4D Full-Waveform Inversion for Reservoir Monitoring

This technical report presents a study on the application of 4D full-waveform inversion (FWI) using towed streamer data for monitoring shallow injectite reservoirs. The study outlines a strategy that improves production monitoring by accurately identifying softening responses associated with gas injection and exsolution. It discusses the challenges of achieving good acquisition repeatability with towed-streamer data and highlights the advantages of FWI in inverting subsurface properties directly from raw data. The report details the methodology employed, including the harmonization of data input and the use of joint 4D FWI updates to minimize noise and enhance interpretability. Results indicate that the joint 4D FWI effectively resolved time-shift signals and identified previously unrecognized softening responses, which may relate to geo-mechanical changes in the overburden. The findings suggest that improved monitoring of oil and gas reservoirs in the North Sea is feasible with the proposed approach.