Slim Holes At Alvord Hot Springs Area (Combs, Et Al., 1999)
Exploration Activity: Slim Holes At Alvord Hot Springs Area (Combs, Et Al., 1999)
|Exploration Activity Details|
|Location||Alvord Hot Springs Area|
|Exploration Technique||Slim Holes|
Anadarko Petroleum Corporation drilled two slimhole discoveries in the 1980s, one at Salt Wells, NV, and the other at Pueblo Valley, OR. Both of these slimholes were hot enough to discharge unassisted and were successfully flow tested. A slimhole at Pueblo Valley, in south-east Oregon was planned and permitted as a test well to evaluate an interval of fractured basalt which had been discovered while drilling an earlier thermal-gradient hole. Using a UDR1500 rig, the hole was rotary-drilled to 1087' and then core-drilled (HQ) to TD of 1479 feet. Artesian wellbore pressures during the core-drilling were controlled with weighted mud. The discharge test did not require airlift to start and the slimhole flowed at 400 gpm through a 4" line and 3" orifice plate. Wellhead pressures and temperatures during discharge were 69-75 psig and 300-3050F, so flow was almost completely liquid, which accounts for the relatively high flow rate horn this size hole. Transmissivity, estimated at 1000 darcy-feet, was also very high. Shut-in wellhead pressure was 64 psi. After a long delay from injunctions sought by environmental groups, two additional slimholes were drilled at this location in 1993 with results similar to the original well in 1989. Using typical exploration success rates and well costs for the Basin and Range province, the reference author estimates that slimholes could reduce exploratory drilling costs by 50% and total exploration costs by 28%.
- Jim Combs, John T. Finger, Colin Goranson, Charles E. Hockox Jr., Ronald D. Jacobsen, Gene Polik (1999) Slimhole Handbook- Procedures And Recommendations For Slimhole Drilling And Testing In Geothermal Exploration