Study On Technology Of Increasing Flow And Promoting Pumping Of Water Jet Cavitation In Parallel Drilling Along Layer

As an effective coal pressure relief and reflection improvement technology,water jet cavitation has the advantages of safety and efficiency.Water jet technique of hole making mainly by high pressure water jet in the coal seam bedding made or wear layers of the soil hole hole hole impact of mass media,and cause soil hole built around the stress drop and produce a large number of cracks,the crack continuous development and expansion,promote the gas desorption,improve the effect of the gas extraction.In terms of regional anti-reflection layer of water jet punching hole rate is low,hole collapse,poor drainage discharge any reason such as bedding water jet piercing application is less,the layer of water jet punching technology used widely,but the cost is high,the layer of water jet punching hole utilization rate is low,therefore,this paper adopts along coal seam water jet drilling"-made den"anti-reflection technology integration,In order to solve the serious problems such as hole punching and hole collapse by water jet,combined with the problems such as low permeability of coal seam,poor drainage effect and fast gas attenuation of Baiyangling Coal Mine of Xiyang Coal Mine of China Coal,the technology of gas increasing flow and promoting drainage by water jet cavitation is carried out in coal seam along the coal seam.By means of theoretical analysis,numerical simulation and field test,this paper firstly introduces the research status of gas extraction technology in China and high-pressure water jet pressure relief and reflection improvement technology at home and abroad,and then analyzes the mechanism of water jet cavitation technology on coal seam pressure relief and reflection improvement.The multi-field coupling mathematical theoretical model of water jet cavitation hole coal body was proposed,and a THREE-DIMENSIONAL geometric model was established.The finite element numerical simulation software COMSOL Multiphysics was used to simulate the plastic damage radius of cavitation hole,the effective gas extraction radius,and the spacing of cavitation hole group under different cavitation radius.Finally,Through the water jet"borehole-cavitation"integrated anti-reflective gas drainage test along the 15108 track of Baiyangling Coal Mine,the single hole drainage effect of water jet cavitation engineering was investigated in the field,and the pressure relief and anti-reflective effect of water jet cavitation holes with different spacing of holes were investigated as well as the gas drainage effect.The main conclusions are as follows:The area around the cavitation hole is divided into plastic residual zone,plastic softening zone and elastic zone from inside to outside.The plastic damage radius increases with the increase of the cavitation radius.The maximum permeability of the plastic zone is about 300 times that of the elastic zone.The effective drainage radius around the cavitation hole increases gradually with the increase of the cavitation hole,and the fitting function between the cavitation hole and the effective drainage radius satisfies the logarithmic function.According to the characteristics of gas pressure distribution and plastic damage range around cavitation hole at 150d,the optimal cavitation radius was determined to be 0.4m,and the effective extraction radius was determined to be 3.4m,which were verified in the field.Based on the optimal cavitation radius,the optimal hole spacing of the cavitation group was finally determined to be 7m under the influence of non-cavitation holes and cavitation holes.Hole hole hole sealing followed by smoking,hundred meters to build the gas flow as the build of the soil hole hole radius increases,among them,the soil hole made hole radius of 0.6 m when the initial gas flow almost made the hole radius of 0.2 m 2 times of initial gas flow rate of the soil hole,the gas flow rate,the greater the effects of gas flow,the more obvious,and with the increase of extraction time decay gradually,By analyzing the dynamic changes of the gas flow,it can be seen that the gas flow attenuation is slow,and the overall gas flow value is relatively high.The flow increasing effect of the cavitation hole is significant,so that the gas pressure around the cavitation hole drops sharply.Single row after implementing along coal seam water jet made holes in different cloth made soil hole hole spacing gas extraction concentrations are higher than the soil hole is not made,the gas extraction concentration increased 3.36 times,the largest gas extraction effect is improved obviously,but overall attenuation trends,holes in the left and right sides of the soil hole of the gas extraction effect is much better than in the middle of the soil hole.In the construction scheme of cavitation holes with different hole spacing,it basically shows high gas purity and fast decay in the initial stage,and then gradually stabilizes after 15 days.After the stabilization,the maximum gas purity can reach0.073m~3/min.When the hole spacing is 7m,the maximum gas purity can be extracted,and the total amount of gas extraction from cavitation holes is 1.41 times higher than that of cavitation holes with 5m hole spacing.The effect of gas extraction is greatly improved.Made the gas extraction flow attenuation coefficient of the soil hole are much smaller than not soil hole,after the water jet hole build gas flow attenuation coefficient reduced3.27 times,in addition,combined with hundreds of meters drilling data extraction flow,also can be seen that made the extraction of the soil hole increases with the flow rate value is significantly higher than not soil hole,and at the end of the month when the gas flow rate still is bigger,as the continued extension of extraction time,The gas drainage effect is still good,which indicates that the water-jet cavitation technology along coal seam can effectively improve the permeability of coal seam,and the flow increase effect is significant.There are 55 figures,13 tables and 76 references.