Facies Characterization of South-East Iraq Asmari Carbonate Platform

Pierre Masse¹, Alexandra Cournot², Catherine Javaux³, and Husnein Ahmed^4
1Total S.A, Pau, France
²Statoil ASA, Stavanger, Norway
³TOTAL, 64018 Pau Cedex, France
⁴Total, Paris, France

Data from South East Iraq Asmari formation concerns the Buzurgan Fauqi & Abu Ghirab fields, discovered by Elf-Iraq in the early seventies. Revisions of in-house field data were undertaken on three cored wells of each field, to actualize biostratigraphy, sedimentology and sequential stratigraphy interpretations. Third-order sequences were dated Chattian to Burdigalian using revised biostratigraphy and ⁸⁷Sr/⁸⁶Sr datings.
Within this framework, a facies classification was established, with environment ranging from sebkha, with paleosoils, to outer ramp, enriched with Lepidocyclina. Stacking patterns and biological content help us defining maximum flooding surfaces and sequence boundaries. Microfaunistic assemblages defined bio-events, like Favreina events. Different depositional models were built, according to the depositional environments (lagoon, outer bars) and system-tracts position. Field analogs of the same age and biological content were used to evaluate the geometries. Besides sandstones reservoir, best carbonate reservoir facies are made of dolomites. Comparison of petrophysical properties is made between sucrosic dolomites and dolomites with anhydrite cement and/or nodules or dolomites with sands. Limestones petrophysical properties are characterized according to their textures, proportion of shales and sands. Porosity-permeability values can be enhanced by diagenetic events at sequence boundaries.

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