Enforced CO2 mineralization in anhydrite-rich rocks

Abstract

Carbon dioxide (CO 2 ) emission is a major contributor to global warming and climate change. Consequently, there is an urgent need to decrease the concentration of CO 2 in the atmosphere and develop reliable methods for its storage. Subsurface carbon mineralization is an effective solution to mitigate atmospheric CO 2 emissions. This study is focused on investigating anhydrite–CO 2 –brine interactions as a means of carbon storage in anhydrite-rich reservoirs. To achieve this, we conducted experiments involving anhydrite-rich rock exposed to supercritical CO 2 -brine environments. Notably, we conducted a novel mineral transformation of an outcrop anhydrite-rich rock within a static reactor, replicating subsurface conditions of high temperature (333 K) and pressure (104 bar). These experiments were conducted over fifteen days, both in the absence and presence of BaCl 2 . A comprehensive suite of mineralogical, elemental, and geochemical analyses was employed, including X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, ion chromatographic (IC) analysis, and micro-computed tomography (micro-CT) assessments. These analyses allowed capturing the changes occurring in the rock's structure and composition due to the CO 2 -brine interactions. The outcomes revealed that anhydrite , when exposed to supercritical CO 2 -saturated brine, undergoes a significant mineral transformation. This mineral modification leads to the formation of stable minerals, including calcite , siderite , feldspar, and barite . Consequently, there was an observed increase in total carbon (TC) content of up to 177 % for the CO 2 -brine treatment and 266 % for the CO 2 -brine + BaCl 2 treatment. These findings provide valuable insights into the potential of anhydrite-based CO 2 storage mechanisms. • Rock–CO 2 –brine interactions for CO 2 storage through mineralization in anhydrite-bearing reservoirs. • Anhydrite exposed to supercritical CO2-brine undergoes significant transformation, forming minerals such as calcite. • Rock with 0.348 wt% TC increased to 0.963 wt% and 1.275 wt% after exposure to CO2-brine without and with BaCl2, respectively. • Substantial TC increase suggests great potential for CO 2 storage through mineralization in anhydrite-rich rocks.