| CPC E21B 43/295 (2013.01) | 5 Claims |
|
1. A gasification method of an underground gasifier, wherein the underground gasifier comprises an inlet gas shaft pipe channel in a direction from ground to a coal seam, a directional inbuilt horizontal pipe channel arranged horizontally in the coal seam, a return gas shaft pipe channel for gas discharge, and an ignition area, wherein both ends of the directional inbuilt horizontal pipe channel are in communication with the inlet gas shaft pipe channel and the return gas shaft pipe channel, and
the underground gasifier further comprises: an underground gasifier pre-control structure,
wherein the underground gasifier pre-control structure comprises: a flame retardant injection system, wherein the flame retardant injection system comprises a flame retardant injection shaft pipe channel drilled from ground to a coal seam and a flame retardant injection channel located in the coal seam, the flame retardant injection channel comprises a first flame retardant injection channel and a second flame retardant injection channel located at both sides of each gasifier and a third flame retardant injection channel located in a horizontal direction of an adjacent gasifier, the first flame retardant injection channel comprises a horizontal section arranged along a strike of the coal seam and a bypass section offset toward the gasifier; the second flame retardant injection channel has the same structure as the first flame retardant injection channel, and the horizontal section of the first flame retardant injection channel and a horizontal section of a second horizontal channel are arranged symmetric about the gasifier;
several flame retardant injection shaft pipe channels, bottoms of shaft pipe channels are in communication with the first flame retardant injection channel and the second flame retardant injection channel, are disposed;
by injecting a flame retardant solution into the corresponding first flame retardant injection channel, second flame retardant injection channel and third flame retardant injection channel through the flame retardant injection shaft pipe channel, a wet coal wall is formed in the coal seam to achieve pre-control on the gasifier; and
the inlet gas shaft pipe channel, the directional inbuilt horizontal pipe channel and the return gas shaft pipe channel form one U-shaped structure; several adjacent gasifiers have a same structure and the several adjacent gasifiers form one gasifier unit and several gasification areas,
the gasification method of the underground gasifier, sequentially comprising the following steps:
a. constructing a single underground gasifier:
firstly, drilling the inlet gas shaft pipe channel to five meters above a coal seam where the inlet gas shaft pipe channel is located and retreating a drill and reinforcing the inlet gas shaft pipe channel;
secondly, performing horizontal directional drilling operation for the coal seam, wherein a directional drilling length is an advance length to be gasified by the gasifier, and completing the directional inbuilt horizontal pipe channel after completing the drilling, and performing shaft drilling of the return gas shaft pipe channel while performing the horizontal directional drilling operation of the coal seam; and
finally, after the directional inbuilt horizontal pipe channel and the return gas shaft pipe channel are communicated, reinforcing the return gas shaft pipe channel so as to complete construction of a single underground gasifier;
b. constructing the flame retardant injection system:
firstly, drilling the flame retardant injection shaft pipe channel to five meters from above the coal seam and retreating the drill and supporting the flame retardant injection shaft pipe channel;
next, performing horizontal directional drilling along the coal seam, and when the length of the horizontal section of the first flame retardant injection channel is identical to a strike length of the gasifier, completing the drilling of the horizontal section of the first flame retardant injection channel; next, adjusting the drilling direction to enable the drilling direction to be offset toward the gasifier; when the offset reaches a radian, drilling a distance along a tangential direction of a circular arc section where the radian is located, so as to form a bypass section of the first flame retardant injection channel;
then drilling the second flame retardant injection pipe channel based on a method same as the method of constructing the first flame retardant injection pipe channel; and
finally, along a direction of a horizontal short section of the coal seam, drilling the third flame retardant injection pipe channel with a length being a sum of horizontal spacings of four adjacent gasifiers and supporting the third flame retardant injection pipe channel in time after completion;
wherein the specific method of drilling the flame retardant injection shaft pipe channel comprises: drilling toward the coal seam by using the drill, and when a horizontal distance from the left side of the directional inbuilt horizontal pipe channel is 22 meters and a distance from the bottom of the return gas shaft pipe channel is 10 meters, stopping drilling,
wherein the circular arc section is ¼ length of a circle with a radius less than 22 meters and drilling of 25 meters is performed along a tangential direction of the circular arc section, and
wherein when the third flame retardant injection pipe channel is constructed, a horizontal directional borehole of the coal seam is enabled to have the same dip angle as the coal seam and is 1.0 to 1.5 meters from a roof of the coal seam where the gasifier is located;
c. completing construction of one unit grid of gasifiers and next completing construction of other unit grids of gasifiers based on steps a and b;
d. blending an aqueous agent: adding a flame retardant of a given concentration by using a ground flame retardant injection system;
e. coal wetting by injecting the flame retardant: by using the ground flame retardant injection system, injecting the flame retardant into the flame retardant injection shaft pipe channels sequentially and allowing the flame retardant to enter the first flame retardant injection pipe channel, the second flame retardant injection pipe channel, and the third flame retardant injection pipe channel and penetrate into adjacent coal seams, so as to form wetted coal pillars, thus preventing spread upon gasification,
for a thin or medium thick coal seam, a constant pressure flame retardant injection of 5 MPa is selected,
for a thick or ultra-thick hard coal seam, an intermittent high and low pressure alternating flame retardant injection mode is selected to perform intermittent high and low pressure alternating flame retardant injection with a low water pressure of 3 MPa and a high water pressure of 9 MPa, such flame retardant injection mode forms an impact, such that a coal mass expands and shrinks in volume continuously, leading to strength fatigue of the coal mass, in this way, a degree of fracture of the coal mass is increased and a connectivity of a fissures of the coal mass is increased, thus directly forming a plurality of new small fissures in the coal seam and greatly improving the efficiency of the flame retardant injection, and
after the flame retardant injection is completed, for the third flame retardant injection channel, sectional borehole packing operation is performed; and
f. ignition for gasification.
|