A time-lapse seismic survey (4D) acquired over Laverda Canyon Field has provided significant value and reduced production uncertainty early in the field lifecycle. At time of monitor one (M1) acquisition completion in April 2020 approximately 9% of the expected ultimate recoverable volumes were produced over the initial nine months of production. Horizontal wells targeting the two high-quality, vertically adjacent, oil and gas bearing reservoirs produce via waterflood. Prior to start-up, compartmentalisation was identified as a key risk due to interpreted high stratigraphic and structural complexity however, initial production data indicated greater connectivity than predicted.
The 4D successfully shows changes resulting from production within the field. Inversion of the final data to compressibility using a wave-equation-based amplitude-versus-offset approach assisted with interpretation by reducing noise and providing a direct property to correlate the impact of changing saturation and pressure within the reservoir. Water sweep, gas evolution, gas movement and pressure increase responses were calibrated at the wells prior to extrapolating interpretation of fluid flow away from well control. These insights were used to guide updates to the reservoir model. An updated fault-framework provides additional structural connectivity via cross-juxtaposition of reservoirs. Polygons corresponding to vertical stratigraphic connectivity via erosive down-cutting channels provides additional stratigraphic connectivity. Dynamic reservoir modelling has utilised connectivity polygons as well as more traditional history-matching parameters to show an overall improvement in replicating field production. Additionally, the reservoir model has been used to simulate the observed 4D response.
Improved understanding of field behaviour unlocked with the 4D has resulted in a higher level of confidence in the model for reservoir management and forecasting. Optimisations to the field operating strategy include revisions to the waterflood strategy to improve sweep and reduce gas migration and improved flexibility in voidage management. Future strategic facility decisions regarding project end of field life, development and assessment of near field tie-in opportunities will benefit.