Перспективи газоносності Коханівської структури в Передкарпатському прогині України

Abstract

Розглянуто можливість використання абіогенної теорії походження родовищ вуглеводнів для побудови газової колони (частина верхньої мантії Землі, де генеруються, концентруються вуглеводневі гази та відбуваються їхні локальні викиди, які сприяють утворенню родовищ вуглеводнів). У Зовнішній тектонічній зоні Передкарпатського прогину докайнозойських порід виділено Коханівську кільцеву структуру, у межах якої ймовірне виявлення родовищ газу.

Last years authors of the article were developing statements of the abiogenic theory of hydrocarbons genesis. Numbers of their articles concerned the problems of hydrocarbons formation in different geological structures of Ukraine and joint regions. Basement point of the author’s version of the theory is an idea about formation of gas column during different tectonic epochs and establishing within their zones of hydrocarbons generation and concentration of hydrocarbon various phases. To create main initial aspects of the practical geological model of hydrocarbons formation and distribution of their fields, large geological structures (Donbas and Karpinskiy’s lineament) were used. According to authors’ geological models, gas column is a part of upper mantle and low levels of the Earth crust where hydrocarbon gases have been generated, concentrated and thrown out as a source of hydrocarbons fields. Vertical section of the gas column stretches from asthenospheric surface up to sedimentary sequence. It is divided into some zones with specific PT-conditions, which reflect formation of different hydrocarbons phases. Gas field and its halo, which is located in upper part, are two main components of the gas column. Authors established system of geological, geophysical, geochemical and isotopic marks to determine depth of the various zones and to estimate composition of their hydrocarbons. Noted statements of the abiogenic theory of hydrocarbon field genesis are discussed in this paper as well as creation of the gas column for the Inner tectonic zone of the Carpathian Foredeep. Authors established gas column within the Kokhanivka rim structure, which is located in the depression. Seismic and thermometry data and information on structure and gas distribution within sedimentary sequence are involved for this purpose. To determine the gas column of the Kokhanivka structure, depths of marks, limiting zones of formation and concentration of gas, main features of the sedimentary sequence, which contain characteristic of the halo, distribution of oil and gas within the halo, have been used. As a result of this investigation, the Kokhanivka rim structure is established, where possibly large gas field is located in sequence of the PreMesozoic rocks. Most possible the gas field is connected to upper part of the Jurassic rocks in centre of the structure, where fluid proof Sarmatian horizon is developed. Gas-bearing horizon can be related here to carbonate-terrigenous sediments of the Upper Jurassic, and to similar Silurian sediments at Poland. Thickness of the gas-bearing sequence is up to 500 m. Probably, within Kokhanivka structure we can meet not only main gas field, but a number of others also, joint to it, at the depths of 2000–3500 m.