doi:10.16186/j.cnki.1673-9787.2022100014

Received:2022/10/06

Revised:2023/04/07

Published:2024/01/25

Optimization of over-emission drilling arrangement for low-permeability coal seams

CHENG Lei1,2, WANG Xin1,2, SHI Haorong1,2, LI Zhengjian1,2

1.College of Safety Science and Engineering，Henan Polytechnic University，Jiaozuo  454000，Henan，China;2.Henan Collaborative Innovation Center of Coal Work Safety and Clean-Efficiency Utilization，Jiaozuo  454000，Henan，China

Abstract: Objective  In order to effectively solve the problem of gas protrusion in low permeability coalseam，the blind area of gas discharge brought by array hole arrangement method and the problems of increasing the number of boreholes and duplicate discharge caused by diagonal circle tangential hole arrangement method are effectively eliminated. Methods  Through theoretical analysis，the array rhombus method is proposed to optimize the arrangement of over-emission holes under the condition that the effective radius of over-emission holes is certain （R is the effective emission radius，and the spacing of coal seam heading emission holes is R），and the number of holes is about 3/4 of that of diagonal circular tangent method，and the duplicated emission area is reduced to 11%，which reduces the duplicated emission area of diagonal circular tangent method and the number of holes. Results The results show that the overall gas pressure within the effective discharge radius of the borehole is less than 0.5 MPa after 20 d of discharge by the array diamond method and less than 0.3 MPa，after 100 d of discharge by the array diamond method，which is better than the diagonal circular tangent method in terms of pressure relief.Cross comparison of the gas pressure distribution around the borehole at 100 d of discharge by array method and diagonal circle tangent method with the gas pressure distribution around the borehole at 20 d of discharge by array rhombus method shows that the pressure relief rate of array rhombus method is faster and the pressure relief range is wider. Conclusion Put forward the array rhombus method design drilling holes，and use the COMSOL Multiphysics for three drilling pressure discharge numerical simulation operation，by comparing found the array diamond drilling way compared with array and diagonal circular method more advantages，and in the same time pressure discharge rate faster，wider range，for low permeability coal seam prevention gas outburst is of great significance.

Key words:low permeability;gas emission;over-emission drilling;optimization of arrangement method;array diamond arrangement method