Case Study: Successful Geological Interpretation of Turbidite Deposits Using Regional Experience and Seismic Innovative Workflow

Thierry Charles, Henri Trichon, Florence Larrouquet, and François Temple
Total E&P, Pau, France

The recently sanctioned Pazflor deep water project (B17 Angola) will develop a group of turbiditic reservoirs scattered over a 600km2 area. This communication presents the geosciences challenges associated to the Acacia Oligocene reservoirs (composed of channels and lobe complexes): compared to neighbouring fields, a poorer seismic quality (due to deeper burial) together with high dips on the flanks of the anticline result in major uncertainties on the depth and lateral positioning of the reservoirs characteristics. Therefore it was required to perform specific time and depth pre-stack processings including anisotropy of the velocity field.

The successful reservoir characterisation relied on first the integration of b17 experience and enhancement of interpretation method. On Acacia, no direct and straightforward link could be made between a single seismic attribute response and the detailed related geology. The interpretation work was carried out on multiple data set: the reservoir characterisation was performed on time data set using several derivative attribute cubes such as AVA, Inversion products (Poisson’s Ratio, P Impedance, …), the geometry was based on depth cubes and fluid contacts on both time and depth data. A complex workflow allowed reconciling all this information in a single geological model. Second, the evaluation of a reliable range of reserves integrated the numerous uncertainties.

Finally a delineation well was drilled. It validated the outcome of the different seismic processing and of their interpretation (geometry, fluid contacts from DHI and reservoir characterisation) for Acacia that can be extended to other similar contexts. It also showed some pressure disconnection within lobes that could be either due to fault throw or lateral facies variation of lobe elements within larger lobe complexes.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery