中拐凸起南斜坡八道湾组油层低阻成因及识别

Genesis and Identification of Low Resistivity of Oil Layers in Badaowan Formation on Southern Slope of Zhongguai Bulge,Junggar Basin

准噶尔盆地中拐凸起南斜坡下侏罗统八道湾组低阻油层与一般低阻油层对比,储集层具有形成时期早、埋藏深度大、岩石粒度较大、泥质含量低等特点,低阻成因具有较强特殊性。在对国内外典型低阻油层成因机理综合研究的基础上,利用该区钻井、录井、测井、试井、岩心化验分析等资料,从构造、沉积、成岩作用、储集层特征、成藏条件等多角度,开展八道湾组油藏低阻主控因素研究。该区油藏低阻的形成受宏观因素和微观因素共同控制,低构造幅度、弱水动力沉积等宏观背景下,低油水分异程度、高地层水矿化度及低凝灰岩岩屑含量,是油藏低阻的主控因素;束缚水饱和度偏低,是油藏低阻的次要控制因素。在此基础上,建立地层电阻率与油气指示系数关系图版,与该区试油和试采资料对比,符合率92.9%,为中拐凸起南斜坡八道湾组低阻油层的识别提供了依据。

Compared to other low⁃resistivity oil layers,the low⁃resistivity oil layers in the Lower Jurassic Badaowan formation on the southern slope of the Zhongguai bulge in the Junggar basin are characterized by early hydrocarbon accumulation,deep burial,large grain size,and low mud content,showing a unique low⁃resistivity genesis.Based on a comprehensive analysis on the genetic mechanisms of typical low⁃resistivity oil layers globally,together with the data of drilling,logging,well testing,and core analysis in the study area,the main control⁃ling factors of the low⁃resistivity oil layers in the Badaowan formation were investigated from various perspectives including tectonics,sedimentation,diagenesis,reservoir characteristics,and hydrocarbon accumulation conditions.It is found that low resistivity of the oil layers in the study area is jointly controlled by macroscopic and microscopic factors.In a macroscopic setting with low tectonic amplitude and weak hydrodynamic sedimentation,low oil⁃water differentiation degree,high formation water salinity,and low tuff debris content are the main controlling factors for low resistivity,while low saturation of bound water is a secondary controlling factor.Accordingly,a chart illustrating the relationship between formation resistivity and oil/gas indicator coefficient was established,which matches the formation/production testing data in the study area by 92.9%.The study results provide a basis for identifying low⁃resistivity oil layers in the Badaowan formation on the southern slope of the Zhongguai bulge.