Sedimentary facies analysis of the subsurface triassic and hydrocarbon potential in the United Arab Emirates |
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Authors: | Dr Abdulrahman S Alsharhan |
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Institution: | (1) Desert and Marine Environment Research Center, United Arab Emirates University, P.O. Box: 17777, Al Ain, United Arab Emirates |
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Abstract: | Summary The Triassic sediments in the subsurface of the United Arab Emirates has been divided into three formations (from bottom to
top): Sudair, Jilh (Gulailah) and Minjur. The Sudair Formation consists of four lithofacies units composed mainly of limestones
and minor dolomites interbedded with terrigenous shaley mudstones and anhydritic dolomitic limestones. These were deposited
in shallow marine supratidal to subtidal settings. The Jilh (Gulailah) Formation has five lithofacies units dominated by anhydritic
dolomitic limestone, fine terrigenoclastic sediments and bioclastic and intraclastic limestones. The formation was laid down
under lagoonal to supratidal sabkha conditions with little normal marine influence. The Minjur Formation is composed of three
lithofacies units characterized by argillaceous quartzitic sandstones, shales, mudstones, dolomitic and ferruginous limestones
with thin coal seams. These facies represent deposition in prograding delta lobes, reflecting humid continental to marginal-marine
conditions.
Diagenesis plays a major role in the reservoir development in the Triassic sediments, the pores are occluded by dolomite and
anhydrite. The grains are compacted, leached or cemented by marine cements. Porosity generally ranges from fair to poor with
values from 6% to 9% in the carbonates and from 6% to 15% in the clastics. Interparticle and vuggy porosities are the main
pore types. The porosity was controlled by diagenesis, depth of burial and lithology.
No oil has been discovered so far in the Triassic sediments of the United Arab Emirates but pronounced gas shows have been
reported from offshore fields. Western offshore United Arab Emirates is a promising area for potential hydrocarbon accumulations.
The Triassic sediments have low to moderate source rock potential; the organic matter is mainly sapropelic kerogen, and the
degree of thermal alteration ranges between mature to highly mature stages. |
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Keywords: | Sedimentary lithofacies Hydrocarbon Potential United Arab Emirates Triassic |
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