The Organic Geochemical Characteristics Research Of The Lower Cambrian Niutitang Black Shale In Northwestern Hunan

Northwestern Hunan is an important region of the shale gas exploration in the south block.The lower Cambrian Niutitang Formation is a series of thick black shale,which is continuous developed and widely distributed.By means of the field reconnaissance and typical profile measurement to the lower Cambrian Niutitang black shale in northwestern Hunan,A total of 14 samples of black shale were collected.The samples are tested in six times,such as TOC,chloroform "A",Ro and GC-MS.Using sedimentology and geochemistry methods,finish the discussion of Niutitang black shale type of organic matter,organic matter abundance,organic matter maturity and kerogen parent material source and sedimentary environment through the data analysis.The under section of Niutitang Formation is mainly black shale with a large amount of phosphite and pyrite,graded bedding,sedimentary structure,overall for deep-sea basin facies sedimentary environment.The under section of Niutitang Formation is a thin layer of siliceous rock with a very thin layer of carbon,which is a thin layer of carbon,and the deposit environment is a shallow sea shelf to the deep sea shelf.To analyzing the basic evaluation parameters of Niutitang black shale,The conclusion is that black shale has high abundance of organic matter,total organic carbon content(TOC)was high and the change range is very large,distributed between 0.23% ~ 0.23%,the average is 4.12%,high organic carbon content is concentrated in Yong shun and Hua yuan,Kerogen type is given priority to ? type,equivalent vitrinite reflectance is 1.81% ~ 3.38%,the average is 2.90%,the degree of evolution is at a high maturity stage.The biomarker characteristics of black shale were analyzed in detail.According to the sample of GC-MS analysis,14 black shale samples were detected abundant n-alkane and isoamyl alkadiene,tricyclic hopane and sterane compounds.The normal alkanes distribution curve is shown as a bimodal,OEP < 1.2,black carbon advantage,the sample is mature;Pr/Ph < 1,to restore the environment.Gave birth to the compounds show that the characteristics of black shale organic matter is mainly derived from Marine aquatic algae,organic matter deposited in strong reducing environment and high salinity salt water environment,and the biodegradation.