Spatial and temporal variability of Paleocene-Miocene organofacies of the Kura Basin, eastern Azerbaijan, and implications for basin evolution and petroleum generation

Observed geochemical variability suggests a complex evolutionary history of the Kura Basin during the Paleocene-Miocene, and this has important implications for hydrocarbon prospectivity in the region. Within the 400 collected samples, total organic carbon (TOC) values range from 0.3 to 6.3%, with Oligocene-Miocene samples showing average values of 1.4%, compared to lower TOC values found in Paleocene-Eocene strata (average = 0.3%). Rock-Eval pyrolysis shows that the majority of strata are organic lean, immature, and mixed oil/gas to gas prone (Type II/III to Type III), with a smaller group of latest Eocene-Early Miocene samples having better oil prone source potential. Gas chromatography and biomarker analysis of 24 samples reinforces the immaturity of most samples, shows varying levels of terrestrial input in all samples, suggests well-oxygenated waters prevailed with periodic suboxic to dysoxic/anoxic events, highlights gross differences between the Paleocene-Eocene and Oligocene-Miocene stratigraphic intervals, and shows generally good lateral correlation between samples. These interpretations reinforce what is seen through inorganic geochemical evaluation of trace metals, bulk composition, and stable isotopic ratios, and offer more detail as to the evolution of this basin and the implications for oil and gas prospectivity of the region.