Shale Gas And Sedimentary Environment Geological Characteristics Of Lower Permain Series Of Kalagang Formation In Jimunai Basin,the North Of Xinjiang Province

This thesis takes shales of lower Permain series of Kalagang formation in Jimunai Basin,the north of Xinjiang Province,for study and selects typical sections and exploratory trenches to survey and sample.And with the method of geochemistry,microscopic flakes,X-ray diffraction whole rock analysis,organic carbon,pyrolysis,chloroform asphalt,kerogen carbon isotope ratio hydrocarbon source rock analysis,scanning electron microscopy?S.E.M.?,nitrogen isothermal adsorption reservoir analysis tests,etc.Also combining with previous geological data,the characteristics of rock type,sedimentary facies,hydrocarbon source rock and reservoir,shale gas and sedimentary environment geological etc.,are studied and conclusions are achieved following outcomes below:1.According to the types of rock,sedimentary structures,the assemblage of sedimentary,etc.The facies of Kalagang formation can be determined into braided river-delta facies and lacustrine facies.Dark shales are distinctly controlled by sedimentary facies,and distributed in front delta facies and predelta facies.Lithology is mainly carbon silty mudstone,argillaceous siltite and siltstone.2.With the geochemistry analysis,dark shales in Jimunai basin deposits in both oceanic and continental island arc,and the sediments comes from both dacite and femic volcanic rocks,also the ancient sediments can be found.And the study of major,trace and rare earth elements?REE?shows that dark shales deposits in a freshwater and reductive environment,and the curve of the paleosalinity changed from high to low to high from the bottom to the top of the middle-upper lower Kalagang formation.Also the paleo-weather was warm and humid.The dark shales of lower Kalagang formation is mainly constituted by carbonaceous shales.3.Through the analysis of characteristics of hydrocarbon source rock,it shows that the organic richness is middle level with TOC ranging from 0.30%to 4.32%and the average being 1.01%.Also through the method of kerogen transmitted light microscopy for organic maceral statistics,it shows the index of kerogen type?T.I.?is-99.5,belonging to type III?humic type?.At the same time,the analysis of carbon isotope(?¹³C)in karogen shows the same conclusion.With the analysis the kerogen of vitrinite reflectance?%Ro?indicats that it ranges from 1.43%to 2.87%and the average is 2.12%,belonging to high mature to over mature degree.4.Analysis of reservoir,with X-ray diffraction whole rock analysis indicates that the content of brittleness minerals is high,mainly being quartz,feldspar,etc.,caly minerals on the secondary,and the brittleness index?B.I.?averages on 66.63%.The enrichment of illite do contribute to the capacity of absorptivity in dark shales.Using the S.E.M.shows that reservoir space is mainly constituted by intragranular and intergranular dissolved pore,micro-pore and micro-cracks intra-and inter-minerals.And Nitrogen isothermal adsorption method shows that micro-reservoir space is mainly constituted by grooved mesopore and foramina.The porosity ranging from0.97%to 1.52%and average being 1.36%,also with permeability ranging from0.0097md to 0.0197md and average being 0.0139md.5.It synthetically indicates that there is great exploration potential of shale gas in Jimunai Basin...