CN117514120B - A vertical well methane in-situ explosion fracturing device and method - Google Patents

Abstract

The application discloses a straight well methane in-situ blasting fracturing device and method, which belong to the field of blasting fracturing and comprise a sleeve and perforations uniformly formed on the outer circular surface of the sleeve, wherein an upper oil pipe and a lower oil pipe are arranged in the sleeve, and are rotationally connected through an arranged ventilation switching mechanism; a lower packer is arranged at the inner bottom of the sleeve, an upper packer is arranged at the upper end of the inner part of the sleeve, and an upper oil pipe penetrates through the upper packer; the lower end of the inner part of the upper oil pipe is provided with a first piston in a sliding manner, and the first piston is provided with a first electromagnetic valve; the upper end in the upper oil pipe is slidably provided with a second piston. According to the application, the sufficiency of methane gas in the explosion process can be ensured, the integral oil pipe is split into the upper oil pipe and the lower oil pipe, and the communication state of the upper oil pipe and the lower oil pipe is switched by the ventilation switching mechanism, so that the separate conveying temporary storage work of combustion-supporting gas and methane gas is respectively completed, and the safety of construction operation is ensured.

Description

A vertical well methane in-situ explosion fracturing device and method

Technical Field

The present invention relates to the field of explosive fracturing, and more specifically to a vertical well methane in-situ explosive fracturing device and method.

Background technique

Since tight gas, shale gas and other reservoirs generally have the characteristics of low porosity and low permeability, fracturing is a necessary means to achieve their commercial exploitation; explosive fracturing technology, also known as pneumatic fracturing, pneumatic pulse fracturing, thermochemical treatment, propellant fracturing, etc., is a new technology that uses high-temperature and high-pressure gases generated by the rapid combustion of gunpowder or rocket propellants to increase the production and injection of oil, gas and water wells.

The explosive fracturing technology can effectively transform the reservoirs of dense, low-permeability and other complex oil and gas reservoirs by fracturing the reservoirs with high instantaneous explosive pressure, breaking through stress concentration and promoting the development of complex fracture networks. It is low-cost and pollution-free. However, the existing explosive fracturing process usually injects explosives formed by mixing a combustion agent and an oxidant into the bottom formation at the same time. Explosives are generally military products and cannot avoid safety issues during transportation and injection. The detonation range is limited. There are great safety hazards in the production, transportation, storage and delivery processes, and high requirements are also placed on the construction management capabilities of the staff.

In response to the above problems, a Chinese patent with authorization announcement number CN112983383B discloses a vertical well methane in-situ explosive fracturing device and method. The device uses a pump truck to pump low-density well-killing fluid from the casing annulus to replace the original well-killing fluid. During this process, the mixed fluid of the target layer is discharged through the one-way valve of the detonator. When methane gas is detected at the wellhead, high-density well-killing fluid is injected, the one-way valve is closed, and the gas storage in the detonator cavity and the casing annulus is completed. Finally, a rod-throwing operation is carried out from the wellhead. The huge impact force causes the lower pressure plate to shear and break, and the combustion-aiding agent together with the clamp quickly contacts the striker, triggering an explosion of methane gas in the formation. The explosive gas flow is ejected at high speed along the pores of the casing, causing the formation to fracture due to impact.

The existing technology has proposed a new combustion and explosion method, which makes the combustion and explosion fracturing operation safer and more efficient, achieving the traditional combustion and explosion effect while reducing the construction risk and cost. However, in actual use, due to the very dense shale reservoir, after perforating the new well, it is not possible to analyze enough methane gas for combustion and explosion fracturing. At the same time, the amount of solid combustion aids provided by the existing technology cannot be sufficient, which will still affect the combustion and explosion effect. Therefore, in the first round of combustion and explosion, it is necessary to inject methane gas into the well section of the target layer and inject gas combustion aids such as oxygen for combustion and explosion. However, the depth of shale gas wells is deep, and the diameter of the wellbore is small. It is difficult to use two sets of pipe strings to transport methane gas and oxygen respectively. Only one set of pipe strings can be used to transport methane gas and gas combustion aids by injecting them successively or simultaneously. However, no matter which method is used, methane gas and gas combustion aids will be mixed in the entire wellbore, so the vibration and friction of the pipe string during the construction process may detonate methane gas and combustion aids. Since the entire wellbore is filled with gas during the transportation process, if an explosion occurs accidentally, the pressure will be transmitted through the wellbore to the wellhead and ground equipment, causing construction failure or even a major safety accident, bringing great safety risks to the entire transportation process.

Summary of the invention

In view of the problems existing in the prior art, the object of the present invention is to provide a vertical well methane in-situ explosion fracturing device and method.

To solve the above problems, the present invention adopts the following technical solutions.

A vertical well methane in-situ explosion fracturing device comprises a casing and perforations evenly arranged on the outer circumferential surface of the casing, an upper oil pipe and a lower oil pipe are arranged inside the casing, and the upper oil pipe and the lower oil pipe are rotatably connected through a ventilation switching mechanism;

A lower packer is provided at the bottom of the casing, an upper packer is provided at the upper end of the casing, and an upper oil pipe runs through the upper packer; a first piston is slidably provided at the lower end of the upper oil pipe, and a No. 1 solenoid valve is provided on the first piston; a second piston is slidably provided at the upper end of the upper oil pipe;

Two connecting excitation mechanisms are symmetrically arranged on both sides of the lower oil pipe, and the two connecting excitation mechanisms jointly support the preliminary solid combustion aid; a striker unit is arranged at the bottom of the lower oil pipe; a limiting groove is arranged inside the lower packer, and a limiting block corresponding to the limiting groove is fixedly connected to the bottom of the outer cylindrical surface of the lower oil pipe.

Furthermore, the ventilation switching mechanism includes a mounting flange fixedly connected to the bottom edge of the upper oil pipe, a rotation groove is provided inside the mounting flange, an inner semicircular cover body is fixedly connected to the top of the lower oil pipe, and the top of the inner semicircular cover body is rotatably connected to the mounting flange through the rotation groove; an outer semicircular cover body is fixedly connected to the bottom of the outer circular surface of the mounting flange; and an anti-leakage mechanism cooperating with the inner semicircular cover body is also provided on the inner arc surface of the outer semicircular cover;

A rotating connecting column is fixedly connected to the bottom of the inner circular surface of the upper oil pipe, and a fixed semicircular cover plate is fixedly connected to the top of the lower oil pipe. The lower end of the rotating connecting column passes through the fixed semicircular cover plate and is rotatably connected to the fixed semicircular cover plate, and the bottom of the rotating connecting column is fixedly connected to the movable semicircular cover plate.

Furthermore, the movable semicircular cover plate and the outer semicircular cover body are symmetrically arranged about the rotating connecting column, and the fixed semicircular cover plate and the inner semicircular cover body are arranged on the same side of the rotating connecting column.

Furthermore, the anti-leakage mechanism includes two longitudinal separation airbags fixedly connected to the two ends of the inner arc surface of the outer semicircular cover, and an annular separation airbag fixedly installed at the bottom of the inner arc surface of the outer semicircular cover, and the longitudinal separation airbags and the annular separation airbags are initially in a negative pressure state; an electromagnetic one-way valve is provided at the bottom of the annular separation airbag, and a No. 2 push switch is provided on the upper surface of the movable semicircular cover.

Furthermore, when the outer semicircular cover body forms a closed passage with the inner semicircular cover body after rotation, the second push switch is just pressed by the fixed semicircular cover plate.

Furthermore, an anti-rotation mechanism is provided in the rotating groove to prevent the lower oil pipe from rotating during the arrangement process. The anti-rotation mechanism includes an electromagnet ring arranged at the top of the rotating groove, and a lower magnet corresponding to the electromagnet ring is provided at the top of the inner semicircular cover body, and the magnetic field of the electromagnet ring is adsorbed by the lower magnet after power is turned on; a push switch No. 1 is also provided in the middle position at the bottom of the limit groove to control the working state of the electromagnet ring.

Furthermore, a feedback mechanism for controlling the operation of the ventilation switching mechanism is fixedly provided at the bottom end of the upper oil pipe. The feedback mechanism includes a lower ring body fixedly connected to the bottom of the inner circular surface of the upper oil pipe, and evenly distributed pressure springs are fixedly connected to the upper surface of the lower ring body. The upper ends of the pressure springs are jointly fixedly connected to the upper ring body, a pressure sensor is provided on one side of the upper surface of the lower ring body, and the upper ring body is provided with a pressure column corresponding to the pressure sensor.

Furthermore, the connecting excitation mechanism includes a connecting port opened on the side wall of the lower oil pipe, the top of the connecting port is connected to an arc-shaped partition plate by a hinge, the bottom of one side of the arc-shaped partition plate is fixedly connected to a counterweight block, and the top of the other side of the arc-shaped partition plate is fixedly connected to a supporting extrusion plate, and the supporting extrusion plates in the two connecting excitation mechanisms support the preliminary solid combustion agent, and an arc-shaped limit plate is fixedly connected to the inner circular surface of the lower oil pipe near the bottom of the connecting port; an anti-impact mechanism is also provided at the upper end of the lower oil pipe.

Furthermore, the anti-impact mechanism includes a lower fixing ring and an upper fixing ring fixed to the side wall of the lower oil pipe. The upper surface of the lower fixing ring is fixed with evenly distributed impact springs in a ring shape. The upper ends of the impact springs are commonly fixed with an impact orifice plate. When the impact spring is at its original length, the impact orifice plate is flush with the upper surface of the upper fixing ring.

A method for using a vertical well methane in-situ explosion fracturing device, characterized by comprising the following steps:

S1: Lower the casing, upper tubing, lower tubing and related components into the well in sequence and complete the layout;

S2: Pump gaseous combustion aids such as oxygen into the upper tubing. When the pressure of the gaseous combustion aid reaches the standard, put the first piston into the upper tubing, continue to pump methane gas into the upper tubing, and when the pressure of the methane gas reaches the standard, put the second piston, and finally pump well killing fluid into the upper tubing to continuously push the first piston and the second piston to move downward;

S3: After the first piston squeezes the feedback mechanism, the feedback mechanism controls the driving device connected between the wellhead and the upper oil pipe to rotate the upper oil pipe, so that the ventilation switching mechanism works, thereby realizing the separate storage of the gaseous combustion aid and the methane gas;

S4: A heavy rod is dropped into the upward oil pipe to perform a rod-throwing operation. The impact of the heavy rod and the pressure difference at the bottom of the well cause the heavy rod to directly press the preliminary solid combustion-supporting agent and collide with the striker unit to preliminarily ignite the methane gas.

S5: At the same time, under the squeezing of the heavy rod, the connecting excitation mechanism works, so that the gas combustion aid is connected and mixed with the methane gas, and the combustion and explosion of the methane gas is completed. The combustion and explosion gas flow is ejected at high speed along the perforation, so that the target soil layer is impact-fractured, and the combustion and explosion fracturing work is completed.

Compared with the prior art, the present invention has the following beneficial effects:

(1) Compared with the prior art, the present application can firstly ensure the sufficiency of methane gas during the combustion and explosion process, thereby avoiding the problem that sufficient methane gas cannot be analyzed for combustion and explosion fracturing after perforating a new well. Secondly, through the coordination of the preliminary solid combustion-supporting agent and the combustion-supporting gas, the sufficiency of the combustion-supporting agent during the entire combustion and explosion fracturing process is ensured, thereby improving the combustion and explosion fracturing effect. Finally, by splitting the entire oil pipe into an upper oil pipe and a lower oil pipe, and using a ventilation switching mechanism to switch the connection state of the upper oil pipe and the lower oil pipe, the combustion-supporting gas and methane gas are separated, transported and temporarily stored, respectively, thereby minimizing the probability of the pipe column vibration, friction and the like detonating the methane gas and the combustion-supporting agent during the construction process, thereby ensuring the safety of the construction operation.

(2) The present application can seal the gap between the outer semicircular cover body and the inner semicircular cover body by setting an anti-leakage mechanism, thereby ensuring the complete separation of the combustion-supporting gas and the methane gas, and further improving the separation effect of the ventilation switching mechanism. At the same time, by setting the No. 2 push switch, when pressed, it can also control the opening time of the No. 1 solenoid valve on the first piston, thereby achieving automatic and precise control, and preventing the No. 1 solenoid valve from being opened before the outer semicircular cover body and the inner semicircular cover body are rotated to the working position, resulting in the mixing of methane gas and the combustion-supporting gas.

(3) The present application sets an anti-rotation mechanism. During the tube lowering process, the electromagnet ring is energized to generate a magnetic field that attracts the lower magnet, thereby fixing the inner semicircular cover body and the upper oil pipe to prevent the inner semicircular cover body and the lower oil pipe from rotating due to collisions during the tube lowering process. In addition, a No. 1 push switch is provided in the limit groove. After the tube is lowered, the lower oil pipe will squeeze the No. 1 push switch, so that the No. 1 push switch controls the electromagnet ring electrically connected to it to cut off the power, thereby ensuring the normal rotation of the ventilation switching mechanism.

(4) The present application sets a feedback mechanism. When the methane gas continuously pushes the first piston to move downward, the position of the contact feedback mechanism is set to the required gas pressure state. At this time, as the first piston continues to move downward a short distance, it will squeeze the upper ring body and drive the pressing column to press the pressure sensor. The pressure sensor has a communication module and can transmit signals to the ground control system after being pressurized, so that the staff can promptly control the ventilation switching mechanism to start working;

(5) The present application sets a connection excitation mechanism, and the support extrusion plates in the two connection excitation mechanisms realize the support of the preliminary solid combustion-supporting agent. The support stability of the preliminary solid combustion-supporting agent can be ensured by the counterweight block-level arc-shaped limit plate. After the rod is thrown, the heavy rod presses the preliminary solid combustion-supporting agent to collide with the striker unit, and at the same time, the heavy rod squeezes the support extrusion plates on both sides, so that the support extrusion plates drive the arc-shaped partition plate and the counterweight block to rotate, open the connection port, and facilitate the automatic connection and mixing of the combustion-supporting gas and the methane gas;

(6) The present application sets an anti-impact mechanism. When high-pressure methane gas enters the lower oil pipe, it first impacts the impact orifice plate. The impact orifice plate is compressed and squeezes the impact spring, causing the impact orifice plate to move downward. Methane gas enters the lower oil pipe through the gap between the upper fixing ring and the impact orifice plate, and the small holes on the impact orifice plate. This avoids the direct impact of high-pressure methane gas on the preliminary solid combustion aid, improves the placement stability of the preliminary solid combustion aid, and also prevents the problem of premature mixing of the gas caused by the connecting port being opened briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic diagram of the overall structure of the present invention;

FIG2 is a schematic diagram of a half-section structure of FIG1 of the present invention;

FIG3 is a schematic diagram of a half-section structure of FIG1 of the present invention after the sleeve is removed;

FIG4 is an enlarged schematic diagram of the structure of point A in FIG2 of the present invention;

FIG5 is an enlarged structural schematic diagram of the feedback mechanism in FIG4 of the present invention;

FIG6 is a schematic diagram of the overall structure of FIG1 of the present invention after the sleeve is removed;

FIG7 is an enlarged schematic diagram of the structure of point C in FIG6 of the present invention;

FIG8 is an enlarged schematic diagram of the structure of point B in FIG2 of the present invention;

FIG. 9 is a schematic flow chart of the method of the present invention.

Description of the numbers in the figure:

1. Casing; 2. Oil pipe;

3. Feedback mechanism; 31. Lower ring body; 32. Upper ring body; 33. Pressing column; 34. Pressure sensor; 35. Pressing spring;

4. Ventilation switching mechanism; 41. Mounting flange; 42. Rotating groove; 43. Outer semicircular cover; 44. Inner semicircular cover; 45. Rotating connecting column; 46. Fixed semicircular cover plate; 47. Movable semicircular cover plate; 48. Lower magnet; 49. Electromagnetic ring; 410. Push switch No. 1; 411. Longitudinal separation airbag; 412. Annular separation airbag; 413. Push switch No. 2; 414. Electromagnetic one-way valve;

5. Anti-impact mechanism; 51. Lower fixing ring; 52. Upper fixing ring; 53. Impact orifice plate; 54. Impact spring;

6. Connecting excitation mechanism; 61. Connecting port; 62. Arc-shaped partition plate; 63. Counterweight block; 64. Arc-shaped limit plate; 65. Supporting extrusion plate;

7. Perforation; 8. Second piston; 9. Upper packer; 10. Preliminary solid combustion aid; 11. Lower oil pipe; 12. Strike unit; 13. Limit block; 14. Limit groove; 15. Lower packer; 16. First piston; 17. Solenoid valve No. 1.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

Please refer to Figures 1 to 9, a vertical well methane in-situ explosion fracturing device includes a casing 1 and perforations 7 evenly opened on the outer circumference of the casing 1, an upper oil pipe 2 and a lower oil pipe 11 are arranged inside the casing 1, and the upper oil pipe 2 and the lower oil pipe 11 are rotatably connected through a ventilation switching mechanism 4;

A lower packer 15 is provided at the bottom of the casing 1, an upper packer 9 is provided at the upper end of the casing 1, and the upper oil pipe 2 is provided through the upper packer 9; a first piston 16 is provided at the lower end of the upper oil pipe 2, and a first solenoid valve 17 is provided on the first piston 16; a second piston 8 is provided at the upper end of the upper oil pipe 2;

Two connecting excitation mechanisms 6 are symmetrically arranged on both sides of the lower oil pipe 11, and the two connecting excitation mechanisms 6 jointly support the preliminary solid combustion aid 10; a striker unit 12 is arranged at the bottom of the lower oil pipe 11; a limiting groove 14 is opened inside the lower packer 15, and a limiting block 13 corresponding to the limiting groove 14 is fixedly connected to the bottom of the outer cylindrical surface of the lower oil pipe 11.

The ventilation switching mechanism 4 includes a mounting flange 41 fixedly connected to the bottom edge of the upper oil pipe 2, a rotation groove 42 is formed inside the mounting flange 41, an inner semicircular cover 44 is fixedly connected to the top of the lower oil pipe 11, and the top of the inner semicircular cover 44 is rotatably connected to the mounting flange 41 through the rotation groove 42; an outer semicircular cover 43 is fixedly connected to the bottom of the outer circumferential surface of the mounting flange 41; and an anti-leakage mechanism cooperating with the inner semicircular cover 44 is also provided on the inner arc surface of the outer semicircular cover 43;

A rotating connecting column 45 is fixedly connected to the bottom of the inner circular surface of the upper oil pipe 2, and a fixed semicircular cover plate 46 is fixedly connected to the top of the lower oil pipe 11. The lower end of the rotating connecting column 45 passes through the fixed semicircular cover plate 46 and is rotatably connected to the fixed semicircular cover plate 46, and the bottom of the rotating connecting column 45 is fixedly connected to a movable semicircular cover plate 47.

As shown in FIG. 7 , the movable semicircular cover plate 47 and the outer semicircular cover body 43 are symmetrically arranged about the rotating connecting column 45 , and the fixed semicircular cover plate 46 and the inner semicircular cover body 44 are arranged on the same side of the rotating connecting column 45 .

When in use, the casing 1 is first lowered into the well, and then the lower packer 15 is lowered into the casing 1, and then the combination consisting of the upper oil pipe 2, the ventilation switching mechanism 4 and the lower oil pipe 11 is lowered, and finally the upper packer 9 is lowered to complete the arrangement of each unit. Then, a combustion-supporting gas such as oxygen is pumped into the upper oil pipe 2. In the initial state, the movable semicircular cover plate 47 and the fixed semicircular cover plate 46 form a circular cover plate to seal the lower oil pipe 11. At the same time, the fixed semicircular cover plate 46 and the inner semicircular cover body 44 are arranged on the same side of the rotating connecting column 45, so that the combustion-supporting gas will enter the annular space composed of the casing 1, the upper oil pipe 2, the lower oil pipe 11, the lower packer 15 and the upper packer 9 from the side when passing through the ventilation switching mechanism 4 for temporary storage. After the concentration and pressure of the combustion-supporting gas reach the requirements, the first piston 16 is lowered into the upper oil pipe 2, and then methane gas is continuously pumped into the upper oil pipe 2. Under the pressure of the methane gas, the first piston 16 continues to move downward;

After the methane gas concentration and pressure meet the requirements, the second piston 8 is lowered into the upper oil pipe 2, and finally the well-killing fluid is pumped into the upper oil pipe 2. Under the pressure of the well-killing fluid, the first piston 16 reaches the predetermined position. At this time, the pumping of the well-killing fluid is stopped, and the ventilation switching mechanism 4 is controlled to work, and the connection state of the upper oil pipe 2 and the lower oil pipe 11 is switched; when the ventilation switching mechanism 4 is specifically working, the driving device (such as a high-power motor, etc.) fixedly connected to the top of the upper oil pipe 2 through the wellhead drives the upper oil pipe 2 to rotate slowly (the inner semicircular cover body 44 is rotatably connected to the upper oil pipe 2 through the rotating groove 42, which is a movable connection relationship. At the same time, after the pipe is lowered, the lower oil pipe 11 will be inserted into the limiting groove 14 inside the lower packer 15. The cooperation between the limiting block 13 and the limiting groove 14 can prevent the lower oil pipe 11 from rotating when the upper oil pipe 2 rotates. Following the rotation, after the upper oil pipe 2 rotates 180 degrees (i.e., the upper oil pipe 2 rotates 180 degrees counterclockwise from the perspective of FIG. 6 ), the outer semicircular cover body 43 rotates to a position symmetrical to the inner semicircular cover body 44 about the rotating connecting column 45, thereby realizing the separation of the aforementioned annular space and the upper oil pipe 2. At the same time, when the upper oil pipe 2 rotates, it will drive the rotating connecting column 45 fixed thereto to rotate, thereby driving the movable semicircular cover plate 47 to rotate 180 degrees, overlapping with the fixed semicircular cover plate 46 in the vertical direction, opening the channel between the upper oil pipe 2 and the lower oil pipe 11, and then, the No. 1 solenoid valve 17 on the first piston 16 is opened, so that the methane gas between the first piston 16 and the second piston 8 enters the lower oil pipe 11 and is stored in the channel formed by the lower oil pipe 11 and the upper oil pipe 2, completing the temporary storage of the methane gas;

After the above operations, the combustion-supporting gas and methane gas are separated, transported and temporarily stored respectively. Finally, a heavy rod is thrown into the upper oil pipe 2 to carry out the rod throwing operation. The impact generated by the heavy rod and the pressure difference at the bottom of the well cause the heavy rod to directly break the parts in the pipe, and press the preliminary solid combustion-supporting agent 10 to collide with the striker unit 12 to preliminarily ignite the methane gas. At the same time, under the squeezing of the heavy rod, the connecting excitation mechanism 6 works, so that the gas combustion-supporting agent and the methane gas are connected and mixed, completing the combustion and explosion of the methane gas, and the combustion and explosion airflow is ejected at high speed along the perforation 7, so that the target soil layer is impact-fractured to complete the combustion and explosion fracturing work.

Compared with the prior art, the present application can firstly ensure sufficient methane gas during the explosion process, thereby avoiding the problem that sufficient methane gas cannot be analyzed for explosion fracturing after perforating a new well; secondly, through the coordination of the preliminary solid combustion aid 10 and the combustion-supporting gas, the combustion aid is ensured to be sufficient throughout the explosion fracturing process, thereby improving the explosion fracturing effect; finally, by splitting the entire oil pipe into an upper oil pipe 2 and a lower oil pipe 11, and using the ventilation switching mechanism 4 to switch the connectivity between the upper oil pipe 2 and the lower oil pipe 11, the combustion-supporting gas and methane gas are separated, transported and temporarily stored, respectively, thereby minimizing the probability of the pipe column vibration, friction and the like detonating methane gas and the combustion aid during the construction process, thereby ensuring the safety of the construction operation.

As shown in Figures 7 and 8, the anti-leakage mechanism includes two longitudinal separation airbags 411 fixedly connected to the two ends of the inner arc surface of the outer semicircular cover body 43, and an annular separation airbag 412 fixedly installed at the bottom of the inner arc surface of the outer semicircular cover body 43, and the longitudinal separation airbags 411 and the annular separation airbags 412 are initially in a negative pressure state; an electromagnetic one-way valve 414 is provided at the bottom of the annular separation airbag 412, and a No. 2 push switch 413 is provided on the upper surface of the movable semicircular cover plate 47.

When the outer semicircular cover body 43 rotates to form a closed passage with the inner semicircular cover body 44 , the second push switch 413 is pressed by the fixed semicircular cover plate 46 .

After the ventilation switching mechanism 4 works, since there is a certain gap between the outer semicircular cover body 43 and the inner semicircular cover body 44 (to ensure the smooth rotation of the outer semicircular cover body 43), the annular space cannot be completely closed, which reduces the separation effect of the ventilation switching mechanism 4;

In the present application, after the ventilation switching mechanism 4 works in place (the outer semicircular cover body 43 rotates to a position symmetrical to the inner semicircular cover body 44 about the rotating connecting column 45, that is, the position where the outer semicircular cover body 43 rotates 180 degrees counterclockwise from the perspective of Figure 7), the No. 2 push switch 413 is pressed by the fixed semicircular cover plate 46 at this time, and the No. 2 push switch 413 turns on the electromagnetic one-way valve 414 to work. The electromagnetic one-way valve 414 is conducted inward, and the longitudinal separation airbag 411 and the annular separation airbag 412 are initially in a negative pressure state. Therefore, the combustion-supporting gas in a high-pressure state in the annular space is gradually pressed into the longitudinal separation airbag 411 and the annular separation airbag 412, causing the longitudinal separation airbag 411 and the annular separation airbag 412 to bulge, thereby sealing the channel composed of the outer semicircular cover body 43, the inner semicircular cover body 44, the upper oil pipe 2 and the lower oil pipe 11;

It should be noted that there is still a small amount of combustion-supporting gas inside the lower oil pipe 11 and the upper oil pipe 2 that cannot be discharged into the annular space, but the structure of the ventilation switching mechanism 4 in the figure is magnified for the convenience of seeing, and the actual ventilation switching mechanism 4 only occupies a very small part of the pipeline connecting the lower oil pipe 11 and the upper oil pipe 2. The total amount of these residual combustion-supporting gas is very small and does not affect the normal temporary storage of methane gas;

The present application sets an anti-leakage mechanism to seal the gap between the outer semicircular cover body 43 and the inner semicircular cover body 44, thereby ensuring the complete separation of the combustion-supporting gas and the methane gas, and further improving the separation effect of the ventilation switching mechanism 4. At the same time, by setting the No. 2 push switch 413, when pressed, it can also simultaneously control the opening time of the No. 1 solenoid valve 17 on the first piston 16, thereby achieving automatic and precise control, and preventing the No. 1 solenoid valve 17 from opening before the outer semicircular cover body 43 and the inner semicircular cover body 44 are rotated to the working position, thereby preventing the methane gas from mixing with the combustion-supporting gas.

As shown in Figures 4 and 7, an anti-rotation mechanism is also provided in the rotating groove 42 for preventing the lower oil pipe 11 from rotating during the arrangement process. The anti-rotation mechanism includes an electromagnet ring 49 arranged at the top of the rotating groove 42, and a lower magnet 48 corresponding to the electromagnet ring 49 is provided on the top of the inner semicircular cover body 44, and the magnetic field of the electromagnet ring 49 is adsorbed with the lower magnet 48 after power is turned on; a push switch 410 for controlling the working state of the electromagnet ring 49 is also provided in the middle position at the bottom of the limit groove 14.

Since the ventilation switching mechanism 4 needs to keep the outer semicircular cover body 43 and the inner semicircular cover body 44 overlapped in the initial state, and open the state of the upper oil pipe 2 and the annular space channel, and the inner semicircular cover body 44 and the upper oil pipe 2 are rotatably connected through the rotating groove 42, bumps and other situations during the lowering process will cause the inner semicircular cover body 44 and the lower oil pipe 11 to rotate, and cannot maintain the initial required working position, which will affect the normal operation of the ventilation switching mechanism 4;

The present application sets an anti-rotation mechanism. During the tube lowering process, the electromagnet ring 49 is energized to generate a magnetic field that is attracted to the lower magnet 48, thereby fixing the inner semicircular cover body 44 and the upper oil pipe 2 to prevent the inner semicircular cover body 44 and the lower oil pipe 11 from rotating due to collisions during the tube lowering process. In addition, a push switch No. 1 410 is provided in the limit groove 14. After the tube is lowered, the lower oil pipe 11 will squeeze the push switch No. 1 410, so that the push switch No. 1 410 controls the electromagnet ring 49 electrically connected thereto to cut off the power, thereby ensuring the normal rotation of the ventilation switching mechanism 4.

As shown in Figures 4 and 5, a feedback mechanism 3 for controlling the operation of the ventilation switching mechanism 4 is fixedly provided at the bottom end of the upper oil pipe 2. The feedback mechanism 3 includes a lower ring body 31 fixedly connected to the bottom of the inner circular surface of the upper oil pipe 2, and evenly distributed pressing springs 35 are fixedly connected to the upper surface of the lower ring body 31. The upper ends of the pressing springs 35 are commonly fixedly connected to the upper ring body 32. A pressure sensor 34 is provided on one side of the upper surface of the lower ring body 31, and the upper ring body 32 is provided with a pressing column 33 corresponding to the pressure sensor 34.

During the operation of the ventilation switching mechanism 4, the start time of its operation needs to be accurately controlled, otherwise it is easy to cause the pressure of the combustion-supporting gas and the methane gas to be unable to be accurately controlled. The present application sets a feedback mechanism 3. When the methane gas continues to push the first piston 16 to move downward, the position of the contact feedback mechanism 3 is set to the required gas pressure state. At this time, as the first piston 16 continues to move downward a short distance, it will squeeze the upper ring body 32 and drive the pressing column 33 to press the pressure sensor 34. The pressure sensor 34 has its own communication module, which can transmit signals to the ground control system after being pressurized, so that the staff can promptly control the ventilation switching mechanism 4 to start working.

As shown in Figures 2 and 8, the connecting excitation mechanism 6 includes a connecting port 61 opened on the side wall of the lower oil pipe 11, and the top of the connecting port 61 is connected to an arc-shaped partition plate 62 by a hinge, and a counterweight block 63 is fixedly connected to the bottom of one side of the arc-shaped partition plate 62, and a supporting extrusion plate 65 is fixedly connected to the top of the other side of the arc-shaped partition plate 62. The supporting extrusion plates 65 in the two connecting excitation mechanisms 6 support the preliminary solid combustion aid 10, and an arc-shaped limit plate 64 is fixedly connected to the inner circular surface of the lower oil pipe 11 near the position below the connecting port 61; the upper end of the lower oil pipe 11 is also provided with an anti-impact mechanism 5.

When performing the rod throwing operation, the heavy rod only impacts and conducts the inside of the channel composed of the upper oil pipe 2, the lower oil pipe 11, and the ventilation switching mechanism 4, and cannot mix the combustion-supporting gas and the methane gas. Therefore, the present application sets a connecting excitation mechanism 6, and the supporting extrusion plates 65 in the two connecting excitation mechanisms 6 support the preliminary solid combustion aid 10. The supporting stability of the preliminary solid combustion aid 10 can be guaranteed by the counterweight block 63 and the arc-shaped limit plate 64. After the rod throwing operation, the heavy rod presses the preliminary solid combustion aid 10 to collide with the striker unit 12, and at the same time, the heavy rod squeezes the supporting extrusion plates 65 on both sides, so that the supporting extrusion plates 65 drive the arc-shaped partition plate 62 and the counterweight block 63 to rotate, and open the connecting port 61, which is convenient for the automatic connection and mixing of the combustion-supporting gas and the methane gas.

As shown in Figures 3 and 8, the anti-impact mechanism 5 includes a lower fixed ring 51 and an upper fixed ring 52 fixed to the side wall of the lower oil pipe 11. The upper surface of the lower fixed ring 51 is fixed with evenly distributed impact springs 54 in a ring shape. The upper ends of the impact springs 54 are commonly fixed with an impact orifice plate 53. When the impact springs 54 are at their original length, the impact orifice plate 53 is flush with the upper surface of the upper fixed ring 52.

After the No. 1 solenoid valve 17 is opened, the high-pressure methane gas between the first piston 16 and the second piston 8 will enter the lower oil pipe 11, which is easy to impact the preliminary solid combustion aid 10, causing the preliminary solid combustion aid 10 to be unstable. At the same time, the impact is also easy to cause the connecting port 61 to be briefly opened, causing premature mixing of the gas. Therefore, the present application sets an anti-impact mechanism 5. When the high-pressure methane gas enters the lower oil pipe 11, it first impacts the impact orifice plate 53. The impact orifice plate 53 is compressed and squeezes the impact spring 54, causing the impact orifice plate 53 to move downward. The methane gas enters the lower oil pipe 11 through the gap between the upper fixing ring 52 and the impact orifice plate 53, and the small holes on the impact orifice plate 53, thereby avoiding the direct impact of the high-pressure methane gas on the preliminary solid combustion aid 10, improving the placement stability of the preliminary solid combustion aid 10, and also preventing the connecting port 61 from being briefly opened, causing the problem of premature mixing of the gas.

A method for using a vertical well methane in-situ explosion fracturing device, as shown in FIG9 , is characterized by comprising the following steps:

S1: lower the casing 1, the upper oil pipe 2, the lower oil pipe 11 and related components into the well in sequence and complete the arrangement;

S2: Pump a gaseous combustion aid such as oxygen into the upper oil pipe 2. When the pressure of the gaseous combustion aid reaches the standard, put the first piston 16 into the upper oil pipe 2, continue to pump methane gas into the upper oil pipe 2, and put the second piston 8 into the upper oil pipe 2 after the methane gas pressure reaches the standard. Finally, pump the well killing fluid into the upper oil pipe 2 to continuously push the first piston 16 and the second piston 8 to move downward;

S3: After the first piston 16 squeezes the feedback mechanism 3, the feedback mechanism 3 controls the driving device fixedly connected between the wellhead and the upper oil pipe 2 to rotate the upper oil pipe 2, so that the ventilation switching mechanism 4 works to realize the separate storage of the gaseous combustion aid and the methane gas;

S4: a heavy rod is thrown into the upward oil pipe 2 to perform a rod throwing operation. The impact of the heavy rod and the pressure difference at the bottom of the well cause the heavy rod to directly press the preliminary solid combustion aid 10 and collide with the striker unit 12 to preliminarily ignite the methane gas;

S5: At the same time, under the squeezing of the heavy rod, the connecting excitation mechanism 6 works, so that the gaseous combustion aid is connected and mixed with the methane gas, and the combustion and explosion of the methane gas is completed. The combustion and explosion gas flow is ejected at high speed along the perforations 7, so that the target soil layer is impact-fractured, and the combustion and explosion fracturing work is completed.

The above is only a preferred specific implementation of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and its improved conception within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims (6)

1. A vertical well methane in-situ explosion fracturing device, comprising a casing (1) and perforations (7) uniformly arranged on the outer circumferential surface of the casing (1), characterized in that an upper oil pipe (2) and a lower oil pipe (11) are arranged inside the casing (1), and the upper oil pipe (2) and the lower oil pipe (11) are rotatably connected via a ventilation switching mechanism (4); A lower packer (15) is provided at the bottom of the casing (1); an upper packer (9) is provided at the upper end of the casing (1), and the upper oil pipe (2) penetrates the upper packer (9); a first piston (16) is slidably provided at the lower end of the upper oil pipe (2), and a first solenoid valve (17) is provided on the first piston (16); a second piston (8) is slidably provided at the upper end of the upper oil pipe (2); Two connecting excitation mechanisms (6) are symmetrically arranged on both sides of the lower oil pipe (11), and the two connecting excitation mechanisms (6) jointly support a preliminary solid combustion aid (10); a striker unit (12) is arranged at the bottom of the lower oil pipe (11); a limiting groove (14) is arranged inside the lower packer (15), and a limiting block (13) corresponding to the limiting groove (14) is fixedly connected to the bottom of the outer cylindrical surface of the lower oil pipe (11); The ventilation switching mechanism (4) comprises a mounting flange (41) fixedly connected to the bottom edge of the upper oil pipe (2), a rotation groove (42) extending through the mounting flange (41), an inner semicircular cover (44) fixedly connected to the top of the lower oil pipe (11), and the top of the inner semicircular cover (44) is rotationally connected to the mounting flange (41) through the rotation groove (42); an outer semicircular cover (43) is fixedly connected to the bottom of the outer circumferential surface of the mounting flange (41); and an anti-leakage mechanism cooperating with the inner semicircular cover (44) is also provided on the inner arc surface of the outer semicircular cover (43); The bottom of the inner circular surface of the upper oil pipe (2) is fixedly connected to a rotating connection column (45), the top of the lower oil pipe (11) is fixedly connected to a fixed semicircular cover plate (46), the lower end of the rotating connection column (45) penetrates the fixed semicircular cover plate (46) and is rotatably connected to the fixed semicircular cover plate (46), and the bottom of the rotating connection column (45) is fixedly connected to a movable semicircular cover plate (47); The movable semicircular cover plate (47) and the outer semicircular cover body (43) are symmetrically arranged about the rotating connecting column (45), and the fixed semicircular cover plate (46) and the inner semicircular cover body (44) are arranged on the same side of the rotating connecting column (45); A feedback mechanism (3) for controlling the operation of the ventilation switching mechanism (4) is fixedly provided at the bottom end of the upper oil pipe (2), the feedback mechanism (3) comprising a lower ring body (31) fixedly connected to the bottom of the inner circular surface of the upper oil pipe (2), the upper surface of the lower ring body (31) being fixedly connected to evenly distributed pressing springs (35), the upper ends of the pressing springs (35) being fixedly connected to the upper ring body (32), a pressure sensor (34) being provided on one side of the upper surface of the lower ring body (31), and the upper ring body (32) being provided with a pressing column (33) corresponding to the pressure sensor (34); The connecting and activating mechanism (6) comprises a connecting port (61) provided on the side wall of the lower oil pipe (11); the top of the connecting port (61) is connected to an arc-shaped partition plate (62) by a hinge; the bottom of one side of the arc-shaped partition plate (62) is fixedly connected to a counterweight block (63); the top of the other side of the arc-shaped partition plate (62) is fixedly connected to a supporting and squeezing plate (65); and the supporting and squeezing plates (65) in the two connecting and activating mechanisms (6) support the preliminary solid combustion aid (10); the inner circular surface of the lower oil pipe (11) is fixedly connected to an arc-shaped limit plate (64) near the position below the connecting port (61); and the upper end of the inner part of the lower oil pipe (11) is also provided with an anti-impact mechanism (5). 2. A vertical well methane in-situ explosion fracturing device according to claim 1, characterized in that: the anti-leakage mechanism includes two longitudinal separation airbags (411) fixedly connected to the two ends of the inner arc surface of the outer semicircular cover body (43), and an annular separation airbag (412) fixedly installed at the bottom of the inner arc surface of the outer semicircular cover body (43), and the longitudinal separation airbag (411) and the annular separation airbag (412) are initially in a negative pressure state; an electromagnetic one-way valve (414) is provided at the bottom of the annular separation airbag (412), and a No. 2 push switch (413) is provided on the upper surface of the movable semicircular cover plate (47). 3. A vertical well methane in-situ explosion fracturing device according to claim 2, characterized in that: when the outer semicircular cover body (43) forms a closed passage with the inner semicircular cover body (44) after rotation, the second push switch (413) is pressed by the fixed semicircular cover plate (46). 4. A vertical well methane in-situ explosive fracturing device according to claim 1, characterized in that: an anti-rotation mechanism for preventing the lower oil pipe (11) from rotating during the arrangement process is also provided in the rotating groove (42), and the anti-rotation mechanism includes an electromagnet ring (49) arranged at the top of the rotating groove (42), and a lower magnet (48) corresponding to the electromagnet ring (49) is provided on the top of the inner semicircular cover body (44), and the magnetic field of the electromagnet ring (49) is attracted to the lower magnet (48) after power is turned on; a push switch (410) for controlling the working state of the electromagnet ring (49) is also provided in the middle position at the bottom of the limit groove (14). 5. A vertical well methane in-situ explosion fracturing device according to claim 1, characterized in that: the anti-impact mechanism (5) includes a lower fixed ring (51) and an upper fixed ring (52) fixed to the side wall of the lower oil pipe (11), the upper surface of the lower fixed ring (51) is annularly fixed with uniformly distributed impact springs (54), the upper ends of the impact springs (54) are commonly fixed with an impact orifice plate (53), and when the impact spring (54) is at its original length, the impact orifice plate (53) is flush with the upper surface of the upper fixed ring (52). 6. A method for using the vertical well methane in-situ explosion fracturing device according to any one of claims 1 to 5, characterized in that it comprises the following steps: S1: lowering the casing (1), the upper oil pipe (2), the lower oil pipe (11) and related components into the well in sequence and completing the arrangement; S2: Pumping a gaseous combustion aid into the upper oil pipe (2), and after the pressure of the gaseous combustion aid reaches the standard, inserting the first piston (16) into the upper oil pipe (2), and continuing to pump methane gas into the upper oil pipe (2), and after the pressure of the methane gas reaches the standard, inserting the second piston (8), and finally pumping a well-killing fluid into the upper oil pipe (2), and continuously pushing the first piston (16) and the second piston (8) to move downward; S3: After the first piston (16) squeezes the feedback mechanism (3), the feedback mechanism (3) controls the driving device connected to the wellhead and the upper oil pipe (2) to rotate the upper oil pipe (2), so that the ventilation switching mechanism (4) works, thereby realizing the separate storage of the gaseous combustion aid and the methane gas; S4: a heavy rod is inserted into the upward oil pipe (2) to perform a rod-throwing operation. The impact of the heavy rod and the pressure difference at the bottom of the well cause the heavy rod to directly press the preliminary solid combustion aid (10) and the striker unit (12) to collide, thereby preliminarily igniting the methane gas; S5: At the same time, under the squeezing of the heavy rod, the connecting excitation mechanism (6) works, so that the gas combustion aid is connected and mixed with the methane gas, and the combustion and explosion of the methane gas is completed. The combustion and explosion gas flow is ejected at high speed along the perforation (7), so that the target soil layer is impact-fractured, and the combustion and explosion fracturing work is completed.