Geoelectrical Evaluation of CO2 Storage in Carbonate Aquifers Using Carbonated Water Injection

Abstract

The rising levels of carbon dioxide (CO₂) in the atmosphere and its role in global climate change have necessitated the development of effective carbon storage strategies. Geological storage of CO₂ in saline aquifers is a viable method to reduce CO₂ emissions due to its extensive size. However, mineral trapping, where CO₂ interacts with aquifer minerals or cations in the brine and converts the injected CO₂ into stable carbonates, is one of the most secure carbon storage mechanisms, contributing to the long-term retention of CO₂. Nevertheless, the dynamic processes governing mineral trapping, especially under different temperature conditions, remain insufficiently understood. Therefore, this study employs real-time electrical resistivity measurements to examine the geochemical interactions and their impact following carbonated water injection. Additionally, the study assesses changes in pore structure, pore connectivity, mineral dissolution, and precipitation behavior through microcomputed tomography scans, effluent fluid analysis, and nuclear magnetic resonance. Results revealed a notable reduction in electrical resistivity after carbonated water injection, attributed to increased ionic strength, highlighting the effectiveness of resistivity logging for real-time monitoring of CO₂ injection. Furthermore, temperature was found to significantly influence wormhole formation, a key outcome of rock dissolution. While dissolution was less evident at 30 °C, a temperature of 50 °C promoted widespread wormhole formation due to enhanced mineral dissolution. However, at 70 °C, mineral dissolution was limited owing to decreased CO₂ solubility at higher temperatures. These findings suggest that 50 °C provides the optimal conditions for long-term CO₂ storage via carbonated water injection in carbonate aquifers, balancing pore structure enhancement with stable mineral trapping.