Możliwości powstawania węglowodorów w utworach mezozoicznych Niżu Polskiego

Abstract

ON POSSIBILITIES OF GENERATION OF HYDROCARBONS IN MESOZOIC ROCKS IN THE POLISH LOWLANDS Summary The analysis of development of Mesozoic strata and their basement in the Polish Lowlands showed that sources of hydrocarbons which form oil and gas deposits in this region should be looked for mainly in Jurassic strata. Such strata yielding sufficiently high amounts of organic matter are known to occur in central, most depressed part of the basin: e.g. marine intercalations in the Lias, mudstone-clay rocks in the Dogger, and limestone-marly- clay rocks in the Malm. A special attention was paid to the degree of catagenetic alteration of organic matter and the time when the strata have entered individual stages of possible generation of oil and gas. These problems were analysed taking into account results of studies on kerogen and vitrinite reflectivity as well as calculations of temperature-time index of alteration of organic matter, made with the use of the N. Łopatkin's method. Complex analysis of the obtained data suggests that Jurassic parent rocks occurring in central part of the basin have been subjected to thermodynamic conditions corresponding to initial stages of the major phase of oil generation as early as the Early Cretaceous. The possibility of simultaneous onset of migration of hydrocarbons makes it necessary to focus attention on old traps, i.e. those formed before the Laramie movements. Such traps are situated at outer slopes of basins surrounding the Kujawy-Gielniów swell.