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Robertson Geo • PS Logger Probe

Product Type
Wireline Logging Tool
Product Snapshot
Product Name
PS Logger Probe
Product Type
Wireline Logging Tool
Robertson Geo
Rent ● Equipment & Operator
Robertson Geo's PS Logger Probe is a low-frequency acoustic sonde designed to measure compressional (P) and shear-wave (S) velocities in soils and soft rock formations. It operates using indirect excitation rather than mode conversion as in a conventional sonic. It is capable of acquiring high resolution P and S wave data in borehole depths of up to 600m in water.

The PS Logger probe contains a unique design of powerful hammer source and two receivers, separated by acoustic damping tubes. To acquire data, the probe is stopped at the required depth and the source is fired under surface command. Firing causes a solenoid-operated shuttle aligned across the borehole axis to strike plates on opposite sides of the probe in turn, setting up a pressure doublet in the surrounding fluid. The resultant fluid motion produces a tube wave at the borehole wall with velocity close to the shear velocity of the formation together with a compressional wave.

As the waves propagate parallel to the borehole axis, they set up corresponding fluid movements that are detected by the two neutral buoyancy 3D hydrophone receivers and geophones, allowing the wave velocity to be determined. The facility to stack multiple shots and filter the data as in normal seismic data acquisition is included in the operating software.
Features & Applications
Key Features
  • High energy shear-wave source has typically 20x power of conventional sonic probes
  • Low-frequency measurement, more representative of engineering situations
  • Stacking of multiple shots
  • Probe separates for shipping
  • Real-time wavelet (wiggle) display
  • Compatible with Robertson Geo Micrologger2
  • Site investigation - foundation studies, wind farms, offshore structures, dam safety
  • Physical properties of soil/rock - shear modulus, bulk modulus, compressibility and Poission's ratio
  • Earthquake engineering - characterisation of strong motion sites
  • Velocity control for seismic reflection surveys
  • Engineering
Operating Conditions
Borehole Type
Open-hole, water-filled
Logging Speed
Static measurements
Probe Specifications
50 mm
Length (Assembled)
6.07m - 7.07m (1m or 2m filter)
Length (Shipping Case)
1.45m (4.75ft) supplied in two transport cases
Weight (Assembled)
26.5kg - 28kg (1m or 2m filter)
Temperature (Max)
Pressure (Max)
Receiver Type
3D hydrophones (p), geophones (s)
Receiver Spacing
1,000mm (3.28ft)
Waveform Acquisition Period
5.12mS - 409.6mS
2.5μs minimum
Downhole Gain
0db - 42db (surface control)
Length (Filter)
1m ● 2m
Launch & Recovery
Related Products
Robertson Geo's High Resolution Optical Televiewer (Hi-OPTV) provides a continuous very high resolution oriented image of the borehole walls using a conventional light source. A unique optical system based on a fisheye lens allows the probe to survey 360 degrees simultaneously. This information is processed in real time to produce a complete 'unwrapped' ... Moreimage of the borehole oriented to magnetic north. The probe offers superior resolution to the High Resolution Acoustic Televiewer (HRAT) and produces images in real colour. While, unlike the HRAT, it can operate in air-filled boreholes, it is unsuitable for boreholes containing mud or cloudy fluids.

WellCad™ Image-Processing Software
WellCad™ is a Windows-based package for processing, interpreting and displaying acoustic and optical televiewer image logs. Standard log presentations include tadpole and stick plots, stereographic projections of poles to planes and azimuth frequency diagrams. The synthetic core display allows convenient comparison of log and field data for orientation of fractured or incomplete core sections.
Robertson Geo's 3-Arm Caliper probe provides a single continuous log of borehole diameter, as recorded by three mechanically coupled arms in contact with the borehole wall. 710mm, 1000mm and 1500mm range calipers are available to suit a range of well diameters. The caliper is a useful first log to determine the borehole conditions before running more ... Morecostly probes or those containing radioactive sources.

Principle of Measurement
Opening and closing of the motor-drivercaliper arms is by surface command, allowing the probe to run into the borehole with the arms retracted. Once opened, the spring-loaded arms respond to borehole diameter variations as the probe is raised up the borehole.
Robertson Geo's Density Guardlog probe uses dual shielded detectors to provide a borehole compensated density measurement with good bed-boundary resolution, similar to the Formation Density probe. The Density Guardlog probe offers an additional LL3 focussed electrical measurement with good vertical resolution and depth of investigation.... More

Principle of Measurement
The Density Guardlog probe contains a detachable 137Cs gamma source and two scintillation gamma detectors. The active windows of the source and detectors are maintained in contact with the borehole wall by a motorised caliper arm. Gamma radiation back-scattered by the formation (Compton effect) reaches the detectors where the relative count rates provide a measure of formation density.
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+44 1492 582323