南鄱阳坳陷油气成藏条件分析

最近几年的区域油气勘探与新资料评价表明：南鄱阳坳陷具有“上张下逆”双层结构的叠合盆地构造背景,晚期伸展沉积的陆相白垩系区域盖层造就了二叠系、三叠系海相-海陆过渡相烃源岩在喜马拉雅期的二次生烃和晚期成藏条件;地处前白垩纪“南北对冲”前缘带的旧夏、二甲村凹陷,二叠系保存状况和白垩系盖层构筑的整体封闭保存条件较好,二叠系龙潭组树皮煤是该区已知的特征性优质煤成油烃源岩;“自生自储型”的龙潭组油气藏是该区其最有勘探前景的油气成藏类型,次为“下生上储型”的白垩系周家店组底部油气藏;而地处“凹中隆”的龙皮构造带则具有浅层油气勘探的现实性,可作为南鄱阳坳陷近期勘探的突破口。

ANALYSIS OF HYDROCARBON RESERVOIRING CONDITIONS IN SOUTH BOYANG DEPRESSION

Based on new regional exploration and evaluation data acquired in recent years, the tectonic setting of South Boyang depression belongs to a superimposed basin with a two-layer structure with "upper extensional faults and lower reverse faults". The nonmarine Cretaceous regional cap rock deposited during late extension stage created favorable conditions for secondary hydrocarbon generation and late reservoiring for Permian and Triassic source rocks of marine-transitional facies during Ximalaya Period. In Jiuxia and Erjiacun sags located on the Pre-Cretaceous "north-south ramp" frontal zone, the preservation of Permian and the sealing capability of Cretaceous cap rocks are relatively good and Permian Longtan Formation bark coal is the known characteristic high quality source rock of coal-derived oil. Longtan Formation reservoir, with source rock and reservoir rock in the same layer, has the largest exploration potential in the study area, followed by reservoirs at the bottom of Cretaceous Zhoujiadian Formation, with source rock below reservoir rock. While the Longpi structural zone located on the "uplift within the sag" has exploration potentials for shallow oil and gas, thus it can be taken as the breakthrough point for exploration in South Boyang depression in the near future.