Hot Dry Rock Exploration Drilling 3,000 m: CMD150T Five-Spud Hole
Executive Summary
A hot dry rock (HDR) exploration hole was drilled to a final depth of 3,000 m with the CORTECH® CMD150T modular rig, running φ127 mm oilfield drillpipe. Because the objective was exploration — proving the deep hot-rock reservoir — the well was built as a five-spud architecture, stepping from φ600 mm at surface to φ152 mm at the production interval, with a planned coring strategy of 10 m of core taken per 100 m drilled and sampling at around 300 m. This case covers the five-spud program and the core-sampling approach that turned a 3,000 m hole into usable HDR exploration data.
Project Background & Challenge
Hot dry rock exploration differs from production geothermal drilling: the hole exists to *understand* the reservoir, not just to deliver fluid. That raises two requirements:
- A robust deep hole: reaching 3,000 m demands a staged, five-spud casing architecture that isolates shallow and unstable intervals on the way down.
- Planned coring: the operator needs structured rock samples — here a defined 10 m-per-100 m coring pattern — to characterize the hot-rock body, rather than cutting a completely open hole.
Our Solution
The CMD150T modular rig ran the five-spud program on φ127 mm oil drillpipe:
| Spud | Setting depth | Drilled diameter |
|---|---|---|
| Spud 1 (surface) | 0 m | φ600 mm |
| Spud 2 | 300 m | φ400 mm |
| Spud 3 | 500 m | φ311 mm |
| Spud 4 | 1,500 m | φ215.9 mm |
| Spud 5 | 2,300 m | φ152 mm |
- Five-stage stepwise reduction: 600 → 400 → 311 → 215.9 → 152 mm, isolating each interval before drilling the next, smaller hole to total depth.
- φ127 mm oilfield drillpipe: oilfield-grade tubulars supplied the strength and hydraulics needed for a 3,000 m exploration hole.
- Coring strategy: core was taken at a planned rate of 10 m per 100 m drilled, with sampling at approximately 300 m, giving the exploration program a systematic rock record down the hole.
- 150 t-class modular rig: the rig's pullback, modular pin-up design and fluid system supported the large shallow holes and the deep coring intervals.
Key Results
| Metric | Value |
|---|---|
| Final depth | 3,000 m |
| Program type | Hot dry rock exploration hole |
| Drillpipe | φ127 mm oilfield drillpipe |
| Wellbody architecture | Five-spud program |
| Spud 1 / 2 / 3 | φ600 mm @ 0 m / φ400 mm @ 300 m / φ311 mm @ 500 m |
| Spud 4 / 5 | φ215.9 mm @ 1,500 m / φ152 mm @ 2,300 m |
| Coring plan | 10 m core per 100 m drilled; sampling at ~300 m |
| Rig | CORTECH CMD150T modular |
For the full technical specifications of the CORTECH® CMD150T, see the CMD150T product page.
Customer Value & ROI
- Exploration data, not just footage: the planned 10 m-per-100 m coring pattern delivered a systematic rock record to evaluate the HDR reservoir — the actual deliverable of an exploration hole.
- Deep hole, staged safely: five spuds isolated shallow ground on the way to 3,000 m, protecting the deep coring intervals from collapse and lost circulation.
- Built for the size range: handling φ600 mm surface holes through to a φ152 mm production interval is within the 150 t modular rig's casing and hoisting envelope.
- Modular mobility for remote exploration: pin-together skid modules let the rig reach and rig up on remote HDR exploration sites.
FAQ
What is a five-spud exploration well?
The well is drilled and cased in five successive sections. Here: 600 mm at 0 m, 400 mm at 300 m, 311 mm at 500 m, 215.9 mm at 1,500 m and 152 mm at 2,300 m, sealing off each interval before drilling the next smaller hole to 3,000 m.
How is core taken in a deep HDR exploration hole?
On this project a planned coring strategy took 10 m of core per 100 m drilled, with sampling at around 300 m — a systematic pattern that gives geologists a controlled rock record of the hot-rock reservoir.
What drill pipe is used for hot dry rock drilling?
This 3,000 m HDR exploration hole was run on φ127 mm oilfield-grade drillpipe, chosen for the strength and hydraulic performance required at depth.
How deep was the CMD150T HDR exploration hole?
The hole reached a final depth of 3,000 m as a five-spud hot dry rock exploration well, drilled with the CMD150T modular rig.