The Characterization of a Fractured Reservoir: a Multi-disciplinary Approach with Application to an Offshore Abu Dhabi Carbonate Reservoir

By

Bertrand D.M. Gauthier¹, Martin Guiton², Michel Garcia³

(1) Totalfinaelf, Paris La Defense, France (2) Totalfinaelf (3) FSS International R&D, Chaville, France

 This study illustrates a systematic work flow for the characterization of fractured reservoirs. It begins with a structural analysis of seismic and well data which defines a structural style and fracture model for the field under study. This model is evaluated with a geomechanical approach which verifies that all mechanical conditions are full-filled. Then, all the parameters which are known to control the fracture activation and propagation are integrated through a full field fracture distribution geostatical method. Finally, the role of the present day stress field upon fracture permeability, is addressed.

The studied Middle East carbonate reservoir is a salt related dome. Pre-existing NW-SE fractures controlled the doming event and imposed a strong mechanical heritage. The fracturing which is presently observed is mainly related to this doming event. Two mains fracture systems are observed. NW-SE pre-existing fractures were re-activated as normal faults and associated fracture corridors. The localization of the faults is controlled by deep basement lineaments and by the opening and sliding deformations associated to the doming process. Fault related fracture corridors are mainly related to the sliding deformation. NE-SW fractures, activated as new fractures during the doming, are related to both the curvature and faulting deformations and are homogeneously distributed with however a higher density at the dome crest. They were kept open after the Zagros orogeny took place. Presently, the Zagros stress field is still acting but cannot be responsible for new fracture activation. Finally, the pertinence of our fracture model is calibrated against dynamic data.