Experimental Study On The Influence Of Pore Structure On Seepage Characteristics In Tight Sandstone Reservoir

Coal-bed methane has become one of the important sources of my country's future supplementary natural gas consumption.However,the migration and blockage of pulverized coal will damage the fractures of the reservoir and the supporting cracks will be blocked by pulverized coal,which reduces the economic benefit of a single well.Therefore,it is of great significance to study the impact of pulverized coal migration and blockage during the development of coalbed methane.Although the predecessors have done a lot of research,there are still few studies on the blockage of pulverized coal during the simultaneous migration of gas,liquid,and solid(pulverized coal).This paper firstly used scanning electron microscope,X-diffraction,microscopy and other technical means to understand the coal rock,pulverized coal and pore structure of the study area;then through the micro model simulation experiment,API diversion experiment,gas-water phase permeability experiment,etc.The characteristics and influencing factors of the migration and blockage of pulverized coal,microbubbles and water during the simultaneous flow of pulverized coal,microbubbles and water are studied from the micro and macro perspectives,and the following main understandings are obtained:1.Structural soft coal in the study area is divided into tight,uniform and large cracks.The three types of coals are closely related to the generation,migration and blockage of pulverized coal.The higher the quartz content,the smaller the particle size of coal powder.2.Discontinuous gas-microbubbles are divided into three types.The first type is small bubbles with gas saturation below 5% and the diameter distribution is between 0.01-0.2mm;the second type is polymerized bubbles,which contain gas.The saturation is higher than 5%,and the diameter is between 0.2-0.8mm;the third type is the plunger bubble,the gas saturation is 10%-15%,and the diameter is between 0.8-1.5mm.3.The coupling effects of microbubbles on pulverized coal include the trapping effect of small bubbles and aggregated bubbles on pulverized coal,the promotion of plunger bubbles on the deposition of pulverized coal,and the lateral migration of small bubbles to form aggregate bubbles.The three coupling effects have an intuitive effect on the migration and blockage of pulverized coal in the supporting cracks.4.The comprehensive clogging modes of microbubbles and coal powder are divided into plunger clogging,coupling clogging,and deposition clogging.The three clogging modes will be transformed and transferred due to differences in flow rate,gas saturation,and silt ratio.5.The silt ratio in the study area is 22%.Controlling the bottom hole velocity of1.74cm/min in the early stage of drainage can minimize the disturbance of the pulverized coal in the supporting fractures.The maximum conductivity can be achieved by controlling the bottom hole flow rate to 3.18cm/min in the middle of the drainage and production period and the main gas production period.6.Due to the difference in size and shape between natural cracks and supporting cracks,the influence of microbubbles on the permeability,the influence of microbubbles on the migration and blockage of pulverized coal in the cracks,the production mechanism of pulverized coal,and the critical gas content Saturation is different in four aspects.These understandings provide a basis for further understanding of the mechanism of pulverized coal blockage and migration in the study area.