Constraining Maikop Source Rock Stratigraphy, Deposition, and Timing Using Chemostratigraphy of Redox-Sensitive Metals, Platinum-Group Elements, and Re-Os Geochronology

Abstract

The Oligocene-Miocene Maikop Series in the South Caspian and Kura Basins is the key petroleum source rock for both offshore and onshore petroleum development in Azerbaijan. The Maikop is a thick (up to 3 km) succession of silty mudstones containing up to 15% total organic carbon (TOC), but is greatly lacking in diagnostic microfaunal assemblages useful for dating and stratigraphically constraining the deposition of the mudstone. Timing constraints are also lacking on the formation and evolution of the basins, the timing of basin isolation, and the subsequent development of anoxic conditions that allowed for the preservation of organic matter. It is generally thought that Maikop deposition began in the late Eocene to early Oligocene prior to the restriction of the Paratethys Sea, an ancient epicontinental sea of which the Kura and South Caspian Basins were a part. Initial isolation of the Paratethys Sea was periodic, as reflected in the deposition of discreet, thin, organic-rich intervals of black shale in the Kura Basin and the departure of restricted sea depositional Os concentrations from open ocean abundances. In this study, samples were taken from these organic-rich intervals and analyzed for TOC; hydrogen index; total sulfur; redox-sensitive trace elements including Mo, V, Cr, U, Th, Na, Ti, and Co; platinum group elements (PGE) Pt, Pd, Rh, Ir, Ru, Au, Re, and Os; and Re-Os radiogenic isotopes for geochronology. Analysis of these elements will allow for stratigraphic constraint of the onshore Maikop Series and simultaneous development of intervals with higher TOC deposited under reducing conditions. This analysis will allow for improved predictive modeling of unconventional resources and for the modeling of hydrocarbon generation and migration both onshore and in the offshore South Caspian Basin. Additionally, Re-Os geochronology and PGE element analysis will improve constraints for Kura and South Caspian Basin evolution and the timing of deposition of the Maikop, which will aid development of basin and petroleum system models.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018