Mineralogy Of Clay In The Shale And Its Impacct On Porosity Of Shale Reservoir

This paper,taking shanxi qinshui basin drilling mud shale ZK07 Wu Xiang area-1 as the research object,the integrated use of shale samples thin section observation,X-ray diffraction analysis,scanning electron microscope(SEM),high-pressure mercury injection test and experiment means,in particularly on the clay mineralogy characteristics and shale reservoir pore structure characteristics correlation research.The mineralogical characteristics of clay minerals in shale samples;the pore characteristics of shale samples were analyzed,and the relationship between the characteristics of clay minerals and shale pore characteristics was analyzed.The main achievements and understanding are as follows.Under the optical microscope,white or brown clay minerals aggregations are found,including kaolinite of blast box shape and some floc aggregations which are unable to identified.Quartz are common in the sample,while pyrite and mica are occasionally oberseved.XRD testing results indicate that clay minerals content of samples in well zk07-1 is 50%~70%,and clay minerals presenting are illite-montmorillonite mixed layer,kaolinite and illite,mainly.Using the Jade software to analyze the X-ray diffraction pattern,the average crystallinity of kaolinite is 32.22%~46.34%,and the average value is 36.34.The pore structure is complex.Intergranular pore,intergranular pore,intragranular dissolved pore,biological pore and organic pore are developed.At the same time,the shale reservoir has extensive development of tectonic fractures,structural shear fractures,interlayer foliation and diagenetic contraction joints.High pressure mercury injection experiment data analysis indicate that radius of shale samples range from micro-pore to macro-pore,wihle micro-pore is well developed,pore connectivity is well.The pore specific surface area and total pore volume of shale reservoir are positively correlated with the content of clay minerals.The content of clay minerals between pore volume depends on pore diameter,for micro-pore,it presents negative,while for mediumand macro-pore,is positivel.There is a positive correlation between the surface area and total pore volume and the content of illite and illite-montmorillonite mixed layer,which is negatively correlated with the content of kaolinite and chlorite.The average particle size of the clay minerals and the crystallinity of kaolinite were weakly correlated with the surface area and total pore volume.