Acoustic Velocity Characterization for CO2 Storage in Saline Aquifer Carbonates: An Experimental Study

In 2023, as part of ADNOC’s goal to reduce carbon intensity by 25% by 2030 and deliver on its Net Zero by 2045 ambition, a CO2 sequestration well was drilled in a carbonate saline aquifer (Xu et al., 2024). The well was completed with fiber optic cable cemented behind casing, which provided the opportunity to monitor plume migration using DAS-VSP technology, with guaranteed repeatability on the receiver side (Mason et al., 2024). Time-lapse seismic quantitative interpretation techniques allowed the detection of acoustic impedance variation due to CO2 injection. A further step is to investigate the relationship of acoustic impedance to CO2 saturation and rock deformation behaviour, through ultrasonic measurements on cores, which is the purpose of this paper. Experiments revealed that pore fluid type may have a significant effect on the velocities measured, especially at lower stress levels tested.