Feasibility of targeted active seismic monitoring of geological carbon storage using refracted waves

Abstract

Active seismic monitoring is a powerful technique that can be employed for conformance and assurance monitoring in geological carbon storage (GCS). This technology was successfully deployed in small-scale research studies and large-scale commercial projects. Usually, in land time-lapse surveys, to ensure time-lapse data quality, the seismic survey is designed to have a very high trace density. This increases the cost of the survey and usually results in high-quality data covering only a very limited area. While this is a good approach if the detailed plume image is required, massive uptake GCS would require the monitoring to be cost-effective. Therefore, it is important to explore the possibility of using a series of daisy-chained wells instrumented with distributed acoustic sensors and paired to permanent seismic sources as a basis for such a system.To this end, we propose using head waves instead of reflected waves in large-scale projects for conformance monitoring (and, maybe, large leakage detection). Using a cartoon model of CarbonNet Pelican site as a motivation, we perform a feasibility study through seismic modelling. We also simulate a similar monitoring approach for a forthcoming shallow fault injection at the CO2CRC's Otway site in the Australian State of Victoria. This experiment can be viewed as a scaled model for larger injections. Based on these modelling results, we provide a short overview of the further field experiments that can be used to validate the proposed approach.