Historical and geological modeling of the processes of hydrocarbon generation in the hettangian–aalenian deposits of the ust’-tym megadepression

O. A. Loktionova, L. M. Burshtein, L. M. Kalinina, V. A. Kontorovich, P. I. Safronov

Результат исследования: Научные публикации в периодических изданияхстатья

Аннотация

Analysis of the geologic structure of the Hettangian–Aalenian deposits of the Ust’-Tym mega depression was carried out. The history of the formation of traps in the Hettangian–Aalenian complex has been reconstructed on the basis of a comprehensive interpretation of seismic materials and deep-drilling data. The oil and gas potential has been estimated. The time of the subsidence of the Togur Formation into the oil window has been determined, and the history of the generation of liquid hydrocarbons (HC) by the organic matter (OM) of the Togur Formation has been reconstructed. The Lower Jurassic and Aalenian deposits overlap the rocks of the pre-Jurassic basement with disagreement and are distributed almost over the entire study area. The complete section of the Hettangian–Aalenian deposits is in the most submerged parts of the territory. The section includes the Urman, Togur, and Salat/Peshkov Formations and the lower Tyumen Subformation. Three oil and gas subcomplexes— Hettangian–Early Toarcian (U16–17), Toarcian–Aalenian (U15), and Aalenian (U11–14) — are distinguished within the Hettangian–Aalenian sediments. Closed positive structures that can serve as hydrocarbon traps have been identified in each of the subcomplexes. Positive structures developed in the Jurassic, Berriasian–Early Aptian, and Aptian–Albian–Turonian time were inherited and finally formed at the post-Turonian stage only. The authors carried out a quantitative assessment of the total oil resources of the D0 category for all promising objects, taking into account the success rate. The heterogeneous organic matter of the Togur Formation is the main source of hydrocarbons in the Hettangian–Aalenian complex. The Togur Formation began to enter the oil window (OW) about 115–110 Ma and fully entered it about 5 Ma. The escape of rocks from the zone of the oil window began about 48 Ma and still continues. The history of the generation of liquid hydrocarbons by the organic matter of the Togur Formation has been reconstructed for types II and III of kerogen. For type II, the generation began about 94 Ma, at the beginning of the Late Cretaceous (Cenomanian), and for type III, it began in Turonian time (89.8 Ma). The most significant volumes of liquid HC were generated in the last 5 Myr. Potential hydrocarbon traps existed throughout the generation process, which allowed accumulation of the generated hydrocarbons in the Hettangian–Aalenian complex. Comparison of the estimated oil resources of the D0 category in the traps of the Hettangian–Aalenian complex with the volumes of generated hydrocarbons leads to the conclusion that the traps might have been filled. The results obtained in the course of the study suggest that the Hettangian–Aalenian complex is oil-and gas-promising and the Togur Formation is the main source of hydrocarbons.

Язык оригиналаанглийский
Страницы (с-по)801-812
Число страниц12
ЖурналRussian Geology and Geophysics
Том60
Номер выпуска7
DOI
СостояниеОпубликовано - июл 2019

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