CN105114116A - Method for strengthening regional gas extraction through hydro-thermal coupling fracturing - Google Patents

Abstract

The invention discloses a gas drainage method in a water-heat coupled fracturing strengthening area. Firstly, the main fracturing holes, branch fracturing holes and guide holes are sequentially constructed on the side of the coal seam, and the main fracturing holes are arranged in the center of an equilateral triangle. position, the opening positions of the branch fracturing holes are respectively arranged at the three vertices of the equilateral triangle, the positions of the final holes meet at the center line of the equilateral triangle, the leading holes are located at the center of the main fracturing hole, On a circle with a radius of 5-15m; the fracturing equipment includes water injection equipment and a powder injector composed of intelligent water tanks and fracturing pumps. The quicklime powder in the powder injector is injected into the main fracturing hole and the branch fracturing hole through the downhole wind pressure; the main fracturing hole is hydraulically fractured through the water injection equipment, and the quicklime powder enters the fracture under the pressure of high-pressure water. The thermal reaction between powder and water generates a large amount of heat, realizing hydrothermal coupling fracturing; through the implementation of hydrothermal coupling fracturing to strengthen the regional gas drainage method, the area affected by fracturing increases, and the concentration of gas drainage increases. The effect is remarkable, which meets the The needs of coal mine field area gas control and other work.

Description

A Method for Strengthening Regional Gas Drainage with Hydrothermal Coupled Fracturing

technical field

The invention relates to a hydrothermal coupling fracturing enhanced regional gas drainage method, which belongs to the technical field of regional gas control in underground coal mines, and is especially suitable for hydrothermal coupling fracturing operations for regional gas control in deep high gas outburst coal seams.

Background technique

The Chinese Academy of Engineering's "National Energy Development Strategy 2030-2050" report proposes that the annual output of coal will be controlled at 3 billion tons in 2050, and coal will be the dominant energy source in my country for a long time. However, the geological conditions of my country's coal mines are complex, high-gas coal seams account for 50%-70%, and high-gas low-permeability coal seams account for about 70% of them. The occurrence characteristics of high gassy and low permeability coal seams in my country are microporosity, low permeability and high adsorption, which often lead to a large amount of gas gushing out during the mining process, especially with the efficient intensification of coal production and the increase in mining depth. The amount of gas gushing out is increasing, and the threat of gas explosion and gas outburst is becoming more and more serious. Therefore, regional gas control operations are often required in the mining process of coal mines. Hydraulic fracturing technology is one of the main measures to increase oil production, and its application in underground coal mines has also achieved certain results.

However, the existing coal seam hydraulic fracturing technology has problems such as unstable technical effect, insufficient pressure relief, and low extraction efficiency. The main reason is that the fracture expansion of traditional hydraulic fracturing technology is not sufficient, and the regional fracture network has not been realized. Moreover, the existence of water after the implementation of traditional hydraulic fracturing technology blocks the channel of gas flow, which inhibits gas desorption, diffusion and penetration, and hydraulic fracturing technology is gradually limited. Therefore, in order to solve the defects of the existing hydraulic fracturing technology, a new type of fracturing technology method is urgently needed to meet the needs of gas prevention and control in the coal mine field area. Combining and absorbing the advantages of existing hydraulic fracturing, drawing on the idea of promoting gas desorption by increasing temperature, increasing the amount of gas desorption after fracturing, reducing the plugging effect of water after fracturing, and using reasonable drilling layout to generate regional fracture networks and form water Thermal coupling fracturing enhanced gas drainage technology method.

Contents of the invention

Technical problem: The object of the present invention is to provide a hydraulic fracturing technology with large fracturing effect area, large gas desorption capacity, obvious gas drainage effect and high success rate in view of the deficiencies in the existing hydraulic fracturing technology in high gas and low permeability coal seams. High-efficiency and low-cost hydrothermal coupling fracturing enhanced regional gas drainage method.

Technical solutions:

The hydrothermal coupling fracturing strengthening regional gas drainage method of the present invention is characterized in that it comprises the following steps:

a. The main fracturing hole and three branch fracturing holes are constructed sequentially on the roadside of the coal seam. The main fracturing hole is arranged at the center of an equilateral triangle, and the opening positions of the three branch fracturing holes are respectively arranged on the equilateral triangle. At the three vertices of the triangle, the terminal holes of the three branch fracturing holes meet at the center line of the equilateral triangle to form a regular triangular pyramid with the equilateral triangle as the base and the branch fracturing holes as the edges, so that The main fracturing hole and the three branch fracturing holes are connected in the coal seam, and the distance between the main fracturing hole and the branch fracturing holes is 2-3m;

b. Construct four guide holes at a distance of 5-15m from the main fracturing hole, so that the four guide holes are located on a circle with the main fracturing hole as the center and a radius of 5-15m;

c. Connect fracturing equipment at the main fracturing hole orifice, and the fracturing equipment includes water injection equipment and a powder injector composed of an intelligent water tank and a fracturing pump. The water outlet pipe of the water injection equipment and the powder outlet pipe of the powder injector are connected together through a tee, and the outlet of the tee is connected with the fracturing pipe through a high-pressure rubber hose. With one-way valve;

d. Drill and seal the main fracturing hole, branch fracturing hole and pilot hole in sequence by using the conventional hole sealing method;

e. Add a certain amount of quicklime powder into the powder injector, inject the quicklime powder in the powder injector into the main fracturing hole through the downhole wind pressure, and stop the powder injection when all the branch fracturing holes are fully discharged;

f. Turn on the fracturing pump, perform hydraulic fracturing on the main fracturing hole through water injection equipment, and create cracks around the main fracturing hole and branch fracturing holes. Quicklime powder enters the cracks under the pressure of high-pressure water, and at the same time A large amount of heat is generated by a thermal reaction to realize hydrothermal coupled fracturing;

g. Repeat steps e and f. When water flows out of all four guide holes, stop the hydrothermal coupling fracturing, remove the fracturing equipment, and connect the main fracturing hole, branch fracturing holes and guide holes into the gas drainage pipe net for gas extraction.

Beneficial effects: Due to the adoption of the above-mentioned technical scheme, the defects of the existing hydraulic fracturing technology are solved, and the hydrothermal coupling fracturing of the coal seam is realized, which promotes the development, expansion and penetration of internal fissures in the coal body, and increases the affected area of fracturing; Highly adsorbable gas desorption, increasing the amount of gas desorption after fracturing; water reacts with quicklime powder, the water content is reduced, and the plugging effect of water after fracturing is reduced. Through the implementation of hydrothermal coupling fracturing to strengthen the regional gas drainage method, the gas concentration of the drainage is increased, the cost is low, and the effect is remarkable, which meets the needs of coal mine site regional gas control and other work.

Description of drawings

Fig. 1 is a drilling layout diagram of the hydrothermal coupling fracturing enhanced regional gas drainage method of the present invention.

Fig. 2 is a schematic diagram of an embodiment of the hydrothermal coupling fracturing enhanced regional gas drainage method of the present invention.

In the figure: 1—road gangway, 2—main fracturing hole, 3—branch fracturing hole, 4—guiding hole, 5—intelligent water tank, 6—fracturing pump, 7—high pressure hose, 8-1—one-way valve , 8-2—one-way valve, 9—valve, 10—tee, 11—fracturing pipe, 12—powder injector, 13—quicklime powder, 14—crack.

Detailed ways:

The specific embodiment of the present invention will be further described below in conjunction with accompanying drawing:

As shown in Figures 1 and 2, a hydrothermal coupling fracturing enhanced regional gas drainage method: first, the main fracturing hole 2 and three branch fracturing holes 3 are sequentially constructed on the coal seam side 1, and the main fracturing hole 2 are arranged at the center of an equilateral triangle, the opening positions of the three branch fracturing holes 3 are respectively arranged at the three vertices of the equilateral triangle, and the final holes of the three branch fracturing holes 3 are located on the equilateral triangle Gather at the center line of the triangle to form a regular triangular pyramid with the equilateral triangle as the base and the branch fracturing hole 3 as the edge, so that the main fracturing hole 2 and the three branch fracturing holes 3 are connected in the coal seam. The opening distance between the fracture hole 2 and the branch fracturing hole 3 is 2-3m; four guide holes 4 are constructed at a distance of 5-15m from the main fracturing hole 2, so that the four guide holes 4 are in the position of the main fracturing hole. Hole 2 is the center of the circle with a radius of 5-15m; fracturing equipment is connected to the opening of main fracturing hole 2, and the fracturing equipment includes water injection equipment and powder injector composed of intelligent water tank 5 and fracturing pump 6 12 compositions. The water outlet pipe of the water injection equipment and the powder outlet pipe of the powder injector are connected together through the tee 10, the outlet of the tee 10 is connected with the fracturing pipe 11 through the high-pressure rubber hose 7, and the outlet pipe of the water injection equipment and the outlet of the powder injector 12 are connected together. A one-way valve 8-1 and a one-way valve 8-2 are respectively installed on the powder pipe; the main fracturing hole 2, the branch fracturing hole 3 and the guide hole 4 are drilled and sealed in sequence by using the conventional hole sealing method; A certain amount of quicklime powder 13 is added to the pulverizer 12, and the quicklime powder 13 in the powder injector 12 is injected into the main fracturing hole 2 through the downhole wind pressure, and the powder injection is stopped when all the branch fracturing holes 3 are fully discharged; Turn on the fracturing pump 6, and perform hydraulic fracturing on the main fracturing hole 2 through the water injection equipment, and generate cracks 14 around the main fracturing hole 2 and branch fracturing holes 3, and quicklime powder 13 enters the cracks 14 under the pressure of high-pressure water. At the same time, quicklime powder 13 reacts with water to generate a large amount of heat, realizing hydrothermal coupling fracturing. The rise in temperature promotes highly adsorbable gas desorption and increases the amount of gas desorption after fracturing; water reacts with quicklime powder, and the moisture content decreases , to reduce the plugging effect of water after fracturing; when water flows out of all four guide holes 4, stop hydrothermal coupling fracturing, remove the fracturing equipment, and place the main fracturing hole 2, branch fracturing hole 3 and guide hole 4 connected to the gas drainage pipe network for gas drainage. Through the implementation of hydrothermal coupling fracturing to strengthen regional gas drainage method, the defects of existing hydraulic fracturing technology have been solved, and hydrothermal coupling fracturing of coal seams has been realized, which can promote the development, expansion and penetration of internal cracks in coal bodies, and increase the concentration of gas drainage , low cost and remarkable effect, which meets the needs of coal mine field area gas control and other work.

Claims (2)

1. A hydrothermal coupled fracturing method for strengthening regional gas drainage, characterized in that it comprises the following steps: a. The main fracturing hole (2) and three branch fracturing holes (3) are sequentially constructed in the coal seam side (1), the main fracturing hole (2) is arranged at the center of an equilateral triangle, and the three branch fracturing holes The opening positions of the fracture holes (3) are respectively arranged at the three vertices of the equilateral triangle, and the terminal holes of the three branch fracturing holes (3) meet at the center line of the equilateral triangle, so that the main fracturing hole (2), three branch fracturing holes (3) run through in the coal seam, and the distance between the main fracturing hole (2) and the branch fracturing holes (3) is 2-3m; b. Construct four guide holes (4) at a distance of 5-15m from the main fracturing hole (2), so that the four guide holes (4) are located at the center of the main fracturing hole (2), with a radius of 5-15m. on a circle of 15m; c. Connect fracturing equipment at the main fracturing hole (2) orifice, and the fracturing equipment includes a water injection equipment composed of an intelligent water tank (5), a fracturing pump (6) and a powder injector (12). The water outlet pipe of the water injection equipment and the powder outlet pipe of the powder injector are connected together through a tee (10), the outlet of the tee (10) is connected with the fracturing pipe (11) through the high-pressure rubber hose (7), and the outlet of the water injection equipment A one-way valve (8-1) and a one-way valve (8-2) are respectively provided on the water pipe and the powder outlet pipe of the powder injector (12); d. Drilling and sealing the main fracturing hole (2), the branch fracturing hole (3) and the pilot hole (4) sequentially by using a conventional hole sealing method; e. Add a certain amount of quicklime powder (13) into the powder injector (12), and inject the quicklime powder (13) in the powder injector (12) into the main fracturing hole (2) by downhole wind pressure, and wait until all When all the powder is discharged from the branch fracturing holes (3), stop powder injection; f. Turn on the fracturing pump (6), carry out hydraulic fracturing to the main fracturing hole (2) through the water injection equipment, and generate cracks (14) around the main fracturing hole (2) and branch fracturing holes (3), quicklime The powder (13) enters the fracture (14) under the pressure of high-pressure water, and at the same time, the quicklime powder (13) reacts with water to generate a large amount of heat, realizing hydrothermal coupled fracturing; g. Repeat steps e and f. When water flows out of all four guide holes (4), stop hydrothermal coupling fracturing, remove the fracturing equipment, and place the main fracturing hole (2) and branch fracturing hole (3) Connect with the guide hole (4) into the gas drainage pipe network for gas drainage. 2. The hydrothermal coupling fracturing enhanced regional gas drainage method according to claim 1, characterized in that: the fracturing pipe (11) is a seamless steel pipe with small holes evenly arranged on the pipe wall, and the diameter of the small holes is 10mm, without The diameter of the seam steel pipe is 25mm, and the total length of the seamless steel pipe is 30m.