Characteristics Of Shale Pore Structure And Its Influencing Factors Of Qiongzhusi Formation Shale In Jingyan-Qianwei

The discovery of the industrial natural gasflow in the Lower Cambrian Qiongzhusi Formation shale in Jingyan—Qianwei located Sichuan Basin shows a good exploration and development prospect.However,the geological research of the Qiongzhusi Formation shale reservoir is in the primary stage.Geological and geochemical conditions,the reservoir characteristics are still unclear.Therefore,it is important to study the geology,geochemtry,pore structure and its influencing factors of Qiongzhusi Formation shale in this area,and to further evaluate shale reservoir capacity and shale gas resource potential in the area.According to the collected samples of shale core,sufficient geochemical,reservoir characteristic analysis and gas-bearing analysis tests have been completed so far,including XRD,clay composition,TOC,high pressure mercury injection,nitrogen adsorption,carbon dioxide adsorption test and scanning electron microscopy experiment.The results show that the shale of Qiongzhusi Formation is mainly composed of mudstone and siltstone,and the total organic carbon content of shale is 0.17%~2.36%,the maturity is 2.77%~3.13%.We can discover various types of cracks under different scales and various pores under scanning electron microscopy.The paper has made three research achievements,(1)The rock facies of Qiongzhusi Formation were divided by the combination of core description and mineral composition analysis.It was clear that black clay shale and grayish clay shale are the most favorable facies of the study area.(2)Based on the accurate characterization of the surface area and pore volume of shales at different scales,the surface area of the shale of Qiongzhusi Formation controlled by organic matter,Yimeng mixed mineral and illite was pointed out.Quartz and clay minerals,carbonate minerals affect the pore volume of shale,and the surface area prediction model based on shale organic matter and mineral composition analysis was established.(3)Through the comparison of the parameters of organic matter,rock facies,specific surface area and pore volume of different layers in Qiongzhusi Formation,two high quality layers are selected.