An experimental study of acoustic responses on the injection of supercritical CO2 into sandstones from the Otway Basin

Abstract

Quantitative knowledge of the acoustic response of rock from an injection site on supercritical CO 2 (scCO 2 ) saturation is crucial for understanding the feasibility of time-lapse seismic monitoring of CO 2 plume migration. A suite of shaley sandstones from the injection interval of the CRC-2 well, Otway Basin, Australia is tested to reveal the effects of supercritical CO 2 injection on acoustic responses. CO 2 is first injected into dry samples, flushed out with brine and then injected again into brine-saturated samples. Such a suite of experiments allows us to obtain acoustic velocities of the samples for a wide range of CO 2 /brine saturations from 0% to 100%. On injection of scCO 2 into brine-saturated samples, the rocks exhibit a decrease of compressional velocities by about 7% with the increase of CO 2 saturation from 0% to a maximum of about 50%. Anisotropy of the shaley sandstones from the Otway Basin must be taken into account as the difference in the velocities normal and parallel to bedding is comparable with the perturbation due to CO 2 injection and the samples of different orientations exhibit transition from Gassmann-Hill to Gassmann-Wood bound at different scCO 2 saturations. Changes of the dry samples before and after the CO 2 injection (if any) are not traceable by acoustic methods.

Saturation-path dependency of P-wave velocity and attenuation in sandstone saturated with CO2 and brine revealed by simultaneous measurements of waveforms and X-ray computed tomography images

“…Several experimental studies have been performed in an attempt to understand the seismic wave characteristics in partially saturated porous media (Murphy, 1982;Knight and Nolen-Hoeksema, 1990;Gist, 1994;Cadoret et al, 1995;Geller et al, 2000;Monsen and Johnstad, 2005;Xue and Lei, 2006;Shi et al, 2007;Lebedev et al, 2009;Xue et al, 2009;Lebedev et al, 2013). In conventional displacement experiments between gas (such as air or nitrogen) and water, some experimental studies have evidenced clear hysteresis in the relationship between P-wave velocity/attenuation and fluid saturation in a drainage-imbibition cycle (Domenico, 1976;Knight and Nolen-Hoeksema, 1990;Yin et al, 1992;Cadoret et al, 1995Cadoret et al, , 1998.…”

Ultrasonic measurements on thin samples: numerical modelling

“…Ultrasonic measurements were performed using the experimental technique described by Lebedev et al (2013). We use V153 1MHz/.5″ transducers (Olympus Panametrics-NDT™) working in shear mode (S-transducers).…”

“…In this work we use S-transducers to emit ultrasonic pulse as it was shown that such technique allows registration not only S-wave but P-wave as well (for more details see Lebedev et al, 2013). However, source S-transducer converts transmitted electrical signal to mechanical displacement parallel to its surface.…”

The Effect of Deep Burial and Folding on Sandstone Reservoirs in some Giant Gas Fields, South America

“…All measurements are conducted under room temperature and radial and axial stresses are equal (referred to as confining pressure). The experimental procedure described in Lebedev et al (2013) is used to measure P-wave and S-wave velocities (Vp and Vs respectively). Tri-axial tests have been run by CSIRO to understand the structural and tectonic history and its relation to the diagenesis and low rank metamorphism of the rocks but the results are not reported here.…”