The Huadian Basin is an oil shale-bearing basin located in northeastern China. Thirteen oil shale layers deposited in this basin, and the characteristics of oil shale are different among these oil shale layers. Based on the core observation and microscope identification, using the organic and inor- ganic data from borehole HD3 and outcrops, the formation conditions of different grade oil shale have been evaluated. Based on measuring oil yield （OY in short） of an oil shale to determine its grade, this paper classifies the oil shale as high grade （OY〉10%）, medium grade （10%〉OY〉5%） and low grade （5%〉OY〉3.5%）. The high grade oil shale is mainly in brown or dark brown, and the bulk density ranges from 1.59 to 1.81 g/cm3. The results of X-ray diffraction indicate the content of carbonate min- erals is 28.0%. The HI （hydrogen index）-Tmax, HI-OI （oxygen index） and S2-TOC （total organic carbon） diagrams indicate the kerogen types are I and II1. The high grade oil shale generally formed in the rela- tively arid paleoclimate, deposited in the brackish water, dysoxic environment, when the bioprodctivity is extremely high, and the information is mainly from the inorganic parameters diagrams of chemical index of alteration （CIA）, Sr/Ba and V/（V＋Ni）. The medium grade oil shale mainly shows grey-black or black-brown color and the bulk density ranges from 1.87 to 2.08 g/cm^3. The average content of carbon- ate minerals is 16.4%, far less than high grade oil shale and the kerogen type is mainly IIm. The inor- ganic parameters diagrams reflect the medium grade oil shale generally formed in the less humid pa- leoclimate, deposited in the brackish water, dysoxic to anoxic environment, when the bioproductivity is medium. The color of low grade oil shale is major in grey-black or dark grey and the bulk density ranges from 2.00 to 2.15 g/cm^3. The average content of carbonate minerals is sharply decreased and the kerogen type is mainly II1. The inorganic parameters diagrams indicate the lo
Yu SongZhaojun LiuPingchang SunQingtao MengRong Liu
