Abstract: Casablanca Oil Field - An Integrated Study Reveals A Highly Complex Carbonate Reservoir

ZACHARAKIS, T. G., J. NAVARRO COMET, E. IZAGUIRRE OZAMIZ, M. ESTEBAN CERDA

The Casablanca Oil Field is a carbonate reservoir discovered in 1975; it is located off the east coast of Spain, in the Valencia Trough. At the time of discovery the recoverable reserve estimates were placed at 90 million bbls. Over the production history of the field, twenty one wells have been drilled. The complexity of the carbonate reservoir has become apparent as uncertainty about the ultimate recoverabe reserves still persist.

In 1995 an integrated task force of geologists, geophysicists, and reservoir engineers was created to re-interpret the existing data and develop a new reservoir model to explain the higher than expected recoverable reserves. The gross rock volume of the reservoir actually decreased with the new 3-D geophysical mapping. The task force created a structural model for the field leading to a new fault system. Based on core studies, a dual lithologic model was proposed, incorporating a zonation of petrophysical properties into karstified layers and fractured compartments.

As tying the new geologic model with the production history still proved to be a difficult task, several simulation models were applied. However, this did not reveal why certain wells produced more oil than others.

To date, Casablanca is the largest oil field in Spain yielding around 140 million bbls. of recoverable reserves. Based on the integrated study, a gas injection program is being devised to revitalize the remaining oil production. Still more can be learned about this complex karstified reservoir before the end of its producing life.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria