鄂尔多斯盆地姬塬地区延长组长2低阻油层成因机理

根据大量铸体薄片、扫描电镜、物性分析、压汞曲线、含油饱和度及矿化度等资料,对鄂尔多斯盆地姬塬地区延长组长2低阻油层的形成机理进行了详细研究。长2油层组低阻油层形成的主要原因有3个方面,即:高束缚水饱和度、低含油饱和度及高矿化度地层水。孔隙结构复杂、高岭石晶间微孔发育及细粒岩石骨架,造成喉道偏细、孔喉半径小,形成高束缚水饱和度;低幅度构造背景、低油柱高度及低油气充注程度,是造成油层低含油饱和度、油水分异差的主因;高矿化度的地层水,降低了油层与水层的电阻率对比度。根据研究区长2地化热解参数统计,结合试油资料及测井孔隙度数据,建立了热解参数轻质油含量与孔隙度的关系图版,以此判断油层、油水同层、水层和干层。 

Forming mechanism of Chang 2 low resistivity oil layer, Yanchang Formation, Jiyuan region, Ordos Basin

Based on data of casting sheet images, SEM, physical property, mercury injection curves, oil saturation and formation water salinity, forming mechanism of Chang 2 low resistivity oil layer of Yanchang Formation in Jiyuan region of the Ordos Basin has been analyzed. There are mainly 3 reasons for the formation of the low resistivity oil layer, including high irreducible water saturation, low oil saturation and high formation water salinity. Complex porosity structure, development of micro-pores among kaolinite crystal and fine grained rock framework form thin throat and small pore throat radius, which cause high irreducible water saturation. Low oil saturation is mainly caused by low amplitude tectonic setting and low oil column height. High formation water salinity reduces resistivity contrast between oil layer and water layer. According to statistics of geochemical pyrolysis parameters of Change 2 oil layer, combined with data of oil testing and well logging porosity, the cross plot of S1 and Φ has been built, by which the Chang 2 low resistivity oil layer of Yanchang Formation in Jiyuan region can be recognized.