Field-scale geometries of Upper Khuff reservoir geobodies in an outcrop analogue (Oman Mountains, Sultanate of Oman)

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.