Identification of Thermogenic and Microbial Gases in Polish Part of the Carpathian Petroleum Province Based on Isotopic Data

The natural gases associated and non -associated with oil the polish carpathian petroleum province were analyzed for molecular and stable isotope compositions as follows: 12,13C in CH4,C2H6,C3H8,CO2 , 1,2H in CH4,and 14,15N in N2 . The polish carpathian petroleum province contains the outer (flysch) carparthians composed of numerous complexes of generally calcareous sandstones and shales (mudstones and claystones ) , ranging in age from late cretaceous to oligocene / early miocene , the outer part of carpathian foredeep filled with the autochthonous moicene strata and their palaeozoic-mesozoic basement. the gaseous hydrocarbons both the outer carpathians and palaeozoic -mesozoic basement are generally genetically related to low -temperature thermogenic processes oil window and occasionally to high -temperature thermogenic processes gas window and also microbial processes. these gases were mainly generated from mixed type II/III kerogen. gases in the devenian and lower carboniferous reservoirs were generated only during thermogenic processes. a significant microbial component was found in methane from a few gas fields of the upper jurassic and upper cretaceous reservoir of the basement. therefore those traps had already been formed and sealed during the migration of microbial methane which was presumably generated in the middle jurassic marine environment. gas fields occurring in the miocene strata of the carpathian foredeep contain gas mainly methane >98% , which was generated within the badenian and asrmatian sequence by the microbial processes of carbon dioxide reduction.