Reactive Transport of CO2 in Saline Aquifers with implicit geomechanical analysis

Abstract

Geological storage of CO2 in saline aquifers is a promising way to reduce the concentration of the greenhouse gas in the atmosphere. Injection of CO2 will, however, lead to dissolution of minerals in regions of lowered pH and precipitation of minerals from transported ions in regions of higher pH. The geomechanical implications of these changes on the stability of the reservoir are of crucial importance in the evaluation of potential injection reservoirs. The possible injection rate for given over-pressures of the injected CO2 depends on the porosity and permeability of the rock matrix in the vicinity of the injection well. Local fracturing in this region can be a tool for increasing the injection flow rate but a geomechanical analysis will be needed in order to make sure that this fracturing will not affect the geomechanical stability outside this limited region to a significant degree. This paper presents a new rewritten version of RetrasoCodeBright (RCB) which have been extended to simulations of CO2 storage in saline aquifers. An advantage of this code compared to other codes is the implicit geo-mechanical module. The code has been rewritten to account for non-ideal gas through corrections of gas density and gas solubility in all transport terms. Newton–Raphson method used to solve the flow and mechanics in RCB has been improved so as to improve convergence even under high gas injecting pressures. A 2D hydro-chemical-mechanical problem is used to illustrate the modified RCB code.