The Yanchang Formation in the Ordos Basin is a typical low permeability reservoir, and a critical problem of the hydrocarbon accumulation research in this area is the petroleum migration and accumulation mechanism in the low permeability reservoir. This paper studies the characteristics of the petroleum migration and accumulation in the Yanchang Formation by means of nitrogen compounds analysis of crude oil, organic inclusion analysis, fluorescent thin slice analysis of oil-bearing sandstone, in combination with physical properties of crude oil, the correlation between oil-bearing characters and physical property changes of sandstones, and so on. Late Jurassic - Early Cretaceous is the main accumulation period of petroleum in the Yanchang Formation. The hydrocarbon generation is a continuous process and there are not multiple periods of accumulation. The petroleum of the Yanchang Formation is of episodic and rapid migration under overpressure; cracks and microcracks are the main passage of oil migration, and the distance of petroleum lateral migration is short;buoyancy of oil is minor compared to the capillary resistance, so the oil can not produce secondary migration. At present, petroleum accumulation remains being injected into reservoirs under abnormal pressure, and repeated high-pressure charges make reservoirs located in the passage of cracks connecting oil sources be infilled again and again, so that valid accumulations of petroleum are generated.%鄂尔多斯盆地延长组为典型的低渗透储集层,石油在低渗透储集层中运移,聚集机理是该地区成藏研究的关键.利用原油含氮化合物分析、有机包裹体分析、含油砂岩荧光薄片分析等方法,结合原油物性特征、砂岩含油性与物性变化的关系等探讨了镇北地区延长组石油运移、聚集特征.研究认为:侏罗纪末期-早白垩世是延长组石油主要成藏期,烃源岩生烃是一个连续的过程,不具备多个成藏期;延长组石油在超压动力下幕式快速运移,沟通油源的裂缝、微裂缝是石油运移的主要通道,在侧向上运移距离短;相对于运移阻力,石油所受到的浮力很小,无法进行二次运移,现今的石油聚集仍保持其在异常高压作用下注入储集层时的状态;高压充注过程反复进行,处于沟通油源的裂缝通道上的储集层可以得到反复充注,从而形成石油有效聚集.
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