The study presents results of a hydrogeological and hydrogeological research conducted on the Mesozoic–Cenozoic sedimentary cover and Precambrian–Paleozoic platform deposits of the Pre-Yenisei petroleum subprovince. The hydrogeological structure of the study area is found to be of a transition type from the West Siberian to Tunguska artesian basins, with its own set of pertinent parameters, such as groundwater depths, rock permeabilities, water chemistry and gas compositions, gas saturation, vertical zoning, etc. The upper part of the sedimentary section is known to be flushed with the infiltration waters to depths of 2–2.5 km. The deeper intervals contain the older sedimentary waters with the moderate metamorphic grade. The results of the study provide implications for the petroleum potential of the area of interest.