ACOUSTIC VELOCITY MEASUREMENT

            

Our company is equipped with an AVS-700 acoustic velocity system that is suitable for weighing each elastic moduli of the core sample in both dry and saturated cases, at max. 700 bar pore pressure and at max. 700 bar confining pressure on 1” or 1.5” diameter and max. 3” length core plugs. The system consists of a fully equipped pressure vessel, an Olympus 5072PR impulser with 35 MHz ultrasonic bandwidth and max. -350 V spike pulse, and a 2-channel Tektronix TDS2012B digital oscilloscope with 100 MHz bandwidth. At the present, such transducers are connected to the impulser that are able to produce compressional and shear waves with 150 kHz central frequency. This  makes it possible to observe the velocity of the waves in the core, in case of optional pore and confining pressure.

We are able to determine the velocity of the elastic waves by an algorithm based on STA/LTA (Short Time Average/Long Time Average) proportion and Akaike information criterion. From the measured speed all elastic moduli, such as the Poisson-ratio, the Young-, the bulk-, the shear- and the P-wave-modulus, the compressibility, the acoustic impedance and the Lamé-constant are calculable, together with their relative errors.