Organic geochemistry and petroleum potential of Jurassic and Cretaceous deposits of the Yenisei–Khatanga regional trough

Abstract

We present results of geochemical studies of organic matter of the Jurassic–Cretaceous deposits in the west of the Yenisei–Khatanga regional trough. The studies were carried out on a representative set of well cores by a complex of modern organic-geochemistry methods (determination of organic-carbon content in rocks, pyrolysis, estimation of the carbon isotope composition in the kerogen of rocks, extraction, liquid and gas–liquid chromatography, and chromato-mass spectrometry). Based on the distribution of biomarkers in the studied bitumens and pyrolysis of rocks, two groups of the samples were recognized: with terrigenous (type III) and marine (type II) organic matter. The terrigenous bitumens are characterized by a low hydrogen index (HI) and a predominance of hydrocarbons C29 among steranes and C19 and C20 among tricyclanes. The marine bitumens, revealed in stratigraphic analogs of the Bazhenovo Formation and in the Malyshevka, Nizhnyaya Kheta, and Shuratovka Formations, show an even distribution of sterane homologues and a predominance of medium-molecular tricyclanes. The Pr/Ph and C35/C34 ratios and the presence of diahopanes testify to the burial of organic matter in suboxidizing sea coast environments. In the Yanov Stan (J3–K1), Gol’chikha (J2–K1), and, to a lesser extent, Malyshevka (J2), Nizhnyaya Kheta, and Shuratovka (K1) Formations, we have recognized widespread stratigraphic levels with marine organic matter of rocks. Its contents and degree of maturity permit these rocks to be considered oil-generating.

An analysis of organic matter sources for surface sediments in the central South Yellow Sea, China: Evidence based on macroelements and n-alkanes

“…However, when organic matter is further buried, the odd-even predominance of n-alkanes disappears. Therefore, OEP is only suitable in sediments from the immature to mature stage (Alaug et al, 2013;Kim and Rodchenko, 2013;Powell, 1986).…”

Geodynamics and Oil and Gas Potential of the Yenisei-Khatanga Basin (Polar Siberia)

“…The rocks contain OM of mixed type (Type-III and Type-II). The OM accumulated both in diffuse and concentrated (coals) form [17,88]. In general, the Jurassic-Cretaceous deposits section is weakly differentiated in terms of C org content.…”

“…In general, the Jurassic-Cretaceous deposits section is weakly differentiated in terms of C org content. The Middle Jurassic-Barremian mudstones have C org concentrations of 0.34-1.6% [17,74], and in some cases 3% [88]. The Jurassic-Lower Cretaceous deposits are usually considered as gas generating [17].…”

“…The Jurassic-Lower Cretaceous deposits are usually considered as gas generating [17]. However, some levels in the Yanov Stan, Gol'chikha, Malyshevka, and Nizhnyaya Kheta formations could have been oil generating [88]. Gases actively migrated from the deep parts of the basin in the upper horizons, and the oils accumulated mostly in the generating complex.…”

Relics of biolipids in kerogen of Cambrian Siberian Platform oil shale

“…In structural studies, special methods for soft destruction of macromolecules are applied (Gordadze, 2002;Kim and Rodchenko, 2013); these are, first of all, thermal methods playing a crucial role in the natural formation of petroleum (Henderson et al, 1968).…”