MetaRock Laboratories, Inc. (MRL) has the capability to undertake research in specific properties of the rock mechanics field. Acoustic measurements of samples (both dry and saturated) can be conducted under both uniaxial and triaxial pressure vessels. Ultrasonic velocity measurements in rock samples are performed utilizing piezoelectric crystals (P&S) of 1MHz resonant frequency. Each transducer is excited independently utilizing a switch matrix as well as a high voltage short duration electrical pulsar. The applied electrical pulse transforms into mechanical pulse and propagates through the rock sample in the form of ultrasonic elastic wave, and is then received by the other end. The receiving transducer, at the opposite end of the rock specimen, is converted back to an electrical pulse and measured as an electrical waveform using a high precision digital oscilloscope. Using the end caps calibration data and the received waveform from each transducer (compressional or shear), the P-wave and S-wave arrival time is measured and velocities, dynamic properties are calculated.

The rock properties are analyzed for realistic reservoir conditions and the stress-induced anisotropy at high axial and radial loads are measured based on P-wave and S-wave velocity change and amplitude change respectively. A detailed report is developed for each sample, and submitted to the client documenting the analysis. Utilizing the integrated pore lines, the sample can be saturated using brine, water and/or oil as per client specifications. The standard of the transducer is proven in aluminum, stainless steel, iron and brass by measuring the velocity under ambient conditions (see Table 1). The calculated velocity has been compared with the standard velocity of these specific metals and the data indicates a strong match.

Dynamic measurements are derived from the acoustic data. For isotropic medium, two dynamic elastic constants are obtained from the acoustic measurements. For transversely isotropic (TI) medium, five dynamic elastic constants are found from the acoustics. The elastic constants calculated from the dynamic measurements will indicate the changes in rock fabrics and other physical properties. The front face of the transducer’s epoxy thickness is estimated based on the wavelength (λ/4) calculated using bench-top measurements.