An experimental study of the elastic properties of the sandstone flooded with supercritical CO₂: the influences of saturation, pressure and temperature

SUMMARY Geological storage of captured CO₂ is essential for reducing anthropogenic greenhouse gas emissions and ensuring the sustainable use of fossil fuels. Understanding the influence of saturation, pressure and temperature on the elastic properties of brine-saturated sandstone flooded with supercritical CO₂ is critical for interpreting seismic and sonic logging data, which aids in monitoring and quantifying subsurface changes associated with CO₂ injection. The experimental results indicate that as scCO₂ saturation increases (0–60 per cent), the P-wave velocity decreases significantly with an average of 14 per cent drop, while the S-wave velocity increases slightly. Temperature variations (80–110 °C) have a minimal effect on both velocities (1–2 per cent), whereas elastic features show notable sensitivity to the variation of confining pressure (20–30 MPa) and pore pressure (10–20 MPa). Ignoring the effects of pore pressure might lead to the bias of interpreting seismic data for monitoring scCO₂ saturation change. The constructed rock physics models well capture the coupled effects of porosity and scCO₂ saturation on the P-impedance and P- and S-wave velocity ratio, which show good agreement with the experimental results. These findings are crucial for improving monitoring methods and enhancing the accuracy of predictive models for CO₂ geological storage.