Paleocene deposits of the Ukrainian Carpathians: geological and petrographic characteristics, reservoir properties

The Paleocene Yamna Formation represents one of the main oil-bearing sequences in the Ukrainian part of the Carpathian petroleum province. Major oil accumulations occur in the Boryslav-Pokuttya and Skyba Units of the Ukrainian Carpathians. In the great part of the study area, the Yamna Formation is made up of thick turbiditic sandstone layers functioning as reservoir rocks for oil and gas. The reconstructions of depositional environments of the Paleocene flysch deposits performed based on well log data, lithological and petrographic investigations showed that the terrigenous material was supplied into the sedimentary basin from two sources. One of them was located in the northwest of the study area and was characterized by the predominance of coarse-grained sandy sediments. Debris coming from the source located in its central part showed the predominance of clay muds and fine-grained psammitic material. The peculiarities of the terrigenous material distribution in the Paleocene sequence allowed singling out four areas with the maximum development (> 50% of the total section) of sandstones, siltstones and mudstones. The performed petrographic investigations and the estimation of reservoir properties of the Yamna Formation rocks in these four areas allowed establishing priority directions of further exploration works for hydrocarbons in the study territory.