Deep Geothermal Well Drilling 2,600 m: CMD150T Four-Spud Program
CORTECH CMD150T deep geothermal well drilling rig executing a four-spud program to 2,600 m
Executive Summary
A geothermal well planned to a design depth of 2,600 m was drilled with the CORTECH® CMD150T modular rig, running φ127 mm drillpipe through a four-spud wellbody architecture. The program deliberately matched the drilling method to each interval: mud-cone drilling in the second spud and screw-motor drilling in the fourth spud, stepping the borehole from φ500 mm at surface down to φ215.9 mm through the four casing points. This case explains the interval-by-interval design — which diameter runs at which depth, and why different bottom-hole assemblies were chosen for shallow versus deep sections.
Project Background & Challenge
A 2,600 m geothermal well is a staged engineering problem:
- Shallow ground needs protection: near-surface unconsolidated and shallow zones must be sealed with a large-diameter surface hole before deeper work begins.
- Different intervals, different tools: the shallow sections benefit from robust mud-cone (roller-cone) drilling, while the deeper, finer production section is better drilled with a downhole screw motor for controlled, efficient rock cutting.
- Heavy tubulars at depth: reaching 2,600 m on φ127 mm drillpipe demands real hoisting and pulldown capacity from the rig.
Our Solution
The CMD150T — a 150 t-pullback modular full hydraulic rig — was selected to run the staged program:
| Spud | Setting depth | Drilled diameter | Method / note |
|---|---|---|---|
| Spud 1 (surface) | 0 m | φ500 mm | Conductor / surface isolation |
| Spud 2 | 34 m | φ406 mm | Mud-cone (roller-cone) drilling |
| Spud 3 | 385 m | φ295 mm | Intermediate casing point |
| Spud 4 | 808 m | φ215.9 mm | Downhole screw (mud) motor drilling |
- φ127 mm drillstring: the chosen drillpipe size balances rigidity, torque transmission and hydraulics for a 2,600 m design depth.
- Mud-cone drilling (spud 2): roller-cone bits handle the shallow, mixed surface interval efficiently.
- Screw-motor drilling (spud 4): the downhole mud motor drives the bit with fluid power, suited to the deeper, smaller-diameter production section.
- Four-spud isolation: each casing point seals off the interval above before the next, smaller hole is drilled deeper.
Key Results
| Metric | Value |
|---|---|
| Designed well depth | 2,600 m |
| Drillpipe used | φ127 mm |
| Wellbody architecture | Four-spud program |
| Spud 1 / diameter | 0 m / φ500 mm |
| Spud 2 / diameter / method | 34 m / φ406 mm / mud-cone drilling |
| Spud 3 / diameter | 385 m / φ295 mm |
| Spud 4 / diameter / method | 808 m / φ215.9 mm / screw-motor drilling |
| Rig | CORTECH CMD150T modular |
For the full technical specifications of the CORTECH® CMD150T, see the CMD150T product page.
Customer Value & ROI
- Method matched to formation: using mud-cone drilling shallow and screw-motor drilling deep optimizes penetration per interval instead of forcing one bottom-hole assembly through the whole well.
- Staged isolation reduces risk: four casing points seal problematic intervals as the well deepens, cutting lost-circulation and collapse exposure.
- Capacity for depth: the 150 t pullback and 35 MPa fluid circuit handle the φ127 mm string and the mud-motor hydraulics needed at 2,600 m design depth.
- Modular site flexibility: pin-together skid modules suit geothermal sites where heavy single-piece rigs are impractical.
FAQ
What drill pipe size suits a 2,600 m geothermal well?
This program used φ127 mm drillpipe — a size that balances string rigidity, torque transmission and circulating hydraulics for a 2,600 m design-depth geothermal well.
What is mud cone drilling?
It is roller-cone bit drilling, used here in the second spud (φ406 mm at 34 m) to efficiently drill the shallow, mixed near-surface interval before intermediate casing.
What is a downhole screw (mud) motor used for?
A downhole screw motor converts circulating mud pressure into rotary power at the bit, used here in the fourth spud (φ215.9 mm) for controlled, efficient drilling of the deeper production section.
What casing program did the CMD150T well use?
A four-spud program: spud 1 φ500 mm at 0 m, spud 2 φ406 mm at 34 m, spud 3 φ295 mm at 385 m, and spud 4 φ215.9 mm at 808 m, on a 2,600 m design depth.