姬塬地区侏罗系延9油层低阻成因分析及识别方法

鄂尔多斯盆地中生界侏罗系局部发育低阻油藏,但由于其成因机理尚不明确,传统的方法难以识别。根据砂岩薄片鉴定、扫描电镜和高压压汞分析等技术手段,结合钻井、录井、测井、试油试采等资料,分析总结姬塬地区侏罗系延9低阻油层的成因。结果表明,地层水矿化度高是最主要的成因;岩石颗粒细导致束缚水饱和度高、构造幅度低致使油水关系复杂是次要成因;储层的弱亲水性和填隙物也有一定程度的影响。在成因分析的基础上,总结形成邻近储层电性对比法、电阻率-含油饱和度交会图版法和综合含油指数法3种针对低阻油层的识别方法,提高了低阻油层识别的精度。

Genetic mechanism and identification methods of low resistivity oil reservoirs in Yan 9 member in Jiyuan area in Jurassic

The low resistivity reservoirs were discovered in the Mesozoic Jurassic,Ordos basin.However,they are often missed or misjudged using traditional identification methods because of uncertainties in their genesis.Studying on the genetic mechanism of low resistivity reservoir in Yan 9 member of Yan'an formation in Jiyuan area,based on a series of measurements and analysis such as thin section observation,scanning electron microscope observation and mercury injection tests etc,combining with data from drilling,well logging and actual oilfield production practice.The result shows that the high formation water salinity is the main factor of the formation of Yan 9 low resistivity oil pays,and the secondary factors are high bound water saturation caused by the fine-grained rock,the complex oil-water relationship due to low structural amplitude.Furthermore,weak hydrophilicity and interstitial material also influence the low resistivity.Based on the analysis of causing factors,three methods of identifying low resistivity reservoirs were proposed contrast method of identifying reservoirs adjacent to low resistivity oil reservoirs,intersection chart method of resistivity and oil saturation and comprehensive oil index method.They all improve the recognition accuracy of the low resistivity reservoir in the study area.