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Advanced Reservoir Modeling in Poor Seismic; October Field, Northern Gulf of Suez, Egypt

Sercombe, William J.1; Thurmon, Leon 3; Morse, James 2
(1)consultant, Orlando, FL. (2) Computational Geology, Weybridge, VT. (3) consultant, Grand Junction, CO.

October field OOIP on discovery was 1.5 billon barrels in the Cretaceous Nubia and 500 million barrels in the overlying Cretaceous Nezzazat. Previous models had not been successful owing to very poor 3D seismic resolution. After 15 years of production a new model build was initiated. This model obtained a perfect predictive match of oil, water and pressure for six years in the Nubia and was the basis for 30 new wells drilled on prognosis. The success of the new static model was based on the integration of re-correlated model layer datums, quantitative dipmeter analysis using SCAT and related principles, and depth stripping the 3D seismic volume to extract subtle conjugate fault patterns. The interpreted fault patterns match fault patterns that can be seen in surface outcrops and were subsequently confirmed by field outcrop observation. The dipmeters were critical as they dispelled a number of existing myths, e.g., that the field was unfaulted and unfolded. The dipmeter azimuths varied widely from well to well but the simple contouring of model layer datums did not indicate much departure from smooth homoclinal dip. The azimuth changes rather suggested no or low fault throws for numerous compartments at different dip azimuths. The 3D seismic volume had been re-processed 50 times, but was still considered poor in resolution. The depth converted 3D volume was depth stripped at short intervals and breaks in amplitude in the horizontal depth slices were digitized. A collection of breaks were then reinterpreted in vertical sections and any consistent collections of breaks were triangulated as a fault. A conjugate fault set across the field was the result. The fault style was consistent with the conjugate faults observable in outcrop onshore. The new model made a perfect dynamic model after years of models that never worked. The perfect model was made through the integration of new top datums, old dipmeters, outcrop study and a previously unusable low resolution 3D seismic volume.

 

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