Well · Exploration
Drillstem Test
A test run with the drill string still in the hole: packers isolate the zone and valves let the reservoir flow to surface for a while.
What it does
It tells whether the discovery can produce at commercial rates. Pressure gauges in the tool record flow and buildup periods that give pressure, permeability and the extent of the reservoir.
Basics
| Isolation | Temporary packers |
| Duration | From an hour to several days or weeks |
| Gives | Pressure, permeability, productivity |
| Hazards | High pressure, possible H2S |
Common failures
- Packer that does not seal, so the test reads the wrong zone
Troubleshooting
- Symptom
- Pressure record does not stabilize
- Likely cause
- Packer leak or plugged tool
- What to check
- Check the packer seat and repeat the flow period