The lithology of thin interbed in G3 and G4 tight oil layers of the Qingshankou formation in the Qijia area of Songliao Basin has a significant effect on the oil-bearing property.In order to calculate the thickness ratio of oil-bearing lithology to the formation accurately(net-to-gross ratio),the thickness,lithology and oil-bearing characteristics of thin interbed are firstly analyzed,and then the SRES curve was used to calculate the net-to-gross ratio(NTG) in different window lengths with 10 Ω · m.m as the oil-bearing limitation.At the same time,based on the resistivity anisotropy model of thin interbed,the NTG was estimated by using the conventional lateral and induction resistivity.In order to analyze remaining oil properties of formations,a cross-plot between sand ratio and resistivity was established.The imaging logging can identify the thin layer more effectively.The thin layer has seven types of lithology with different resistivities and mineral contents.The lower limit of the bearing-oil lithology is muddy siltstone,and the NTG calculated based on the imaging and conventional logging curves can reflect the lithology of the formation effectively.The cross-plot shows that when the sandstone ratio is less than 0.5 and the resistivity is less than 10 Ω · m.m,the formation does not contain oil.When the sand ratio is greater than 0.5 and the resistivity is greater than 10 Ω · m.m,the formation contains oil.Especially when the resistivity is greater than 22 Ω · m.m,the formation contains more oil.The sand ratio can contribute to the identification of effective reservoir and the selection of fracturing interval.%松辽盆地齐家地区青山口组(K2 qn2+3)高台子油层高三、高四油层组致密油薄互层岩性对含油性有明显的控制作用.为准确计算致密油含油有利岩性占地层的比例(砂地比),分析了致密油薄层厚度、岩性和含油性特征;以10 Ω·m作为致密油含油电阻率下限,利用成像测井SRES曲线计算地层不同窗长内的砂地比;基于薄互层电阻率各向异性模型,利用常规侧向、感应电阻率计算地层的砂地比;区分地层含油性,建立砂地比与电阻率的交会图.致密油薄层发育7类岩性,不同岩性的电阻率和岩性扫描矿物含量不同;致密油含油岩性下限为泥质粉砂岩;基于成像和常规测井曲线计算的砂地比均能有效反映地层的岩性发育情况;当砂地比小于0.5、电阻率小于10 Ω·m时地层不含油;当砂地比大于0.5、电阻率大于10 Ω·m时地层具有一定的含油性;当地层电阻率大于22 Ω·m时地层的含油性更好.地层砂地比的计算可为储层识别和压裂层段优选提供一定的借鉴和参考.
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