are highly sensitive to temperature. This study, based on numerical multi-phase simulations, investigates thermal effects during CO2 injection into a deep carbonate formation. Different thermal processes and their influence on the chemical and mineral reactivity of the saline reservoir are discussed. This study underlines both the minor effects of intrinsic thermal and thermodynamic processes on mineral reactivity in carbonate aquifers, and the influence of anthropic thermal processes (e.g. injection temperature) on the carbonates' behaviou

Analytical solution for Joule–Thomson cooling during CO2 geo-sequestration in depleted oil and gas reservoirs

“…However, temperature declines are greatest for the high temperature scenario. This is surprising because the Joule-Thomson coefficient,˛, diminishes with increasing temperature (see André et al, 2010). The larger temperature declines are caused by the increased pressure gradients resulting from the injection of greater volumes of low density CO 2 (recall discussion in the previous section).…”

“…Previously JTC during CO 2 geo-sequestration has been explored using laboratory experiments (Maloney and Briceno, 2009) and numerical simulation (Oldenburg, 2007a;Bielinski et al, 2008;André et al, 2010). For wider accessibility and application, analytical solutions are preferable, especially those that can be implemented in simple spreadsheet software (e.g.…”

Heat transport and pressure buildup during carbon dioxide injection into depleted gas reservoirs

“…The neglect of partial miscibility (vaporization and dissolution) between the CO 2 and the residual brine represents a limitation of the numerical simulations conducted in the current study as well. Andre et al (2010) studied effects associated with partial miscibility in this context at a reservoir pressure of 15 MPa and an injection temperature of 40 • C. They found temperature variation due to vaporization and dissolution to be around 1-3 • C, respectively. Inspection of the empirical equation for the solubility limit of CO 2 in water proposed by Spycher, Pruess & Ennis-King (2003) suggests that dissolution is likely to be an order of magnitude less in the context of the low-pressure environments considered in this article.…”

“…These include cooling due to expansion, heating due to compression, heating and cooling due to dissolution and vaporization, respectively, differences in temperature associated with injection and reservoir fluids, and heating due to viscous heat dissipation (Oldenberg 2007;Andre, Azaroual & Menjoz 2010;Han et al 2010). Owing to the Joule-Thomson coefficient of CO 2 being larger at lower pressures, such processes are likely to be of greater significance in low-pressure depleted gas reservoirs as opposed to hydrostatic or overpressured saline aquifers .…”

“…Andre et al 2010;Mathias et al 2013a). Exceptions to these include Han et al (2012), who considered a minimum initial pressure of 6.89 MPa, Ziabaksh-Ganji & Kooi (2014), who assumed an initial pressure of 6 MPa, Afanasyev (2013), who assumed a minimum initial pressure of 4.5 MPa, and Singh, Goerke & Kolditz (2011) and Singh et al (2012), who considered an initial pressure of 4 MPa.…”