Underground gasification ignition method

Abstract

An underground gasification ignition method comprises the following steps: making a directional drilling and a vertical well to construct an underground gasification furnace; using a cold fracturing method to pre-penetrate a coal seam; and igniting in the vertical well at an end of the directional drilling.

1 . A method of underground gasification ignition, comprising the following steps:
 (1) creating a directional drilling and vertical well(s) to construct an underground gasification furnace;   (2) pre-penetrating the coal seam in the manner of cold fracturing; and   (3) igniting in the vertical well at the end of the directional drilling.   
     
     
         2 . The method according to  claim 1 , further comprising step (4) following step (3), wherein after an ignition source is formed, a gas inlet hole and a gas outlet hole are switched and a gasification channel is processed with firepower. 
     
     
         3 . The method according to  claim 2 , wherein the gas inlet hole and the gas outlet hole are switched to the status that gas is discharged through the ignition vertical well. 
     
     
         4 . The method according to  claim 2 , wherein the ignition source is considered to be formed when coal-burning volume is ≧0.5 cubic meter. 
     
     
         5 . The method according to  claim 1 , wherein the number of the vertical well is 1; and wherein in step (3) ignition is made in the vertical well at the end of the directional drilling and gas is discharged through the directional drilling. 
     
     
         6 . The method according to  claim 1 , wherein the number of the vertical wells is at least 2; and wherein in step (3), ignition is made in one of the vertical wells at the end of the directional drilling, gas is discharged through at least one of the other vertical wells and pressure maintenance is made in the directional drilling at the same time. 
     
     
         7 . The method according to  claim 6 , wherein the pressure maintenance is maintaining pressure within 0.3-1.0 MPa. 
     
     
         8 . The method according to  claim 1 , wherein the coal is brown coal and the vertical distance between the vertical well and the directional drilling channel is 2-10 meters. 
     
     
         9 . The method according to  claim 1 , wherein the coal is bituminous coal and the vertical distance between the vertical well and the directional drilling channel is 1-5 meters. 
     
     
         10 . The method according to  claim 1 , wherein oxygen-containing gas is used as a gasification agent for ignition and its oxygen concentration is ≧21%.