Characterization of petrophysical and seismic properties for CO2 storage with sensitivity analysis

Abstract

Saline aquifers are considered as highly favored reservoirs for CO₂ sequestration due to their favorable properties. Understanding the impact of saline aquifer properties on the migration and distribution of CO₂ plume is crucial. This study focuses on four key parameters—permeability, porosity, formation pressure, and temperature—to characterize the reservoir and analyse the petrophysical and elastic response of CO₂. First, we performed reservoir simulations to simulate CO₂ saturation, using multiple sets of these four parameters to examine their significance on CO₂ saturation and the plume migration speed. Subsequently, the effect of these parameters on the elastic properties is tested using rock physics theory. We established a relationship of compressional wave velocity ($V_p$) and quality factor ($Q_p$) with the four key parameters, and conducted a sensitivity analysis to test their sensitivity to $V_p$ and $Q_p$. Finally, we utilized visco-acoustic wave equation simulated time-lapse seismic data based on the computed $V_p$ and $Q_p$ models, and analysed the impact of CO₂ saturation changes on seismic data. As for the above numerical simulations and analysis, we conducted sensitivity analysis using both homogeneous and heterogeneous models. Consistent results are found between homogeneous and heterogeneous models. The permeability is the most sensitive parameter to the CO₂ saturation, while porosity emerges as the primary factor affecting both $Q_p$ and $V_p$. Both $Q_p$ and $V_p$ increase with the porosity, which contradicts the observations in gas reservoirs. The seismic simulations highlight significant variations in the seismic response to different parameters. We provided analysis for these observations, which serves as a valuable reference for comprehensive CO₂ integrity analysis, time-lapse monitoring, injection planning and site selection.