Abstract: In order to solve the problem of low extraction flow rate and concentration caused by borehole deformation in the process of extraction, theFLAC^3D software was used to build a deformation model of coal body around the borehole based on creep law, and the creep displacements and plastic-zone shape change of coal body around conventional and preset screen pipe were compared and analyzed. The technology of sealing hole inner screen extraction was put forward to improve the borehole support force and ensure the borehole extraction section, and the industrial test was carried out. The results show that after the completion of the borehole, the hole wall is affected by the circumambient pressure, and the coal body presents the creep pressing characteristics towards the direction of borehole, that compared with conventional borehole, the shape variable of sieve tube drilling is obviously smaller, and that after adopting the sealing technology of preset screen pipe extraction, on the 65 day of extraction, the volume of extraction increases by 191% and concentration increases by 137% compared with the conventional sealing technology, and the extraction efficiency is significantly improved.

Key words: gas extraction, creep law, screen, boreholes, FLAC^3Dsimulation