GeoLog Pty Ltd
The ELOG or electric log is the classic water-well combination probe combining shallow, medium and deep penetrating resistivity measurements with self-potential (SP) and natural gamma (optional).
Principles of Measurement
The down-hole ELOG probe is equipped with electrodes, measurement electronics and an insulated bridle. A low-frequency bi-directional electric current from a source electrode on the probe returns through the formation to the cable armour above the bridle. Potentials due to this current flow are measured on various sense electrodes on the probe with respect to a voltage-reference ‘fish’ normally located at the surface. The spacing between the source and individual sense electrode determines the depth of investigation of the measurement. These measurements are converted to apparent formation resistivities within the probe and digitally transmitted to the surface.
The SP is a voltage measurement between a non-polarising down-hole electrode and a reference ‘fish’ at the surface.
Digital down-hole measurement avoids errors due to cable effects in deeper boreholes
Constant-power down-hole current source give 4 decades of measurement without manual range switching
Automatic real-time correction for borehole diameter and well-fluid resistance
Optional natural-gamma measurement and temperature
16" Normal resistivity
64" Normal resistivity
Self potential (SP)
8" and 32" Normal resistivity (optional)