Lithological-petrophysical characteristic of Neogene deposits of Transcarpathian oil- and gas-bearing area

While searching and prospecting for hydrocarbon deposits, the efficiency of geological-prospecting works, exactly selection of optimal technologies of deposits discovering and their extraction, to a considerable extent depends on the availability of reliable information on probable types of reservoir rocks and their petrophysical properties. Here the results of researches of Neogene deposits of Transcarpathian deep of the Carpathian oil- and gas-bearing province were stated. Methods of researches contained an analysis of available geological-petrophysical information on lithological-petrographical, structural-textural peculiarities and petrophysical properties of deposits, laboratory investigations of core, mathematical-statistical processing of data, study of correlation ties between capacity-filtration and industrial-geophysical parameters, studies of the influence of geological factors upon the formation of different types of reservoir rocks. In the Transcarpathian deep, industrial accumulation of gas were reveald in deposits of Badenian, Sarmatian and Pannonian and fractured ones. In the Badenian complex, gravelites, sandstones, aleurolites and at least tuffs and tuffites are reservoir rocks. Open porosity of sand resevoirs is from 8 to 22 per cent mainly, and permeability: (0.1–20.2) ∙ 10−3 μm2, open porosity of tuffaceous rocks varies from 3.7 to 24.4 per cent, and permeability from 0.1 ∙ 10−3 to 31.5 ∙ 10−3 μm2. Main role in improvement of capacity-filtration properties of reservoir rocks in undersalt thickness belongs to fracturing. In the Sarmatian deposits, sandstones and tuff rocks are reservoir rocks. Porosity of terrigenous reservoirs is from 10 to 20 per cent and permeability reaches 5 ∙ 10−3 μm2, porosity of tuffs and tuffites varies from 7.1 to 9 per cent, and permeability: (0.1–176) ∙ 10−3 μm2. Sand rocks that are characterizes by high capacity-filtration properties are known to be reservoir rocks in Pontian-Pannonian deposits. Open porosity is from 9.5 to 27 per cent, and permeability: (0.02–140) ∙ 10−3 μm2. Thus, executed researches have indicated that in the sedimentary complex, reservoir rocks of different type from low-porous consolidated granular to composite-structured porous-fractured-cavernous were present that was caused by the influence of sedimentary, geotectonic, thermobaric, geothermical and other geological factors that rocks underwent in the course of their forming.