Sedimentation and High-Resolution Sequence Stratigraphy of the Upper Cretaceous Simsima Formation, Onshore Abu Dhabi Oil Field, United Arab Emirates

Magdy A. Hozayen*, Christian J. Strohmenger, Klaus Müller, and Salman H. Al-Marzouqi
ADCO
*[email protected]

An important carbonate oil field, located onshore Abu Dhabi, has been producing from the Upper Cretaceous (Maastrichtian) Simsima Formation since 1983. A detailed sedimentological and high-resolution sequence stratigraphic study has been carried out, integrating approximately 7,000 ft of core material, approximately 3,500 thin sections, and all available well-log data from 46 wells. Core description, together with semi-quantitative petrographic examination of thin sections, established a new depositional model for the Simsima Formation. Sixteen lithofacies types (LF1 to LF16) representing a wide variety of depositional environments, ranging from upper ramp, rudist-bioclastic shoals to open marine mid to outer ramp mud-dominated settings. The newly developed, high-resolution sequence stratigraphic framework suggested that the Simsima Formation comprises one complete third-order composite sequence and the transgressive systems tract of an overlying second third-order composite sequence. These third-order composite sequences include seventeen high-frequency, fourth-order sequences (HFS). HFS 1 to HFS 12 build the older, third-order composite sequence, HFS 13 to HFS 17 form the transgressive system tract of the overlying, younger third-order composite sequence. The fourth-order, high-frequency sequences were tied to re-processed and re-interpreted 3-D seismic data. Fourth-order sequences 1 to 6 clearly show onlap on a pre-existing high (pre-Simsima unconformity surface) whereas the top part of the Simsima Formation (sequences 13 to 17) show erosion on seismic cross-sections. The established high-resolution sequence stratigraphic framework will provide the layering scheme for the new Simsima 3-D static model, which will be used as input for reservoir flow modeling.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain