The Azeri, Chirag, and Gunashli (ACG) fields, located offshore Baku in the Caspian Sea, are being developed under a 30 yr Production Sharing Agreement. Contiguous with the ACG accumulation, the shallow-water Gunashli (SWG) field has produced in excess of 800 MMSTB since 1980 from more than 220 wells.

SWG provides an opportunity to study the static and dynamic behavior of reservoirs important to the development of ACG.

BP, operator of ACG, contracted with the Reservoir Modeling Centre of the State Oil Company of Azerbaijan to perform a study of the Balakhany IX and Balakhany X reservoirs in the SWG development.

This study comprised construction of geologic descriptions for both reservoirs and their use in dynamic simulation models. This was achieved using hand-contoured geologic mapping, incorporating depositional trends such as channel architecture. Matching historical per formance data from these reservoirs verified the underlying geologic models and provided confidence in predictions derived from them.

Results of this study show that channel width was the key to accurate estimation of stock tank oil initially in place, and that to achieve this, as many wells as possible must be incorporated.

In addition, vertical communication between sublayers of the reservoir was defined using geologically derived maps referred to as interface transmissibility. Thus, a set of deterministic maps based on well data provided an approximate three-dimensional (3-D) representation of the Balakhany IX and Balakhany X stacked channel architecture.

This work will assist in the planning and optimization for the development of the ACG field.