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Full-waveform imaging of laser-ultrasound measurements on CO2-injected sandstones

Geosequestration, or storing anthropogenic CO2 in deep sedimentary geologic formations, is an important strategy for minimising greenhouse gas emissions.  However, key questions remain in how CO2 interacts with host sandstone formations over a variety of time scales. The research partnership between UWA and the University of Auckland is developing innovative technologies to measure, monitor and verify these subsurface processes through combined strengths in laboratory rock-physics experimentation to study changes in rock properties due to sandstone-CO2 interactions, along with the 3D seismic modelling, imaging and inversion analyses that corroborate these experiments and help to establish site-specific responses to CO2 storage activities.

Carbon geosequestration, or the geologic storage of CO2, is an emerging field of research and technological innovation of increasing importance for Australia’s energy security future. In recognition of the role that geosequestration can play in Australia’s national energy portfolio, the Commonwealth government has awarded the first National Flagship Project – the National Geosequestration Laboratory (NGL) – to a consortium of WA institutions that includes UWA. The main NGL project goal is to demonstrate the viability of long-term storage of CO2 in deep porous sandstone units. UWA Geophysics will play a central role in the measurement, monitoring and verification (MMV) of these activities.

A key NGL research theme is how to accurately model and remotely sense the physical and chemical changes caused by introducing CO2 into the pore space of sandstone geologic units. Currently, a good understanding is lacking of the geochemical alteration induced by sandstone exposure to CO2and how seismic methods can be used to monitor these time-lapse (4D) changes. In particular, comprehensive laboratory experiments on sandstone borehole core have yet to be conducted, and industry best practices are not yet developed. These issues remain as scientific barriers to the broad adoption of geosequestration.

In this project we are demonstrating that constraining CO2-induced changes in sandstone cores may be accomplished using a four-step procedure: (1) develope spatio-temporal models and physical experiments of CO2-sandstone chemical reactions; (2) calibrate models through numerical simulation to establish 4D physical observables; (3) obtain high-resolution measurements for these parameters for site-specific sandstone cores at different CO2 concentrations and time-scales; and (4) use acquired data and developed models to estimate 4D changes in drill core through seismic imaging (and ideally full-waveform inversion). While each of these procedural steps represents an active field of research, they have yet to be applied together in a cohesive multidisciplinary approach.

This research collaboration investigates key procedural steps using a suite of realistic synthetic computational and initial physical experiments, including rock-fluid reactivity modelling and experimentation; laser-ultrasound experiments on drill core; and numerical modelling, imaging and inversion of the synthetic and measured data. The physical experiments are being conducted at unique research lab facilities at the University of Auckland, while numerical seismic simulations are being undertaking at UWA using world-class IVEC HPC facilities.

Collaborator/s

  • Dr. Mila Adam and Dr. Kasper Van Wijk, University of Auckland