Application of spectral analysis in sequence stratigraphy and Milancovich cycles identification in Sarvak Formation in Kupal Oilfield

The Sarvak Formation (Albian to Turonian) is one of the carbonate units in the southwest Iran that was deposited on Neotethys margin. The purpose of this study is to analysis sequence stratigraphy and to identify Milankovitch cyclesof this formation in wells No. 20 and 48 in the Kupal Oilfield. This study was done by MESA spectral analysis method, using Cyclolog software and gamma ray data. The study of 250 thin sections led to identification of 9 microfacies that were deposited in three depositional environments including lagoon, shoal and open marine. In additions two third order depositional sequences (based on facies variations and changes PEFA and INPEFA curves) were identified. Examination of Milankovitch cycles, using both interval variations between gamma ray peaks and MESA spectral analysis methods showed that most of them formed 100,000 years cycles type. Orbital age determination with respect to counting of these cycles showed that this part of drilled formation has 11 to12 million years age.