Sonic / CBL Sonde
The Geovista sonic sonde features a modular design allowing for reduced
dimensions and easier handling. Each module behaves as an individual sonde with its own address, leading to unparalleled configuration flexibility. Typically, it can be used for Sonic Transit Time, CBL and Full Waveform logs.
CBL (Cement Bond Log): For this application, the sonde uses one transmitter and two receiver modules separated by insulating sections.
Transit Time / Full Waveform: the addition of another transmitter and insulator section allows for compensated formation sonic transit time and full waveform data to be acquired.

Specifications:
Transducers ceramic piezoelectric with 23 KHz resonant frequency
Spacing: Variable. Typically TX to RX1: 915 mm; TX to RX2: 1524 mm
Sampling rate: Variable ( 500 samples at 4 mSec or slower )
Resolution: 16 bit; Record length: min 2 mSec
Gain settings: 16 levels with selectable AGC
Maximum number of receivers: 4Sonde Dimensions and weight: Variable according to configuration.

Sonde Diameter: 60 mm
TX length: 360 mm, Weight: 6.0 kg
RX length: 280 mm, Weight: 5.0 kg
Long Spacer length: 640 mm; Weight: 4.0 kg
Short Spacer length: 490 mm; Weight: 3.7 kg
Overall Weight: Variable – Typically 18 Kg
Recommended borehole diameter range: 80 mm to 300 mm
Logging speed: typically 3 to 6m/min

Micro-Velocity Sonde (MVP)
The Micro-Velocity Probe (MVP) is an easy to use tool that logs interval velocities within boreholes in rock or concrete structures as an aid to structural safety analysis. Measured parameters include P & S wave velocity (leading to crack density, saturation and dynamic moduli)
The measurements provide a powerful method to determine material property changes with distance into a structure. They are particularly useful in analysing damaged zones around excavations, or through rock pillars, and in monitoring changes in these zones over time. In a mining environment, the data can be used to infer changing rock mass conditions and to aid in decision making on extraction procedures and ground support.

Both P- and S-wave velocity measurements are performed, allowing for rock microfracture density, saturation and stress state to be analysed over very short ray paths of 10 to 30 cm. These short ray paths allow very dense, high-resolution measurements to be performed into the rock volume. Waveform cross-correlation is used between recordings so as to image small changes in velocity along the borehole.

The ASC InSite Seismic Processing software configures and controls the probe and then allows for data acquisition, storage, visualisation and processing. Full waveform data is stored enabling further analysis or quality control of measurements performed in the field. An automated high resolution cross-correlation method is used for the determination of changing velocity.

The transducers are mounted onto a rail within the sonde to facilitate changes in the spacing of the receivers. Contact with the borehole wall is achieved by using a combination of a spring-loaded mechanism and a motorised backup system. Acoustic coupling is best achieved in damp conditions and/or using a grease based couplant applied to the borehole wall. In horizontal boreholes, push-rods can be used.

Specifications:
Operating Frequency Range .: 35kHz to 1MHz centred at 100kHz
Resolution …………………….: 12 bit at 5MHz sampling
Waveform length ………....: configurable between 512 to 4096 data points
Gain Settings ……………..: configurable between 0 and 18 dB
Number of transducers….…...: 1 TX and 2 RX with variable in 2.5 cm steps
Sonde dimensions ….. ………: 35 mm diameter x 1940mm long - Weight: 7 kg
Borehole diameter range …....: 38 to 110mm
Power Supply …………………: 12 V dc
Data acquisition to PC .…….. : via RS232 port
Processing software ………...: InSite Seismic Processing - Win9x/NT/2000/ME compatible
( from ASC – Applied Seismology Consultants Ltd)