--> Abstract: Sub-Regional High-Resolution Sequence-Stratigraphic Correlation of Upper Thamama (Lower Cretaceous) Reservoir and Non-Reservoir Zones, Abu Dhabi, United Arab Emirates, by Abdulla Al-Mansoori, John C. Mitchell, and Christian J. Strohmenger; #90072 (2007)

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Sub-Regional High-Resolution Sequence-Stratigraphic Correlation of Upper Thamama (Lower Cretaceous) Reservoir and Non-Reservoir Zones, Abu Dhabi, United Arab Emirates

Abdulla Al-Mansoori1, John C. Mitchell2, and Christian J. Strohmenger1
1Abu Dhabi Company for Onshore Oil Operations (ADCO), Abu Dhabi, United Arab Emirates
2ExxonMobil Upstream Research Company, Houston, TX

Important hydrocarbon accumulations occur in platform carbonates of the Lower Cretaceous Kharaib (Barremian and Early Aptian) and Shuaiba (Aptian) formations (Upper Thamama Group) of Abu Dhabi. These formations contain three reservoir units bounded by low porosity/permeability dense zones.
On the basis of faunal content, texture, sedimentary structures, and lithologic composition, thirteen reservoir lithofacies and eight non-reservoir (dense) lithofacies are identified from core. Depositional environments of reservoir units range from lower ramp to shoal crest to near-back-shoal. Dense zones (locally with features indicative of very shallow water deposition and exposure) were deposited in a restricted shallow-lagoonal setting.
The Lower and Upper Kharaib reservoir units as well as the Upper Dense Zone are part of the late transgressive sequence set of a second-order supersequence, built by two third-order composite sequences. The overlying Lower Shuaiba Reservoir Unit belongs to the late transgressive sequence set and the early highstand sequence set of this second-order supersequence and is built by one third-order composite sequence. These third-order composite sequences consist of fourth-order parasequence sets. Within the Kharaib Formation, third-order transgressive systems tracts are formed by mud-dominated moderate to high porosity but low to moderate permeability carbonates, whereas grain-dominated, high to very high porosity and permeability carbonates occur in third-order highstand systems tracts.
Thickness and facies changes are minor within one field and only become obvious on a sub-regional and regional view. The lower Kharaib reservoir unit thins by nearly one-half from west to east, most likely due to lap-out. A facies change follows this trend: orbitolinid-rich skeletal wackestone/packstone (west) becomes bioturbated wackestone/packstone (east).
The established stratigraphic framework and the sequence stratigraphy-keyed environment of deposition maps allow a better prediction of the distribution of reservoir rocks throughout the ADCO concession.

 

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece