Study On Characteristics Of Pore Parameters Of Longmaxi Formation Shale Reservoir In Changning Area

This article selects the shale reservoir of Longmaxi formation in Changning area as the research object.The tow aspects researches in this paper obtained through various experimental methods including outcrops survey,scanning electron microscopy(SEM),geochemical analyses,all-rock X-ray diffraction.Firstly,it systematically analyze the micropore parameters of the shale reservoir in Longmaxi formation in the study area,such as pore type,pore size,area porosity,shape factor and so on.Based on the study of the sedimentary environment of the Longmaxi formation in the study area,the characteristics of stratum distirbution,geochemical and mineral composition of the Longmaxi formation shale reservoir in the study area are researched clearly.It is found that the distribution of the Longmaxi formation in Changning area present a little change trend,the shale thickness is larger in north area than in south area.The high frequency of the high-quality source rock samples with the TOC content above 2.0% is high,which reflects the high organic carbon content of the Longmaxi Formation in Changning area,which is a good source rock and has good hydrocarbon generation conditions.The vitrinite reflectivity Ro shows that the shale reservoir in the study area has evolved into the mature stage,and the dry gas is mainly produced.The shale mineral composition of the Longmaxi formation in the study area is complex and the brittle mineral content Higher,which is conducive to the late shale gas fractures into the seam,improve shale gas production capacity.Various pore characterization methods was adopted to describe the morphology under SEM and the structure characteristics of the whole-aperture pores quantitatively.Combining ImageJ image analysis software,different types of pore characteristic parameters,including the number of pore development,size,form factor and other parameters,were statisticed quantitatively.Results showed that among the shale reservoir of Longmaxi formation in Changning area the inter-crystal(particle)pore was the most development,then followed by the inter-crystal crack,intra-crystal(particle)pore and organic pore.Calculate the probability distribution of different sample pore shape factor and analyze its influencing factors,the clay minerals content and degree of thermal evolution of organic matter which were the main control effect to the pore morphology.By analyzing the experiment of liquid nitrogen adsorption at low temperature and high pressure mercury injection in characterization of mocro-pore structure,a method for characterization of the whole-aperture pore structure were estabilished.According to the pore size distribution curve and the pore size distribution curve of the high pressure mercury intrusion method,the full pore size distribution curve was established to quantitatively characterize the pore structure characteristics of the rich organic mud shale reservoir in the whole scale.On the basis of summarizing the research of various experimental data,the analysis of diagenesis,the different mineral composition,organic matter content and evolution degree of the influence of pore structure characteristics in the study area,the article expounded the influence factors of the mud shale pore development in the study area were mainly the brittle minerals content,organic matter characteristics of organic matter content(TOC)which controlled the level of micropore and the mespore in the pore of the shale development,and the brittle minerals content which controlled the level of mesopore and the macropore in the pore of the shale development,and organic matter thermal maturity(Ro)controlled the pore formation and evolution of the organic matter.