Pujiagou area is located in the south of Xiasiwan oilfield. Less work was executed in the analysis of oil reservoir distribution and reservoir characteristic in Yanchang formation Chang 7, we need to do the geological basis study further in depth. Hydrocarbon accumula-tion factors in Chang 7 reservoirs in Yanchang formation were researched based on the anal-ysis results of previous scholars, according to the three elements including sedimentary fa-cies, hydrocarbon source rocks and oil-gas migration. Besides, reservoir characteristics were analysed by using the data about physical propeties, scanning electron microscope(SEM) pictures and high-pressure mercury injection of cores. And comparing with water saturation calculated by log data with moisture content counted by practical production data in Chang 7 reservoirs. It is shown that the reservoir lithology in Chang 7 is mainly feldspar sandstone, the reservoirs are of the characteristics such as tiny pore throat radius, high displacement pressure, and more complex pore structure. Furthermore, because the phenomenon that pore-throat space generally is filled by the clay minerals is existed, oil bearing evaluation of reservoirs is influenced due to lots of clay minerals. And water saturation counted by Archie model can't represent the true oilness in reservoirs.There is an advice about the proper con-ducting volume model which is based on the complicated pore structure should be selected or be established to precisely calculate oil saturation for the Chang 7 reservoirs, it can pro-vide the solid foundation for the effective exploration and development in Chang 7 reservoirs in Pujiagou and even entire reservoirs in Yanchang formation.%下寺湾油田蒲家沟区块位于甘泉县南部,其延长组长7段油藏分布及储层特征研究还较少,地质基础研究还有待进一步深入.本文基于以往学者研究分析结果,从沉积相、烃源岩及油气运移条件三方面综合分析延长组长7储层的成藏因素.此外,基于蒲家沟组长7储层岩心物性分析结果、扫描电镜图片及岩心压汞实验数据分析储层特征.并对比分析气藏测井解释含水饱和度与实际生产含水率.结果表明:蒲家沟长7段储层岩性以长石砂岩为主,孔隙中普遍存在被黏土矿石充填的现象,导致储层孔喉半径细小,排驱压力高,孔隙结构更加复杂化.同时由于黏土的大量存在,会间接影响储层含油性评价,导致常用的阿尔奇公式计算含水饱和度误差较大,难以准确反映储层含油性.建议在该地区进一步选取或建立考虑储层孔隙结构的导电体积模型,从而更为精准地确定储层含水饱和度,为后期蒲家沟长7油藏乃至整个延长组油藏的有效勘探开发提供坚实的基础.
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