Design and deployment of a buried geophone array for CO2 geosequestration monitoring: CO2CRC Otway Project, Stage 2C

Abstract

Stage 2C of the CO2CRC Otway project aims to demonstrate the stabilization of a gas plume following the injection of approximately 15,000 tonnes of CO2-rich gas mixture into the saline aquifer and examine the capabilities of 4D seismic to detect and track the plume in the subsurface. The ability to detect and monitor the plume is controlled by both strength of the signal and level of the time-lapse noise. Extensive modeling and field trials show that the use of buried receiver arrays for long-term monitoring of the CO2 geosequestration has the potential to reduce both land impact for landowners and cost impact to the project. To this end, a buried receiver array was designed and deployed at the CO2CRC Otway site. The array comprises ∼900 high-sensitivity geophones deployed at 4 m depth below the surface. Preliminary benchmark tests show a significant improvement in raw data quality compared to surface geophones. Absence of cables and other seismic infrastructure on the surface (with the exception of eleven cross-line boxes) significantly reduces the impact of the survey on farming activities as only the sources will need access to the farmland for the future monitor surveys.