Probabilistic Seismic Inversion of a West of Shetlands Deepwater Turbidite Field

The Schiehallion Field oil reservoir, located West of Shetland on the UK Continental Shelf, lies in a Palaeocene deep marine turbidite complex characterized on seismic data by direct hydrocarbon indicators. A new subsurface model for the Schiehallion Field is being built for infill drilling, field management, reserve estimations and production forecasting. To use this model with confidence and to achieve a satisfactory production history match in a shorter time, it is important for the model to honour all the subsurface data available. Seismic amplitude attributes significantly influence the sand distribution in this new subsurface model. A comparison of 3D synthetic seismic generated from the model and real seismic data is a fundamental quality check for subsurface models. A probabilistic 3D inversion, using the Shell proprietary software (PROMISE) to update the Net-to-Gross in the model, has improved the match between synthetic and real seismic data while honouring petrophysical and geological constraints. This probabilistic inversion approach allows for property updating of the reservoir model without a full model rebuild and also provides a means to define subsurface uncertainty and generate associated high and low case models that still honour the seismic response.