塔中北斜坡奥陶系鹰山组碳酸盐岩高阻层分布特征及其意义

塔里木盆地奥陶系油藏储集层具有很强的非均质性,其油气水分布规律复杂。综合钻井、录井、测井等资料对鹰山组高阻层段岩性、厚度进行了统计分析,并在此基础上根据单井柱状图建立了各井区及内外带的连井剖面图,总结了其分布特征规律。结果表明,鹰山组高阻层岩性主要为泥晶灰岩,且在成像测井图像上呈亮黄色成层性特征,空间上具有"横向分布不稳定,纵向叠置"的分布特征。通过实验手段对高阻层段岩石矿物铸体薄片进行鉴定,初步认为高阻层的成因机制主要包括机械-化学充填作用和大气降水选择性溶蚀作用。高阻层厚度与其下伏原油的物性、油气日产量及气油比显示出较好的相关性,即随着高阻层厚度增大,其下伏油气的日产量及气油比逐渐增大,而油气的密度及粘度却逐渐减小。高阻层对下伏油气的分布具有一定的控制作用。由此推断,鹰山组高阻层可以作为一套或多套隐蔽"盖层",与下伏储层可能形成良好的"储-盖"组合配置关系。

Distribution and significance of high-resistivity carbonates of Ordovician Yingshan Formation of northern slope of Tazhong area,Tarim Basin

The Ordovician oil reservoirs in Tarim Basin are highly heterogeneous with a complex distribution pattern of fluids.Drilling data,mud logging and well logging data were integrated to analyze the lithology and thickness of high-resistivity layers in the Yingshan Formation.Well tie profiles of each wellblock and inner-outer zones based on single well histograms were generated and the distribution patterns of these high-resistivity carbonates were mapped.The lithology of high resistivity layers in the Yingshan Formation is mainly micritic limestone.They occur as layered bright yellow on imaging logs and show spatial distribution featuring in "lateral unstableness and vertical superimposition".Examination of rock mineral cast thin sections of high resistivity layers indicates that the high resistivity layers were formed mainly by mechanical-chemical filling and selective dissolution by atmospheric water.In addition,the thickness of high resistivity layer correlate well with properties of oil in the underlying reservoir,daily oil/gas production and gas/oil ratio.With increasing thickness of high resistivity layer,daily oil/gas production and gas/oil ratio increase,while density and viscosity of oil decrease,suggesting that high resistivity layers could have a certain control on underlying oil and gas distribution.The high resistivity layers in the Yingshan Formation could act as a set or multiple sets of subtle local seals for the underlying reservoir.