Vertjukh A. Geological Structure and Hydrocarbon Exploration Perspectives for the Lower Carboniferous Strata in the Southern Peri-Flank Zone of the Dnieper-Donets Depression.

A detail litho-stratigraphic subdivision of Tournaisian, Visean and Serpoukhovian sediments onto pay horizons with bed-to-bed correlation and indexation is made that allowed building of a confident stratigraphic framework to refine structure and petroleum potential of the area studied. It was found and traced changes in lithological composition and thickness of pay horizons, updated the peculiarities of their lateral development, and facies characterization. For the first time it was recognized typical section of the Tournaisian – Lower Visean pay reservoirs of carbonate facies, in particular: Yuriivskyi (T-4 pay horizon), Pereshchepinskyi (T-3 pay horizon), Machuskyi (T-2 pay horizon), Marenytskyi (T-1 pay horizon) for Tournaisian complex and Tsyganskyi (V-27 pay horizon), Pereshchepinskyi (V-26 pay horizon) and Mozharivskyi (V-25 and V-24 pay horizons) for the Lower Visean complex. Detailed lithology-petrographic, paleontological and geophysical characteristics for each of the typical sections are given. A presence of zonal and local gaps in sedimentation in the Lower Carboniferous sedimentary record to impacting hydrocarbon traps formation and fields’ localization is established. Structural-tectonic studies of the Southern Peri-Flank zone of the DDB were conducted and a number of the structural surfaces of 1: 100 000 scale were constructed, namely on the top of the Devonian sedimentary deposits, top of Tournaisian carbonate rocks, bottom of Upper Visean, top of Lower Serpukhovian and base of the Mesozoic sedimentary succession. It was detailed geological structure of the central and eastern parts of the Southern Peri-Flank zone (Reshetnyaky-Zatyshnya area), and restored development history of its structural evolution and refined perspectives of petroleum exploration. Upon results of complex and tectoni-structural analysis it was recognized prospective areas to search for hydrocarbon fields in the traps of non-structural type, including carbonate ones as following: the Khortytsia-Mekhedivka, Ozeryany-Kibintsy, Tyshchenkivka-Gorobtsi and Pereshchepino-Zatyshne. Prospects for shale gas exploration in the Lower Carboniferous deposits of the of the Southern Peri-Flank zone of the DDB are evaluated. According to the set of geological criteria, it is established that the Tournaisian, Lower Visean and Upper Serpukhovian deposits have low prospecting value for shale gas exploration. Alaterbatively, it was delineated the Gorobtsi-Bliznyuki (for Lower Serpukhovian sediments) and Okhynki-Zatyshne (for Upper Visean sediments) zones to shale gas exploration.