THE OIL-GAS CHARACTERISTICS OF THE FORELAND BASIN IN THE SOUTHEASTERN MARGIN OF THE DABIE MOUNTAINS

The foreland basin in the southeastern margin of the Dabie mountains experienced an evolution of marine sedimentation-marine-continental sedimentation-continental sedimentation and characterized by superimposed-composited pattern.From the deposit sequence of the foreland basin and combined with characteristics of source rocks and oil-gas system,it can be seen that the continental deposit system of the foreland during early Mesozoic overlies the marine deposit of the passive continental margin during late Paleozoic,and formed upper continental facies and lower marine facies hydrocarbon-bearing rock systems and oil-gas forming systems.Among the conditions,the key for oil-gas accumulation is development and preservation of the marine source rocks underlying the foreland basin.It proves that,the marine source rocks are high quality in the deposit on the passive continental margin during late Paleozoic period,moderate or higher geothermal evolution,which can produce oil and gas;the good container rock is marine-continental molasses;the high quality cover rock is gypsum rock in the marine-continental-evaporation facies,the correlation of generation-reservoir-cover rock is good,and which proved the foreland basin possess the basic conditions for oil-gas occurrence.