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

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. Introduction Large oil accumulations have been discovered and produced from the Upper Cretaceous (Maastrichtian) Simsima Formation in Abu Dhabi since 1983. The Simsima Formation was deposited on an actively growing paleo-high in shallow marine environment. It is capped by the basal shale member of the Umm Er Radhuma Formation and overlies the crest of partly eroded former structure of the Aruma Group. It ranges in thickness from 323 ft in the crest of the field structure to 628 ft in the flank. Recently, approximately 7,000 feet of core and 3,500 thin sections along with well-log data from 46 wells were studied. A total of sixteen lithofacies types were identified. As a result of the core study, seventeen high-resolution fourthorder sequences were established. They constitute a complete third-order composite sequence and the transgressive systems tract of an overlying second third-order composite sequence. The high-resolution sequence stratigraphy identified from cores was integrated with the 3-D seismic by tying the fourth-order sequences to the seismic data. An integrated layering scheme will be used for the next generation Simsima 3-D static model, which will be used as input for reservoir flow (dynamic) model.

Seismic Attribute Utilization for FFDP Well Placement Optimization, Upper Cretaceous Fractured Complex Carbonate Reservoir, Onshore Oil Field, U.A.E.

“…The structural growth of the anticline continued during the deposition of the Simsima Formation resulting in a clearly defined thickness variation, thin in the crest and thick in the flanks. Some related publications discussed the context (Hozayen et al, 2008, Ali et al, 2011, and Sirat et al, 2012. Fig.…”

Seismic modelling of a fractured carbonate reservoir in Abu Dhabi, United Arab Emirates

“…The field is producing from the Upper Cretaceous (Maastrichtian) Simsima Formation. The Simsima Formation was deposited on an actively growing palaeo-high in a shallow-marine environment (Hozayen et al, 2008).…”