With the analysis of the element geochemistry characteristics,the ancient lake information evolution history of the argillaceous source rocks in Lucaogou(芦草沟)Formation in Sangonghe(三工河)area is reconstructed.According to the ancient lake information and total organic matter(TOC)characteristics of argillaceous source rocks,the study section is divided into 6 Subsections.Subsection I mainly developed low-quality source rocks.This is because of the arid climate,high salinity,low lake productivity,unstable preservation conditions in this Subsection.Subsection II mainly developed high-quality source rocks.This is because of the humid climate,low salinity,high lake productivity,stable preservation conditions in this Subsection.Though the paleoclimate was humid and preservation conditions were stable.Lake productivity and the water salinity changed frequently.So Subsection III mainly developed medium-quality source rocks.Because of the humid climate,high lake productivity,medium sedimentary rate and stable preservation conditions,high-quality source rocks were developed in Subsection IV.The preservation conditions were stable,but other ancient lake information changed frequently.Therefore,the quality of the formed source rocks in Subsection V was different.Subsection VI mainly developed high-quality source rocks because of the humid climate,medium sedimentary rate,high lake productivity,low salinity and good preservation conditions.In summary,the ancient lake information parameters and TOC characteristics of each Subsection are different from each other.
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 inorganic 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/cm^3.The results of X-ray diffraction indicate the content of carbonate minerals is 28.0%.The HI(hydrogen index)-Tmax,HI-OI(oxygen index)and S_2-TOC(total organic carbon)diagrams indicate the kerogen types are I and II1.The high grade oil shale generally formed in the relatively 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 carbonate minerals is 16.4%,far less than high grade oil shale and the kerogen type is mainly II1.The inorganic parameters diagrams reflect the medium grade oil shale generally formed in the less humid paleoclimate,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 low grade oil shale generally formed in the relatively humid paleoclimate,deposited in the fres
Yu SongZhaojun LiuPingchang SunQingtao MengRong Liu
