--> ABSTRACT: The LHS Prograding Carbonate System (Early Cretaceous-Sultanate of Oman): From Seismic Stratigraphy and Outcrop Analysis to Reservoir Modeling, by Dujoncquoy, Emmanuel; Razin, Philippe; Grélaud, Carine; Imbert, Patrice; Labourdette, Richard; #90135 (2011)

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The LHS Prograding Carbonate System (Early Cretaceous-Sultanate of Oman): From Seismic Stratigraphy and Outcrop Analysis to Reservoir Modeling

Dujoncquoy, Emmanuel 1; Razin, Philippe 1; Grélaud, Carine 1; Imbert, Patrice 2; Labourdette, Richard 2
(1)Institut Egid Bordeaux3, Bordeaux, France. (2) TOTAL.S.A., Pau, France.

The Lekhwair/Habshan/Salil (LHS) system is a carbonate succession that prograded across the eastern part of the Arabian plate from Berriasian to early Barremian. The three formations that comprise this system correspond to the inner platform (Lekhwair Fm.), platform margin (Habshan Fm.) and slope to basin facies associations (Salil Fm.). On seismic, this system shows a conspicuous prograding character with well-expressed clinoforms. The formations imaged on seismic crop out in slightly more distal position in the Oman Mountains, so that a comparison can be carried out.

The comparison went through a combination of outcrop analysis and seismic interpretation. Then, forward synthetic seismic models of the outcrop-based sections were built in order to check what scale of reservoir characteristics could be validly interpreted from seismic.

The clinoforms that make the LHS system on seismic have a vertical amplitude ranging from 50 to 180 m in the studied area of NE Oman. The clinoforms show variable geometries with slope angles ranging from 0.1° to 15°. Seismic stratigraphy allowed interpreting RSL changes as the main factor controlling geometries. Wells/seismic calibration allowed to match geometries with facies, and especially to understand the development of the ooid reservoir facies in this system (Habshan Fm.).

The outcrops show five main stratigraphic units, separated by facies downward shifts. These shifts highlight the role of RSL fluctuations in defining the sediment architecture of the LHS system. In these five units, the development of the facies is controlled by three main factors: geometry of depositional profile, accommodation space and paleo-oceanographical conditions.

Seismic and outcrop interpretations were replaced into a eustatic and tectonic framework.

This integrated outcrop/subsurface study and synthetic seismic modelling show that the development of ooid intervals is favoured by high-angle depositional profiles associated with high hydrodynamic energy and high accommodation rates. Therefore, some ooïd intervals can be associated with flat seismic reflexions meaning that the ooïds develop along high angle clinoform at the scale of the depositional sequence, below seismic resolution.

These results were applied to build a static reservoir model based on the seismic geometries, with facies ascribed on the basis of the observations made on cores and at the outcrop. The petrophysical values were extracted from the core facies measurements.

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.