(1D and 3D Available)
The velocity survey combines both seismic and well logging techniques to measure the one way travel time of a seismic pulse. The pulse is generated from an energy source such as:
The pulse propagates to a geophone detector or detectors placed at a known depth in the borehole. Using the measured total travel time and the measured depth, the average velocity of the pulse from the datum (e.g. ground level) to that depth is calculated. Interval velocities may be calculated between check shot horizons.
The results may also be compared with the sonic velocity log and the latter corrected for various borehole conditions.
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A Synthetic Seismogram may be created to assist in matching well log measurements to seismic attributes. By correlating wavelets produced by this technique, geologic units on seismic sections may be identified. Primary reflections on seismic sections may also be seen. It also assists in the prediction of stratigraphic variations away from the borehole, projecting units identified from the well logging and geological data.
A Vertical Seismic Profile (VSP) is produced by measuring the elapsed time for the pulse from the source to the geophone(s) while capturing the complete wave train.
Normal seismic operations capture propagated waves from a surface or near-surface geophone array. The VSP allows the seismic response to be traced with depth and allows a unified interpretation of seismic and borehole logging data. Multiple seismic source locations will give more detailed sub-surface information than a single source survey. Triaxial downhole geophones allow the recording of both shear and compression signals.
Specifications
Detector Sensor Geophones (1 or 3)
8hz 375ohmRange 0 to 80 dB Length 1600mm Weight 12.5Kg Max. Working Temperature 60° C Max. Working Pressure KPg/PSI 21000/3000 Supply Voltage Range 28/75 Nominal Current(mA) 24/90 Communications Digital
Auslog