High-Resolution Sequence Stratigraphy and Reservoir Characterization as Input to Geological Modeling of Upper Thamama Reservoirs (Lower Cretaceous Shu’aiba and Kharaib Formations), Abu Dhabi, United Arab Emirates
A new sequence stratigraphy-keyed geological model has been built for the upper Thamama (Lower Cretaceous) Kharaib and Shu’aiba formations. The Kharaib Formation contains two reservoir units (Lower and Upper Kharaib Reservoir Units) with 80 and 170 ft thickness, respectively, separated and encased by three low porosity and permeability dense zones. The overlying Shu’aiba Formation is separated from the Kharaib Formation by the Upper Dense Zone (Hawar) and contains two reservoir units, only partly separated by dense intervals. The thickness of the Lower and Upper Shu’aiba Reservoir Units is approximately 55 and 90 ft, respectively. Core and well-log data of a giant onshore oil field in Abu Dhabi, as well as outcrop data from Wadi Rahabah (Ras Al-Khaimah) were used to establish a lithofacies scheme and a sequence stratigraphic framework. The scheme is applicable to all four reservoir units and the three dense zones. The Lower and Upper Kharaib Reservoir Units, as well as the Upper Dense Zone, are part of the late transgressive systems tract (TST) of a second-order supersequence, built by two third-order composite sequences. The overlying Lower and Upper Shu’aiba Reservoir Units belong to the late TST and highstand systems tract (HST) of this second-order supersequence built by four third-order composite sequences. The six third-order composite sequences are composed of twenty-six fourth-order parasequence sets that form the basic building blocks of a new generation static model. On the basis of faunal content, texture, sedimentary structures, and lithologic composition, fourteen reservoir lithofacies and ten non-reservoir (dense) lithofacies are identified from core. Reservoir units range from lower ramp to shoal crest to near back shoal open platform environments.
AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain