Resolution of Water Influx Patterns Through Application of Multidisciplinary 3D Reservoir Modeling

Paula L. Wigley, David Masson, Jerry Hadwin, and Richard W. A. Keech

The Sayyala Field is located in Oman, some 530 km southwest of the capital, Muscat. The oil accumulation lies in the fluvial sediments of the Permian Upper Gharif Formation, at depths of around 1200m. The penultimate primary grid location was drilled as a horizontal well in 1993 and produced only water when tested, despite continued oil production from nearby vertical wells. A field review and multidisciplinary 3D reservoir modeling project was therefore started in late 1993. The primary objectives of the modeling exercise were to resolve the incoming water pattern and to assess the possibility of locating bypassed oil through infill drilling, prior to any further drilling activity in the field.

A number of 3D geological realisations were built using a probabilistic modeling package and subsequently 3D reservoir property models were constructed based on revised petrophysical parameters for each of the modeled facies. The resultant models led to a re-evaluation of STOIIP distribution in the field with respect to the modeled location of channel belts and overbank deposits. A number of reservoir simulations were carried out using the 3D geological and property models as input. A "simulation prover" will be drilled in late 1995 in order to test the integrity of the models and the applicability of probabilistic modeling for location of remaining reserves in complex fluviatile reservoirs. A plan for further field activity will be compiled based on the 3D modeling and the test well, the results of which will be presented.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California