Integrated Geochemical Modeling for CO2 Sequestration in the San Juan Basin, New Mexico

Abstract This paper aims to investigate the geochemical impact of CO2 storage in the San Juan Basin, particularly within the Entrada Sandstone formation. It focuses on examining the importance of interactions between injected CO2 and formation minerals and fluid, investigating mineral dissolution and precipitation, and the effect of these phenomena on rock properties. In this study, a fully compositional reservoir simulator was utilized to simulate the coupled geochemical reactions and several other trapping processes that occur during CO2 injection into the Entrada formation of the San Juan Basin. Prior to the geochemical modeling, injection and pressure data from nearby saltwater disposal wells were used to history-match the hydrodynamic model. By fine-tuning the model against field data, the geological and petrophysical properties of the integrated model were calibrated, ensuring its predictive capability. The simulation integrated reactive transport modeling, which encompasses a broad spectrum of mineral interactions and equilibrium reactions essential for an accurate depiction of geochemical alterations. The study examined the impact of CO2 injection on fluid and rock properties. Our findings revealed that the majority of injected CO2 maintains a supercritical state, closely followed by residual trapping, which emphasizes the dominance of structural trapping and hysteresis as the key mechanisms for CO2 sequestration. Mineral trapping, in contrast, contributes minimally. Notably, despite considerable precipitation of quartz and calcite, the dissolution of other minerals counteracts it, keeping the decrease in porosity under 0.1%. Changes in ion concentration in the fluid follow the dissolution/precipitation trend of the minerals. This research provides detailed insights into the effects of CO2 sequestration on reservoir fluid dynamics, mineral compositions, and rock attributes within the San Juan Basin. It highlights the vital role of reservoir simulation in evaluating the long-term impact and efficacy of CO2 storage with a focus on geochemical interactions, contributing valuable knowledge to the field of carbon capture and storage.