CN112901118A - Method for hydraulic seam cutting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal seam - Google Patents
Method for hydraulic seam cutting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal seam Download PDFInfo
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- CN112901118A CN112901118A CN202110291905.9A CN202110291905A CN112901118A CN 112901118 A CN112901118 A CN 112901118A CN 202110291905 A CN202110291905 A CN 202110291905A CN 112901118 A CN112901118 A CN 112901118A
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- liquid nitrogen
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/006—Production of coal-bed methane
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/255—Methods for stimulating production including the injection of a gaseous medium as treatment fluid into the formation
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/263—Methods for stimulating production by forming crevices or fractures using explosives
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F7/00—Methods or devices for drawing- off gases with or without subsequent use of the gas for any purpose
Abstract
The invention discloses a method for hydraulic seam cutting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal bed, which is suitable for permeability increasing of soft low-permeability coal bed. By the method and the steps, the permeability and the gas extraction effect of the soft coal can be further increased, the extraction radius is increased, and the outburst risk is reduced.
Description
Technical Field
The invention relates to the technical field of coal seam permeability improvement, in particular to a method for combining hydraulic seam cutting, liquid nitrogen frost heaving and blasting with permeability improvement.
Background
50% -70% of coal seams of coal mines in China belong to high gas coal seams, the coal seams extend downwards at a mining speed of 10-20 m each year at present, the mining depth of mines is increased, the coal seam geology and occurrence conditions are more complex, the coal seam pressure and the gas pressure are increased, and gas disasters such as coal and gas outburst and coal seam gas explosion are more and more serious.
The high-efficiency extraction and utilization of the gas can ensure the safe production of coal mines, and the gas can be used as a green energy source, but most of coal seams in China have low gas permeability, and various control measures such as hydraulic cutting, hydraulic fracturing, coal seam blasting and the like are adopted to control gas disasters and improve the gas permeability of the coal seams. However, in practical tests, the effect is not ideal after the measures are taken alone, and the effect is worse particularly on soft coal seams with low air permeability. As an anhydrous cracking technology, liquid nitrogen cracking is adopted, and in recent years, more scholars perform experimental research on the anti-reflection effect of the anhydrous cracking technology. However, these methods have a problem of a small influence range when they are operated alone in a soft and low permeability coal seam. The slotting range is originally small, the liquid nitrogen frost heaving action range is small, the liquid nitrogen is volatile, when the gas extraction is carried out in a soft coal seam, due to the fact that the action time is short and the influence range is small, under the condition, the initial flow is large, but due to the negative pressure influence, in a short time, a large number of cracks in a coal body are closed, the drilling hole is seriously deformed, the extraction range is small, and the extraction effect is poor. When blasting operation is carried out on the soft coal layer, due to the energy absorption effect of the broken soft coal body, the stress wave propagation distance is short, the blasting permeability increasing effect is poor, and the influence range is small.
Therefore, in order to increase the extraction effect of the soft low-permeability coal seam, a new method needs to be provided, and hydraulic cutting, liquid nitrogen frost heaving and blasting are combined to work together, so that the permeability increasing effect is improved.
Disclosure of Invention
In order to overcome the defects, the invention aims to provide a method for hydraulic seam cutting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal bed, aiming at the problems of small influence range, low extraction efficiency and short extraction time of permeability-increasing of the conventional soft low-permeability coal bed.
In order to achieve the purpose, the invention is implemented according to the following technical scheme:
a method for hydraulic seam cutting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal seam comprises the following steps:
step1, collecting a coal sample in an underground permeability-increasing region required to be implemented, and measuring the mechanical properties of the coal sample in a laboratory to determine the pressure required by slotting and the pressure of liquid nitrogen;
step2, drilling fracturing drill holes in the anti-reflection area, penetrating into the coal seam, and performing hydraulic cutting at different depth positions along the fracturing drill holes, wherein the cutting requirements are to ensure that the number of the cutting slots is as uniform as possible, reduce the stress concentration of the coal seam and maximize the influence range of the cutting slots;
step3, after the slotting is finished, withdrawing the drill rod, taking the slotting hole as a liquid nitrogen injection hole, and filling a large amount of liquid water into the slotting drill hole by utilizing the low-temperature frost heaving characteristic of the liquid nitrogen, but because the coal seam is softer and the slotting effect is not ideal, the coal body and the water are changed into an organic whole after the liquid nitrogen is injected; because the temperature of the liquid nitrogen is extremely low, the residual water in the drill hole and the cracks around the drill hole can be solidified into ice, and because the water has the phenomenon of volume expansion in the freezing process, the rock mass around the drill hole and the cracks can be extruded in the water condensation ice process, so that the crushing degree of the rock mass is increased, and the air permeability of the coal mass is further increased; the water-containing coal body is initiated to generate more fine cracks under the low-temperature action of liquid nitrogen, the cracks in a slotted area are developed, the liquid nitrogen is injected from the bottom of a slotted drilled hole, and the gas pressure in the drilled hole is rapidly increased due to the fact that the liquid nitrogen is gasified in a short time, so that the crack density of the coal body is increased to a certain extent, and the air permeability is increased;
step4, arranging a liquid nitrogen gas outlet beside the orifice of the liquid nitrogen injection hole, wherein the orifice of the liquid nitrogen gas outlet is positioned at the position closest to the slit groove, and releasing gas gasified by the liquid nitrogen by using the liquid nitrogen gas outlet;
step5, after the liquid nitrogen is gasified and discharged, the coal body and the water are still in a frozen state, and the emulsion explosive is put into the slotted hole to be blasted; because the strength of the coal body is increased, after blasting is carried out, the influence range of fracturing holes is greatly enlarged compared with that of independently carrying out slotting or blasting, the air permeability of a coal layer is increased, and high-concentration gas can be continuously extracted; at the moment, liquid water in the drill hole and gaps around the drill hole is all condensed into solid ice after liquid nitrogen is added, so that the solid ice has small attenuation to mechanical waves generated by blasting during blasting, can be transmitted to a farther area to a greater extent, and has longer ground crack expansion distance generated by blasting, so that the blasting ground effect is greatly increased. The residual heat generated after blasting can melt the solid ice and change the solid ice into liquid state again to flow out or directly evaporate the solid ice into gas state, the gas state water cannot be discharged in time in the blasting process and can also increase the air permeability of the drill hole, and the cracks are generated in the coal bed permeability increasing process of emptying the coal bed and can become coal bed gas extraction ground channels in the coal bed gas extraction process so as to increase the coal bed gas extraction efficiency;
step6, after blasting, performing gas extraction by utilizing a slotted drill hole;
step7, after the gas extraction reaches the standard, sequentially performing the steps of Step 2-Step 6 at certain intervals;
further, in Step2, the fracture borehole comprises a bedding borehole and a through-layer borehole;
further, in Step2, the equipment used for slotting is slotting equipment commonly used in mines, the slotting radius is generally small and is at most 3m, slotting effect in soft coal is poor, the strength of the soft coal is low mainly because the coal is easy to close in a short time after slotting is implemented;
further, in Step4, a pressure gauge and a valve are arranged at a liquid nitrogen outlet, and when the pressure of the pressure gauge reaches a preset pressure, the valve at the liquid nitrogen outlet is opened to release the gas after the liquid nitrogen is gasified.
Compared with the prior art, the method for hydraulic seam cutting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal seam has the following beneficial effects:
the method is characterized in that a method combining hydraulic slotting, liquid nitrogen frost heaving and blasting permeability increasing is respectively implemented in the same drill hole according to steps, so that permeability increasing effects are superposed, wherein water left in gaps in the hydraulic slotting process is specifically utilized, high-pressure liquid nitrogen is added, as a coal bed is softer, the slotting effect is possibly not ideal, and after liquid nitrogen is injected, coal bodies and water are changed into an organic whole; because the temperature of the liquid nitrogen is extremely low, the residual water in the drill hole and the cracks around the drill hole can be solidified into ice, and because the water has the phenomenon of volume expansion in the freezing process, the rock mass around the drill hole and the cracks can be extruded in the water condensation ice process, so that the crushing degree of the rock mass is increased, and the air permeability of the coal mass is further increased; the water-containing coal body is initiated to generate more fine cracks under the low-temperature action of liquid nitrogen, the cracks in a slotted area are developed, the liquid nitrogen is injected from the bottom of a slotted drilled hole, and the gas pressure in the drilled hole is rapidly increased due to the fact that the liquid nitrogen is gasified in a short time, so that the crack density of the coal body is increased to a certain extent, and the air permeability is increased; when blasting is carried out, solid state has small attenuation to mechanical waves generated by blasting, and the mechanical waves can be transmitted to a farther area to a greater extent, and ground cracks generated by blasting have a longer extension distance, so that the blasting ground effect is greatly increased. The residual heat generated after blasting can melt the solid ice and change the solid ice into liquid state again to flow out or directly evaporate the solid ice into gas state, the gas state water cannot be discharged in time in the blasting process and the air permeability of the drill hole can be increased, ground cracks are generated in the process of emptying the coal bed for permeability increase, the cracks can become coal bed gas extraction ground channels in the coal bed gas extraction process, and the coal bed gas extraction efficiency is increased.
The permeability increase principle of the coal seam in the prior art only utilizes pressure and blasting pressure for permeability increase; the invention has the advantages that the permeability increasing process left after pressurized water injection mainly depends on the solidification volume increasing effect of water to realize the permeability increasing effect, the hydraulic slotting, liquid nitrogen frost heaving and blasting permeability increasing three methods are respectively and reasonably arranged in the implementation sequence to realize the front and back matching among the methods, the effect that the former method provides convenience for the subsequent operation or enhances the effect of the subsequent method is achieved, and the permeability increasing effect of the soft coal seam is more scientifically and reasonably increased.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic flow chart of the method of the present invention.
Detailed Description
The invention will be further described with reference to the drawings and specific embodiments, which are illustrative of the invention and are not to be construed as limiting the invention.
The method for hydraulic slotting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal seam shown in figure 1 comprises the following steps:
and Step1, collecting coal samples in an anti-reflection area required to be implemented underground, and measuring the mechanical properties of the coal samples in a laboratory to determine the pressure required by slotting and the pressure of liquid nitrogen.
Step2, drilling fracturing drill holes in the anti-reflection area, penetrating into the coal seam, and performing hydraulic cutting at different depth positions along the fracturing drill holes, wherein the fracturing drill holes comprise bedding drill holes and cross-layer drill holes, and the cutting is required to ensure that the number of the cutting is as uniform as possible, reduce the stress concentration of the coal seam and maximize the influence range of the cutting; the device used for slotting is slotting device commonly used in mines, the radius of the slotting is generally small and is at most 3m, slotting effect is poor when the slotting is carried out in soft coal, the intensity of the soft coal is low mainly due to the fact that coal bodies are easy to close in a short time after the slotting is carried out.
Step3, after the slotting is finished, withdrawing the drill rod, taking the slotting hole as a liquid nitrogen injection hole, and filling a large amount of liquid water into the slotting drill hole by utilizing the low-temperature frost heaving characteristic of the liquid nitrogen, but because the coal seam is softer and the slotting effect is not ideal, the coal body and the water are changed into an organic whole after the liquid nitrogen is injected; because the temperature of the liquid nitrogen is extremely low, the residual water in the drill hole and the cracks around the drill hole can be solidified into ice, and because the water has the phenomenon of volume expansion in the freezing process, the rock mass around the drill hole and the cracks can be extruded in the water condensation ice process, so that the crushing degree of the rock mass is increased, and the air permeability of the coal mass is further increased; the water-containing coal body is initiated to generate more fine cracks under the low-temperature action of the liquid nitrogen, the cracks in the slotted area are developed more, the liquid nitrogen is injected from the bottom of a slotted drilled hole, the liquid nitrogen can be gasified in a short time, the gas pressure in the drilled hole can be increased rapidly, the crack density of the coal body can be increased to a certain extent, and the air permeability is increased.
And Step4, arranging a liquid nitrogen gas outlet beside the orifice of the liquid nitrogen injection hole, arranging a pressure gauge and a valve at the orifice of the liquid nitrogen gas outlet at a position close to the nearest slotted groove, and opening the valve of the liquid nitrogen gas outlet when the pressure of the pressure gauge reaches a preset pressure to release gas gasified by the liquid nitrogen gas outlet.
Step5, after the liquid nitrogen is gasified and discharged, the coal body and the water are still in a frozen state, and the emulsion explosive is put into the slotted hole to be blasted; because the strength of the coal body is increased, after blasting is carried out, the influence range of fracturing holes is greatly enlarged compared with that of independently carrying out slotting or blasting, the air permeability of a coal layer is increased, and high-concentration gas can be continuously extracted; at the moment, liquid water in the drill hole and gaps around the drill hole is all condensed into solid ice after liquid nitrogen is added, so that the solid ice has small attenuation to mechanical waves generated by blasting during blasting, can be transmitted to a farther area to a greater extent, and has longer ground crack expansion distance generated by blasting, so that the blasting ground effect is greatly increased. The residual heat generated after blasting can melt the solid ice and change the solid ice into liquid state again to flow out or directly evaporate the solid ice into gas state, the gas state water cannot be discharged in time in the blasting process and the air permeability of the drill hole can be increased, ground cracks are generated in the process of emptying the coal bed for permeability increase, the cracks can become coal bed gas extraction ground channels in the coal bed gas extraction process, and the coal bed gas extraction efficiency is increased.
Step6, after blasting, performing gas extraction by utilizing a slotted drill hole;
and Step7, after the gas extraction reaches the standard, sequentially implementing the steps of Step 2-Step 6 at certain intervals.
The technical solution of the present invention is not limited to the limitations of the above specific embodiments, and all technical modifications made according to the technical solution of the present invention fall within the protection scope of the present invention.
Claims (4)
1. A method for hydraulic seam cutting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal seam is characterized by comprising the following steps:
step1, collecting a coal sample in an underground permeability-increasing region required to be implemented, and measuring the mechanical properties of the coal sample in a laboratory to determine the pressure required by slotting and the pressure of liquid nitrogen;
step2, drilling fracturing drill holes in the anti-reflection area, and performing hydraulic cutting at different depth positions along the fracturing drill holes to uniformly distribute slots;
step3, after the slotting is finished, withdrawing the drill rod, taking the slotting hole as a liquid nitrogen injection hole, and injecting high-pressure liquid nitrogen;
step4, arranging a liquid nitrogen gas outlet beside the orifice of the liquid nitrogen injection hole, wherein the orifice of the liquid nitrogen gas outlet is positioned at the position closest to the slit groove, and releasing gas gasified by the liquid nitrogen by using the liquid nitrogen gas outlet;
step5, after the liquid nitrogen is gasified and discharged, the coal body and the water are still in a frozen state, and the emulsion explosive is put into the slotted hole to be blasted;
step6, after blasting, performing gas extraction by utilizing a slotted drill hole;
and Step7, after the gas extraction reaches the standard, sequentially implementing the steps of Step 2-Step 6 at certain intervals.
2. The method for hydraulic slotting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal seam according to claim 1, wherein in Step2, the fracturing drill holes comprise bedding drill holes and through-layer drill holes.
3. The method for hydraulic slotting, liquid nitrogen frost heaving and blasting combined permeability-increasing coal seam according to claim 2, wherein in Step2, the slot radius of the hydraulic slotting is at most 3 m.
4. The method for hydraulic slotting, liquid nitrogen frost heaving and blasting combined anti-reflection coal seam according to claim 1, wherein a pressure gauge and a valve are arranged at a liquid nitrogen gas outlet in Step4, and when the pressure of the pressure gauge reaches a preset pressure, the valve of the liquid nitrogen gas outlet is opened to release gas gasified by liquid nitrogen.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114810197A (en) * | 2022-05-19 | 2022-07-29 | 贵州一和科技有限公司 | Gas permeability increasing method for coal roadway driving face dynamic and static combined action |
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Application publication date: 20210604 Assignee: Qingdao Rui Xin Engineering Technology Co.,Ltd. Assignor: SHANDONG University OF SCIENCE AND TECHNOLOGY Contract record no.: X2023980037098 Denomination of invention: A Method for Combining Hydraulic Cutting, Liquid Nitrogen Frost Heaving, and Blasting to Enhance Permeability of Coal Seams Granted publication date: 20230113 License type: Common License Record date: 20230628 |