| Title | Exploration, Suspension, Perforation, Extraction. The WK265 Success Story |
|---|---|
| Authors | Wilson, Daniel ., Bixley, Paul . and Siega, Christine |
| Year | 2014 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Perforation, Well suspension, Contact Energy, Wairakei |
| Abstract | Since 2005, Contact has drilled 30 new production wells in the north-western part of the Wairakei resource (Te Mihi) to support additional generation. Drilling conditions in this area can be difficult with under-pressured and unstable formations, together with very high permeability. These conditions resulted in abandonment of two of the early wells and several more were sidetracked to reach their planned targets. While the best permeability and temperatures for production are usually found at 800-1500m, the field development strategy has been to spread the production risk and target permeability over a range of depths. WK265 was originally designed to target production from below 2000 metres. Cementing the production casing for WK265 was unsuccessful due to a strong interzonal flow in the casing annulus. Attempts to employ backfill cementing over a two week period also proved unsuccessful - with more than 900 tonnes of additional cement pumped during the 12 backfill attempts. A decision was made to suspend WK265, while the subsurface conditions could be fully evaluated, and the rig subsequently proceeded successfully to complete additional wells on the same pad. Following the suspension of WK265, downhole surveys showed that temperatures suitable for production were present in the zone of uncemented casing. Two years after the original drilling, the production casing was perforated close to the permeable zones. Subsequent testing showed the recompleted well to have a capacity to produce more than 10MWe. |