Correlation Between Microscopic Pore Fractal Characteristics And Permeability Of Sandstone

In this thesis,four typical mines in the North China coal field(Malan Mine,Tunlan Mine,Gequan Mine,Gaohe Mine)are taken as research targets.Based on the analysis of the existing data,the main coal seam roof sandstone in each coal mine is explored.Permeability is the purpose of the study.The collected cores were subjected to indoor permeability measurement,polarized light microscope observation and scanning electron microscopy..The average porosity of Gequan Mine,Gaohe Mine,Malan Mine and Tunlan Mine was 4.06%,1.44%,5.93% and 3.43%,respectively;the permeability was 0.0137 mD,0.0346 mD and 0.0066 mD,respectively.0.0250 mD;observed by polarized light microscopy,sandstone samples are mainly composed of quartz,calcite and feldspar,and contain a small amount of gravel.The components are highly cemented,dense and less porous.The micro-parameter extraction selection object is a sandstone scanning electron microscope image,and the target parameters are extracted as perimeter,permeability,radius,number of pores,etc.The application tool software is Image Pro Plus,Photoshop and Matlab.Two unequal hair bundle tube models are established based on Darcy's theorem,Poiseuilli's formula and fractal theory.The island method calculates the permeability by establishing the relationship between area and perimeter.The box counting method is to calculate the permeability by the total number of capillaries and the equivalent radius.The fractal dimension calculated by the island method is in the range of 1.2-1.6,the calculated permeability is less than 0.1md and greater than the measured value,and the theoretical value has a close correlation with the actual value.Although the box counting method cannot accurately quantify the permeability,it can assist the island method in qualitative analysis on the permeability classification.The two methods have low requirements on rock specimens,easy operation and easy promotion,and can provide quantitative and qualitative assistance for coal mine water prevention and control work.