南华北盆地鹿邑凹陷太原组泥岩微观孔隙特征及影响因素OA

The Taiyuan Formation in Luyi Sag is a key area for marine-continental transitional shale gas exploration in Southern North China Basin.Taking the mudstone of the Taiyuan Formation in well LY1 as the research subject,this study employs experimental methods such as organic geochemistry,X-ray diffraction,scanning electron microscopy,CO2 adsorption,N2 adsorption,and high-pressure mercury intrusion to investigate the microscopic pore characteristics and influencing factors of the mudstone in Taiyuan Formation.The results indicate that the pore types of the mudstone in Taiyuan Formation pri-marily classified as interlayer fractures of clay minerals,shrinkage fractures,residual intergranular pores,intergranular dissolution pores,and organic pores.The pore size distribution is dominated by mesopores,followed by micropores,with macropores being the least developed.Micropores with pore sizes of 0.40-0.80 nm and mesopores with pore sizes of 2.00-6.00 and 10.00-40.00 nm contribute the most to pore volume.Pore morphology is divided into three types:type Ⅰ is mainly composed of ink bot-tle shaped pores and wedge-shaped pores with one or both ends open,showing poor pore development;types Ⅱ and Ⅲ are dominated by tubular pores with both ends open and parallel plate-shaped pores with four open sides,exhibiting better pore development,type Ⅲ has a higher degree of mesopore develop-ment.Pore development in mudstone is controlled by multiple factors.Organic matter is a crucial factor influencing micropore development,with a positive correlation between them;quartz is beneficial for the preservation of macropores and mesopores,pyrite promotes macropore development due to intergranular pores and shrinkage fractures;kaolinite and illite are beneficial for the preservation of micropores and macropores due to their unique crystal structures.The alkaline environment during the formation of car-bonate minerals and illite/montmorillonite mixed layers,as well as their filling of macropores,are unfa-vorable for the preservation of micropores and macropores,but favorable for the preservation of meso-pores.Compaction and cementation are the primary factors causing significant pore size reduction,while organic matter thermal maturation,dissolution,and fracturing have constructive effects on pore devel-opment.These findings provide a basis for the detailed evaluation and research of shale gas reservoirs in the Luyi Sag.