Model id: Robertson Geologging Focussed Electric Probe with natural gamma
Purpose: formation electrical resistivity
Description: A focussed resistivity measurement with excellent vertical resolution and reasonable depth of investigation. The guard log works well when high borehole fluid salinity and high formation resistance cause the16" and 64" Normal resistivity logs to give inaccurate results. The probe includes a central current-source electrode mounted between two guard electrodes, maintained at the same potential by internal electronics. Current from the central electrode is constrained to a thin disk by the presence of the guards and returns to the cable armour above a 10m insulated section. The potential of the central electrode with respect to a surface voltage-reference stake and the measured current are combined by a down-hole microprocessor to calculate the apparent formation resistivity.
Characteristics: focussed resistivity
|Vertical resolution:||0.010 m|
|Typical logging speed:||5.00 m/min|
|Maximum pressure:||20.0 MPa|
conductive liquidThe borehole has to be filled with a conductive liquid.
|Type of datatransfer:|
cableData are transferred in real time via a cable.
|Required type of logging cable:|
4 conductorA logging cable with 4 conductors.
GO4Connector according to GO 4 standard (4 conductors).
Implement search on winches with this cable head.
|Type of signal:|
digitalDigital signal transmission.
|Maximum diameter:||0.042 m|
|Belongs to toolstring:|
standaloneA stand alone tool that cannot be integrated in a tool string.
|Usage conditons:||Commercial usage allowed/welcome.|
|Additional usage conditions:||Logging as service by Lund University|
Operator and contact:
|Operator:||Lund University, Engineering Geology|
|Contact person:||Per-Gunnar Alm|
John Ericssons väg 1|
|223 63 Lund, Sweden|