Simulation of CO2 Injection in Mature Oil Fields: Implications for Geothermal Energy Generation

The urgent need to combat climate change underscores the importance of reducing anthropogenic CO2 levels in the atmosphere through geological sequestration. While Carbon Capture and Storage(CCS) has been applied in various settings and has demonstrated its potential over the recent decades, economic challenges associated with CCS continue to be a significant barrier to its extensive large-scale implementation. This abstract discusses a promising solution: using CO2 as a geothermal working fluid to extract heat from deep, naturally porous, and permeable geologic formations, a concept known as CO2 Plume Geothermal (CPG). Oil fields in particular are attractive candidates for the deployment of CPG due to the presence of existing well infrastructure, extensive reservoir and production data, and an effective caprock. This innovative approach not only enables enhanced oil recovery through CO2-EOR, at an initial stage, and sustainable power generation but also ensures permanent carbon sequestration. Consequently, CPG in oil fields can serve as a catalyzer to deploying large-scale CCS projects, leveraging multiple co-benefits such as energy offset, decarbonization, carbon market development, and extended operational field life.

Through a combination of advanced non-isothermal and compositional numerical reservoir models, we comprehensively examine the geotechnical feasibility of deploying CPG at oil fields. The primary objectives of this study include evaluating the geothermal energy extraction efficiency, assessing the economic and environmental co-benefits, and addressing associated performance uncertainties. Building on crucial insights from existing CO2-EOR studies, we consider factors such as the mobility differences between injected and displaced fluids, interactions between CO2, oil, reservoir brine, and rock, and flow channeling through high-permeability pathways created by the heterogeneous nature of geological reservoirs. Furthermore, we delve into the thermal and compositional variations within the reservoir induced by water flooding operations during the secondary oil recovery stage, analyzing their effects on CPG performance in comparison to unperturbed saline aquifers. Integrating geothermal energy production, enhanced oil recovery, and permanent carbon sequestration, CPG in oil reservoirs can advance the integration of renewable energy and greenhouse gas management in the global effort to combat climate change.