| Title | Recent subsurface insights at Rotokawa: Case study of a new well |
|---|---|
| Authors | B. Murphy, M. Kelley, J. Sia, D. Subekti |
| Year | 2025 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Rotokawa Geothermal Field, geothermal well drilling, geothermal geology, reservoir conditions, casing design |
| Abstract | In 2024, an injection well was drilled at the Rotokawa Geothermal Field, targeting feed zones indicated by offset wells. The injection well was designed to replace a previous injection well which had wellbore integrity issues. By re-targeting feed zones from offset wells, the new well provided an opportunity to validate current reservoir models and gather fresh subsurface data. The well design leveraged learnings from nearby wells to improve the likelihood of success and reduce drilling risk. The planning included both primary and contingency completion options to address potential challenges associated with expected high subsurface temperatures and weak rock strength conditions. With both primary and secondary completion designs prepared in advance, the drilling team was able to “dynamically” install the design that fitted the formation characteristics collected as the well was drilled. The drilling program was completed on schedule and to plan. The target feedzones were successfully intercepted, with excellent permeability encountered. The maximum measured temperature of this well was 338°C after heat-up, possibly the hottest so far recorded in New Zealand. Although the well was drilled near existing wells, the encountered subsurface conditions highlighted that significant changes in reservoir characteristics can occur over short distances in the field. Data from the new injection well revealed, in particular, more detailed information about the potential nature of the deep reservoir boundary and new insights on stratigraphic and structural controls on reservoir conditions in the injection area. These results will be used to refine the conceptual model and support future well planning at Rotokawa. |