Petroleum accumulation rules in hysterogenetic reconstructive-syngenetic rift basins, North Jiangsu Basin

There are different points of view about the type of North Jiangsu Basin, which affects the understanding of petroleum accumulation. According to the ideas and indicators of an eogenetic morphologic basin, hysterogenetic reconstructive basin and syngenetic rift basin, the North Jiangsu Basin was a hysterogenetic reconstructive-syngenetic rift basin which developed from a great depression during the Taizhou and Funing periods, and changed to a syngenetic rift basin of dustpan shape after strong deformation. Subsequently, the syngenetic rift basin and fading depression superimposed during the Dainan-Sanduo and Yancheng-Dongtai periods, respectively, finally forming a syngenetic-hysterogenetic rift basin. Based on geochemical theory and experimental data, and taking into consideration the fact that no success has been made in the exploration for immature oils in the past 30 years, we believe that hydrocarbon in the study area mainly developed from kerogen during the late stage, and hydrocarbon maturity and the kitchen distribution varied among areas. An early immature and low-maturity hydrocarbon generation zone, double-peak mode hydrocarbon generation, immature and low-maturity oils do not exist. Source rocks in the basin have a low abundance of organic matter. Effective mature source rocks which can provide enough hydrocarbon and multiple roles of faults are the key controls for hydrocarbon accumulation. Oil and gas migrated mainly in a lateral direction, and re-servoirs distributed of fan shape along half-graben hydrocarbon kitchens in the hysterogenetic reconstructive basin. Petroleum migrated mainly in the vertical direction, structural pools lay above hydrocarbon kitchens like bead strings, and structural-lithologic oil pools superimposed and distributed on the rim of syngenetic rift basin. Petroleum accumulations are discontinuous throughout the whole basin.