Azimuthal Radial Acoustic Velocity (Stressed & Unstressed) Testing
The “stress memory” of rock, observed from studying and quantifying strain recovery from drilled core, permits insitu stress estimation.
Compared to expensive insitu hydraulic fracturing test and lab-based techniques using AE, DSCA, ASR techniques, monitoring changes in ultrasonic properties upon strain relaxation via azimuthal acoustic velocity measurement is a viable alternative.
Acquisition of azimuthal velocity is performed by mounting the sample (whole core or plug) on a rotary table and transmitting P or S-wave velocity across the sample.
The setup facilitates sample rotation as low as 1o and vertical movement of acoustic transducer as small as 0.025 mm.
The same measurement can also be performed under stress, at any stress path using radial ring. However, the ring only permits acquiring velocity at every 45o. Additionally, data acquisition can only be performed on plug sample.
Recommended Sample Dimensions:
Unstressed measurement: sample diameter – 1" to 4” (both plug and whole core); data acquisition interval – 1o
Stressed measurement: sample diameter – 1" to 1.5” (only plug sample); data acquisition interval – 45o