Signature of Geochemistry on Density‐Driven CO Mixing in Sandstone Aquifers

Abstract

Density‐driven mixing resulting from CO 2 injection into aquifers leads to the CO 2 entrapment mechanism of solubility trapping. Crucially, the coupled flow‐geochemistry and effects of geochemistry on density‐driven mixing process for “sandstone rocks” have not been adequately addressed. Often, there are conflicting remarks in the literature as to whether geochemistry promotes or undermines dissolution‐driven convection in sandstone aquifers. Against this backdrop, we simulate density‐driven mixing in sandstone aquifers by developing a 2‐D modified stream function formulation for multicomponent reactive convective‐diffusive CO 2 mixing. Two different cases corresponding to laboratory and field scales are studied to investigate the effect of rock‐fluid interaction on density‐driven mixing and the role of mineralization in carbon storage over the project life time. A complex sandstone mineralogical assemblage is considered, and solid‐phase reactions are assumed to be kinetic to study the length‐ and time‐scale dependency of the geochemistry effects. The study revealed nonuniform impact of rock‐fluid and fluid‐fluid interaction in early‐ and late‐time stages of the process. The results show that for moderate Rayleigh (Ra) numbers, rock‐fluid interactions adversely affect solubility trapping while improving the total carbon captured through mineral trapping. Simulation results in the range of 1,500 < Ra < 55,000 in the field‐scale model showed more pronounced impact of geochemistry for higher Ra numbers, as geochemistry stimulates the convective instabilities and improves the total sequestered carbon. This study gives new insights into the effect of rock‐fluid interactions on density‐driven mixing and solubility trapping in sandstone aquifers to improve estimation of the carbon storage capacity in deep saline aquifers.

Dynamics of CO2 Density‐Driven Flow in Carbonate Aquifers: Effects of Dispersion and Geochemistry

“…are negligible and do not affect the hydrodynamics at all (a similar conclusion was drawn by [Fu et al, 2015;Sainz-Garcia et al, 2017;Erfani et al, 2020]…”

“…However, different reaction paths at different time scales and different locations of the aquifer (subsequent to plume propagation) were neglected. Such considerations were later shown to be crucial in sandstone aquifers by Erfani et al [2020].…”

“…Due to relatively slow reactions, the kinetic approach is usually implemented to study the effects of geochemistry on CO 2 convective mixing in sandstones [Erfani et al, 2020]. Ennis-King and Paterson [2007] concluded that the density increase due to ion concentrations of Ca 2+ , Mg 2+ can be of the same order of magnitude as the density increase due to dissolved CO 2 .…”

“…They concluded that such form of interactions can curtail the solute spreading and convective onset in the system. Erfani et al [2020] showed the scale-and time-dependency of geochemical interactions in a typical sandstone aquifer. They showed that in the field-scale, the geochemical interactions decrease the solubility trapping, while increasing the total amount of sequestered carbon through mineralization (same conclusion as [Ghesmat et al, 2011b] and [Cardoso and Andres, 2014]).…”

Experimental and Modelling Study of Gravity Drainage in a Three-Block System

“…Two-phase flow in fractured rocks is relevant to various application, ranging from geothermal energy (Babaei and Nick 2019;Erfani et al 2019), groundwater contamination (Gleeson et al 2009;Sebben et al 2015;Aminnaji et al 2019;Aljuboori et al 2019;Dejam 2019), carbon capturing and storage (Emami-Meybodi et al 2015;Babaei and Islam 2018;Erfani Gahrooei and Joonaki 2018;Dejam and Hassanzadeh 2018;Erfani et al 2020;An et al 2020b;Ershadnia et al 2020), and soil salinization (Weisbrod and Dragila 2006) to enhanced hydrocarbon recovery (Farajzadeh et al 2012;Rokhforouz and Akhlaghi Amiri 2017;Rokhforouz and Amiri 2018;Bakhshi et al 2018;Rabbani et al 2020a;Chen et al 2020;An et al 2020a). The complexity of the fluid flow in highly heterogeneous rocks is caused by the notion that the fluid flows in two different media, matrix block and fracture, which separates the fluids into flowing and stagnant regions due to property contrast (Erfani et al 2019;Hasan et al 2019;Soltanian et al 2019;An et al 2020c;Aziz et al 2020;Rabbani et al 2020b;Hasan et al 2020).…”