Abstract

ABSTRACT

This paper provides data on the lateral continuity and geometry of potential reservoir geobodies in outcrops of Upper Khuff Formation time-equivalent strata in the Jebel Al Akhdar area (Oman Mountains, Sultanate of Oman). It presents outcrop-based quantitative data of shoal-associated grainstone bodies in a sequence stratigraphic framework on the scale of an average Khuff gas field. Such data may be useful for correlation and modelling of subsurface reservoirs.

A stratigraphic correlation of five outcrop sections, based on facies, sequence analysis and gamma-ray pattern, was used as a framework for mapping the distribution and lateral extent of grainstone geobodies over an area of 8 × 8 km. Four grainstone bodies were traced laterally along distinct marker beds over several hundreds of metres.

The stratigraphic architecture shows a general layer-cake pattern. The thickness and lateral extent of reservoir geobodies is strongly influenced by their stratigraphic position. High-energy shoal facies developed preferentially in the regressive parts of cycles of multiple hierarchies. Individual grainstone bodies may reach a thickness of 6 m, and those thicker than 3 m extend across the area of interest. Clinoforms or shingle-type geometries were explicitly searched for, but were not present.

The observed systematic variations in extent and two-dimensional sedimentary architecture of Khuff grainstone bodies were used as input for 3D static facies modelling. Outcomes of this study have been used to reduce uncertainty on grainstone geometries, production-scale correlation strategies and definition of lateral facies successions in subsurface models of the Khuff reservoir.

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