A method and device for completing a roadway-type horizontal well

Abstract

The present invention discloses a method and device for forming a well in a coalbed methane roadway-type horizontal well. The drill pipe with a cutter slowly rotates and retreats in the open-hole horizontal section, causing the coal and rock around the open hole to be scraped off and the coal cuttings to return to the ground with the mud, and the open-hole horizontal section is enlarged into a roadway-type horizontal well. The method includes the first step: drilling an open-hole horizontal well; the second step: lowering a drill pipe with a spray gun at the end to the farthest end of the horizontal section of the open-hole horizontal well; the third step: starting a mud pump and injecting high-pressure sand-mixed mud into the drill pipe; the fourth step: slowly rotating the drill pipe and slowly lifting it with a top drive rig, so that the hydraulic cutter slowly rotates and retreats, scraping the coal and rock around the horizontal section of the open-hole horizontal well to form a roadway-type horizontal well meeting the design requirements. The present invention creates space for the stress release of the coal seams on both sides of the horizontal well, achieving the purpose of increasing the coal seam permeability and significantly increasing the gas production per well in the area.

Description

Technical Field

[0001] The present invention relates to the technical field of coalbed methane development, and particularly relates to a method and device for forming a well in a roadway-type horizontal well for coalbed methane. Background Art

[0002] The output of coalbed methane wells around coal mines and on both sides of coal mine roadways has increased abnormally, making it a widely recognized consensus in the industry to develop coalbed methane by stress release. However, except for coal mine roadway excavation or mining, there is no ground development method to achieve stress release.

[0003] For the coal seam stress release device and method (CN201811093392.5), the main approach is to use a double-packer in cooperation with a screen pipe string. Fluids are ejected at high speed from several small holes, and the broken coal and rock enter the annulus between the casing and the tubing through large holes and return to the ground. In this method, the small holes are extremely easy to expand, resulting in a reduced flow rate and a limited injection distance, which is insufficient to break the coal and rock at a distance and cannot achieve large-scale stress release of the coal and rock on both sides of the horizontal section.

[0004] Chinese Patent Publication No. CN 101709629A is a method and equipment for reverse circulation air-powered cavity formation in coalbed methane wells. By using procedures such as gas injection, pressure buildup, blowdown, and well flushing, cavities are formed around the coalbed methane wells. However, such methods cannot solve the problem of limited cavity formation range in coal seams, with a small cavity formation force, a low reaming rate, and being difficult to control, and cannot meet the purpose of large-area and long-distance uniform cavity formation in coal seams.

[0005] Chinese Patent Publication No. CN104278952A is a hydraulic-mechanical combined coal seam cavity formation device and method. Such methods have a good effect on single-point cavity formation in vertical wells. However, in the horizontal well section, it is difficult for the mechanical cutter wings to reset, and the coal cuttings are not easily returned. The mechanical equipment will wear, deform, and even break during long-term downhole operations, causing complex accidents, and cannot be used for continuous multi-point cavity formation, let alone for forming a well in a roadway-type horizontal well.

[0006] None of the above methods can achieve a roadway-type horizontal well similar to a coal mine roadway. Therefore, it is necessary to provide a method for forming a well in a roadway-type horizontal well. Summary of the Invention

[0007] The first object of the present invention is to provide a drill pipe for forming a well in a roadway-type horizontal well that can achieve stress release on both sides of the coal seam.

[0008] To achieve the above object, the present invention is configured as follows: A method for forming a well in a roadway-type horizontal well, during the well formation process, a drilling device including a drill pipe and a spray gun is required. The drill pipe slowly rotates and retreats in the open-hole horizontal section with a cutter, causing the coal and rock around the open hole to be scraped and fall off, and the coal cuttings return to the ground with the mud, and the open-hole horizontal section is expanded into a roadway-type horizontal well. The method includes the following steps:

[0009] Step 1: Drill a barehole horizontal well using conventional methods and use mud to stabilize the wellbore of the barehole horizontal well;

[0010] Step 2: Lower the drill pipe to the farthest end of the horizontal section of the barehole horizontal well;

[0011] Step 3: Start the mud pump connected to the drill pipe on the ground, inject high-pressure sand-mixed mud into the drill pipe, and the mud sprays out at high speed from the two radial nozzles of the spray gun to form a hydraulic cutter for cutting; the mud sprays out from the axial nozzle of the spray gun to play a role in impacting and crushing the coal blocks in the roadway;

[0012] Step 4: Slowly rotate and slowly lift the drill pipe using a top drive rig, so that the hydraulic cutter slowly rotates and retreats, scraping the surrounding coal and rock of the horizontal section of the barehole horizontal well to form a roadway-type horizontal well that meets the design requirements. During the retreat process of the drill pipe, the scraped coal chips return to the ground along with the liquid in the annulus between the drill pipe and the barehole, and the conventional barehole horizontal section is enlarged into a roadway-type horizontal well;

[0013] Step 5: The coal chips and mud return to the ground together, enter a filtering vibrating screen to filter out the coal chips, and the mud continues to enter the mud pump for recycling;

[0014] Step 6: Monitor the mud properties in real time and add chemicals to maintain the sand-carrying performance and the performance of stabilizing the wellbore;

[0015] Step 7: Measure the volume of the returned coal chips, infer whether the diameter of the roadway-type horizontal well reaches the design requirements, and timely adjust the pressure, displacement, viscosity, and sand ratio;

[0016] Step 8: After all the horizontal sections in the coal seam are cut into roadways, lift out the drill pipe;

[0017] Step 9: Lower the casing to the junction of the rock and the coal seam and perform cementing;

[0018] Step 10: Lower the drill pipe with the drill bit and screen pipe into the well, lower the screen pipe into the roadway-type horizontal section, and hang the upper part of the screen pipe in the casing;

[0019] Step 11: Hand over the well to the next process and carry out the following lifting equipment and drainage and production work.

[0020] Further, the mud sprays out at high speed from the two radial nozzles of the spray gun in Step 3, and is characterized in that: the pressure difference between the inlet and outlet of the radial nozzle is between 10 MPa and 40 MPa; it has the performance of stabilizing the wellbore, and the viscosity of the mud is maintained between 20 mPa·s and 200 mPa·s.

[0021] Further, the measurement of the volume of the returned coal cuttings in the seventh step and the calculation of whether the diameter of the roadway-type horizontal well meets the design requirements mainly include: calculating the roadway volume using the unit length and the designed diameter of the roadway-type horizontal well, multiplying it by the density of coal and rock to obtain the mass of coal required for the designed well completion; weighing dozens of liters of coal cuttings to calculate the apparent density value of the coal cuttings, measuring the external dimensions of the coal cuttings heap body for the roadway-type horizontal well per unit length, and calculating its volume; dividing the volume of the heap body by the apparent density to obtain the mass of the coal cuttings; if the mass of coal required for the design is equivalent to the mass of the coal cuttings produced by cavity formation, it can be considered that the diameter of the roadway-type horizontal well meets the design requirements; if it is judged that the diameter is less than the design requirements, increase the pressure and displacement of the pumped mud; otherwise, decrease them.

[0022] Further, for the cementing step described in the ninth step, if the formation above the coal seam is unstable, the cementing in the ninth step can be advanced to before the second step, that is, first cement the vertical well section, and then lower the drill pipe and the spray gun to scrape the open-hole horizontal section into a roadway horizontal well.

[0023] The present invention further includes a device for well completion of a roadway-type horizontal well. The device for well completion is used to implement the steps of the method for well completion of a roadway-type horizontal well, and is characterized in that it mainly includes a mud pump, a top drive drilling rig, a high-pressure water hose, a swivel, a drill pipe and a spray gun.

[0024] Further, the front end of the drill pipe body is threadedly connected to the spray gun; the spray gun is provided with radial nozzles and axial nozzles. There are two radial nozzles which are symmetrically distributed, and the axial nozzle extends forward along the axis of the spray gun.

[0025] Further, the spray gun includes a gun body. A jet cavity is arranged inside the gun body. The axial nozzle extends forward at the front end of the jet cavity, and the radial nozzles which extend symmetrically to both sides are arranged in the middle of the jet cavity.

[0026] Further, a centralizer ring is sleeved on the outer wall of the spray gun at the rear end of the radial nozzle. The outer diameter of the centralizer ring is larger than the projected outer diameter of the radial nozzle and also larger than the outer diameter of the drill pipe collar.

[0027] Further, each of the radial nozzles is composed of an inner nozzle, an outer nozzle and an outer sleeve. The inner nozzle and the outer nozzle are respectively threadedly connected to the outer sleeve. A cavity is formed between the inner nozzle and the outer nozzle, and the diameter of the cavity is twice the diameter of the inner nozzle or the outer nozzle; the diameter of the radial nozzle of the spray gun is 8 mm to 18 mm.

[0028] Beneficial effects:

[0029] The present invention is based on the theory of stress release for developing coalbed methane. A large amount of coal cuttings are removed from the horizontal section to complete the construction of a roadway-type horizontal well, creating space for stress release in the coal seams on both sides of the horizontal well, aiming to increase the coal seam permeability and the gas production per well in the area by more than three times.

[0030] The present invention creatively proposes to use a hydraulic cutter in an open-hole well without casing to continuously scrape coal and rock, and continuously and slowly rotate and pull back in the open-hole well to form a continuous large-diameter roadway-type horizontal well, realizing stress release on both sides and regionally increasing the permeability of large areas of coal seams on both sides.

[0031] Multiple roadway-type horizontal wells are connected to form a roadway. The permeability of the coal and rock on both sides is greatly improved, and coalbed methane is quickly extracted. Coal mines can directly excavate roadways for coal mining, ventilation, etc. near the roadway-type horizontal wells, eliminating the excavation of lower rock roadways, which will bring very considerable economic and safety benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the process for forming a roadway-type horizontal well in Example 1;

[0033] Figure 2 It is a schematic diagram after the formation of a roadway-type horizontal well;

[0034] Figure 3 It is a schematic diagram of the spray gun structure;

[0035] Figure 4 It is a schematic diagram of the nozzle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The following further elaborates on the specific embodiments of the present invention in conjunction with the drawings. However, the present invention is not limited to these embodiments. Any improvement or substitution based on the basic spirit of this embodiment, such as mechanical cutters other than hydraulic cutters, still falls within the scope protected by the claims of the present invention.

[0037] Example 1: As Figure 3-4 shown, this embodiment provides a device for forming a roadway-type horizontal well, and specifically provides: a drill pipe for forming a roadway-type horizontal well, with a spray gun arranged at the end of the drill pipe. The spray gun is provided with radial nozzles and axial nozzles. There are two radial nozzles which are symmetrically distributed, and the axial nozzle extends forward along the axis of the spray gun.

[0038] See attached Figure 3, the spray gun 4 includes a gun body 43. A jet cavity 46 is arranged inside the gun body, and radial nozzles 41 symmetrically extending towards both sides are arranged in the middle of the jet cavity 46. The radial nozzles are designed to cut the coal seam at a long distance under submerged conditions. An axial nozzle 42 extending forward is further arranged at the front end of the jet cavity, and the front end refers to the end far from the drill pipe.

[0039] As another implementation manner in this embodiment, a tapered screw hole 45 is arranged at the rear end of the jet cavity, which is convenient for connecting with the head of the drill pipe body.

[0040] As another implementation manner in this embodiment, a centralizer 44 is sleeved outside the gun body. The centralizer is located at the rear end of the radial nozzle. The outer diameter of the centralizer is larger than the projected outer diameter of the radial nozzle. At the same time, the outer diameter of the centralizer is about larger than the outer diameter of the drill pipe collar and significantly smaller than the open hole inner diameter. One of the functions of the centralizer is to protect the nozzle, and the second is to prevent large coal chips from entering the annulus layer to avoid the occurrence of sticking accidents.

[0041] See attachment Figure 4 , as another implementation manner in this embodiment, the two symmetrically arranged radial nozzles are respectively composed of an inner nozzle 41-1, an outer nozzle 41-2 and an outer sleeve. The inner nozzle and the outer nozzle are respectively threadedly connected to the outer sleeve, and a cavity 41-3 is formed between the inner and outer nozzles. The diameter of the cavity is about twice the diameter of the nozzle. The inner nozzle is a primary nozzle and the outer nozzle is a secondary nozzle. The cavitation blasting force at the outlet of the primary nozzle provides a thrust for the secondary nozzle to enhance the jetting distance of coal breaking at a long distance.

[0042] Embodiment 2: As Figure 1-4 shown, this embodiment provides a method for forming a roadway-type horizontal well. The coal seam 2 is located below the rock stratum 1. The method includes the following steps

[0043] The first step: Drill an open hole horizontal well by a conventional method and use mud to stabilize the wellbore of the open hole horizontal well.

[0044] See attachment Figure 1 , the open hole horizontal well X includes an X1 vertical well section and an X2 open hole horizontal section.

[0045] The second step: Lower a drill pipe with a spray gun at the end to the farthest end of the horizontal section of the open hole horizontal well. The drill pipe adopts the drill pipe in Embodiment 1.

[0046] See attachment Figure 1 , a spray gun 4 is arranged at the head of the drill pipe 3. The spray gun at the head of the drill pipe enters from the ground inlet of the vertical well section to the farthest end (the front end) of the open hole horizontal section of the open hole horizontal well.

[0047] Step 3: Start the mud pump located on the ground and connected to the drill pipe, inject high-pressure sand-mixed mud into the drill pipe. The mud sprays out at high speed from the two radial nozzles of the spray gun to form a hydraulic cutter, which plays a cutting role; the mud sprays out from the axial nozzle of the spray cavity to play a role in impacting and crushing the coal blocks in the roadway.

[0048] The mud sprayed out at high speed from the radial nozzles forms a hydraulic cutter to scrape the coal and rock. While the mud after jet pressure relief returns to the ground through the annulus formed by the drill pipe and the open hole, it carries the scraped coal chips back to the ground. The function of the axial nozzle is to increase the flow velocity of the annulus fluid and improve the ability to carry coal chips. If the flow rate of the radial nozzles is sufficient to enable the annulus fluid to carry the coal chips, the axial nozzles can be not set.

[0049] Step 4: Use the top drive rig to slowly rotate the drill pipe and slowly lift it at the same time, so that the hydraulic cutter slowly rotates and retreats, scraping the coal and rock around the horizontal section of the open hole horizontal well to form a roadway-type horizontal well that meets the design requirements. During the retreat process of the drill pipe, the scraped coal chips return to the ground along with the fluid in the annulus between the drill pipe and the open hole, and the conventional open hole horizontal section is enlarged into a roadway-type horizontal well.

[0050] See attachment Figure 2 , roadway-type horizontal well X h , including a vertical well section X1 same as the open hole horizontal well, and an enlarged roadway-type horizontal section X3. There may be fallen coal blocks 6 in the roadway-type horizontal section X3.

[0051] Step 5: The coal chips and the mud return to the ground together, enter the filtering vibrating screen to filter out the coal chips, and the mud continues to enter the mud pump for recycling.

[0052] Step 6: Monitor the mud performance in real time, add chemicals to maintain the sand-carrying performance and the performance of stabilizing the wellbore.

[0053] Step 7: Measure the volume of the returned coal chips, calculate whether the diameter of the roadway-type horizontal well reaches the design requirements, and adjust the pressure, displacement, viscosity, and sand ratio in a timely manner.

[0054] In the seventh step, the calculation method for the coal production quality required for well completion design is: calculate the roadway volume using the unit length and the design diameter of the roadway-type horizontal well, and then multiply it by the coal and rock density (i.e., the true density, generally 1.4 g / cm 3The actual coal cuttings quality calculation method is as follows: Weigh dozens of liters of coal cuttings to calculate the apparent density (or bulk density) value of the coal cuttings; Measure the external dimensions of the coal cuttings pile produced by the horizontal well in the roadway type per unit length and calculate its volume; Multiply the volume of the pile by the apparent density to obtain the mass of the coal cuttings, which is the actual mass of the coal cuttings produced by cavity making. If the designed required coal output mass is equivalent to the mass of the coal cuttings produced by cavity making, it can be considered that the diameter of the horizontal well in the roadway type meets the design requirements. If it is less than the design requirements, increase the pressure and displacement of the pumped slurry; Otherwise, decrease them.

[0055] Among them, the viscosity of the slurry is maintained between 20 mPa·s and 200 mPa·s, generally controlled at about 35 mPa·s to ensure carrying rock and reducing flow resistance. According to the distance of remote coal breaking required, the best sand ratio range is given in laboratory experiments. After the abrasive sand and coal cuttings are returned to the ground together with the slurry and settle at the bottom of the liquid-solid separator, the abrasive sand needs to be added again according to the design ratio when injecting the slurry to enable the high-speed jetting slurry to achieve the best coal breaking effect.

[0056] The eighth step: After all the horizontal sections in the coal seam are cut into roadways, pull out the drill pipe.

[0057] The ninth step: Lower the casing to the junction of the rock and the coal seam and perform cementing.

[0058] If the upper rock formation is unstable, the ninth step can be advanced to the second step. According to the data of the surrounding exploration wells, during the drilling process before encountering the coal seam, if there are obvious collapses, losses, and diameter contractions in the upper rock formation, it is regarded as unstable and is not conducive to maintaining a complete open hole state for a long time, and it is necessary to lower the casing and perform cementing in time. During the drilling process of this well, use the same method to further judge the stability of the rock formation. If the upper rock formation is stable and can maintain a stable and complete open hole well for a long time, the casing can be temporarily not lowered, and operations such as tripping the pipe string and jetting to form a cavity can be carried out in a larger annular space.

[0059] The tenth step: Lower the drill pipe with the drill bit and screen pipe into the well, lower the screen pipe 5 into the horizontal section of the roadway type, and the upper part of the screen pipe 5 is suspended in the casing; The length of the screen pipe is designed to be about one-tenth of the length of the horizontal section.

[0060] The eleventh step: Hand over the well to the next process and carry out the following lifting equipment and drainage and production work.

[0061] Pay attention when designing specific parameters:

[0062] 1) Ensure that the pressure difference between the inlet and outlet of the radial nozzle is between 10 MPa and 40 MPa to achieve the best coal breaking effect. Options include but are not limited to 10 MPa, 20 MPa, 30 MPa, and 40 MPa;

[0063] 2) The pump pressure is equal to the flow friction of the mud in the drill pipe + the nozzle pressure difference + the friction of the mud flowing back up through the annulus;

[0064] 3) The inner diameter of the drill pipe and the diameter of the open hole should be reasonably matched to keep the friction at the lowest level;

[0065] 4) The radial nozzle diameter is 8 mm to 18 mm, and 8 mm, 10 mm, 13 mm, 15 mm, 18 mm, etc. can be selected but are not limited to;

[0066] 5) The screen holes of the shale shaker are smaller than the radius of the radial nozzle;

[0067] 6) The abrasive particle size is smaller than the radius of the radial nozzle. According to the coal and rock characteristics of the specific implementation area, the radius of the roadway horizontal well (i.e., the jet coal-breaking distance), the drill pipe model, the open hole diameter, and the mud performance parameters, the specific nozzle size is given by experiments.

[0068] This embodiment is based on the theory of stress release for developing coalbed methane. A large amount of coal cuttings in the horizontal section are removed to complete the construction of the roadway-type horizontal well, creating space for the stress release of the coal seams on both sides of the horizontal well, achieving the purpose of increasing the coal seam permeability and significantly improving the gas production per well in the area. This embodiment creatively proposes to use a hydraulic cutter in an open hole without casing to continuously scrape coal and rock, and continuously and slowly rotate and pull back in the open hole to make it a continuous large-diameter roadway-type horizontal well, realizing the stress release on both sides and regionally increasing the permeability of large areas of coal seams on both sides. Multiple roadway-type horizontal wells are connected into a roadway, the permeability of the coal and rock on both sides is greatly improved, and coalbed methane is quickly produced. The coal mine can directly excavate roadways for coal mining, ventilation, etc. near the roadway-type horizontal well, reducing the excavation of rock roadways in the lower part of the coal seam, which will bring very considerable economic and safety benefits.

Claims

1. A method for forming a roadway-type horizontal well. During the well formation process, a drilling device including drill pipes and spray guns is required. It is characterized in that: The drill pipe with a cutter slowly rotates and retreats in the open-hole horizontal section, scraping off the coal and rock around the open hole. The coal cuttings return to the ground with the mud, and the open-hole horizontal section is enlarged into a roadway-type horizontal well. A method for forming a roadway-type horizontal well includes the following steps: Step 1: Drill an open-hole horizontal well using a conventional method and use mud to stabilize the wellbore of the open-hole horizontal well. Step 2: Lower the drill pipe to the farthest end of the horizontal section of the open-hole horizontal well. Step 3: Start the mud pump connected to the drill pipe on the ground, inject high-pressure sand-mixed mud into the drill pipe. The mud sprays out at high speed from the two radial nozzles of the spray gun to form a hydraulic cutter for cutting. The mud sprays out from the axial nozzle of the spray gun to impact and break the coal blocks in the roadway. Step 4: Use the top drive rig to slowly rotate the drill pipe and slowly lift it at the same time, so that the hydraulic cutter slowly rotates and retreats, scraping the coal and rock around the horizontal section of the open-hole horizontal well to form a roadway-type horizontal well that meets the design requirements. During the retreat of the drill pipe, the scraped coal cuttings return to the ground with the liquid in the annulus between the drill pipe and the open hole. The conventional open-hole horizontal section is enlarged into a roadway-type horizontal well. Step 5: The coal cuttings and the mud return to the ground together, enter the filtering vibrating screen to filter out the coal cuttings, and the mud continues to enter the mud pump for recycling. Step 6: Monitor the mud performance in real time and add chemicals to maintain the sand-carrying performance and the performance of stabilizing the wellbore. Step 7: Measure the volume of the returned coal cuttings, calculate whether the diameter of the roadway-type horizontal well reaches the design requirements, and adjust the pressure, displacement, viscosity, and sand ratio in a timely manner. Step 8: After all the horizontal sections in the coal seam are cut into roadways, lift out the drill pipe. Step 9: Lower the casing to the junction of the rock and the coal seam and perform cementing. Step 10: Lower the drill pipe with the drill bit and the screen pipe into the well, and lower the screen pipe into the roadway-type horizontal section. The upper part of the screen pipe is suspended in the casing. Step 11: Hand over the well to the next process and carry out the following lifting equipment and drainage and production work.

2. The method for forming a roadway-type horizontal well according to claim 1. The mud in the third step is ejected at high speed from the two radial nozzles of the spray gun. It is characterized in that: The pressure difference between the inlet and outlet of the radial nozzle is between 10 MPa and 40 MPa; it has the performance of stabilizing the wellbore, and the viscosity of the mud is maintained between 20 mPa·s and 200 mPa·s.

3. The method for forming a roadway-type horizontal well according to claim 1. Measuring the volume of the returned coal cuttings in the seventh step and calculating whether the diameter of the roadway-type horizontal well meets the design requirements mainly includes: Calculate the roadway volume using the unit length and the designed diameter of the roadway-type horizontal well, and multiply it by the density of the coal and rock to obtain the designed coal output quality required for well completion. Weigh dozens of liters of coal cuttings to calculate the apparent density value of the coal cuttings. Measure the external dimensions of the coal cuttings pile mined from the roadway-type horizontal well per unit length and calculate its pile volume. Divide the pile volume by the apparent density to obtain the coal cuttings mass. If the designed coal output quality is equivalent to the coal cuttings mass mined from the cavity, it can be considered that the diameter of the roadway-type horizontal well reaches the design requirements. If it is judged that the diameter is less than the design requirements, increase the pressure and displacement of the pumped mud; otherwise, decrease them.

4. The method for forming a roadway-type horizontal well according to claim 1. The well cementing in the ninth step. It is characterized in that: If the formation above the coal seam is unstable, the cementing in Step 9 can be advanced to before Step 2, that is, first cement the vertical well section, and then lower the drill pipe and the spray gun to scrape the open-hole horizontal section into a roadway horizontal well.

5. A device for forming a roadway-type horizontal well. The well-forming device is used to implement the steps of the method for forming a roadway-type horizontal well according to any one of claims 1 to 4. It is characterized in that: It mainly includes a mud pump, a top drive rig, a high-pressure hose, a swivel, a drill pipe, and a spray gun.

6. The device for forming a roadway-type horizontal well according to claim 5. It is characterized in that: The front end of the drill pipe body is threadedly connected to the spray gun; the spray gun is provided with radial nozzles and axial nozzles, there are two radial nozzles and they are symmetrically distributed, and the axial nozzle extends forward along the axis of the spray gun.

7. The device for forming a roadway-type horizontal well according to claim 5. It is characterized in that: The spray gun includes a gun body, a jet cavity is arranged inside the gun body, the axial nozzle extends forward from the front end of the jet cavity, and the radial nozzles that symmetrically extend towards both sides are arranged in the middle of the jet cavity.

8. The device for forming a roadway-type horizontal well according to claim 5. It is characterized in that: A centralizing ring is sleeved on the outer wall of the spray gun at the rear end of the radial nozzle, and the outer diameter of the centralizing ring is larger than the projected outer diameter of the radial nozzle and also larger than the outer diameter of the drill pipe coupling.

9. The device for forming a roadway-type horizontal well according to claim 5. It is characterized in that: The radial nozzles are respectively composed of an inner nozzle, an outer nozzle and an outer sleeve. The inner nozzle and the outer nozzle are respectively threadedly connected to the outer sleeve, a cavity is formed between the inner and outer nozzles, and the diameter of the cavity is twice the diameter of the inner nozzle or the outer nozzle; the diameter of the radial nozzles of the spray gun is 8 mm to 18 mm.

Images