Well · Exploration
Logging Tool String
A stack of sensors run on the wireline that measure the rock and its fluids foot by foot along the well.
What it does
Gamma ray estimates shale, resistivity points to hydrocarbons, density and neutron give porosity, and sonic ties the well to the seismic. Specialty tools add images, NMR, formation pressures, fluid samples and sidewall cores.
Basics
| Triple combo | Gamma ray, resistivity, density and neutron |
| Quad combo | Triple combo plus sonic |
| Specialty | Imaging, NMR, formation tester, sidewall coring |
Common failures
- Tool stuck in the open hole, which can turn a logging run into a fishing job
Troubleshooting
- Symptom
- Tension rising while pulling up
- Likely cause
- Tool sticking against the wall or in a ledge
- What to check
- Stop, work the cable within limits and plan the run with less time stationary