Horizontally butted well hydraulic scour migration pressure relief outburst elimination gas extraction method

The invention discloses a horizontally butted well hydraulic scour migration pressure relief outburst elimination gas extraction method. Firstly, a plumb shaft (8) is drilled, the cased hole completion is performed above a coal seam roof, and the barefoot completion is performed below the coal seam roof; an inclined section (4) of a horizontally butted well (3) is drilled, and the casing cementing is performed; then, a horizontal section (5) channel is drilled by a conventional method, and is in butt joint with the plumb shaft (8), and the barefoot completion is performed; a screen pipe (15) and a continuous play pipe (13) are put down onto the horizontal section (5), the screen pipe (15) has a screen hole (14), and a piston seal (12) is additionally mounted at the top end of the continuous play pipe (13); high-flow high-head clear water is continuously injected into the plumb shaft (8) to scour coal powder through the screen hole (14) to form coal powder slurry, and a plug head is moved to repeatedly operate; the coal powder slurry is discharged to the ground through a horizontal well mouth annulus part (3); and a gas, coal and water separation device (7) is used for separating, coal and gas are collected and stored, and water is circulated for downhole jetting and scouring. The horizontally butted well hydraulic scour migration pressure relief outburst elimination gas extraction method provides a new solution for low-permeation soft coal seam ground pressure relief outburst elimination gas extraction.