Monitoring CO2 Injection within a Produced Gas Field: Initial Feasibility Studies for Angel CCS

Monitoring CO2 injection into the Angel depleted gas field is an important enabler of the Angel CCS project. Conventional seismic monitoring can be challenged within reservoirs containing depleted gas, so a suite of technologies is assessed for suitability to monitor the CO2. 1D rock physics modelling indicates that seismic monitoring within brine saturated parts of the reservoir may be effective, but monitoring CO2 saturation within parts of the reservoir containing residual gas saturation is more complex. Preliminary timelapse gravity modelling of the CO2 plume over time indicates that gravitational field changes are likely to exceed detectability thresholds within five years of injection, flagging this technology as a possible technology for monitoring plume movement within the residual gas column. Timelapse CSEM modelling shows that this technology would not be able to detect the planned CO2 injection volume due to the reservoir depth below mudline and the resistive underburden. Timelapse seismic and gravity are assessed as technologies worth continuing to evaluate for monitoring the CO2 plume in the Angel CCS project.