| Title | A review of non-condensable gases (NCGs) reinjection within the geothermal industry and a comparison with other carbon capture and storage (CCS) technologies |
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| Authors | A. Carmichael, S.J. Zarrouk |
| Year | 2023 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Non-condensable gas, Reinjection, Geothermal field, Carbon capture and storage |
| Abstract | Greenhouse gases (GHGs), including carbon dioxide (CO2), are the primary drivers of global warming and climate change. To combat this urgent issue, there have been global efforts to reduce GHG emissions from energy production through initiatives like the Paris Agreement and national carbon taxes. In the geothermal, oil and gas, and coal bed methane (CBM) industries, various strategies have been explored to mitigate emissions. This report reviews the current status of Non-Condensable Gas (NCG) reinjection within the geothermal industry and compares the techniques used with other carbon capture and storage (CCS) methods. The geothermal industry has shown promise in reducing GHG emissions by reinjecting NCGs. Pilot projects in multiple countries have successfully demonstrated NCG reinjection, primarily through basaltic mineralization and residual trapping. However, further research is needed to assess the potential of NCG reinjection in different geothermal reservoir geologies. In the oil and gas, and Coal Bed Methane (CBM) industries, various CCS methods have been investigated. These include CO2-enhanced oil recovery (CO2-EOR), CO2-enhanced gas recovery (CO2-EGR), CO2-enhanced coal bed methane (CO2-ECBM), and CO2 storage in saline aquifers and depleted oil and gas fields. CO2-EOR has extensive project experience but is primarily an enhanced oil recovery technique rather than a climate change mitigation method. CO2-ECBM faces challenges such as coal swelling and decreased permeability. CO2-EGR is still in development and has limited project experience. Saline aquifers and depleted oil and gas fields are seen as long-term storage solutions, but uncertainties remain regarding modelling and cap rock integrity, and there is also a current lack of financial incentive for these methods. In summary, these approaches contribute to global efforts to reduce GHG emissions. These methods differ significantly in their strategies. Further research and development are necessary to optimise these methods and address their limitations for effective climate change mitigation. |