CCS coupled with CO2 plume geothermal operations: Enhancing CO2 sequestration and reducing risks

• A field-data-informed reservoir model of the active Aquistore CCS site is used. • Integrated modelling workflow combining reservoir, wellbore, and surface models. • CPG operations provide baseload geothermal energy. • CPG enhances CO 2 sequestration operations by increasing CO 2 mass density and saturation. • CO 2 production enhances CO 2 plume control, sweep efficiency, and predictability. The transition to a low-carbon economy is essential for mitigating climate change, particularly in hard-to-abate sectors. Carbon Capture Utilisation and Storage (CC U S) is expected to play a pivotal role in this transition. This numerical study integrates CO 2 Plume Geothermal (CPG) systems with conventional CCS using field data from the Aquistore CCS project. By employing an integrated subsurface-surface modelling workflow, we simulate and compare two 30-year scenarios with nearly identical masses of sequestered CO 2 : a) “Business-as-usual” CCS and b) coupled CPG-CCUS The results suggest that coupled CPG-CCUS operations provide a stable source of geothermal energy, which could potentially reduce or offset energy costs, such as those associated with the CO 2 capturing process. Additionally, coupling CPG with CCS enhances CO 2 sequestration efficiency by increasing CO 2 mass density in reservoir regions that become thermally depleted due to the sustained injection of CO 2 at temperatures lower than the native reservoir temperature. Although thermally depleted regions develop during both CCS and CPG-CCUS operations, they are significantly more pronounced during the latter due to the combined effect of both cold CO 2 injection and heat extraction. Moreover, CPG‑CCUS operations result in a more concentrated CO 2 plume around the wells. While the production well induces a pressure gradient, this gradient primarily directs fluid flow along the injection-to-production well axis, effectively focusing the CO 2 plume and limiting widespread lateral diffusion of the fluids (brine and CO 2 ) to the far-field reservoir. This localised CO 2 accumulation improves CO 2 plume control and reduces risks associated with uncontrolled CO 2 migration, thereby enhancing the predictability of CO 2 accumulation. This synergistic combination of CCS and CPG operations offers a pathway for the energy transition, enhancing both the CCS technology and the geothermal resource potential, while improving CO 2 sequestration safety.