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Khuff Reservoir in North Oman: A High Resolution Sequence Stratigraphic Approach

Claps, Michele *1; Aigner, Thomas 2; Aghbari, Ibrahim 1; Glover, Stephen 1; von Winterfeld, Claus 3; Bizarro, Paulo 4; Moranville, Mike 1; Mahrooqi, Shabib 1; Barodi, Tibor 1
(1) Petroleum Development Oman, Muscat, Oman. (2) Tubingen University, Tubingen, Germany. (3) A/S Norske Shell, Tananger, Norway. (4) Partex Oil & Gas, Lisboa, Portugal.

The Khuff Fm is one of the reservoirs with the highest economic significance in the Middle East region. It comprises mixed carbonate/evaporitic sequences of Late Permian-Early Triassic age deposited on a large and flat epeiric carbonate ramp. In North Oman the Khuff houses important hydrocarbon accumulation, and features a field-scale layer-cake geometry characterized by relatively thin reservoir geobodies, with internal property contrast.

In the recent years the application of High Resolution Sequence Stratigraphy (HRSS) to carbonate reservoirs at exploration and production scales has gained a considerable impetus. In this view, and because of its intrinsic geological nature, the Khuff Fm represents an ideal candidate to test how stratigraphic sequences and depositional cycles nested hierarchies (at the 3rd and 4th order scale) can be used to control the distribution of reservoir geobodies in 3D models.

This application builds upon an integrated approach, based on combining surface outcrop analogues, regional paleogeographic trends, biostratigraphy and detailed sedimentological core studies. The identification in cores of important stratal surfaces, vertical facies stacking patterns/trends and early diagenetic overprints allows to unravel the depositional cyclicity at the core level. This initial skeleton of 1D sequence stratigraphic architecture is complemented with precise core-to-log correlation to identify HRSS packages away from cored wells and ultimately to build a robust 2D framework. As a result a set of surfaces of sequence stratigraphic significance is generated in the 3D geomodel.

This newly established HRSS 3D framework has been then confirmed and updated by subsequent appraisal wells and the reservoirs layers correlatability re-calibrated in an iterative loop.

The application of HRSS to the Khuff has allowed to evolve the traditional petrophysical-based framework into a geologically-driven and more detailed reservoir zonation scheme. Facies and petrophysical properties have been distributed within this high-resolution reservoir architecture.

The static-to-dynamic upscaling has been optimized by selectively capturing property variability and heterogeneity in the critical flow units, and therefore limiting simulation run-time.

From a development plan perspective, the geological correlatability of good reservoir quality layers has ultimately increased the opportunity to maximize well productivity by targeting predictable reservoir layers.


AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain