Characterisation of the Elastic Behaviours of Sandstone Reservoirs for CO2 Storage in the North Sea

Abstract

Depleted-gas sandstone reservoirs in the Dutch North Sea are being evaluated for offshore carbon storage under the ARAMIS project. The variability in geomechanical properties urges an investigation of the elastic parameters. This study involved cored samples and logs from five Slochteren and Solling formations wells. It aims to characterize seventeen cored samples’ static and dynamic elastic behaviour experimentally via triaxial compression tests with active acoustics. Substantial variability was shown in wave velocities, moduli, Poisson and velocity ratios highly correlated to porosity, density and confining pressure variations. Therefore, empirical correlations were established between elastic moduli, confining pressure and porosity from the lab measurements. Another empirical correlation was established between the dynamic and the static Young’s modulus with a high correlation coefficient of 0.8. To enable elastic moduli log predictions with the absence of S-wave velocity log measurements, a workflow was developed to predict S-wave velocities using empirical correlations from lab measurements, nearby wells, and literature to evaluate the estimation quality. Comparisons between measured and predicted dynamic moduli showed agreement, validating the physics of the different datasets. However, it is important to mention that discrepancies existed for parameters like Poisson Ratio, indicating that factors like porosity affect predictions. Although there is limited data from logs and experiments, this study provides important geomechanical insights and predictive capabilities for this initial stage of geomechanical reservoir characterization for the ARAMIS CCS project.