Integrated Reservoir Characterization from Core to Geomodel: Example of a Cretaceous Mixed Clastic/Carbonate Oil Field, West Africa

Duval, Christine ¹; Mabille, Cedric ²; Virgone, Aurelien ²; Rebelle, Michel ¹; Vernay, Paul ¹
(1) EP/GSR/TG/COP/INT, Total, Pau, France. (2) EP/GSR/TG/ISS/CARB, Total, Pau, France.

A cretaceous mixed clastic/carbonate oil field is described throughout an integrated study from sedimentary context to static reservoir model.

Core data understanding of field sedimentary and diagenesis evolution is integrated with petrophysics and log responses to provide Petro-Geological Groups (PGG). These PGG are to be relevant both for electro-facies modeling from logs and for geological facies maps and trends used to populate the geomodels.

On the other hand, Petrophysical Groups (PG), strictly relying on petrophysical properties, appear to be more pertinent for petrophysical parameters distribution. Regarding saturation laws, several approaches were attempted to model them from PC data (Wooddy-Wright-Johnson; J Leverett function, Sw as function of height above free water level), the last one being finally selected for geomodeling purposes.

Petrophysics (porosity, permeability, saturation) will be consequently propagated into the geological model through a relationship between PGG and PG. To establish this relationship was a key issue for geomodeling.

A supervised model of PGG provides a good result in terms of petrophysical characterization and propagation for most of the studied wells. The vertical sequences and lateral evolutions on maps validate their geological consistency. The Similarity Threshold Method (STM) computed for this supervised model highlights the good reliability of the propagation with regards to the log responses. This propagation on all wells is the base for sedimentary and diagenesis maps and evolution trends.

In such a heterogeneous carbonate field, the comparison between small scale permeability derived from cores and logs and larger scale permeability derived from well test demonstrates upscaling rules which are consequently implemented to improve the reservoir models.

This integrated study provides geological and petrophysical guidelines to populate the reservoir model and improve its overall consistency.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.