Towards industrial deployment of pressure tomography for CO2 storage monitoring: Uncertainty and megatonne scale-up

Abstract

Pressure tomography was successfully demonstrated as a viable CO${}_2$ storage monitoring technique in the Otway Stage 3 field project. In this work, we build on the initial pilot demonstration, using the results to assess megatonne-scale industrial deployment. Firstly, we develop an uncertainty analysis approach which facilitates risk-based decision making. We present a Bayesian model averaging approach which estimates statistical bounds on the estimated CO${}_2$ plume footprints for each monitor survey, and delineates the increasing confidence in the plume locatability as more CO${}_2$ is injected. To facilitate well-array design at other sites, we demonstrate the use of a gate system; a single well-pair to monitor encroaching CO${}_2$, which could be useful for key-risk areas such as spill-points or fault regions. Finally, non-dimensional analysis reveals the key control of the well separation, $r$, in operational design; the minimum water injection time scales with $r^2$, and peak-pressure scales with $1/r^2$. Realistic well separations $<$2 km are found to be desirable, which is adequate to capture key migration pathways and risk areas in most megatonne-scale industrial operations.