RU2472941C1 - Coal bed hydraulic fracturing method - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: method involves drilling of through holes in coal massif from outpost workings parallel to working face; cutting of initiating slots on walls of the above holes, their sealing and formation of coal hydraulic fracturing cracks by supplying the fluid to them. Besides, cutting of the next initiating slot is performed simultaneously with sealing of the previous initiating slot and by formation in it of coal hydraulic fracturing crack. Cutting of initiating slots in each subsequent hole is performed with a shift of cutting pitch relative to initiating slots of each preceding hole.

EFFECT: enlarging the area of uncovering of fractured coal massif.

3 dwg

Description

The technical solution relates to mining and can be used for the degassing of coal seams.

There is a known method of degassing a coal mass, including conducting degassing wells from a conveyor drift to the area where a ventilation drift is carried out so that the wells intersect the perimeter of future production. To increase the degassing efficiency of the coal massif, wells are drilled and connected to the degassing network well in advance 80–90 m ahead of the bottom of the mine (experience with the use of degassing of developed formations to reduce the gas mobility of the mine workings at the V.I. Lenin mine, Bulletin of the Scientific Center for Work Safety in the coal industry, No. 1, 2009, Kemerovo, p. 18-28).

The disadvantage of this method is that through the walls of the wells gas is released from a very small zone of the coal seam in the vicinity of the well. Therefore, the efficiency of gas recovery by coal seams in this way is insufficient to ensure the safe conduct of work in these conditions.

The closest in technical essence and a combination of essential features is a method of softening of hard coals according to the patent of the Russian Federation No. 2394991, Е21С 41/18, Е21В 43/26, publ. 07/20/2010, including drilling holes in a weakened massif, cutting initiation slots on the walls of these holes, sealing them and forming hydraulic fractures in coal by injecting liquid into them. At the same time, the bore holes are drilled through the worked out sub-floor, and the cutting of the subsequent initiating gap is carried out simultaneously with the sealing of the previous initiating gap and the formation of a coal fracture in it.

The disadvantage of this method is that the distance between adjacent initiating slots is determined by the dimensions of the slot former and the sealant, and the coal mass in this section of the well remains in an undestroyed state. Therefore, the gas recovery of the coal mass in this place will be carried out only through the walls of the well, which reduces the effectiveness of subsequent degassing of the formation when using the method for this purpose.

The technical task of the proposed solution is to increase the efficiency of subsequent degassing of coal seams by increasing the area of exposure of the fractured coal mass by reducing the distance between hydraulic fractures of neighboring wells.

The problem is achieved in that in a method of hydraulic fracturing of coal seams, including drilling through holes in a coal mass from contouring workings parallel to the face, cutting initiating slits on the walls of said wells, sealing them and forming fractures of coal by injecting liquid into them, and cutting the subsequent initiating cracks are carried out simultaneously with sealing the previous initiating cracks and the formation of coal hydraulic fractures in it, according to the technical solution arezanie initiating slits in each subsequent well produce step cutting with a shift with respect to each previous initiating crevices wells.

The specified set of features allows you to significantly increase the exposure area of the fractured coal mass due to the increase in the number of fractures in the coal mass per unit length of neighboring wells and thereby increase its gas recovery, which increases the efficiency of degassing of coal seams.

It is advisable to choose this shift equal to half the distance between the initiating slots, which will ensure uniform distribution of hydraulic fractures in the coal mass along neighboring wells and put them in equal conditions for the gas recovery process, which improves the efficiency of degassing of coal seams.

The essence of the technical solution is illustrated by an example implementation of a method for developing coal seams and drawings 1-3, where

figure 1 shows a flow chart of the preparation, development and fracturing of a coal seam in plan;

figure 2 is a section aa in figure 1;

figure 3 is a section bB in figure 2.

The method is implemented as follows.

Drilling machine 1 (Fig. 1) drills through holes 2 in the coal mine 3 in parallel to the mine face 4 (Figs. 2 and 3) from contouring workings, for example, from a conveyor drift 5 to a ventilation drift 6. Then, from the conveyor drift 5, installation is carried out in borehole 2 of the equipment, including the drilling rig 7, a slotting machine 8 with a sealing device 9. Through a flexible pipe 10, the sealing device 9 is connected to a pumping station 11 located in the ventilation drift 6. Then from the side of the conveyor drift 5 They cut the initiating slots 12 while maintaining the cutting step L (Fig. 1), which is equal to the sum of the lengths of the sealing device 9 and the slot former 8. This makes it possible to seal and break each previous initiating slit 12 when cutting each subsequent initiating slit 12, which allows combining operations cutting initiating slots 12 and their hydraulic fracturing. To rupture the cut initiating slots 12 from the pumping station 11 through the flexible pipe 10, the working fluid is supplied under pressure to the sealing device 9 - the area of the well in which the initiating slot 12 is located is pressurized. working fluid in the initiating gap 12 and produce hydraulic fracturing and the formation of cracks 13 hydraulic fracturing.

After the completion of the hydraulic fracturing of the coal mass 3 along the entire length of the first well 2, they proceed to similar work in the subsequent subsequent well 2 adjacent to it, while the initiation slots 12 are cut in the same way and with the same cutting step L. However, the cutting of the initiation slots 12 in the subsequent well 2 is carried out with a shift of the cutting step relative to the initiating slots 12 of the previous well 2 by an amount equal to half the distance between the initiating slots 12. Thus, the distance between the fractures 13 of the hydraulic fracturing of the coal mass of neighboring wells is halved and becomes equal to L / 2 (figure 1), therefore, the area of exposure of the coal mass will be twice as large, which increases the efficiency of subsequent degassing of the coal seam.

Subsequent wells 2 are treated in the same sequence.

Claims (2)

1. The method of hydraulic fracturing of coal seams, including drilling through holes in a coal mass from contouring workings parallel to the face, cutting initiating slots on the walls of these wells, sealing them and forming coal fractures by injecting liquid into them, and cutting the subsequent initiating gap is carried out simultaneously with sealing previous initiating slit and the formation of coal fracture in it, characterized in that the cutting of the initiating slots in each subsequent the well is produced with a shift of the cutting step relative to the initiating slots of each previous well. 2. The method of hydraulic fracturing of coal seams according to claim 1, characterized in that said shift is chosen equal to half the distance between the initiating slots.

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