I.V. Kunitsyna, A.V. Derduga, V.E. Verzhbitskiy, N.A. Malyshev, N. Vasileva, E.A. Khairullina
Prediction of Kungurian salt-bearing deposits occurrence in North Caspian
Key words: Southern Urals; frontal folds; seismic stratigraphy sequences; oil and gas bearing sequences; unconventional reservoir; local exploration targets; oil; gas.
For citation: Kunitsyna I.V., Derduga A.V., Verzhbitskiy V.E., Malyshev N.A., Vasileva N., Khairullina E.A. Prediction of Kungurian salt-bearing deposits occurrence in North Caspian. Geologiya nefti i gaza. 2022;(3):17–27. DOI: 10.31087/0016-7894-2022-3-17-27. In Russ.
The authors discuss the focal problem of regional geology: determination of the area of Kungurian deposits occurrence in North Caspian waters; namely, in the North Caspian fold and thrust zone. The Lower Permian salt-bearing Kungurian deposits play a role of regional impermeable bed for oil and gas accumulations. Absence of evaporite sequence considerably raises geological risks of hydrocarbon accumulation integrity and, thus reduces the likelihood of oil and gas field detection. 2D seismic data made the basis for the studies since there are almost no drilling data for Palaeozoic deposits in this zone. It is found that a rather thick (up to 1.5 km) evaporite sequence is present in the northern part of the North Caspian fold and thrust zone. The presented seismic and stratigraphy sections show that thickness of Kungurian deposits reduces to hundreds of metres, and then the deposits incrop below the surface of pre-Jurassic unconformity. The most ambiguous area is the Kurmangazy uplift, where single seismic survey lines demonstrate bodies morphologically associated with salt pillows. However, the presence of (thin) salt-bearing Kungurian deposits persistent over the area remains a matter of debate. The revealed patterns of the Kungurian sequence occurrence allowed concluding that northern and southern areas of the North Caspian fold and thrust zone have the lowest geological risks in terms of impermeable bed presence and integrity of hydrocarbon accumulations in Palaeozoic deposits.