Time‐lapse full waveform inversion of vertical seismic profile data: Workflow and application to the CO2CRC Otway project

Vertical seismic profile (VSP) is one of the technologies for monitoring hydrocarbon production and CO2 geosequestration. However, quantitative interpretation of time‐lapse VSP is challenging due to its irregular distribution of source‐receiver offsets. One way to overcome this challenge is to use full waveform inversion (FWI), which does not require regular offsets. We present a workflow of elastic FWI applied to offset vertical seismic profile data for the purpose of identification and estimation of time‐lapse changes introduced by injection of 15,000 t of CO2‐rich gas mixture at 1.5 km depth. Application of this workflow to both synthetic and field data shows that elastic FWI is able to detect and quantify the time‐lapse anomaly in P wave velocity with the magnitude of 100–150 m/s. Key Points Time‐lapse elastic full waveform inversion is conducted on onshore offset vertical seismic profile data set The inversion of baseline data provides high‐resolution P and S velocity models near the well The inversion of monitor data detects a time‐lapse anomaly in P wave velocity introduced by CO2 sequestration