RHOB – Bulk Density
| Log Name | RHOB |
|---|---|
| Math notation | \rho_B |
| Units | g/cc |
| Sandstone scale | |
| Carbonate scale |
Density tool is measuring the intensity of gamma radiation at a fixed distance from gamma source which is proportional to electron concentration in the media.
Except few isotops the electron concentration is proportional to the deuteron concentration and hence the concentration of molecular mass which is density of the matter.
The tool readings \rm GG_{log} are normalized on the freshwater tool readings \rm GG_w and termed bulk density \rho_B:
| (1) | \rho_B = \rm \frac{GG_{log}}{GG_w} |
The bulk density
\rho_B is measured in
\rm \big[ 10^3 \cdot \frac{kg}{m^3} \big] = \big[ \frac{g}{cc} \big].
(2)
\rho_B = \phi_e \, \rho_f + V_{sh} \rho_{sh} + V_m \rho_m = \phi_e \, \rho_f + V_{sh} \rho_{sh} + (1 - \phi_e - V_{sh}) \rho_m
(3)
\rho_f = s_{xo} \rho_{mf} + (1-s_{xo}) ( s_w \rho_w + s_o \rho_o + s_g \rho_g )
(4)
\rho_m = \sum_i V_{mi} \rho_{mi}
PeF – Photoelectric Factor
The photoelectric factor is measuring the gamma radiation in a certain energy spectrum which is characteristic for photo effect gamma scaterring and very specific to some molecules in popular minerals.
This helps identify the rock lithology.