Acoustic Velocity System. P, S1, S2 Measurement under Hydrostatic Conditions ©

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The system is designed to allow the collection and analysis of acoustic velocity from a sample held under hydrostatic conditions in a core flow cell. Separate pumps allow the application of measured pore fluid pressure and hydrostatic pressure. The Pore Pressure application unit is a floating piston device, which allows the aqueous pore fluid to be separated from the oil-filled hydraulic pump generating the pressure.

The cylindrical core flow cell has removable end plugs, which allow for easy sample loading and unloading. The end plugs are retained by threaded rings, which screw into the cell. The cell can be rotated on its stand for easy access to each end in turn.

The sample is located between two platens, which contain the acoustic transmitter and receiver stacks. The platens are forced into contact with the sample as a result of the application of the totally surrounding hydrostatic pressure.

The cell end plugs provide interfaces for the pore pressure lines, temperature sensor and electrical signals. Hybrid signal cables are terminated at the intermediate sockets on the bottom end plug, where they are separated into acoustic and switching functions. The hybrid cables comprise a coaxial acoustic line and a multi-core relay-switching line.

All the lines go through high-pressure electrical feedthrus in the cell base plug. Inside the cell, separate lines fitted with miniature Fischer multi-core and Microdot co-axial connectors attach to the platens and the cell base plug. Plugs and receptacles are designed for rapid and reliable mounting and dismounting of core samples.

Mounted at the rear of the cell stand is the Uni-axial Straining Frame. This is designed as an assembly aid for the core sample and provides a secure mounting for the base platen.

The straining rods and the upper yoke piece allow the application of strain to the sample so that the performance of the test core sample and acoustic stacks can be evaluated before the sample is loaded into the cell. It is possible to perform testing of the core sample in a sleeved (shown here) or un-sleeved condition.

The Transducer Interface Unit provides an interface to the core environment for reading Pore Pressure, Hydrostatic Pressure and temperature in digital format. The controlling computer runs software that displays the data in engineering units

The Acoustic Transducer Interface Unit provides the acoustic energy and performs the switching function for selecting the P, S1 and S2 waveforms. Signal repetition rate and pulse width can be varied from the front panel controls

The Digital Storage Oscilloscope allows the user to visualise the received waveform from the test core sample. In addition, spectral analysis can be performed in real time. A computer interface and software allows the waveform to be captured for analysis and report generation.

This drawing is copyright (c) and the associated procedure is the property of ErgoTech. It is issued confidentially to parties interested in acquiring the process and to authorised/licensed clients using it. The drawing is not to be reproduced or circulated by any parties without the written consent of ErgoTech which will not be unduly withheld. The drawing must not be mounted on any display boards or reproduced in reports without the written consent of ErgoTech. When permission is granted the reproduction must be identical to the original and the ownership of the drawing and the process embodied acknowledged to ErgoTech by displaying "ErgoTech (c)"