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

Abstract

Abstract An important carbonate oil field, located onshore Abu Dhabi, has been producing from the Upper Cretaceous (Maastrichtian) Simsima Formation since 1983. To optimize and increase production of the field, seismic and high-resolution sequence stratigraphy was integrated by tying fourth-order, high-frequency sequences identified from core to 3-D seismic data. To establish the sequence stratigraphic framework, a new detailed sedimentological and high-resolution sequence stratigraphy study had been carried out, integrating approximately 7,000 feet 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-frequencies, 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. 3-D seismic cross-sections show that fourth-order high-frequency sequences HFS-1 to HFS-6 of the older third-order composite sequence clearly show onlap on a pre-existing high (pre-Simsima unconformity surface), whereas the top part of the Simsima Formation (high-frequency sequences HFS-13 to HFS-17) show various degree of erosion. The established high-resolution sequence stratigraphic framework provides the layering scheme for the next generation Simsima 3-D static model, which will be used as input for the reservoir flow (dynamic) model.