Eocene-Miocene oil shales in Azerbaijan: Stratigraphic controls on formation, distribution and hydrocarbon generation

Abstract

Based on the results of many years of field surveys, new information is presented on previously unknown oil shale outcrops in Azerbaijan. New boundaries of the distribution of oil shale-bearing facies were established. Role of stratigraphic controls in the distribution of oil shales within areas and outcrop sections, and their oil or gas generation capabilities were substantiated. The study of the source of oil shale parent rocks, and the features of oil shale basin that formed in the Eocene, Lower Maikop (first discovered in this study) and Miocene (Upper Maikop, Chokrakian and Diatom), made it possible to obtain some new regularities. Our results show that the kerogens of Eocene and Diatom oil shales demonstrate similar evolutionary histories that are noticeably different from the Maikop ones. Eocene oil shale kerogens, which show a closer connection with the marine environment demonstrate the ability to generate only oil, like Diatom kerogens, while the kerogen evolved in the Upper Maikop basin, which is subject to more terrigenous inputs and formed in a relatively freshwater environment, mainly shows the ability to generate gas.

Geochemical proxies of the gryphon breccia of mud volcanoes in East Azerbaijan: regularities in the distribution of chemical elements and spatial characteristics of sedimentation

“…The preservation of high amounts of U in organic-rich rocks can be explained by the role of U leached from tuffaceous rocks genetically associated with a more acidic composition. This idea is consistent with the conclusion made in [9]. Thus, this literature shows that pyroclastic sediments brought into the paleobasin play a decisive role in the formation of Middle Eocene and Diatom oil shales [11] rich in organic matter (on average about 20 %) in Central and Southern Gobustan.…”

“…The thickness of the sedimentary cover in coastal areas belonging to the deepest part of the Lower Kura depression is about 20 km, half of which consists of Neogene and younger deposits [19]. However, the thickness of the sedimentary cover in the areas of the volcanoes belonging to the northern part is much less; therefore, the maximum contribution of older deposits, Paleogene, especially Eocene, to the formation of breccias belonging to these volcanoes cannot be ruled out [9]. If we take into account the published results of studies of the relationship of Eocene deposits with the sea in East Azerbaijan [13; 14], the correctness of our conclusion is beyond doubt.…”

“…This is probably due to the higher contribution of Upper Maikop sediments to the formation of the breccia of this mud volcano. The result of studies carried out in [9] shows that the protoliths of some Upper Maikop oil shales, containing more quartz (about 40%) and having more mature features in Central Gobustan are associated with granitic sources. Another interesting issue relates to the higher U values in the Aghdam and Shekikhan samples (Table 2), which, like Kichik-Mereze, are separated from other samples in the Rb/Sr vs. Rb/Ba plot.…”