Physiochemical and Mechanical Aspects of CO2 Storage in Deep Saline Aquifers: An Experimental Study

Abstract The storage of carbon dioxide (CO2) in subsurface reservoirs is an important option for mitigating anthropogenic greenhouse gas emissions and addressing the global challenge of climate change. However, implementing carbon capture and storage (CCS) technologies involves many complex and coupled processes requiring thorough investigation. These complexities arise from the complex interactions in the subsurface between geological, hydrological, geochemical, and geomechanical factors. Understanding and managing these multifaceted processes are essential for successful and safe deployment of CCS as a vital component of sustainable energy and environment strategies. This experimental study investigates the multi-threaded impact of CO2 storage within a sandstone reservoir. We employ a comprehensive approach, integrating batch reactor, X-ray diffraction (XRD), inductively coupled plasma (ICP) analysis, acoustic measurements, and routine core analysis (RCA) to examine the physiochemical and mechanical response of the selected rock-fluid system. We measured the changes in Berea sandstone before and after 30 days of CO2 storage at selected reservoir conditions (1500 psi and 150°F). Cores and effluent fluids collected at the end of the storage period were analyzed to measure the changes in the critical geochemical and geomechanical parameters (i.e., rock porosity, permeability, mineralogy, mechanical properties) between post-storage and pre-storage. The novelty of this work lies in its comprehensive and multi-dimensional approach to studying CO2 storage in sandstone reservoirs (i.e., saline aquifers), providing valuable insights for the advancement of sustainable carbon capture and storage solutions. The results reveal significant alterations in mineralogy, fluid chemistry, and geomechanical stability. Notably, XRD analysis indicated the formation of new mineral phases, such as halite, and the dissolution of carbonate minerals. ICP analysis showed substantial increases in bicarbonate and sulfate ion concentrations, indicating intense mineral dissolution and ion exchange processes. RCA data demonstrated a decrease in porosity by 0.5% and permeability by 24.0%, attributed to mineral precipitation within pore spaces. Acoustic measurements highlighted changes in geomechanical stability, with alterations in acoustic velocities reflecting changes in rock stiffness and density This research advances our quantitative understanding of the complex interactions within sandstone reservoirs during CO2 storage at the selected timescale that can capture the first order changes in the rock-fluid system. It provides critical information on kinetics, petrophysical properties and geomechanics, contributing essential knowledge for safe and efficient carbon capture and storage (CCS) technology implementation.