Abstract
There is a potential for synergy effects in utilizing CO2 for both enhanced gas recovery (EGR) and geothermal energy extraction (CO2-plume geothermal, CPG) from natural gas reservoirs. In this study, we carried out reservoir simulations using TOUGH2 to evaluate the sensitivity of natural gas recovery, pressure buildup, and geothermal power generation performance of the combined CO2-EGR–CPG system to key reservoir and operational parameters. The reservoir parameters included horizontal permeability, permeability anisotropy, reservoir temperature, and pore-size-distribution index; while the operational parameters included wellbore diameter and ambient surface temperature. Using an example of a natural gas reservoir model, we also investigated the effects of different strategies of transitioning from the CO2-EGR stage to the CPG stage on the energy-recovery performance metrics and on the two-phase fluid-flow regime in the production well. The simulation results showed that overlapping the CO2-EGR and CPG stages, and having a relatively brief period of CO2 injection, but no production (which we called the CO2-plume establishment stage) achieved the best overall energy (natural gas and geothermal) recovery performance. Permeability anisotropy and reservoir temperature were the parameters that the natural gas recovery performance of the combined system was most sensitive to. The geothermal power generation performance was most sensitive to the reservoir temperature and the production wellbore diameter. The results of this study pave the way for future CPG-based geothermal power-generation optimization studies. For a CO2-EGR–CPG project, the results can be a guide in terms of the required accuracy of the reservoir parameters during exploration and data acquisition.
Highlights
The effects of global warming on the environment are on the rise due to anthropogenic emissions of greenhouse gases, namely carbon dioxide (CO2 )
The technology known as carbon capture and storage (CCS), which features the capture of CO2 from flue gases of power plants that are stored in suitable, carefully selected geological formations, is one of the technologies that can contribute to achieving net-zero CO2 emissions [1,2,3]
CO2 injection into partially depleted or depleted natural gas reservoirs can enhance the production of the gas, which is a typical example of combining CO2 utilization and storage
Summary
The effects of global warming on the environment (including sea-level rise, extreme weather conditions etc.) are on the rise due to anthropogenic emissions of greenhouse gases, namely carbon dioxide (CO2 ). The development and use of clean, low-carbon, energy-efficient technologies and renewable energy sources are ways of reducing such emissions. To this effect, the technology known as carbon capture and storage (CCS), which features the capture of CO2 from flue gases of power plants (and other large CO2 -emitting industrial plants) that are stored in suitable, carefully selected geological formations, is one of the technologies that can contribute to achieving net-zero CO2 emissions [1,2,3]. The coupling of CCS to the industrial utilization of the captured CO2 , termed carbon capture, utilization, and storage (CCUS) can reduce its costs. CO2 injection into partially depleted or depleted natural gas reservoirs can enhance the production of the gas (enhanced gas recovery, EGR), which is a typical example of combining CO2 utilization and storage
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