大别山东南缘前陆盆地含油气特征

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

大别山东南缘前陆盆地经历了由海相—海陆过渡相—陆相的演化历程,具有复合叠合盆地特征。从盆地层序上看,早中生代陆相前陆沉积体系下伏晚古生代海相被动陆缘沉积体系;从烃源岩系和含油气系统特征上看,具有陆相和海相两大套烃源岩系和成油气体系。其中,前陆盆地下伏海相被动陆缘烃源岩的优劣和保存条件是能否形成油气藏的关键。研究证明,晚古生代海相被动陆缘沉积发育优质烃源层系,热演化中等偏高,油气兼生;海相和陆相碎屑岩具有良好储集条件;海相和陆相蒸发相含膏岩系为优质盖层,生储盖配置关系良好,具有形成油气赋存的基本石油地质条件。

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 cor-relation of generation-reservoir-cover rock is good,and which proved the foreland basin possess the basic conditions for oil-gas occurrence.