f Inversion of a 3D Seismic Dataset Offshore Sarawak: F23 Case Study

The F23 field lies in Sarawak waters within Block SK-308, some 150 km offshore Sarawak. F23 is an isolated, platformtype Miocene (Tortonian-Messinian) carbonate build-up. The original depositional texture controls to a large extent the pore types and therefore the porosity/permeability character of the various lithofacies in F23. The large variability seen in porosity! permeability character within a specific lithofacies is related to textural variations associated with depositional cyclicity. The distribution of the porosity/permeability within the carbonate build-up will affect the development strategy of F23. A seismic inversion project was therefore carried out on the F23 field with the following objectives: - To generate an acoustic impedance dataset suitable for stratigraphic interpretation which was used to fine-tune the structural interpretation of the build-up - To generate a porosity volume for analysis for the porosity! permeability trend to assist in the design of the future development wells The Jason CSSI inversion was carried out attempting to meet the above-mentioned objectives. The data used were a full stack seismic volume, well logs from ten wells, five seismic horizons and a seismic velocity volume The essential processes in the project consist of seismic-to-well ties, wavelet estimation, construction of earthmodel and finally the generation of the acoustic impedance data. Based on the cross-plot of the inverted P-impedance and well porosities, a regression curve was derived for the conversion of the inverted P-impedance volume to the porosity volume. The refined structural interpretation based on the inverted P-impedance seismic and the porosity volumes were subsequently exported to Petrel for the building of structural framework and for the property modelling for the F23 static model. The current poster will show the seismic inversion workflow and the results of the F23 seismic inversion project.