Study On The Effect Of Solid Particle Proppant On Fracture Support And Diversion In Coal Seam

After taking hydraulic fracturing,blasting and other enhanced permeability enhancement measures in high-gas and low-permeability coal seams.Under the action of in-situ stress,the fissure will be compressed or even closed to a certain extent.This greatly affects the effect of gas extraction.The above problems can be solved by the support and diversion effect of proppant.In this paper,theoretical analysis and numerical simulation are used to study the supporting and diversion mechanism of solid particles on coal seam fissures.The main research contents and results are as follows:Models of coal bodies with different strengths including fractures are constructed.Using RFPA software to simulate and study the effect of in-situ stress on the mechanical behavior and permeability characteristics of coal fissure closure with different strengths.Under the same ground stress,coal fractures with different strengths produce closing behavior and are accompanied by increased stress in fractured coal.The stress increases rapidly at the mouth of the fracture and slowly at the tip.After the fracture is closed,the permeability coefficient drops sharply from 500 m·d^-1to 0.1 m·d^-1.The greater the coal strength,the longer the time for the fracture closure behavior;As the in-situ stress increases,the time elapsed for the fissure closing behavior is shorter.The stress concentration of the coal body near the right side of the crack tip is more obvious.The more obvious the decrease in permeability coefficient.Compared with hard coal,soft coal has larger fracture coal body stress,and the coal body stress concentration coefficient near the crack tip is larger,which is not conducive to the diversion of coal body gas.Models of coal bodies with different strengths supported by solid particles are constructed.The effects of solid particles on the mechanical behavior and permeability characteristics of coal fracture supports with different strengths were simulated by using RFPA software.At the same time,due to the support of solid particles,the stress distribution in the fracture area and the solid coal is uniform,and there is no stress concentration phenomenon.Under the action of solid-particle conductivity,the permeability coefficient of coal bodies with different strengths is increased by nearly a thousand times,and its conductivity is greatly improved.Models of fracture conductivity under different influencing factors is constructed.The effects of different solid particle types,particle sizes and solid particle breakage on fracture conductivity were simulated by Meyer software.Under the condition of the same particle size,after the fracture is closed,the 40-70 mesh quartz sand supports the fracture with wider fracture width,longer fracture and higher fracture height.And 40～70 mesh ceramsite supports better flow conductivity of cracks.Under the same type of conditions,the larger the solid particle size is,the larger the fracture height and width of the support after the fracture is closed,and the better the flow conductivity.The smaller the breakage rate of the solid particles,the better the fracture conductivity of the supported fractures.The study on the mechanism of solid particles on the support and diversion of coal seam fractures has positive significance for evaluating the effectiveness of gas anti-penetration effect and improving and maintaining the enhanced anti-penetration effect.The paper has 54 Figures,13 tables,79 references.