CN111173513B - Low-temperature fracturing roof caving method for hard roof of coal mine goaf - Google Patents
Low-temperature fracturing roof caving method for hard roof of coal mine goaf Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 34
- 239000003245 coal Substances 0.000 title claims abstract description 32
- 239000012530 fluid Substances 0.000 claims abstract description 158
- 230000008014 freezing Effects 0.000 claims abstract description 112
- 238000007710 freezing Methods 0.000 claims abstract description 112
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 104
- 238000002347 injection Methods 0.000 claims abstract description 70
- 239000007924 injection Substances 0.000 claims abstract description 70
- 239000002775 capsule Substances 0.000 claims abstract description 32
- 238000005336 cracking Methods 0.000 claims abstract description 18
- 238000007789 sealing Methods 0.000 claims abstract description 14
- 230000008859 change Effects 0.000 claims abstract description 9
- 125000004122 cyclic group Chemical group 0.000 claims abstract description 5
- 238000005553 drilling Methods 0.000 claims description 19
- 238000005520 cutting process Methods 0.000 claims description 17
- 238000012544 monitoring process Methods 0.000 claims description 13
- 239000011435 rock Substances 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 6
- 238000007599 discharging Methods 0.000 claims description 6
- 238000010276 construction Methods 0.000 claims description 5
- 229910000831 Steel Inorganic materials 0.000 claims description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 3
- 239000001569 carbon dioxide Substances 0.000 claims description 3
- 230000008878 coupling Effects 0.000 claims description 3
- 238000010168 coupling process Methods 0.000 claims description 3
- 238000005859 coupling reaction Methods 0.000 claims description 3
- 238000004146 energy storage Methods 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 239000010959 steel Substances 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 6
- 238000005728 strengthening Methods 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 6
- 238000005422 blasting Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 2
- 239000002360 explosive Substances 0.000 description 2
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- 239000002994 raw material Substances 0.000 description 1
- 238000010257 thawing Methods 0.000 description 1
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- E21—EARTH OR ROCK DRILLING; MINING
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- E21C41/00—Methods of underground or surface mining; Layouts therefor
- E21C41/16—Methods of underground mining; Layouts therefor
- E21C41/18—Methods of underground mining; Layouts therefor for brown or hard coal
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK 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 OR ROCK DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C37/00—Other methods or devices for dislodging with or without loading
- E21C37/06—Other methods or devices for dislodging with or without loading by making use of hydraulic or pneumatic pressure in a borehole
- E21C37/14—Other methods or devices for dislodging with or without loading by making use of hydraulic or pneumatic pressure in a borehole by compressed air; by gas blast; by gasifying liquids
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Abstract
A low-temperature fracturing roof caving method for a hard roof of a coal mine goaf is suitable for the technical field of strengthening fracturing of the roof of the coal mine goaf. Sequentially constructing a plurality of fracturing drill holes and a hollow hole on a hard top plate of the gob by utilizing a digital display type temperature instrument, a temperature sensor, a water injection pipe, a low-temperature fluid freezing pipe, a capsule hole packer, a high-pressure water injection system and a low-temperature fluid tank car; the method comprises the steps of connecting a spiral low-temperature fluid pipe, a water injection pipe and a capsule hole packer, sending the spiral low-temperature fluid pipe, the water injection pipe and the capsule hole packer into a plurality of fracturing drill holes, adopting the capsule hole packer to perform high-pressure hole sealing, freezing cylindrical hole expanding sections of the orifices of the fracturing drill holes to form a self-sealing hole structure, freezing the plurality of fracturing drill holes, and fracturing a coal seam roof by utilizing water-ice phase change. When the temperature of the temperature sensors is raised to be higher than 3 ℃, the temperature sensors are repeatedly frozen to form frost heaving-melting-frost heaving cyclic cracking. The method is simple, convenient to operate, low in cost, simple to operate and good in cracking effect.
Description
Technical Field
The invention relates to a low-temperature fracturing roof caving method for a hard roof of a coal mine goaf, which is particularly suitable for a coal seam goaf roof which is compact, hard, difficult to collapse naturally and must be artificially strengthened to fracture.
Background
With the continuous propulsion of the underground coal face of the coal mine, the length of the roof left in the goaf and the area of the suspended roof are larger and larger, the strength for supporting the roof coal pillar in the goaf is smaller and smaller, stress concentration is easy to form, and roof collapse is easy to cause injury and mine pressure impact accidents for a long time. For a high gas mine, local accumulated gas is easily formed at the top plate of the goaf, so that gas accidents are caused. Therefore, the roof of the goaf needs to be cracked in advance, and the roof is artificially collapsed purposefully and accumulated in the goaf, so that the accidents of gas and roof collapse are prevented. Generally, when the strength of the top plate of the goaf is low, the top plate is collapsed by means of the ground stress and the gravity of the top plate, and when the top plate is hard, the top plate is cracked by means of the traditional deep hole blasting and high-pressure hydraulic fracturing methods.
However, the traditional fracturing method has certain defects, for example, a large amount of explosive is needed in the deep hole blasting method, the stress wave in the blasting process generates strong stress disturbance to the original rock, the stress distribution of the original rock is changed, and rock burst accidents are easily induced; in addition, the coal mine underground goaf is easy to accumulate gas, and the gas explosion is easily induced by adopting an explosive blasting and cracking mode. The high-pressure hydraulic fracturing equipment is large in size and poor in adaptability to narrow underground space, and due to the fact that water pressure is high, drilling and hole sealing difficulty is large, and failure probability is high. Therefore, aiming at the problems, a novel safe goaf hard roof fracturing roof caving device and method are urgently needed in coal mines, and on the premise of ensuring safety, water resources can be saved, and the roof can be fractured efficiently.
Disclosure of Invention
The technical problem is as follows: the invention aims to overcome the traditional roof fracturing method and provide the low-temperature fracturing roof caving method for the hard roof of the coal mine goaf, which has the advantages of simple operation, low cost, safety, reliability and good fracturing effect.
The technical scheme is as follows: the invention discloses a low-temperature fracturing roof caving method for a hard roof of a coal mine goaf, which comprises the following steps of adopting a digital display type temperature instrument, a temperature sensor, a water injection pipe, a low-temperature fluid freezing pipe, a capsule hole packer, a high-pressure water injection system and a low-temperature fluid tank car:
a. drilling construction: sequentially constructing a plurality of fracturing drill holes and a hollow hole on a hard top plate of a goaf, constructing the fracturing drill holes to the deepest point position K4 of the fracturing drill holes in the hard top plate of the goaf by using a common drill bit, withdrawing the common drill bit, replacing the common drill bit with a positioning pressure-controlled cutting drill bit for drilling, when the positioning pressure-controlled cutting drill bit reaches the initial point position K1 of a reaming section, opening the cutting edge of the positioning pressure-controlled cutting drill bit, stopping the drilling at the final point position K2 of the reaming section for reaming the drill holes to form a cylindrical reaming section, retracting the positioning pressure-controlled cutting drill bit with the reaming cutting edge to withdraw from a drill rod, and constructing a hollow hole in the middle of the plurality of fracturing drill holes after the construction is completed;
b. equipment arrangement: arranging a temperature sensor in a fracturing drill hole, connecting the temperature sensor with a digital display type temperature instrument outside the fracturing drill hole through a data line, connecting a first capsule hole packer and a second capsule hole packer in series, penetrating the first water injection pipe, the second water injection pipe, the first low-temperature fluid freezing pipe and the second low-temperature fluid freezing pipe, then sending the two pipes into the fracturing drill hole, respectively locating the first capsule hole packer and the second capsule hole packer at the position A and the position B of the fracturing drill hole, sealing the first capsule hole packer and the second capsule hole packer at high pressure through a water injection system, connecting the second low-temperature fluid freezing pipe with a discharge pipe through a one-way valve, directly connecting the first low-temperature fluid freezing pipe with the discharge pipe, installing the second one-way valve at the pipe orifice of the discharge pipe to control the discharge of the low-temperature fluid after heat exchange, connecting an injection pump between a low-temperature fluid tank truck and a main pipeline, and connecting the low-, simultaneously freezing and fracturing a plurality of fracturing drill holes;
c. freezing the cylindrical hole expanding section: opening a valve on a first water injection pipe, connecting a first quick connector of the first water injection pipe with a water injection valve on a water injection system, injecting high-pressure water into the cylindrical chambering section, monitoring a pressure gauge on the first water injection pipe, closing the valve to stop water injection after the water pressure in the cylindrical chambering section reaches 1.2MPa and can be kept for 30 minutes, and removing the first quick connector; opening a valve on the first cryogenic fluid freezing pipe, connecting the first cryogenic fluid freezing pipe with a cryogenic fluid valve of a cryogenic fluid tank car by using a quick coupling IV, injecting cryogenic fluid into the first cryogenic fluid freezing pipe, and discharging the cryogenic fluid from a one-way valve; monitoring the temperature of the initial point position K1 of the reaming section by a digital display type temperature instrument until the temperature of the initial point position K1 of the reaming section is reduced to be lower than-2 ℃, and closing a valve;
d. freezing and fracturing the drill hole: opening a valve on a second water injection pipe, connecting a second quick connector on the second water injection pipe with a water injection valve on a water injection system, injecting high-pressure water into the K3 position at the middle point of the fracturing drill hole, monitoring a pressure gauge on the second water injection pipe, closing the valve to stop water injection after the pressure displayed by the pressure gauge reaches 1.2MPa and can be kept for 30 minutes, and removing the second quick connector; opening a valve on a cryogenic fluid freezing pipe II, connecting a quick joint III with a cryogenic fluid valve of a cryogenic fluid tank car, injecting cryogenic fluid into the cryogenic fluid freezing pipe II, freezing water in the fracturing drill hole, enabling the cryogenic fluid to flow into a cryogenic fluid freezing pipe I through a one-way valve while freezing, enabling the cryogenic fluid to continuously exchange heat with an ice column in a frozen state in the cryogenic fluid freezing pipe I, maintaining the cylindrical reaming section in the frozen state, and discharging the cryogenic fluid after heat exchange through the one-way valve II; monitoring the temperature of the deepest point K4 of the fracturing drill hole, the middle point K3 of the fracturing drill hole and the initial point K1 of the reaming section on a digital display type temperature instrument, and closing a valve after freezing and fracturing when the temperature values of 3 positions are all reduced to-2 ℃;
e. and (3) drilling holes by circulating frost heaving and cracking: the frozen ice in the fracturing drill hole gradually melts along with the temperature of the rock mass of the hard roof of the coal mine goaf, and when a digital display type temperature monitoring instrument monitors that the overall temperature in the fracturing drill hole is all increased to be higher than 3 ℃, a one-time water ice phase change frost heaving fracturing cycle is completed;
f. and c, repeating the steps c-e, and performing frost heaving-melting-frost heaving cyclic cracking on the fractured drill hole again until water flows out of the hollow hole.
The temperature sensors comprise a first temperature sensor arranged at the deepest point position K4 of the fracturing drill hole, a second temperature sensor arranged at the middle point position K3 of the fracturing drill hole and a third temperature sensor arranged at the starting point position K1 of the reaming section.
The water outlet of the first water injection pipe is arranged in the cylindrical reaming section, the water outlet of the second water injection pipe is arranged at the position K3 of the middle point of the fracturing drill hole, a connecting port of the first low-temperature fluid freezing pipe and the discharge pipe is arranged between the first check valve and the second check valve, and the first check valve of the second low-temperature fluid freezing pipe, which is connected with the discharge pipe, is arranged in the cylindrical reaming section.
When the cylindrical hole expanding section is formed, water is injected into the cylindrical hole expanding section for freezing, and the icicle formed after freezing forms a self-sealing hole structure in the cylindrical hole expanding section.
The structure of the first low-temperature fluid freezing pipe and the second low-temperature fluid freezing pipe is a spiral structure with good heat exchange performance, the two low-temperature fluid freezing pipes are connected through a discharge pipe, the one-way flow of the low-temperature fluid is controlled by the first check valve, so that the low-temperature fluid in the second low-temperature fluid freezing pipe flows into the first low-temperature fluid freezing pipe, the low-temperature fluid in the first low-temperature fluid freezing pipe cannot flow into the second low-temperature fluid freezing pipe, and the low-temperature fluid freezing pipes are made of steel pipes with the pressure bearing capacity of more than 1.2MPa and the temperature resistance range of.
The temperature in the first cryogenic fluid freezing pipe and the second cryogenic fluid freezing pipe is less than or equal to minus 10 ℃, and the medium in the cryogenic fluid freezing pipes is liquid nitrogen, liquid carbon dioxide or cryogenic energy storage fluid.
The number of the fracturing drill holes is 3-6.
The aperture of the plurality of fracturing drill holes is 80mm, and the distance between the adjacent fracturing drill holes is 1-2 m.
The aperture of the hollow hole is 2-3 times of that of the fracturing drill hole.
Has the advantages that: by adopting the technical scheme, the invention adopts the technical scheme that when frost heaving and fracturing are carried out, the fractured drill hole is frozen in sections, the water-ice phase change phenomenon and the advantages of low-temperature fluid are combined and applied to the fracturing roof caving of the hard roof in the coal mine goaf, the fractured drill hole with the cylindrical reaming section is designed, double-capsule series hole sealing is used, the high-efficiency heat transfer spiral-structure low-temperature fluid freezing pipe is designed, water is injected to freeze the cylindrical reaming section to realize a self-hole sealing structure, then the fractured drill hole section is frozen, and cyclic freezing and fracturing can be carried out according to the fracturing condition, so that the hard roof naturally collapses under the conditions of ground stress and self weight. The water ice phase change is a common physical phenomenon in the nature, the volume of the process of forming ice by water can be increased by 9.1 percent, the acting force generated by volume expansion can reach 200MPa at most, and the phenomenon of rock breakage caused by frost heaving often occurs in high-cold high-altitude areas; various low-temperature fluids are convenient to prepare, the raw material sources are wide, the liquid can be quickly frozen, and the high-efficiency low-temperature fluid can be used as a high-efficiency refrigerating fluid and is applied to the aspect of coal seam cracking and permeability increasing of a coal mine. Compared with the prior art, the invention fully utilizes the characteristics of various low-temperature fluids, so that the water ice phase change volume expansion generates huge pressure of more than 200MPa, designs the cylindrical self-sealing hole cavity, solves the problem of difficult hole sealing, changes the expansion force from axial expansion into radial expansion, enhances the cracking effect, can perform circulating freeze thawing, forms the cycle of frost heaving-thawing-frost heaving, increases the generation of roof cracks, and enables the roof to be easier to naturally collapse. The design of the cavity provides a free surface for frost heaving force, controls the expansion direction of cracks, improves the cracking effect, and simultaneously, the frost heaving force cracking top plate is a relatively slow process, so that the stress change around the cracking drill hole can not be caused, the occurrence probability of rock burst accidents is reduced, and the rock burst accidents are relatively safe. The water-ice phase-change fracturing fluid uses a small amount of water and low-temperature fluid in the fracturing process, solves the problems of high application cost and large use amount of low-temperature fluid in a coal mine, has good fracturing effect by utilizing the water-ice phase change, and saves water resources because the two fluids are clean fluids and cannot cause pollution, so that the application of a hydraulic measure in a water-deficient area becomes possible. Compared with the blasting method, the method is safer, saves water resources and does not pollute the environment compared with various hydraulic measures, and has the advantages of simple method, convenient operation, low cost, good cracking effect and wide practicability.
Drawings
FIG. 1 is a sectional view A-A of a hard roof low-temperature fracturing roof caving method of a coal mine goaf;
FIG. 2 is a schematic diagram of the high pressure water injection system of the present invention;
figure 3 is a schematic illustration of a cryogenic fluid tanker of the present invention;
FIG. 4 is a schematic view of the temperature sensor arrangement of the present invention;
FIG. 5 is a schematic view of the water injection tube of the present invention;
figure 6 is a schematic diagram of a cryogenic fluid freezing tube arrangement of the present invention;
figure 7 is a schematic illustration of the flow path of cryogenic fluid of the present invention in cryogenic fluid freeze tube two;
figure 8 is a schematic illustration of the flow path of cryogenic fluid of the present invention in a cryogenic fluid freezing tube one;
fig. 9 is a schematic view of the drilling arrangement of the present invention.
In the figure: 1-a digital display type temperature instrument, 2-a data line, 3-a temperature sensor, 3-1-a temperature sensor I, 3-2-a temperature sensor II, 3-3-a temperature sensor III, 4-a water injection pipe I, 4-1-a quick connector I, 4-2-a valve, 4-3-a pressure gauge, 5-a water injection pipe II, 5-1-a quick connector II, 5-2-a valve, 5-3-a pressure gauge, 6-a low temperature fluid freezing pipe II, 6-1-a quick connector III, 6-2-a valve, 6-3-a check valve I, 7-a low temperature fluid freezing pipe I, 7-1-a quick connector IV, 7-2-a valve and 7-3-a check valve II, 8-cylindrical reaming section, 9-fracturing drilling hole, 10-goaf hard top plate, 11-capsule hole packer I, 12-capsule hole packer II, 13-high pressure water injection system, 13-1-high pressure water injection valve, 14-cryogenic fluid tank wagon, 14-1-cryogenic fluid valve, 14-2-flow divider, 14-3-injection pump, 15-discharge pipe, 16-hollow hole, K1-reaming section starting point position, K2-reaming section end point position, K3-fracturing drilling hole intermediate point position and K4-fracturing drilling hole deepest point position.
Detailed Description
The invention will be further described with reference to an embodiment in the drawings to which:
as shown in fig. 1-6 and 9, the low-temperature fracturing roof-caving method for the hard roof of the coal mine goaf comprises the steps of adopting a digital display type temperature instrument 1, a temperature sensor 3, a water injection pipe, a low-temperature fluid freezing pipe, a capsule hole packer, a high-pressure water injection system 13 and a low-temperature fluid tank car 14, wherein the low-temperature fracturing roof-caving method comprises the following specific steps:
a. drilling construction: and sequentially constructing a plurality of fracturing drill holes 9 and a hollow hole 16 on the hard top plate of the goaf, wherein the number of the fracturing drill holes 9 is 3-6, the aperture of each fracturing drill hole 9 is 80mm, and the distance between every two adjacent fracturing drill holes 9 is 1-2 m. The aperture of the one empty hole 16 is 2-3 times of the aperture of the fracturing drill hole. The method comprises the following steps that four fracturing drill holes 9 are formed, a common drill bit is used for constructing one fracturing drill hole 9 to the deepest point position K4 of the fracturing drill hole in a hard top plate 10 of a goaf, then the common drill bit is withdrawn and replaced by a positioning pressure-controlled cutting drill bit for drilling, when the positioning pressure-controlled cutting drill bit reaches the initial point position K1 of a reaming section, the cutting edge of the positioning pressure-controlled cutting drill bit is opened, the drilling hole 9 is reamed to the end point position K2 of the reaming section, a cylindrical reaming section 8 is formed, the positioning pressure-controlled cutting drill bit is retracted to withdraw a drilling rod, 3 fracturing drill holes 9 are continuously constructed according to the method, the four fracturing drill holes 9 form a square, and a hollow hole 16 is constructed in the middle of the four fracturing drill holes 9; when the cylindrical hole expanding section 8 is formed, water can be injected into the cylindrical hole expanding section 8 for freezing, and the ice column formed after freezing forms a self-sealing hole structure in the cylindrical hole expanding section 8, so that the drilling is facilitated to crack.
b. Equipment arrangement: arranging a temperature sensor 3 in a fracturing drill hole 9, wherein the temperature sensor 3 comprises a first temperature sensor 3-1 arranged at the deepest point position K4 of the fracturing drill hole, a second temperature sensor 3-2 arranged at the middle point position K3 of the fracturing drill hole and a third temperature sensor 3-3 arranged at the starting point position K1 of a reaming section; the device is characterized in that a data line 2 is respectively connected with a digital display type temperature instrument 1 outside a fracturing drill hole, a first capsule hole packer 11 and a second capsule hole packer 12 are connected in series and pass through a first water injection pipe 4, a second water injection pipe 5, a first low-temperature fluid freezing pipe 7 and a second low-temperature fluid freezing pipe 6 to be sent into the fracturing drill hole 9, the first capsule hole packer 11 and the second capsule hole packer 12 are respectively positioned at a position A and a position B of the fracturing drill hole 9, the first capsule hole packer 11 and the second capsule hole packer 12 are subjected to high-pressure hole sealing through a water injection system 13, the second low-temperature fluid freezing pipe 6 is connected with a discharge pipe 15 through a one-way valve 6-3, the first low-temperature fluid freezing pipe 7 is directly connected with the discharge pipe 15, the second one-way valve 7-3 is arranged at the pipe orifice of the discharge pipe 15 to control the discharge of the low-temperature fluid after heat exchange, and an, the low-temperature fluid pipes in the other multiple fracturing drill holes 9 are connected through the flow divider 14-2, and the four fracturing drill holes are subjected to freezing fracturing; the water outlet of the first water injection pipe 4 is arranged in a cylindrical hole expanding section 8 between a first capsule hole packer 11 and a second capsule hole packer 12, the water outlet of the second water injection pipe 5 is arranged at the position K3 of the middle point of a fracturing drill hole, a connecting port of the first low-temperature fluid freezing pipe 7 and the discharge pipe 15 is arranged between a first check valve 6-3 and a second check valve 7-3, and the first check valve 6-3 of the second low-temperature fluid freezing pipe 6 connected with the discharge pipe 15 is arranged in the cylindrical hole expanding section 8; the structure of the low-temperature fluid freezing pipe I7 and the low-temperature fluid freezing pipe II 6 is a spiral structure with good heat exchange performance, the low-temperature fluid freezing pipe I7 and the low-temperature fluid freezing pipe II 6 are connected through a discharge pipe 15, the flow of the low-temperature fluid is controlled by utilizing a one-way valve I6-3, so that the low-temperature fluid in the low-temperature fluid freezing pipe II 6 can flow into the low-temperature fluid freezing pipe I7, the low-temperature fluid in the low-temperature fluid freezing pipe I7 can not flow into the low-temperature fluid freezing pipe II 6, and the low-temperature fluid freezing pipe is made of a steel pipe with the pressure bearing; the temperature in the first cryogenic fluid freezing pipe 7 and the second cryogenic fluid freezing pipe 6 is less than or equal to minus 10 ℃, and the medium in the cryogenic fluid freezing pipes is liquid nitrogen, liquid carbon dioxide or cryogenic energy storage fluid.
c. Freezing the cylindrical hole expanding section: opening a valve 4-2 on a water injection pipe I4, connecting a quick connector I4-1 of the water injection pipe I4 with a water injection valve 13-1 on a water injection system 13, injecting high-pressure water into the cylindrical hole expanding section 8, monitoring a pressure gauge 4-3 on the water injection pipe I4, closing the valve 4-2 to stop water injection after the water pressure in the cylindrical hole expanding section reaches 1.2MPa and can be kept for 30 minutes, and removing the quick connector I4-1; opening a valve 7-2 on a cryogenic fluid freezing pipe I7, connecting a cryogenic fluid valve 14-1 of a cryogenic fluid tank wagon 14 with a quick coupling IV 7-1, injecting cryogenic fluid into the cryogenic fluid freezing pipe I7, and discharging the cryogenic fluid from a check valve 7-3; monitoring the temperature of the initial point position K1 of the reaming section by a digital display type temperature instrument 1, and closing a valve 7-2 when the temperature of the initial point position K1 of the reaming section is reduced to be lower than-2 ℃;
d. freezing and fracturing the drill hole: opening a valve 5-2 on a water injection pipe II 5, then connecting a quick connector II 5-1 on the water injection pipe II 5 with a water injection valve 13-1 on a water injection system 13, then injecting high-pressure water into the K3 position at the middle point of the fracturing drill hole 9, monitoring a pressure gauge 5-3 on the water injection pipe II 5, closing the valve 5-2 to stop water injection after the pressure displayed by the pressure gauge 5-3 reaches 1.2MPa and can be kept for 30 minutes, and removing the quick connector II 5-1; opening a valve 6-2 on a cryogenic fluid freezing pipe II 6, connecting a quick joint III 6-1 with a cryogenic fluid valve 14-1 of a cryogenic fluid tank wagon 14, injecting cryogenic fluid into the cryogenic fluid freezing pipe II 6, freezing water in a cracking drill hole 9, enabling the cryogenic fluid to flow into a cryogenic fluid freezing pipe I7 through a one-way valve I6-3 while freezing, continuously performing heat exchange between the cryogenic fluid and an ice column in a freezing state in the cryogenic fluid freezing pipe I7, maintaining the cylindrical reaming section 8 in the freezing state, and discharging the cryogenic fluid after heat exchange through the one-way valve II 7-3; monitoring the temperatures of the deepest point position K4 of the fracturing drill hole, the middle point position K3 of the fracturing drill hole and the initial point position K1 of the reaming section on a digital display type temperature instrument 1, and when the temperature values of 3 positions of a first temperature sensor 3-1 at the deepest point position K4 of the fracturing drill hole, a second temperature sensor 3-2 at the middle point position K3 of the fracturing drill hole and a third temperature sensor 3-3 at the initial point position K1 of the reaming section are all reduced to-2 ℃, finishing freezing and fracturing, and closing a valve 6-2;
e. and (3) drilling holes by circulating frost heaving and cracking: the frozen ice in the fracturing drill hole 9 gradually melts along with the temperature of the rock mass of the hard top plate 10 in the coal mine goaf, and when the digital display type temperature monitor 1 monitors that the temperatures of three position temperature sensors at the initial point K1 of the reaming section, the middle point K3 of the fracturing drill hole and the deepest point K4 of the fracturing drill hole are all increased to be higher than 3 ℃, the overall temperature in the fracturing drill hole 9 is all increased to be higher than 3 ℃, and one-time water ice phase change frost heaving fracturing cycle is completed;
f. and repeating the steps c-e, and performing frost heaving-melting-frost heaving cyclic cracking on the cracking drill hole 9 again until water flows out of the hollow hole 16.
As shown in fig. 7 and fig. 8, the flowing directions of the low-temperature fluid in the second 6 and the first 7 temperature fluid freezing pipes are shown, when the low-temperature fluid is injected into the first 7 temperature fluid freezing pipe, the low-temperature fluid is blocked by the first 6-3 check valve, cannot enter the second 6 temperature fluid freezing pipe, and can only flow out of the second 7-3 check valve; when the cryogenic fluid is injected into the cryogenic fluid freezing pipe II 6, the cryogenic fluid flows into the cryogenic fluid freezing pipe I7 through the check valve I6-3 to continuously freeze the cylindrical reaming section 8. The cylindrical hole expanding section 8 is frozen firstly, and then is frozen after fracturing and drilling, and when being frozen, the cylindrical hole expanding section maintains a frozen state to form a self-sealing hole structure.
Claims (9)
1. The low-temperature fracturing roof caving method for the hard roof of the coal mine goaf comprises the steps of adopting a digital display type temperature instrument (1), a temperature sensor (3), a water injection pipe, a low-temperature fluid freezing pipe, a capsule hole packer, a high-pressure water injection system (13) and a low-temperature fluid tank car (14), and is characterized by comprising the following steps of:
a. drilling construction: sequentially constructing a plurality of fracturing drill holes (9) and a hollow hole (16) on a hard top plate of a goaf, constructing the fracturing drill holes (9) to the deepest point position K4 of the fracturing drill holes in the hard top plate (10) of the goaf by using a common drill bit, withdrawing the common drill bit, replacing the common drill bit with a positioning pressure-controlled cutting drill bit for drilling, opening the cutting edge of the positioning pressure-controlled cutting drill bit when the positioning pressure-controlled cutting drill bit reaches the initial point K1 of a reaming section, reaming the fracturing drill holes (9) to the final point K2 of the reaming section, forming a cylindrical reaming section (8), retracting the reaming cutting edge of the positioning pressure-controlled cutting drill bit from a reaming section to withdraw from a drill rod, and constructing the hollow hole (16) in the middle of the plurality of fracturing drill holes (9) after the construction of the plurality of fracturing drill holes (;
b. equipment arrangement: arranging a temperature sensor (3) in a fracturing drill hole (9), connecting the temperature sensor with a digital display type temperature instrument (1) outside the fracturing drill hole through a data line (2), connecting a capsule hole packer I (11) and a capsule hole packer II (12) in series through a water injection pipe I (4), a water injection pipe II (5), a low-temperature fluid freezing pipe I (7) and a low-temperature fluid freezing pipe II (6) and then sending the two into the fracturing drill hole (9), respectively locating the capsule hole packer I (11) and the capsule hole packer II (12) at the point A and the point B of the fracturing drill hole (9), carrying out high-pressure hole sealing on the capsule hole packer I (11) and the capsule hole packer II (12) through a water injection system (13), connecting the low-temperature fluid freezing pipe II (6) with a discharge pipe (15) by utilizing a one-way valve I (6-3), and directly connecting the low-temperature fluid freezing pipe I (7) with the discharge pipe (15), a check valve II (7-3) is arranged at the pipe orifice of the discharge pipe (15) to control the discharge of the low-temperature fluid after heat exchange, an injection pump (14-3) is connected between the low-temperature fluid tanker (14) and the main pipeline, the low-temperature fluid tanker is connected with low-temperature fluid freezing pipes in other fracturing drill holes (9) through a flow divider (14-2), and the fracturing drill holes are frozen and fractured simultaneously;
c. freezing the cylindrical hole expanding section: opening a valve (4-2) on a water injection pipe I (4), connecting a quick connector I (4-1) of the water injection pipe I (4) with a water injection valve (13-1) on a water injection system (13), injecting high-pressure water into a cylindrical hole expanding section (8), monitoring a pressure gauge (4-3) on the water injection pipe I (4), closing the valve (4-2) to stop water injection after the water pressure in the cylindrical hole expanding section reaches 1.2MPa and can be kept for 30 minutes, and removing the quick connector I (4-1); opening a valve (7-2) on a cryogenic fluid freezing pipe I (7), connecting a cryogenic fluid valve (14-1) of a cryogenic fluid tank car (14) by using a quick coupling IV (7-1), injecting cryogenic fluid into the cryogenic fluid freezing pipe I (7), and discharging the cryogenic fluid after heat exchange from a check valve II (7-3); monitoring the temperature of the starting point position K1 of the reaming section by a digital display type temperature instrument (1), and closing a valve (7-2) when the temperature of the starting point position K1 of the reaming section is reduced to be lower than-2 ℃;
d. freezing and fracturing the drill hole: opening a valve (5-2) on a second water injection pipe (5), connecting a second quick connector (5-1) on the second water injection pipe (5) with a water injection valve (13-1) on a water injection system (13), injecting high-pressure water into the middle point K3 of the fracturing drill hole (9), monitoring a pressure gauge (5-3) on the second water injection pipe (5), closing the valve (5-2) to stop water injection after the pressure displayed by the pressure gauge (5-3) reaches 1.2MPa and can be kept for 30 minutes, and removing the second quick connector (5-1); opening a valve (6-2) on a cryogenic fluid freezing pipe II (6), connecting a quick joint III (6-1) with a cryogenic fluid valve (14-1) of a cryogenic fluid tank wagon (14), injecting cryogenic fluid into the cryogenic fluid freezing pipe II (6), freezing water in a fracturing drill hole (9), enabling the cryogenic fluid to flow into a cryogenic fluid freezing pipe I (7) through a check valve I (6-3) while freezing, continuously performing heat exchange between the cryogenic fluid and an ice column in a frozen state in the cryogenic fluid freezing pipe I (7) to maintain a cylindrical reaming section (8) in the frozen state, and discharging the cryogenic fluid after heat exchange through the check valve II (7-3); monitoring the temperatures of the deepest point K4 of the fracturing drill hole, the middle point K3 of the fracturing drill hole and the initial point K1 of the reaming section on the digital display type temperature instrument (1), and closing a valve (6-2) after freezing and fracturing are finished when the temperature values of 3 positions are all reduced to-2 ℃;
e. and (3) drilling holes by circulating frost heaving and cracking: the frozen ice in the fracturing drill hole (9) is gradually melted along with the temperature of the rock mass of the hard roof (10) of the coal mine goaf, and when the integral temperature in the fracturing drill hole (9) monitored by the digital display type temperature monitor (1) is all increased to be higher than 3 ℃, a one-time water ice phase change frost heaving fracturing cycle is completed;
f. and repeating the steps c-e, and performing frost heaving-melting-frost heaving cyclic cracking on the cracking drill hole (9) again until water flows out of the hollow hole (16).
2. The coal mine goaf hard roof low-temperature fracturing roof caving method according to claim 1, characterized in that: the temperature sensor (3) comprises a first temperature sensor (3-1) arranged at the deepest point position K4 of the fracturing drill hole, a second temperature sensor (3-2) arranged at the middle point position K3 of the fracturing drill hole and a third temperature sensor (3-3) arranged at the starting point position K1 of the reaming section.
3. The coal mine goaf hard roof low-temperature fracturing roof caving method according to claim 1, characterized in that: the water outlet of the first water injection pipe (4) is arranged in a cylindrical hole expanding section (8) between the front capsule and the rear capsule, the water outlet of the second water injection pipe (5) is arranged at the middle point K3 of the fracturing drill hole, a connecting port of the first low-temperature fluid freezing pipe (7) and the discharge pipe (15) is arranged between the first check valve (6-3) and the second check valve (7-3), and the first check valve (6-3) for connecting the second low-temperature fluid freezing pipe (6) and the discharge pipe (15) is arranged in the cylindrical hole expanding section (8).
4. The coal mine goaf hard roof low-temperature fracturing roof caving method according to claim 1, characterized in that: when the cylindrical hole expanding section (8) is formed, water is injected into the cylindrical hole expanding section (8) for freezing, and the icicle formed after freezing forms a self-sealing hole structure in the cylindrical hole expanding section (8).
5. The coal mine goaf hard roof low-temperature fracturing roof caving method according to claim 1, characterized in that: the structure of the first low-temperature fluid freezing pipe (7) and the second low-temperature fluid freezing pipe (6) is a spiral structure with good heat exchange performance, the two are connected through a discharge pipe (15), and the one-way flow of the low-temperature fluid is controlled by using a one-way valve (6-3), so that the low-temperature fluid in the second low-temperature fluid freezing pipe (6) can flow into the first low-temperature fluid freezing pipe (7), the low-temperature fluid in the first low-temperature fluid freezing pipe (7) cannot flow into the second low-temperature fluid freezing pipe (6), and the first low-temperature fluid freezing pipe (7) is made of steel, has the pressure bearing capacity of more than 1.2MPa, and.
6. The coal mine goaf hard roof low-temperature fracturing roof caving method according to claim 1 or 5, characterized in that: the temperature in the first (7) and second (6) freezing pipes is less than or equal to-10 ℃, and the medium in the freezing pipes is liquid nitrogen, liquid carbon dioxide or low-temperature energy storage fluid.
7. The coal mine goaf hard roof low-temperature fracturing roof caving method according to claim 1, characterized in that: the number of the fracturing drill holes (9) is 3-6.
8. The coal mine goaf hard roof low-temperature fracturing roof caving method according to claim 1 or 7, characterized in that: the aperture of the plurality of fracturing drill holes (9) is 80mm, and the distance between the adjacent fracturing drill holes (9) is 1-2 m.
9. The coal mine goaf hard roof low-temperature fracturing roof caving method according to claim 1, characterized in that: the aperture of the one empty hole (16) is 2-3 times of the aperture of the fracturing drill hole.
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| PCT/CN2020/113348 WO2021184694A1 (en) | 2020-03-16 | 2020-09-04 | Cryogenic fracturing and roof caving method for hard roof in goaf of coal mine |
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