鄂尔多斯盆地中生界石油运移特征分析

ANALYSIS ON THE MIGRATION CHARACTERISTICS OF THE MESOZOIC PETROLEUM IN THE ORDOS BASIN

鄂尔多斯盆地中生界构造简单平缓,储层主要为低孔、低渗,油气运移独具特色。侏罗系和延长组上部储集层孔隙度、渗透率条件较好,油气运移聚集驱动力以浮力为主,三叠系顶部不整合面和侏罗系古河道砂体共同构成了侏罗系油藏的油气主要运移通道,其油气主要分布在侏罗系古河道内及不整合面附近。延长组中下部储集层在石油大量生成时期,储集层已非常致密,地层基本丧失水交替能力,异常压力为石油二次运移的主要动力,石油沿渗透性砂体主要向东北和西南两大方向运聚成藏,多分布在生烃中心及周边地区。

The Mesozoic structures in the Ordos Basin are simple and smooth, with reservoirs mainly of low porosity and low permeability and distinctive hydrocarbon migration. The conditions of porosity and permeability are better in the Jurassic and the upper reservoirs of the Yanchang Formation, and the driving forces of hydrocarbon migration and accumulation are dominated by buoyancy. The surfaces of unconfor-mity on the top of the Triassic and the paleochannel sandbodies of the Jurassic constituted the major migration pathways of hydrocarbon in the Jurassic oil pools, and the oil reservoirs were distributed mainly in the Jurassic paleochannels and the places near the surfaces of unconformity. During the period of a large amount of petroleum creation, the middle and lower reservoirs of the Yanchang Formation were very dense, and the formations basically losed water alternating ability. Abnormal high pressure then exceeded static buoyancy and became the main dynamic of secondary petroleum migration. Permeable sandstone was the main petroleum migration pathway to northeast and southwest, and oil reservoirs were distributed chiefly in hydrocarbon-generating centers and regions around them.