| Title | CO2 injection well design in the geothermal industry |
|---|---|
| Authors | C. Finnegan |
| Year | 2024 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | New Zealand, Drilling, CO2, Geothermal, Well Design, Drilling, Completion, CCS, Cement, Metallurgy, Phase Behavior, Regulations, Monitoring |
| Abstract | The geothermal industry is keen to reduce the climate impact for all their operations. Capturing associated CO2 and reinjecting it returns the naturally occurring geothermal CO2 back underground to where it came from. Globally, CO2 re-injection is still in its infancy. In all of Australia, there is only one CO2 injection project currently in operation and globally there are still many valuable lessons being learned. Many aspects of drilling CO2 injection wells are similar to drilling a conventional geothermal well though there are significant differences between them. This paper shall discuss key differentiators between conventional well design techniques and CO2 injection wells. Areas addressed include: • Regulations • Geological Characterization • Metallurgy • Cementing • Load cases • Well integrity • Monitoring and Verification • Risk Assessment • Contingency planning including well control • Design process • Legacy wells and abandonment of existing wells There are two options available for CO2 injection: re-using existing wells with remediation, workover, or recompletion activities, or drilling new wells dedicated to CO2 injection. Each option has its own advantages and disadvantages, but the main goal is always to ensure that the wellbore and reservoir can securely hold the CO2 for an extended period without any leaks into sensitive zones, such as to an aquifer or the atmosphere. To choose the most suitable well design, it is important to have a thorough understanding of the pressure and temperature profile throughout the lifecycle of the well. These parameters will behave differently compared to a geothermal well. Analysis is necessary to accurately assess and mitigate any risks associated with the well. To ensure the effectiveness of the CO2 injection well, a monitoring and verification plan may be necessary to ensure the containment of CO2 and to identify any potential anomalies. Monitoring may include pressure, temperature, logging of tubing integrity, and even conducting seismic surveys. |