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Jean Borgomano1, Masse Jean-Pierre2, Al Maskiry Salim3
(1) Shell EP Technical Application and Research, Rijswijk, Netherlands
(2) Univ. Provence
(3) Petroleum Dev. Oman

Abstract: The Shuaiba carbonates in Jebel Akhdar, Northern Oman: Impact on static reservoir modelling for Shuaiba petroleum reservoirs

Outcrops in Jebel Akhdar offer a unique opportunity to study the depositional architecture of the Lower Aptian Shuaiba carbonate platform. Detailed stratigraphical correlations supported by GR logging allow the 2D geometry of the sedimentary bodies to be established.

The distance to the platform edge had a greater impact on facies distribution than the lateral changes in accommodation space on the platform. Inner platform bodies, dominated by mudstone facies are thick (2-10 m) and laterally continuous (6-40 km). They can be locally interbedded with thin (< 2m) and less continuous grainstone units (6-10 km). Outer platform bodies, dominated by grainstones, are less continuous dipwise (1-6 Km) but they are stacked on each other and build thick (5-50 m) units. These 2D outcrop models have a significant impact on static modelling of the Shuaiba reservoirs at field scales (5-50 Km):

  • Low energy, inner platform facies are characterised by thick bodies that are laterally continuous. Reservoir units are correlatable over entire fields (Al Ghubar)
  • High energy, inner platform facies consists of thin discontinuous bodies. Reservoir units are not always correlatable at field scale (Qarn Alam Field).
  • High energy, outer platform facies are dominated by thick stacked bodies. Reservoir units are not always correlatable at field scale (Al Huwaisah Field).

These trends imply that probabilistic modeling of reservoir units in the Shuaiba reservoirs must be supported by specific sedimentological databases for each paleoenvironmental settings. For example rudistid grainstones that form usually the best Shuaiba reservoirs, are associated to different body geometries depending on their situation on the carbonate platform.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana