Neutron tool is measuring the intensity of neutron radiation at a fixed distance from neutron source which is proportional to primarily the hydrogen concentration in the media.
The tool has two sensors: near and far .
The tool delivers the neutron count ration between the two sensors:
| (1) | N_{\rm log} = \rm \frac{N_{far}}{N_{near}} |
The CNL readings are measured in frac (unitless).
The tool readings can be simulated by following equation:
| (2) | N_{\rm log} = \phi_e \, N_f + V_{sh} \, N_{sh} + V_m \, N_m |
| (3) | N_{\rm log} = \phi_e \, N_f + V_{sh}\, N_{sh} + (1 - \phi_e - V_{sh}) \,N_m |
| (4) | N_{\rm log} = N_m + (N_f - N_m) \, \phi_e + (N_{sh} - N_m) \, V_{sh} |
Unlike litho-density tool the above equations are not always accurate but in the most practical applications can be considered as a fair approximation.
| (5) | N_f = s_{xo} N_{mf} + (1-s_{xo}) ( s_w N_w + s_o N_o + s_g N_g ) |
| (6) | N_m = \sum_i V_{mi} N_{mi} |
See Also
Petroleum Industry / Upstream / Data Acquisition / Well & Reservoir Surveillance / Well Logging / Open-Hole Formation Logging (OHFL)
[ Petrophysics (PP) / Reservoir Data Logs ][ Well & Log Analysis ]