Barque Pre-SDM - Shallow Initial Geological Model Building, and Impact on Deep Reservoir Imaging

To de-risk the development of the Barue PH01 extension, there was a need to further improve the quality of the existing (2000) Pre-SDM imaging. Especially the shallow strata, i.e. the Liassic and the Upper Triassic, demonstrate a strong deformation. During the inversion of the Solepit basin they formed Riedel shears with strongly tilted fault blocks. The impact these dipping strata might have on the Pre-SDM velocities has been recognised as one of the main causes of the pre-existing imaging uncertainties. Hence, in the new velocity-depth model-building exercise, most attention has been given to the construction of a ‘geologically plausible’ velocity field for the shallow strata. As tomographic updating based upon RMO only will most probably not give a satisfactory result due to lack of (shallow) offsets, an initial geological model has been built using sonic data, seismic dip, faults and paleo-surfaces. This initial model has subsequently been updated using standard tomographic updating techniques. The final Pre-SDM image, resulting from this procedure, shows a marked improved over earlier depth imaging results; similarly, the existing TZ-conversion uncertainties have been significantly reduced.