Genesis and Identification of Low Resistivity of Oil Layers in Badaowan Formation on Southern Slope of Zhongguai Bulge,Junggar Basin
Compared to other low-resistivity oil layers,the low-resistivity oil layers in the Lower Jurassic Badaowan formation on the south-ern 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,sedi-mentation,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 test-ing 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.
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