Research On The Effective Extraction Radius Of Gas Extraction Drilling Based On Hydraulic Punching Technology In Xinzhuang Coal Mine

The No.32 Coal Seam,the main coal seam of Xinzhuang Coal Mine,is an outburst coal seam.According to the production layout of 39011 working face,the regional outburst prevention measures of cross seam drilling and directional drilling for pre drainage of coal seam gas need to be taken on site.In order to improve the extraction effect of cross layer drilling,hydraulic punching and permeability enhancement measures are adopted on site.According to Article 67 of the "Detailed Rules for the Prevention and Control of Coal and Gas Outburst",the effective extraction radius of the drilling hole needs to be measured before construction drilling.This article comprehensively determines the effective extraction radius of the drilling hole through numerical simulation and on-site testing.The research results are as follows:Based on the seepage field equation and stress field equation,the gas-solid coupling model is constructed,and the gas-solid coupling model is introduced into COMSOL simulation software to simulate the effective extraction radius of the cross bed drilling before and after the hydraulic perforation and the directional drilling along the bed,so as to obtain the effective extraction radius and determine the reasonable drilling spacing.The results show that the gas content in the extraction area increases from 6.72 m when the drilling time is 180 days and the spacing between boreholes is 8meters before the use of hydraulic punching and permeability enhancement measures3/ T dropped to 4.13 m 3/ Below t,it is possible to achieve pumping compliance.After using hydraulic punching and permeability enhancement measures,the gas content in the extraction area increases from 6.72 m when the interval between boreholes is 14 m and the extraction time is 120 days 3/ T dropped to 4.32 m 3/ Below t,it is possible to achieve pumping compliance.The interval between directional boreholes along the bed is 18 m.When the drainage time is 120 days,the gas content in the drainage area is6.72 m 3/ T descends to 4.33 m 3/ Below t,it is possible to achieve pumping compliance.Based on the pressure drop method,the effective extraction radius before and after penetration drilling for enhanced permeability was tested.The results showed that when the extraction time before enhanced permeability was 180 days,the effective extraction radius was 4 meters,and the gas pressure decreased from 0.49 MPa to 0.24 MPa,achieving the extraction standard.When using hydraulic punching measures based on coal unloading capacity of 0.5t/m,and the extraction time is 120 days,the effective extraction radius is 7m,and the gas pressure drops from 0.5MPa to 0.24 MPa,which can achieve the extraction standard.Based on the flow method,the effective extraction radius of the bedding directional drilling is tested.The results show that the effective extraction radius is 5.7m when the extraction time is 120 days,and 6.6m when the extraction time is 180 days.The results obtained by numerical simulation and on-site testing are relatively consistent,indicating the reliability of the numerical simulation results.When the diameter of the drilling hole is larger,the effective extraction radius of the drilling hole is larger,but the hole formation rate of the large diameter drilling hole is low.When arranging the pre extraction drilling hole in practice,the diameter of the perforation hole is 94 mm,and the diameter of the directional hole is 113 mm.The impact of negative pressure on the effective extraction radius is relatively small,but maintaining a stable negative pressure can timely remove gas from the hole.Therefore,the negative pressure for drilling and extraction is 13 k Pa.When other factors remain unchanged,the effective extraction radius of the drilling hole will gradually increase with the increase of extraction time in the early stage of extraction.However,when the extraction time reaches a certain amount,the growth rate of the effective extraction radius will decrease.Therefore,based on the actual on-site situation,the extraction time is 120 days.This thesis has 45 figures,13 tables,and 84 references.