GR (Gamma Ray Logging Tool)

Deployment	Borehole
Log Name	GR
Measured Property	natural gamma emission from surroundings rocks
Sensor Type	Scintillation counter
Units
SI	R /s
Oil Metric	μ R /hr = 2.8 ·10^-10R /s
Oil Field	GAPI = 4.2^·10^-10R /s = 1.5^μ R /hr

* – for scintillation detectors

Applications

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

Sample Logs

Tool Schematic

Mathematical Model

$\begin{array}{l}\displaystyle GR = (1-\phi_e) \cdot GR_{m} + \phi_e \cdot s_w \cdot GR_w\end{array}$

where $\begin{array}{l}GR_w\end{array}$ is natural gamma radioactivity of formation water and $\begin{array}{l}GR_m\end{array}$ is natural gamma radioactivity of rocks:

$\begin{array}{l}\displaystyle GR_m = \sum_i GR_{mi}\end{array}$

where $\begin{array}{l}GR_{mi}\end{array}$ natural gamma radioactivity of i-th mineral.

Page tree

GR (Gamma Ray Logging Tool)

Applications

Sample Logs

Tool Schematic

Mathematical Model