Geomodel Update Using 4-D Petrophysical Seismic Inversion on the Troll West Field

This paper presents results from the R&D collaboration between CGGVeritas and Statoil on 4-D Petrophysical Seismic Inversion (PetroSI-4D) on the Troll field. The proposed 4-D petrophysical inversion workflow inverts simultaneously multiple angle stacks from several time-lapse seismic surveys in order to estimate the time evolution of the hydrocarbon saturation and update the geometrical and petrophysical properties of an input geomodel. Inversion results can be used directly for well planning. The 4-D seismic data on the Troll field are used to monitor production effects such as the thinning of the oil column, while the main production challenge is the optimisation of in-fill drilling locations. The main objective of our study is to improve the existing fine-scale geo-model and coarser scale flow model that host more than 10 years of production information. As permeability is not directly accessible from seismic measurements, the targets are porosity estimation in the oil leg for sand quality prediction and saturation changes.