Identification and Modeling of Inter-Reservoir Communication Using an Integrated Multi-Disciplinary Structural Framework in a Giant Offshore Carbonate Field, UAE

Abstract

The challenges to effectively manage a field with stacked reservoirs that are in known hydraulic communication are enormous. Conventional management of such fields can result in many undesired outcomes such as premature water production caused by cross-communication from different reservoirs, inefficient pressure support to some of the individual reservoirs, or large volumes of bypassed oil. The major challenge is to identify the reasons and magnitude of inter-reservoir communication, and accurately capture these in the models which are utilized for optimized well placement and efficient field development. This paper discusses an integrated multi-disciplinary approach to identify and model inter-reservoir communication in a giant offshore carbonate field from UAE. Tracer study conducted for several years combined with detailed seismic interpretation suggest that the cross-flow of reservoirs due to fault juxtapositions is the major cause of inter-reservoir communication. This observation is further supported by pressure-transient analysis, logs, cores, drilling reports and regional structural studies. Hence, it becomes absolutely essential to build a robust static and dynamic model that can accurately capture the communication between different reservoirs. This paper proposes a novel approach to build a full-field integrated framework that allows coupling of multiple reservoirs that have been previously modeled independently. The methodology includes; detailed reinterpretation of faults and key chronostratigraphic surfaces, qualitative/ quantitative attribute analysis using reprocessed 3D seismic (post-stack time migrated) data, interpretation of pressure transit analysis, logs, surveillance data and regional structural history studies. The updated framework ensures accurate fault throw and fault extension in order to capture fault juxtapositions. The ability of the new model to allow inter-reservoir communication has been tested and confirmed in dynamic simulation model. This was achieved through series of simulation sensitivities where tracers injected in wells targeting specific reservoirs were successfully sampled from different reservoirs due to inter-reservoir communication through fault juxtaposition. Based on the results of sensitivity test, it is expected that the new integrated framework will provide a much improved history match in faulted areas where cross-communication across reservoir is very prominent. The improved model will lead to a better understanding of field and possibly will be used as guidance for field development plan.