Online Journal for E&P Geoscientists

Steuber, Thomas ^*1; El Wazir, Zinhom ²; Duan, Rutai ¹; Mueller, Klaus ²
(1) The Petroleum Institute, Abu Dhabi, United Arab Emirates. (2) ADCO, Abu Dhabi, United Arab Emirates.

The stratigraphy of Barremian -Aptian carbonate platforms of the Middle East and their complex archictecture are relatively well constrained since they host several large reservoirs and have therefore attracted substantial research. Nevertheless, regional and local correlation of sedimentary sequences can be difficult. We have used a combination of carbon and Sr-isotope chemostratigraphy to test regional sequence stratigraphic models, improve local correlation of sedimentary sequences, and place them in a global context of environmental change.

Examples are provided how to derive precise numerical ages using Sr-isotope stratigraphy. Most importantly, diagenetic alteration of the original seawater Sr-isotopic composition must be excluded by careful selection of sample material and geochemical screening. Precision of age-dating is +/- 0.7 my in the case study presented, and factors affecting the reliability of numerical ages are discussed.

Once the numerical ages of sequence boundaries and other correlative surfaces are established, the validity of problematic correlations can be easily tested. We provide examples of age-dating sedimentary sequences along and across the Aptian platform margin in the subsurface of the UAE, including numerical ages for the Late Aptian prograding units that are particularly difficult to correlate.

The Aptian sedimentary sequences of the Middle East provide excellent examples of complex carbonate platform and reservoir architecture. Chemostratigraphy, and particularly numerical ages, allow for the correlation with global environmental change (oceanic anoxic events, extinction events of carbonate producers, sea-level change) that ultimately leads to an improved understanding of the evolution of the regional Aptian carbonate platforms, and the distribution of their characteristic reservoir facies.