Determining the brine extraction well type, location, and rate for optimal pressure and carbon dioxide plume management

Abstract

Brine extraction strategies can be applied in carbon capture and storage (CCS) projects to overcome two technical barriers to the commercial deployment of CCS technology: (1) managing reservoir pressure and (2) controlling the carbon dioxide (CO2) plume in the subsurface. Numerical simulations were performed to evaluate changes in reservoir pressure and CO2 saturation during brine extraction. A series of scenarios were simulated to determine the optimal brine extraction strategies through the sensitivity study of well type, well location, extraction rate, and perforation interval. The simulation results were analyzed for their efficacy to manage reservoir pressure and the CO2 plume. Differential pressure, CO2 storage efficiency, and the distance of the CO2 plume to the extraction well were used as metrics to evaluate performance. With an injection-to-extraction ratio of 1:1 (volumetric balance), the optimal location for a vertical extraction well is in a direction perpendicular to high hydraulic conductivity direction, and on the down-dip side, with perforation(s) within the injection zone. A horizontal extraction well has the following advantages over a vertical extraction well: it presents less risk of drilling into an existing CO2 plume; CO2 storage efficiency is improved; a lower extraction rate, thus less volume of brine extraction, is required to move the CO2 plume and reduce reservoir pressure; and it has less impact on the lateral movement of the CO2 plume, which could result in lower CO2 storage efficiency and CO2 plume leaving the area of review. To minimize brine extraction yet have a noticeable effect on reservoir pressure and movement of the CO2 plume, this study recommends injection-to-extraction ratios of 2:1 for a vertical well and 4:1 for a horizontal well, which correspond to extraction rates of 10,000 and 5,000 stb/day, respectively, when injecting 1 million metric tons of CO2 per annum. These findings can be used to guide similar studies on brine extraction to manage CO2 storage.