Geochemical features of the organic matter from Jurassic sediments of the Nadym‑Taz interfluve

Abstract

This paper deals with the evaluation of oil-generation potential derived from the geochemical data on deep-buried Jurassic sedimentary rocks of the Nadym-Taz interfluve being part of the West Siberian petroleum basin (PB). The study provides analysis of samples from ultra-deep and deep wells that penetrated the Mesozoic-Cenozoic sedimentary cover in the north of the central part of PB (En-Yakhinsky, Evo-Yakhinsky, Yarudeysky, Tyumensky areas, etc.). The research focuses on the insoluble organic matter (OM) from Upper, Middle and Lower Jurassic sediments (54 samples). A comprehensive study of the kerogen by elemental, isotope analyses and pyrolysis Rock-Eval allowed obtaining the data critical for determining the genetic type of OM, its thermal maturity and residual petroleum generating potential. Using the Surfer and Corel Draw software, schematic maps and diagrams of variations in the most informative (i.e. area-specific and depth-dependent) geochemical parameters of the kerogen on the studied area and also down the section (from the Upper to the Lower Jurassic) were constructed and analyzed. The obtained geochemical data indicate that in the Jurassic sediments of the Nadym-Tazovsky interfluve, the highest OM generation potential is found in the Bazhenov horizon, as well as in individual members of the Malyshevsky, Leontievsky, Sharapovsky and Kiterbyutsky horizons. Based upon the level of OM maturity in the Upper and Middle Jurassic sediments, deposits of mainly oil and fat gases could be preserved, and in the Lower Jurassic – deposits of fat and dry gases.