CN104405358B - A kind of method in high pressure gas fracturing coal seam - Google Patents

Abstract

A method for fracturing a coal seam with high-pressure gas, comprising: 1) drilling an oblique hole from a slate roadway in the lower part of the coal seam to the upper coal seam; Polyurethane; 3) inject cement mortar into the borehole by the first grouting pipe, until the cement mortar overflows from the second grouting pipe, close the first valve provided on the rear end of the first grouting pipe; 4) 12~ After 24 hours, inject plugging mucus containing particles into the borehole from the second grouting pipe; 5) inject high-pressure gas with a pressure of 30-60 MPa into the borehole from the fracturing extraction pipe. In the present invention, under the action of air pressure, the plugging mucus containing particulate matter is pressed into the pores and fissures of the rock section, and the mucus is used to block the high-pressure gas, which effectively solves the problem of high-pressure gas leakage during the coal seam fracturing process and ensures the gas flow of the fracturing coal seam. The pressure reaches the fracturing pressure of the coal seam.

Description

A method for high-pressure gas fracturing of coal seams

technical field

The invention relates to a high-pressure gas fracturing method for coal seams, in particular to a high-pressure gas fracturing method suitable for drilling surrounding rocks with relatively high porosity.

Background technique

At present, the pressure relief and permeability enhancement measures commonly used in high-gassy and low-permeability coal seams include deep hole loosening blasting, water jet slotting technology, hydraulic punching technology and underground coal seam hydraulic fracturing technology, etc., but deep hole blasting, water jet slotting technology 1. The hydraulic punching technology has problems such as small effective drilling range, heavy workload, and complicated construction technology.

Hydraulic fracturing technology has achieved certain results in the enhancement of permeability of underground coal seams in coal mines. The shortcomings of this technology are mainly manifested in the fact that after high-pressure water in the coal seam enters the coal body, it is difficult to discharge the water due to the capillary force of the coal body, which weakens the hydraulic fracturing. The effect of penetrating coal. When the fracturing medium changes from water to gas, the above problems will be overcome. However, due to the compressibility of gas, the fracturing pressure of gas fracturing coal seams will be much higher than water pressure, and high-pressure gas fracturing coal seams will face sealing problems. , once the seal is not tight, the gas pressure of the fracturing coal seam cannot reach the fracturing pressure of the coal seam, resulting in the failure of the high-pressure gas fracturing coal seam. For this reason, it is urgent to find a method of high-pressure gas fracturing coal seams with high sealing performance.

Contents of the invention

The invention provides a method for fracturing a coal seam with high-pressure gas, which can fracture the coal seam on the basis of ensuring the high sealing performance of the bore hole.

Technical scheme of the present invention:

A method for high-pressure gas fracturing coal seams, characterized in that the specific process steps are as follows:

1) Construct inclined drilling from the floor rock roadway in the lower part of the coal seam to the upper coal seam, the inclination angle between the axis of the drilling hole and the horizontal plane of the coal seam is greater than 20°, and the end of the drilling hole exceeds the coal seam by 0.5~1m;

2) Insert the first grouting pipe, the second grouting pipe and the fracturing extraction pipe into the borehole, inject polyurethane (3) with a thickness of 20-50cm into the borehole to seal the borehole opening.

3) Inject expansive cement into the borehole from the first grouting pipe until the expansive cement overflows from the second grouting pipe, then close the first valve provided on the rear end of the first grouting pipe.

4) After 12 to 24 hours, inject the plugging mucus containing particulate matter into the borehole from the second grouting pipe until the plugging mucus overflows from the fracturing (drainage) pipe, then close the back end of the second grouting pipe. Set the second valve.

5) Inject high-pressure gas with a pressure of 30-60 MPa into the borehole from the fracturing (drainage) pipe, and press the plugging viscose containing particulate matter into the mucus diffusion zone around the borehole.

6) When the gas injection pressure drops below 20MPa, stop fracturing after continuous gas injection for 30 to 60 minutes.

Furthermore, the front end of the first grouting pipe exceeds the front end of the polyurethane by 20~50cm, the front end of the fracturing (drainage) pipe is located at the junction of the borehole and the bottom of the coal seam, and the front end of the second grouting pipe is 3~5 cm away from the front end of the fracturing (drainage) pipe. 6m.

Further, the particulate matter in the plugging mucus is fly ash, the particle size of the particulate matter is 200-500 mesh, and the volume percentage is 5%-15%.

Beneficial effects of the present invention: under the action of air pressure, the plugging mucus containing particles is pressed into the pores and fissures of the rock section, and the mucus is used to block the high-pressure gas, which effectively solves the problem of high-pressure gas leakage during the coal seam fracturing process and ensures the pressure The gas pressure of the cracked coal seam reaches the fracturing pressure of the coal seam.

Description of drawings

Figure 1 is a schematic diagram of the specific application of the present invention.

In the figure: 1. The first valve, 2. Floor rock roadway, 3. Polyurethane, 4. The first grouting pipe, 5. Expansive cement, 6. Fracturing drainage pipe, 7. Mucus diffusion area, 8. Cracks, 9, coal seam, 10, particulate matter, 11, plugging mucus, 12, the second grouting pipe, 13, drilling, 14, the second valve.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings.

As shown in accompanying drawing 1, a kind of method for high-pressure gas fracturing coal seam is characterized in that concrete process steps are as follows:

1) From the floor rock roadway in the lower part of the coal seam to the upper coal seam, the angle between the horizontal plane and the horizontal plane is greater than 20° and the drilling hole is inclined upward, and the end of the drilling hole exceeds the coal seam by 0.5~1m.

2) Insert the first grouting pipe, the second grouting pipe and the fracturing extraction pipe into the borehole respectively, and the borehole opening is sealed with polyurethane with a length of 20-50cm.

3) Inject expansive cement into the borehole from the first grouting pipe until the expansive cement overflows from the second grouting pipe. At this time, the space between the front end of the second grouting pipe and the front end of the polyurethane is filled with expansive cement, and close the first grouting The first valve provided on the pipe rear end stops the grouting.

4) After standing for 12~24 hours, after the expansive cement is fully set, inject the plugging mucus containing particles into the borehole from the second grouting pipe until the plugging mucus overflows from the fracturing drainage pipe, at this time the second injection The plugging mucus is filled between the front end of the grout pipe and the front end of the fracturing drainage pipe, and the second valve arranged on the rear end of the second grout pipe is closed.

5) Inject high-pressure gas with a pressure of 30-60 MPa into the borehole from the fracturing drainage pipe for 20-60 minutes. At this time, the plugging mucus enters the mucus diffusion area around the borehole under the action of high pressure of the gas, and is then compressed. It can effectively solve the leakage phenomenon of high-pressure gas in the coal seam fracturing process, and ensure that the gas pressure for fracturing the coal seam reaches the fracturing pressure of the coal seam.

6) When the gas injection pressure drops below 20MPa, it means that the coal seam has been fractured, and the fracturing is stopped after the gas injection is continued for 30-60 minutes to further develop the fractures.

Furthermore, the front end of the first grouting pipe exceeds the front end of the polyurethane by 20~50cm, the front end of the fracturing (drainage) pipe is located at the junction of the borehole and the bottom of the coal seam, and the front end of the second grouting pipe is 3~5 cm away from the front end of the fracturing (drainage) pipe. 6m.

Further, the particulate matter in the plugging mucus is fly ash, the particle size of the particulate matter is 200-500 mesh, and the volume percentage is 5%-15%.

Note: The high-pressure gas includes nitrogen, air, carbon dioxide or mixed gases.

Particulate matter (10) includes fly ash.

Plugging mucus (11) is a product purchased on the market, and the product name is thickener, thickener or viscous agent.

Claims (2)

1. a method for high-pressure gas fracturing coal seam, is characterized in that comprising the steps: (1) Construct oblique drilling from the floor rock roadway in the lower part of the coal seam to the upper coal seam, the inclination angle between the axis of the drilling hole and the horizontal plane of the coal seam is greater than 20°, and the end of the drilling hole exceeds the coal seam by 0.5~1m; (2) Insert the first grouting pipe, the second grouting pipe and the fracturing extraction pipe into the borehole, and inject polyurethane with a thickness of 20-50 cm into the borehole to seal the borehole opening; (3) Inject expansive cement into the borehole from the first grouting pipe until the expansive cement overflows from the second grouting pipe, then close the first valve provided on the rear end of the first grouting pipe; (4) After 12 to 24 hours, inject the plugging mucus containing particles into the borehole from the second grouting pipe until the plugging mucus overflows from the fracturing drainage pipe, close the setting on the rear end of the second grouting pipe. the second valve; (5) Inject high-pressure gas with a pressure of 30-60 MPa into the borehole from the fracturing drainage pipe, and press the plugging viscose containing particulate matter into the mucus diffusion zone around the borehole; (6) When the gas injection pressure drops below 20MPa, stop fracturing after continuous gas injection for 30~60min; the front end of the first grouting pipe exceeds the front end of polyurethane by 20~50cm, and the front end of the fracturing extraction pipe is located at the bottom of the borehole and the coal seam At the junction of the second grouting pipe, the distance between the front end of the second grouting pipe and the front end of the fracturing drainage pipe is 3~6m. 2. the method for high-pressure gas fracturing coal seam according to claim 1, it is characterized in that, in the plugging mucus, particulate matter is fly ash, and the particle diameter of particulate matter is 200～500 orders, and the volume percentage that particulate matter accounts for plugging mucus is 5%~15%.