Injection of Supercritical CO2 into Deep Saline Carbonate Formations - Predictions from Geochemical Modeling (SPE-121272)

摘要

Carbon Capture and Storage (CCS) is one of the most technically mature options to increase energy supply while reducing CO2 emissions. Previous research has concentrated on evaluating the impact of CO2 injection on saline aquifers from siliciclastic formations. Nevertheless, their limited availability, or their too deep occurrences, in certain specific regions with high CO2 emissions, leads saline aquifers in carbonate formations to be considered as alternative solutions for CO2 Storage. Modeling of supercritical CO2 injection into a deep carbonate formation (calcite and dolomite, with minor anhydrite) was performed using TOUGHREACT Pitzer ion-interaction model. The formation brine is ?250,000 ppm (NaCl dominant), temperature at 102oC and pressure at 225 bars. CO2 injection rate was considered constant and for a period of 1 year, through a vertical well in a 2D radial model domain, and a horizontal well in a 3D model domain, respectively. The effect of faults was evaluated for the second case. The simulations found that: (1) a dryout zone is developed within a few meters from the injection well due to displacement by supercritical CO2 and evaporation of water into CO2; (2) at the dryout zone front, brine is further concentrated due to water evaporation, pH is lowered to 3.1, halite (NaCl) and anhydrite (CaSO4) precipitate and the brine becomes CaCl2-dominant; (3) porosity reduces by ~5%-10% due to halite precipitation (dryout zone) (4) HCl gas is generated from the dryout front; (5) calcite dissolves close to the injection well and precipitates at areas far from the well, however, 6) the overall mineral trapping is not significant in hundreds of years for this carbonate formation. These findings are valuable for the assessment of CO2 sequestration, injectivity changes, and near well- bore stability of saline aquifers in carbonate formations.