Lithofacies characteristics and logging identification method of marine-continental transitional shale
Compared with marine shale,marine and continental transitional shale has more complex lithology and stronger heterogeneity.Conventional three-terminal lithofacies classification method based on mineral components and conventional logging data cannot accurately reflect the changes of lithology and heterogeneity.Taking the shale of 3rd sub-member,2nd member of Permian Shanxi Formation(P1s32)of Daning-Jixian area in the eastern margin of Ordos Basin as the research object,based on X-ray diffraction,core thin sections and organic carbon to realize the favorable shale lithofacies division with"sedimentary environment indication+organic carbon+mineral composition"as the core.Through the mutual calibration of core and logging data,the logging response characteristics of different shale lithofacies are summarized.On the basis of selecting sensitive logging parameters,Bayes discriminant method is used to establish logging identification methods for different shale lithofacies.Among the findings:①There are 3 major categories,7 subcategories and 11 subdivided shale types in the target layer,among which organic-rich siliceous shale and organic-rich mixed shale are the best shale types with good indexes of organic matter,physical property,gas content and brittleness,followed by organic-rich clay shale and organic-medium clay shale,and the parameters of anaerobic shale in the same type of shale are relatively better.②By selecting six sensitive logging curves including density neutron envelope area,acoustic resistivity envelope area,gamma deuranium gamma difference,deep and shallow resistivity ratio,brittleness index and thorium content,Bayes discriminative equation is established,which can accurately and effectively identify different shale facies types in P1s23 of the study area.The research results provide favorable technical support for the fine evaluation of subsequent parameters and fracturing formation selection of Marine and continental transitional shale reservoirs.
万方数据
维普
