Well · Exploration
Cores
Real pieces of the reservoir rock brought to surface, either as a long cylinder cut with a hollow bit or as small plugs taken from the borehole wall.
What it does
Cores reveal reservoir properties that logs alone cannot see. In the lab they give porosity, permeability, saturations, grain density and rock texture, and they calibrate the logs.
Basics
| Whole core diameter | 1.75 to 5.25 in (4.45 to 13.34 cm) |
| Typical cut | About 30 ft (9 m) per barrel |
| Sidewall | Up to about 90 depths per run on wireline |
| Analysis | Porosity, permeability, saturation |
Common failures
- Core jammed or lost in the barrel, so the key interval is not recovered
Troubleshooting
- Symptom
- Low core recovery
- Likely cause
- Jamming, broken rock or a worn core catcher
- What to check
- Shorten the run, adjust parameters and check the catcher