Full waveform inversion of time-lapse offset VSP data - CO2CRC Otway project case study

Abstract

Vertical Seismic Profile (VSP) is a useful tool for time-lapse monitoring. We conduct elastic 2D Full Waveform Inversion (FWI) on offset Vertical Seismic Profile (VSP) data to detect and quantify the time-lapse anomaly introduced by the CO2 geosequestration. Two datasets are being studied: a 2D synthetic dataset and the field dataset acquired during the Stage 2C of the CO2CRC Otway project. FWI proves capable of detecting the timelapse anomaly on both datasets, however, the strength of the anomaly in the field data inversion results is lower than expected from theoretical predictions. We attribute this to 3D effects, which are not taken into account. In the end, FWI proves to be an instrument that fits the monitoring problem well. The inversion of the monitor dataset is significantly quicker than the baseline inversion, which enables the time-lapse anomaly identification shortly after the data acquisition.