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AAPG Bulletin


AAPG Bulletin, V. 86, No. 9 (September 2002), P. 1513-1529.

Copyright ©2002. The American Association of Petroleum Geologists. All rights reserved.

The lower Aptian Shuaiba carbonate outcrops in Jebel Akhdar, northern Oman: Impact on static modeling for Shuaiba petroleum reservoirs

J. Borgomano,1 J.-P. Masse,2 S. Al Maskiry3

1Shell International EP Technology Applications and Research, PB 60, 2280 AB, Rijswijk, Netherlands; email: [email protected]
2University of Provence, PRESA 6019 du CNRS, 13331 Marseille Cedex 03, France
3Shuram Company, Muscat, Sultanate of Oman; email: [email protected]


Jean Borgomano obtained a Ph.D. in carbonate geology in 1987 at the University of Marseilles (France). Since 1988 he has been employed by Shell in various exploration-production Shell companies. Since 1999 he has been senior carbonate geologist at the Shell research offices in Rijswijk (Netherlands).

Jean-Pierre Masse is a director of research at the French Research Council in Marseilles (France). He has spent most of his research time (since 1976) on Lower Cretaceous shelf carbonates throughout the world.

S. Al Maskiry worked as an exploration and field geologist for Petroleum Development Oman until 1999, and then founded his own consultancy company, Oil Shuram, based in Muscat.


We are thankful to the Ministry of Petroleum and Minerals of the Sultanate of Oman and Petroleum Development Oman (PDO) who authorized the publication of this article. We also wish to thank Wolfgang Witt and Jeroen Peters (PDO) who actively supported the field campaign in 1991-1992. We are also grateful to the many PDO geologists whose work contributed to the compilation of the Shuaiba paleogeographic map in Figure 10, especially Wolfgang Witt, Dieter van der Baan, and Paula Borgomano-Bouchard.


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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