CN114482932A - Method for achieving preset coal seam gas extraction through cross-layer drilled gas coal seam - Google Patents

Abstract

The invention discloses a method for drilling gas through a seam through a gas coal seam to realize a predetermined coal seam gas extraction method. Section 14, No. 13 and No. 9 coal seam gas efficient drainage. It mainly includes the following steps: drilling holes with a drilling rig, sealing holes in No. 14 and No. 13 coal seams with upper and lower packers, fracturing No. 14 and No. 13 coal seams with liquid nitrogen foam and sanding, releasing pressure and extracting gas in No. 14 and No. 13 coal seams, and releasing No. 14 and No. 13 coal seams. The No. 13 coal seam was sealed with a packer, the upper and lower packers were used to seal the No. 9 high-gas coal seam, the No. 9 coal seam was fractured by adding sand with liquid nitrogen foam, and the No. 9 coal seam was drained by pressure relief. The invention can realize multi-coal mine gas extraction by sections, improve the coal mine gas extraction effect, improve the gas extraction rate, ensure the coal mine safety production, avoid resource waste, and realize the coal mine gas extraction safety and efficiency.

Description

A method of drilling through a gas coal seam through a seam to realize a predetermined coal seam gas extraction method

technical field

The invention mainly relates to the field of underground gas drainage in coal mines, and in particular relates to a method for drilling gas through a layer through a gas coal seam to realize gas drainage in a predetermined coal seam, which is suitable for the gas extraction of different coal seams in sections by drilling a hole in a coal mine, and realizes the predetermined coal seam gas drainage. efficient extraction.

Background technique

At present, the overall gas drainage effect of coal mines in my country is not good. The specific performance is that the gas drainage rate is low, which is not conducive to the safe production of coal mines, and causes a lot of waste of resources. In 2020, the extraction rate of my country's key coal mines is only about 40%. The reasons for the low gas extraction rate in my country's coal mines come from two aspects: one is the objective reason, the coal seam is low in permeability, and the coal seam is soft, making gas extraction difficult On the other hand, it is a subjective reason, which is mainly manifested in short extraction time, insufficient drilling engineering volume, poor sealing quality, single extraction method, unmatched extraction system and inadequate management.

The invention can extract multi-stage coal seam gas in underground coal mines, increases the permeability of coal seams, has longer mining time, excellent hole sealing effect, novel mining method, greatly increases the coal mine gas extraction rate, and at the same time ensures the coal mine gas extraction rate. The gas engineering volume is reduced and the process is simplified, so as to realize efficient gas extraction in coal mines.

SUMMARY OF THE INVENTION

Aiming at the problems of poor coal mine gas drainage effect, low gas drainage rate, influence on coal mine safety production, waste of resources, etc., the invention proposes a method of drilling through the gas coal seam through the layer to realize the gas drainage method of the predetermined coal seam, aiming at improving the coal mine gas drainage. The effect of gas drainage can improve the gas drainage rate, ensure the safe production of coal mines, avoid waste of resources, and achieve efficient gas drainage in coal mines.

In order to achieve the above purpose, the technical scheme of the present invention is as follows: the present invention discloses a method for drilling gas through a gas coal seam through a seam to realize a predetermined coal seam gas extraction method. From the No. 14 and No. 13 coal seams to the No. 9 coal seam with high gas, the efficient extraction of gas from the No. 14, No. 13 and No. 9 coal seams is carried out in two stages; the main steps include the following steps: use a drilling rig to drill holes, and seal the No. 14 and No. 13 coal seams with upper and lower packers. The No. 14 and No. 13 coal seams were fractured with liquid nitrogen foam and sand, the gas was extracted from the No. 14 and No. 13 coal seams by pressure relief, and the No. 14 and No. 13 coal seams were released from the packers, and the No. 9 high-gas coal seam was sealed up and down. The No. 9 coal seam was fractured with liquid nitrogen foam and sand, and the No. 9 coal seam was extracted by pressure relief.

A method for drilling gas through a layer through a gas coal seam to realize a predetermined coal seam gas extraction method, characterized in that it includes the following steps:

Step 1. Use the drilling rig to drill upwards with an inclination angle of 75° and pass through the adjacent coal seams of No. 14 and No. 13 containing gas to reach 1m above the roof of No. 9 coal seam with high gas. The diameter of the drilled hole is 91 mm. After that, retract the rig.

Step 2: Use a packer with a diameter of 91mm to seal the upward drilling holes at 1m above the roof of the No. 13 coal seam and 1m below the bottom of the No. 14 coal seam, and pressurize the packers with liquid to seal the holes. The isolation strength is more than 20MPa, and the drilling hole is isolated.

Step 3: Select a dual-purpose high-pressure pipe with a diameter of 30-60mm according to the coalbed gas accumulation degree, connect it with the lower packer, and expose about 50mm, and use the liquid nitrogen foam sand blasting method to separate the dual-purpose high-pressure pipe and the lower packer. The high-pressure pump is connected, the pressure gauge and valve are installed at the connection, and high-pressure liquid is injected to fract the No. 14 and No. 13 coal seams. The cracks are in the shape of tree roots. After the liquid return is completed, close the valve and remove the high pressure pump.

Step 4. Connect the dual-purpose high-pressure pipe to the gas extraction pipe, set up a flow meter and valve at the connection, and after checking that the air tightness is good, implement pressure relief extraction, and monitor the gas concentration display of the flow meter at all times. When the gas extraction concentration of No. 13 coal seam is lower than 0.5%, close the valve and stop the extraction.

Step 5: Depressurize the packers at the No. 14 and No. 13 coal seams, withdraw the liquid in the packers, send the upper packer to 1m above the roof of the No. 9 coal seam, and send the lower packer to the bottom of the No. 9 coal seam floor 1m, pressurize and seal the hole.

Step 6: The No. 9 coal seam is flushed in the same way as in Step 3 of the coal seam flushing method.

Step 7: The same as the gas extraction method in Step 4, gas extraction is performed on the No. 9 coal seam.

Step 8. After all coal seam gas extraction is completed, recover the gas extraction pipe first, and then release the pressure of the packer for recovery; complete the staged extraction of No. 9 high gas coal seam and No. 14 and No. 13 gas-bearing coal seams .

Further, in step 1, in addition to 91mm, the diameter of the borehole can be selected according to the actual situation, such as 75mm and 110mm, and the diameter of the packer can also be changed accordingly.

Further, in the third step, the dual-purpose high-pressure pipe is used not only as a high-pressure hose for injecting back fracturing fluid, but also as a drainage pipe during gas extraction.

Further, in step 4, the displayed gas concentration index at the time of stopping the extraction can be changed correspondingly according to the actual production.

Beneficial effects of the present invention: the present invention cleverly uses the packer to seal the upward drilling holes and can be effectively recovered, which can avoid the time-consuming and consumption of using cement slurry to seal the side walls of the fractured coal seam after gas extraction. The use of liquid nitrogen and sand blasting method can effectively increase the permeability of the coal seam and improve the gas drainage rate; the dual-purpose high-pressure pipe can be used as a high-pressure hose during fracturing, and can also be used for gas drainage. The extraction pipe avoids the waste of space caused by both the high-pressure hose and the extraction pipe, saves manpower and material resources, and improves the extraction efficiency.

Description of drawings

FIG. 1 is a schematic diagram of a method of drilling gas through a seam to extract gas-bearing coal seams to achieve predetermined coal seam gas extraction.

FIG. 2 is a schematic diagram of No. 13 and No. 14 coal seam drainage in a method for drilling gas-containing coal seams through seam drilling to achieve predetermined coal seam gas drainage.

In the figure: (1) No. 15 coal seam has been mined; (2) No. 14 coal seam containing gas; (3) No. 13 coal seam containing gas; (4) No. 9 coal seam with high gas; (5) Up-drilling (6) is the upper packer; (7) is the lower packer; (8) is the packer injection return pipe; (9) is the dual-purpose high-pressure pipe; (10) is the valve; (11) It is a high pressure pump for the packer; (12) is a rock formation.

Detailed ways

The method of the present invention will be described in further detail below with reference to the specific embodiments of the drawings.

The invention provides a method for drilling gas through a gas coal seam through a layer to realize a predetermined coal seam gas extraction method, comprising the following steps:

Step 1. Use a drilling rig to drill upwards with an inclination angle of 75°, and drill upwards (5) through the gas-containing No. 14 coal seam (2) and No. 13 gas-containing coal seam (3) in turn to reach the top of the high-gas No. 9 coal seam (4) At 1m, the diameter of the hole (5) is 91mm. After the hole is drilled, retract the drilling rig.

Step 2. Use a packer (6, 7) with a diameter of 91mm to seal the upward drilling hole (5) at 1m above the top plate of the No. 13 coal seam (3) and 1m below the bottom plate of the No. 14 coal seam (2). Use liquid to pressurize the packers (6, 7), the packing strength is over 20MPa, and the borehole (5) is sealed.

Step 3. Select a dual-purpose high-pressure pipe (9) with a diameter of 30-60mm according to the coal seam gas enrichment degree, connect it with the lower packer (7), and expose about 50mm; adopt the liquid nitrogen foam sand blasting method, Connect the dual-purpose high-pressure pipe (9) to the high-pressure pump, attach a pressure gauge and valve (10) to the connection, inject high-pressure liquid to fract No. 14 and No. 13 coal seams (2, 3), and the cracks are in the shape of tree roots; After the gas is cracked to meet the gas extraction requirements, the rotary valve (10) is used for liquid return and pressure relief. After the liquid return is completed, the valve (10) is closed and the high-pressure pump is removed.

Step 4. Connect the dual-purpose high-pressure pipe (9) with the gas extraction pipe, set up a flow meter and valve (10) at the connection, check that the air tightness is good, perform pressure relief extraction, and monitor the flow meter gas at all times. The concentration shows that when the gas extraction concentration of No. 14 and No. 13 coal seams (2, 3) is lower than 0.5%, close the valve and stop the extraction.

Step 5. Depressurize the packers (6, 7) at the No. 14 and 13 coal seams (2, 3), draw back the gas or liquid in the packers (6, 7), and put the upper packer (6) It is sent to 1m above the roof of the No. 9 coal seam (4), and the lower packer (7) is sent to 1m below the bottom of the No. 9 coal seam (4) to seal the holes with pressure.

Step 6: The No. 9 coal seam (4) is flushed in the same way as in Step 3 of the coal seam flushing method.

Step 7: The same as the gas extraction method in Step 4, gas extraction is performed on the No. 9 coal seam (4).

Step 8. After all coal seam gas extraction is completed, the gas extraction pipe is recovered first, and then the packers (6, 7) are decompressed and recovered, and the No. 9 high-gas coal seam (4) and No. 14 and No. 13 coal seams are completed. Staged extraction of gas-bearing coal seams (2, 3).

Further, in step 1, in addition to 91mm, the diameter of the drill hole (5) can be selected according to the actual situation, such as 75mm, 110mm, etc., and the diameter of the packer (6, 7) can also be changed accordingly.

Further, in the third step, the dual-purpose high-pressure pipe (9) is used not only as a high-pressure hose for injecting back fracturing fluid, but also as a extraction pipe during gas extraction.

Further, in step 4, the displayed gas concentration index at the time of stopping the extraction can be changed correspondingly according to the actual production.

Claims (4)

1. A method for realizing gas extraction of a preset coal seam by drilling a gas coal seam through a cross-layer hole is characterized by comprising the following steps:

step one, sequentially penetrating 14 and 13 adjacent coal seams containing gas to 1m above a top plate of a No. 9 coal seam with high gas through upward drill holes with an upward drill inclination angle of 75 degrees by using a drilling machine, wherein the drill holes are 91mm in diameter; after the drilling is finished, the drilling machine is withdrawn;

step two, sealing the upward drilled hole by using a packer with the diameter of 91mm at a position 1m above the No. 13 coal seam top plate and a position 1m below the No. 14 coal seam bottom plate, and pressurizing the packer by using gas or liquid, wherein the packing strength is more than 20MPa, and the drilled hole is sealed;

selecting a dual-purpose high-pressure pipe with the diameter of 30-60 mm according to the enrichment degree of the coal bed gas, connecting the dual-purpose high-pressure pipe with a lower packer, exposing the dual-purpose high-pressure pipe by about 50mm, connecting the dual-purpose high-pressure pipe with a high-pressure pump by adopting a liquid nitrogen foam sand-adding fracturing method, attaching a pressure gauge and a valve to the joint, and injecting high-pressure liquid to fracture coal beds No. 14 and 13, wherein the fracture is in a tree root shape; after fracturing is completed to meet the gas extraction requirement, returning the liquid by the rotary valve for pressure relief, closing the valve after the liquid is returned, and removing the high-pressure pump;

step four, connecting the dual-purpose high-pressure pipe with a gas extraction pipe, arranging a flowmeter and a valve at the connection position, performing pressure relief gas extraction after checking good gas tightness, monitoring the gas concentration of the flowmeter at all times, displaying, closing the valve and stopping gas extraction when the gas extraction concentration of No. 14 and No. 13 coal seams is lower than 0.5%;

step five, releasing pressure of the packers at the coal seams of No. 14 and No. 13, pumping gas or liquid in the packers, conveying the upper packer to a position 1m above the top plate of the coal seam of No. 9, conveying the lower packer to a position 1m below the bottom plate of the coal seam of No. 9, and pressurizing and sealing holes;

sixthly, performing the coal bed No. 9 by adopting the same coal bed cracking method as the coal bed cracking method in the third step;

seventhly, performing gas extraction on the No. 9 coal seam in the same way as the fourth gas extraction method;

and step eight, after all coal seam gas is completely extracted, firstly withdrawing the gas extraction pipe, then releasing pressure and recovering the packer, and finishing the sectional extraction of the No. 9 high gas coal seam, the No. 14 coal seam and the No. 13 coal seam containing the gas.

2. Further, in the step one, the diameter of the drill hole is selected to be 91mm, and the diameter of the packer can be selected according to the actual diameter of the drill hole such as 75mm, 110mm and the like, and the diameter of the packer is also selected in a corresponding change mode.

3. Further, in the third step, the dual-purpose high-pressure pipe is used as a high-pressure hose for injecting back fracturing fluid and an extraction pipe for gas extraction.

4. Further, in the fourth step, the gas display concentration index at the time of stopping extraction can be changed correspondingly according to actual production.

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