[Gamma Ray Logging Tool]
Downhole logging sensor measuring the natural gamma emission from surroundings rocks
Measure Unit = [GAPI]
1 GAPI = 0.005 (GR_{RA} - GR_{NRA})
where
GRRA is GR tool reading against radioactive part of Calibration Stand in University of Houston
GRNRA is GR tool reading against non-radioactive part of Calibration Stand in University of Houston
Scope of Applicability
- Depth Matching between cased-hole and open-hole logs
- Pick up radioactive anomalies caused by saline water invasion
- Pick up radioactive anomalies caused by water invasion or radioactive tracers
Mathematical Model
| GR = (1-\phi_e) \cdot GR_{m} + \phi_e \cdot GR_f |