E3S Web Conf.
Volume 205, 20202nd International Conference on Energy Geotechnics (ICEGT 2020)
|Number of page(s)||6|
|Section||CO2 Sequestration and Deep Geothermal Energy|
|Published online||18 November 2020|
Seismic velocity change in sandstone during CO2 injection
1 Civil and Environmental Engineering, Colorado School of Mines, Golden, CO 80401, USA
2 Petroleum Engineering, Colorado School of Mines, Golden, CO 80401, USA
* Corresponding author: email@example.com
This paper presents analytical and experimental studies of the effects of supercritical CO2 injection on the seismic velocity of sandstone initially saturated with saline water. The analytical model is based on poroelasticity theory, particularly the application of the Biot-Gassmann substitution theory in the modeling of the acoustic velocity of porous rocks containing two-phase immiscible fluids. The experimental study used a high pressure and high temperature triaxial cell to clarify the seismic response of samples of Berea sandstone to supercritical CO2 injection under deep saline aquifer conditions. Measured ultrasonic wave velocity changes during CO2 injection in the sandstone sample showed the effects of pore fluid distribution in the seismic velocity of porous rocks. CO2 injection was shown to decrease the P-wave velocity with increasing CO2 saturation whereas the S-wave velocity was almost constant. The results confirm that the Biot-Gassmann theory can be used to model the changes in the acoustic P-wave velocity of sandstone containing different mixtures of supercritical CO2 and saline water provided the distribution of the two fluids in the sandstone pore space is accounted for in the calculation of the pore fluid bulk modulus.
© The Authors, published by EDP Sciences, 2020
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