A 3-D geological model of the Kimmeridgian-Tithonian Manifa, Hith, Arab, and Upper Diyab formations in the area of the onshore Central Abu Dhabi Ridge was based on a newly established sequence stratigraphic, sedimentologic, and diagenetic model. It was part of an inter-disciplinary study of the large sour-gas reserves in Abu Dhabi that are mainly hosted by the Arab Formation. The model was used for dynamic evaluations and recommendations for further appraisal and development planning in the studied field. Fourth-order aggradational and progradational cycles are composed of small-scale fifth-order shallowing-upward cycles, mostly capped by anhydrite within the Arab-ABC. The study area is characterized by a shoreline progradation of the Arab Formation toward the east-northeast marked by high-energy oolitic/bioclastic grainstones of the Upper Arab-D and the Asab Oolite. The Arab-ABC, Hith, and Manifa pinch out toward the northeast. The strongly bioturbated Lower Arab-D is an intrashelf basinal carbonate ramp deposit, largely time-equivalent to the Arab-ABC. The deposition of the Manifa Formation over the Arab Formation was a major back-stepping event of the shallow-water platform before the onset of renewed progradation in the Early Cretaceous. Well productivity in the Arab-ABC is controlled mainly by thin, permeable dolomitic streaks in the fifth-order cycles at the base of the fourth-order cycles. This has major implications for reservoir management, well completion and stimulation, and development planning. Good reservoir properties have been preserved in the early diagenetic dolomitic streaks. In contrast, the reservoir properties of the Upper Arab-D oolitic/bioclastic grainstones deteriorate with depth due to burial diagenesis. A rock-type scheme was established because complex diagenetic overprinting prevented the depositional facies from being directly related to petrophysical properties. Special core analysis and the attribution of saturation functions to static and dynamic models were made on a cell-by-cell basis using the scheme and honoring the 3-D depositional facies and property model. The results demonstrated the importance of integrating sedimentological analysis and diagenesis with rock typing and static and dynamic modeling so as to enhance the predictive capabilities of subsurface models.

A 3D OBC survey was acquired over an offshore Field in Abu Dhabi, Middle East during 2000. The acquisition geometry of the survey provides data that is well sampled with respect to azimuth and offset range. Sensitivity analysis indicated that the data is suitable for azimuthal Pwave AVO studies. Data processing was designed to preserve offset-azimuth amplitude variations. A subset of the 3D data volume was extracted for azimuthal P-wave AVO analysis. The results suggest that there is a dominant trend of open fractures within the study volume. Acquisition and Data Processing The 3D survey area is approximately 236 km west offshore Abu Dhabi in water depths ranging from 10-40m. The primary geologic zones of interest are the Uweinat reservoir at around 1.7-1.9s TWT, Khuff between 2.0-2.2s and the pre-Khuff at 2.3-2.5s. The 3D OBC survey was acquired over this area during 2000 using a wide azimuth, high-fold patch acquisition geometry in order to resolve the fault-orientation in the area.

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