Abstract

Outcrops in the Jebel Akhdar (north Oman Mountains) offer a unique opportunity to study the depositional architecture of the lower Aptian Shuaiba carbonate that is the main hydrocarbon-producing interval in north Oman. This carbonate formation belongs to an early Aptian platform complex that can be divided into inner- and outer-shelf domains with a sharp transition to the basinal environment toward the north. Detailed outcrop studies were carried out to establish a stratigraphic data set that could be used as an analog for reservoir characterization in the subsurface. High-resolution stratigraphic correlations between as closely spaced as possible sections allow two-dimensional (2-D) geometry of sedimentary bodies to be interpreted within a sequence-stratigraphic framework. The environment restriction and the situation relative to the shelf margin have the greatest impact on the development and geometry of the facies. Inner-shelf rudist beds have a variable thickness (1-10 m) and are laterally continuous (10-45 km). They can be locally interbedded with thin (<2 m) grainstone beds characterized by lateral dimensions comprised between 5 and 35 km. Outer-shelf rudist and grainstone units are characterized by variable lateral continuity (1-12 km) and thickness (1-15 m) and can be very thick toward the shelf edge (>20 m). For a given facies, overall body thickness is 40% thinner in the inner shelf, whereas body length is 30% shorter in the outer shelf. Interpreted stratigraphic systems tracts, transgressive and regressive, also are characterized by specific facies developments in combination with the paleogeographic situation. Descriptive statistics of the stratigraphic data set are provided. Such basic numerical data can support static modeling of Shuaiba reservoirs in north Oman's main oil fields in relation to the paleogeographic setting and the stratigraphic systems tracts.

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