黔西南下石炭统旧司组页岩气富集条件及其控制因素OA

To clarify the enrichment characteristics and controlling factors of the Lower Carboniferous Jiusi Formation shale gas in southwestern Guizhou,the geological characteristics of the Lower Carboniferous Jiusi Formation shale gas enrichment of the investigation wells in different sedimentary facies belts were systematically analyzed by means of the experimental methods including field emission scanning electron microscopy(FESEM),overburden pressure porosity and permeability test,X-ray diffraction(XRD),organic geo-chemistry analysis,on-site desorption,and high-pressure isothermal adsorption,and the controlling factors of the Lower Carboniferous Ji-usi Formation shale gas enrichment such as total organic carbon(TOC)content,organic matter maturity,mineral composition,lithofa-cies,porosity-permeability characteristics,and burial depth are discussed.The results show that:the muddy shale of the Jiusi Forma-tion in southwestern Guizhou has a large sedimentary thickness(50～150 m),moderate organic matter abundance(with an average of 1.68%),mainly type Ⅱ1 andⅡ2 organic matter,and is in the high-maturity to early over-maturity stage,providing a good material ba-sis for shale gas enrichment.The main rock-forming minerals of the Jiusi Formation shale are quartz and clay minerals,with high brittle-ness index(average51.75%).The shale reservoir is controlled by sedimentary facies,and the lithofacies are dominated by clay-bear-ing siliceous shale and silica-bearing argillaceous shale,among which the clay-bearing siliceous shale facies is favorable lithofacies.TOC content is positively correlated with gas content,the specific surface area and gas content are positively correlated with the mass fraction of quartz but negatively correlated with the mass fraction of carbonate mineral.It is held that organic matter abundance,rock mineral composition,and burial depth are the main controlling factors of the shale gas enrichment in the Jiusi Formation of southwestern Guizhou,and the favorable lithofacies and high brittleness index provide favorable conditions for shale gas storage and reservoir reconstruction.