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Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
High Resolution Sequence Stratigraphy and Reservoir Development of the Kurrachine Dolomite, Ash Shaer Field, Palmyra, Syria
(1) Cambridge Carbonates Ltd, Ashbourne, United Kingdom.
(2) Petro-Canada UK, London, United Kingdom.
(3) Petro-Canada Palmyra CV, Damascus, Syrian Arab Republic.
The Triassic Kurrachine Dolomite Formation of the Ash Shaer Field, Palymyra, Syria comprises repeated cycles of shale, dolomitised carbonate mudstone and wackestone, peritidal limestone and subaqueous anhydrite deposited in a restricted intra-shelf basin, sometimes connected to the Neotethys Ocean.
The aim of this paper is to demonstrate a high resolution sequence stratigraphic model for the Kurrachine Dolomite that may explain and predict the distribution of porosity through the reservoir. Cycles observed and described in core were used to validate the field stratigraphy, such that Fischer plot analyses could be extended to uncored logged intervals for each well. The corresponding correlations of cycle number versus net deviation of cycle thickness from average cycle thickness demonstrates the influence and control of high and low order sea level variations on porosity development and preservation. High frequency sequence stratigraphy has aided the identification and characterisation correlatable productive intervals in the Triassic Upper and Middle Kurrachine of the Ash Shaer Field, Palmyra province. This has enhanced our understanding of reservoir connectivity and stacking providing a valuable tool for improved development well planning. The following cycle types were defined:
- Subtidal cycles: are argillaceous laminated and bioturbated carbonate mudstone and shales. Cycle boundaries are non-emergent. Maximum flooding events are bioclast-rich shales that may form field-scale correlative layers. These cycles are mainly limestone with little dolomitisation.
- Subtidal cycles with anhydrite: anhydrite beds occur in the subtidal cycles that formed during draw-down events and may form field-scale correlative layers. Dolomitisation is much more prevalent in these cycles than the subtidal cycles.
Peritidal cycles: are subtidal cycles capped by peritidal facies. Occasional anhydrite beds were deposited in local hypersaline lagoons and are not useful for correlation.
The sequence architecture of the Kurrachine Dolomite reservoir is controlled by the interplay of lower and higher orders of sea level variations:
Low order regressions cause basinward stacking of high order peritidal and subtidal with anhydrite cycles because of reducing accommodation space.
Low order transgressions cause higher order subtidal cycles to back-step towards the basin margin.
Low order high stands cause higher order subtidal cycles to stack progressively basinward.