Coal bed gas fracturing device and fracturing system

Abstract

According to the coal bed gas fracturing device and system, a fracturing fluid pumping assembly conveys fracturing fluid into a first barrel, when the fracturing fluid passes through a hydraulic rotation driving mechanism, the hydraulic rotation driving mechanism drives a driving sleeve to rotate, and the driving sleeve drives a frequency modulation speed reduction pipe section and a pulse pressurization pipe section to rotate. Fracturing fluid enters the first bearing water guide pipe of the second barrel, when the fracturing fluid passes through the frequency modulation speed reduction mechanism, the fluid supply frequency of the fracturing fluid is adjusted, and meanwhile the flow speed of the fracturing fluid can be reduced. And then, the fracturing fluid enters a second bearing water guide pipe of the third barrel, a booster pump is used for pressurizing the fracturing fluid, and a pulse generator is used for providing pressure fluctuation for the fracturing fluid. In the rotating process of the pulse pressurizing pipe section, the fracturing fluid outlet can periodically move to the position communicated with a perforation of a well wall casing pipe, pulse water hammer pressure fluctuation is formed in cooperation with pressure fluctuation of fracturing fluid, the strong pulse hydraulic fracturing effect is achieved, and the problem that conventional hydraulic fracturing pressure is insufficient is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, and in particular to a coal bed gas fracturing device and a fracturing system. Background Art

[0002] As an important unconventional natural gas resource, the development of coalbed methane is of great significance for optimizing energy structure and ensuring energy security. However, my country's low-permeability coal seams generally have complex geological characteristics and low reservoir permeability. Coalbed methane is mainly stored in the micropores of coal rock matrix in an adsorbed state, and its exploitation requires a complex process of "desorption-diffusion-seepage". At present, the industry generally adopts the "drainage-pressure reduction-desorption" mining mode. Among them, hydraulic fracturing technology, as the mainstream reservoir transformation method, faces multiple technical bottlenecks in practical applications: First, the low fracture pressure and significant plasticity of coal seams lead to limited crack expansion, and conventional fracturing is difficult to form an effective fracture network; second, the development of thin interlayers and the influence of interlayers cause a large amount of proppant to settle in non-target layers; third, the water-sensitive interaction between fracturing fluid and coal reservoirs is prone to cause secondary damage; fourth, shallow (<1000m) coal seams are restricted by the complexity of the ground stress field, and it is difficult to control the crack height. The crack extension distance is insufficient, and it is difficult to effectively communicate the natural cleat system.

[0003] In response to the above problems, existing technologies such as the Chinese patent with publication number CN209875128U propose a high-pressure pulse wave fracturing method driven by explosive energy, which forms a multi-level fracture network in the coal seam through the shock wave generated by explosives or liquid explosive materials. Although this technology can break through the fracture extension limit of hydraulic fracturing to a certain extent, it has exposed significant defects in engineering practice: 1) The structure of the explosion device is complex, and there are uncontrollable risks in the storage and detonation process of liquid explosives, which can easily cause wellbore collapse or underground explosion accidents; 2) The energy of the explosion shock wave decays quickly, and the stress concentration in the near-well area can easily lead to the destruction of the coal rock structure, affecting the stability of subsequent drainage; 3) Explosive residues and explosion products (such as nitro compounds) can easily penetrate into the cracks of the coal seam and cause groundwater pollution, which is contrary to the requirements of green mining; 4) The explosion energy and formation parameters are poorly matched, making it difficult to achieve directional expansion control of the fractures.

[0004] Therefore, it is urgent to develop a new coalbed methane production enhancement technology that is safe, environmentally friendly, and reservoir adaptable. Under the premise of avoiding the use of explosive materials, innovative energy loading methods can be used to achieve the coordinated transformation of the coal reservoir matrix-microcrack-macrocrack system, thereby improving the desorption efficiency and seepage capacity. This technical demand has become a key issue that needs to be broken through in the current field of efficient coalbed methane development. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a coal seam gas fracturing device and a fracturing system, aiming to solve the problem of low fracturing pressure when the conventional hydraulic fracturing technology is used for coal seam gas reservoirs in the related art.

[0006] The present invention provides a coal seam gas fracturing device, comprising: A rotary drive pipe section, including a fracturing fluid pumping assembly, a first cylinder, a hydraulic rotary drive mechanism and a drive sleeve. The fracturing fluid pumping assembly is arranged at the upstream end of the first cylinder for conveying fracturing fluid into the first cylinder. The drive sleeve is arranged at the downstream end of the first cylinder and is rotationally and sealingly connected to the first cylinder. The hydraulic rotary drive mechanism is arranged inside the first cylinder and is in transmission connection with the drive sleeve; A frequency modulation and speed reduction pipe section, including a second cylinder, a first load-bearing water conduit, a frequency modulation and speed reduction mechanism and a driven sleeve. The upstream end of the second cylinder is connected to the drive sleeve, and the driven sleeve is connected to the downstream end of the second cylinder. The first load-bearing water conduit is arranged inside the second cylinder, and the upstream end of the first load-bearing water conduit is communicated with the inside of the first cylinder through the drive sleeve. The downstream end of the first load-bearing water conduit is connected to the driven sleeve, and the frequency modulation and speed reduction mechanism is communicated with the first load-bearing water conduit; A pulse boosting assembly, including a third cylinder, a second load-bearing water conduit, a booster pump, a pulse generator and a sealing baffle. The upstream end of the third cylinder is connected to the driven sleeve, and the sealing baffle is sealingly connected to the downstream end of the third cylinder. The second load-bearing water conduit is arranged inside the third cylinder, and the upstream end of the second load-bearing water conduit is communicated with the first load-bearing water conduit through the driven sleeve. The downstream end of the second load-bearing water conduit is sealingly connected to the sealing baffle. A plurality of fracturing fluid outlets communicating the inner and outer sides of the second load-bearing water conduit are arranged on the third cylinder and the second load-bearing water conduit. The plurality of fracturing fluid outlets are distributed along the axial direction of the third cylinder, and the distance between two adjacent fracturing fluid outlets is equal to the distance between two adjacent perforations on the wellbore casing.

[0007] According to the coal seam gas fracturing device provided by the present invention, the fracturing fluid pumping assembly includes a liquid storage tank and a liquid pump. The first side of the liquid storage tank is sealingly connected to the upstream end of the first cylinder, the second side of the liquid storage tank is used for connecting to a fracturing fluid source, and the liquid pump is arranged inside the first cylinder and is connected to the first side of the liquid storage tank.

[0008] According to the coal seam gas fracturing device provided by the present invention, the hydraulic rotary drive mechanism includes a turbine and a turbofan.

[0009] According to the coal seam gas fracturing device provided by the present invention, a check valve is further arranged in the first carrying water conduit, and the check valve is arranged on the upstream side of the frequency modulation speed reduction mechanism.

[0010] According to the coal seam gas fracturing device provided by the present invention, the frequency modulation speed reduction mechanism includes: A housing, in which a main flow channel, a pair of accommodating grooves, a pair of first bypass flow channels and a pair of second bypass flow channels are arranged. The main flow channel is communicated with the first carrying water conduit. The pair of accommodating grooves are symmetrically arranged on both sides of the main flow channel and communicated with the main flow channel. One end of the first bypass flow channel is communicated with the upstream end of the main flow channel, and the other end is communicated with the lower half part of the side of the same-side accommodating groove away from the main flow channel. One end of the second bypass flow channel is communicated with the downstream end of the main flow channel, and the other end is communicated with the upper half part of the side of the same-side accommodating groove away from the main flow channel; Gears, including two gears, which are respectively arranged in the two accommodating grooves and rotatably connected with the housing. The rotation axes are parallel to each other and in the horizontal direction. The two gears are meshed in the main flow channel, and the pitch circle diameter of the gears is equal to the inner diameter of the accommodating grooves.

[0011] According to the coal seam gas fracturing device provided by the present invention, it further includes a guide shoe, and the guide shoe is arranged on the side of the sealing baffle away from the third cylinder.

[0012] According to the coal seam gas fracturing device provided by the present invention, the guide shoe is hemispherical or semi-ellipsoidal.

[0013] The present invention also provides a fracturing system, including the coal seam gas fracturing device as described above.

[0014] Due to the above technical solutions adopted by the present invention, it has the following advantages: When the coal seam gas fracturing device provided by the present invention is working, the fracturing fluid pumping assembly conveys the fracturing fluid into the first cylinder. When the fracturing fluid passes through the hydraulic rotation driving mechanism, the hydraulic rotation driving mechanism drives the driving sleeve to rotate, the driving sleeve drives the frequency modulation speed reduction pipe section to rotate, and the frequency modulation speed reduction pipe section drives the pulse boosting pipe section to rotate through the driven sleeve. Subsequently, the fracturing fluid enters the first carrying water conduit of the second cylinder. When passing through the frequency modulation speed reduction mechanism, the supply frequency of the fracturing fluid is adjusted, and at the same time, the flow rate of the fracturing fluid is reduced. Subsequently, the fracturing fluid enters the second carrying water conduit of the third cylinder. The booster pump is used to boost the pressure of the fracturing fluid, and the pulse generator is used to provide pressure fluctuations for the fracturing fluid. During the rotation of the pulse boosting pipe section, the fracturing fluid outlet will periodically move to the position communicated with the perforation of the wellbore casing, and cooperate with the pressure fluctuation of the fracturing fluid to form a pulse water hammer pressure fluctuation, so as to achieve the effect of strong pulse hydraulic fracturing and solve the problem of insufficient pressure in conventional hydraulic fracturing.

[0015] Further, in the fracturing system provided by the present invention, due to the provision of the coal seam gas fracturing device as described above, it has the same advantages as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 is a cross-sectional view of the coal seam gas fracturing device provided by an embodiment of the present invention; Figure 2 is a cross-sectional view of the rotary drive pipe section provided by an embodiment of the present invention; Figure 3 is a cross-sectional view of the frequency modulation speed reduction pipe section provided by an embodiment of the present invention.

[0018] Reference Numerals: 100: Rotary drive pipe section; 110: Liquid storage tank; 120: Liquid pump; 130: First cylinder; 140: Turbine and fan; 150: Drive sleeve; 200: Frequency modulation speed reduction pipe section; 210: Second cylinder; 220: First load-bearing water conduit; 230: Check valve; 241: Housing; 242: Main flow channel; 243: First bypass flow channel; 244: Second bypass flow channel; 245: Accommodation groove; 246: Gear; 250: Driven sleeve; 300: Pulse pressurization pipe section; 310: Third cylinder; 320: Second load-bearing water conduit; 330: Booster pump; 340: Pulse generator; 350: Fracturing fluid outlet; 400: Sealing baffle; 500: Guide shoe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0020] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0021] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0022] In the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled", "fixed", etc. should be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0024] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0025] The present invention provides a coal seam gas fracturing device, which includes a rotary drive pipe section, a frequency modulation speed reduction pipe section, and a pulse boosting pipe section. The rotary drive pipe section includes a fracturing fluid pumping assembly, a first cylinder body, a hydraulic rotary drive mechanism, and a drive sleeve. The fracturing fluid pumping assembly is arranged at the upstream end of the first cylinder body and is used to convey fracturing fluid into the first cylinder body. The drive sleeve is arranged at the downstream end of the first cylinder body and is rotationally and sealingly connected to the first cylinder body. The hydraulic rotary drive mechanism is arranged inside the first cylinder body and is drivingly connected to the drive sleeve. The frequency modulation speed reduction pipe section includes a second cylinder body, a first load-bearing water conduit, a frequency modulation speed reduction mechanism, and a driven sleeve. The upstream end of the second cylinder body is connected to the drive sleeve, and the driven sleeve is connected to the downstream end of the second cylinder body. The first load-bearing water conduit is arranged inside the second cylinder body, and the upstream end of the first load-bearing water conduit is communicated with the inside of the first cylinder body through the drive sleeve. The downstream end of the first load-bearing water conduit is connected to the driven sleeve, and the frequency modulation speed reduction mechanism is communicated with the first load-bearing water conduit. The pulse boosting pipe section includes a third cylinder body, a second load-bearing water conduit, a booster pump, a pulse generator, and a sealing baffle. The upstream end of the third cylinder body is connected to the driven sleeve, and the sealing baffle is sealingly connected to the downstream end of the third cylinder body. The second load-bearing water conduit is arranged inside the third cylinder body, and the upstream end of the second load-bearing water conduit is communicated with the first load-bearing water conduit through the driven sleeve. The downstream end of the second load-bearing water conduit is sealingly connected to the sealing baffle. A plurality of fracturing fluid outlets communicating the inner and outer sides of the second load-bearing water conduit are arranged on the third cylinder body and the second load-bearing water conduit. The plurality of fracturing fluid outlets are distributed along the axial direction of the third cylinder body, and the distance between two adjacent fracturing fluid outlets is equal to the distance between two adjacent perforations on the wellbore casing. During operation, the fracturing fluid pumping assembly conveys fracturing fluid into the first cylinder body. When the fracturing fluid passes through the hydraulic rotary drive mechanism, the hydraulic rotary drive mechanism drives the drive sleeve to rotate. The drive sleeve drives the frequency modulation speed reduction pipe section to rotate, and the frequency modulation speed reduction pipe section drives the pulse boosting pipe section to rotate through the driven sleeve. Subsequently, the fracturing fluid enters the first load-bearing water conduit of the second cylinder body. When passing through the frequency modulation speed reduction mechanism, the supply frequency of the fracturing fluid is adjusted, and at the same time, the flow rate of the fracturing fluid is reduced. Subsequently, the fracturing fluid enters the second load-bearing water conduit of the third cylinder body. The booster pump is used to boost the pressure of the fracturing fluid, and the pulse generator is used to provide pressure fluctuations for the fracturing fluid. During the rotation of the pulse boosting pipe section, the fracturing fluid outlet will periodically move to a position communicating with the perforation of the wellbore casing. Combining with the pressure fluctuations of the fracturing fluid, a pulsed water hammer pressure fluctuation is formed to achieve the effect of strong pulsed hydraulic fracturing and solve the problem of insufficient pressure in conventional hydraulic fracturing.

[0026] The following combines Figures 1 to 3 to describe the coal seam gas fracturing device of the present invention.

[0027] An embodiment of the present invention provides a coal seam fracturing device, which includes a rotary drive pipe section 100, a frequency modulation speed reduction pipe section 200, and a pulse boosting pipe section 300. The rotary drive pipe section 100, the frequency modulation speed reduction pipe section 200, and the pulse boosting pipe section 300 are connected in sequence. The fracturing fluid enters from the rotary drive pipe section 100, and the energy of the fracturing fluid is converted into rotational mechanical energy through the rotary drive pipe section 100, thereby driving the frequency modulation speed reduction pipe section 200 and the pulse boosting pipe section 300 to rotate synchronously. After the fracturing fluid is frequency modulated and speed reduced by the frequency modulation speed reduction pipe section 200, a pulsed fracturing fluid is formed after passing through the pulse boosting pipe section 300, generating a water hammer pressure fluctuation, and finally performing pulsed hydraulic fracturing after passing through the perforation of the wellbore casing.

[0028] The rotary drive pipe section 100 includes a fracturing fluid pumping assembly, a first cylinder 130, a hydraulic rotary drive mechanism, and a drive sleeve 150. The fracturing fluid pumping assembly is arranged at the upstream end of the first cylinder 130 for conveying the fracturing fluid into the first cylinder 130. The drive sleeve 150 is arranged at the downstream end of the first cylinder 130 and is rotationally and sealingly connected to the first cylinder 130. The hydraulic rotary drive mechanism is arranged inside the first cylinder 130 and is in transmission connection with the drive sleeve 150.

[0029] Specifically, as Figure 1 shown, the fracturing fluid pumping assembly includes a liquid storage tank 110 and a liquid pump 120. The top surface of the liquid storage tank 110 is provided with a fracturing fluid inlet for connecting with a fracturing fluid source. The bottom surface of the liquid storage tank 110 is sealingly connected to the top end face of the first cylinder 130, and the center of the bottom surface of the liquid storage tank 110 is communicated with the inside of the first cylinder 130. The liquid pump 120 is arranged inside the first cylinder 130 and is communicated with the liquid storage tank 110. The liquid pump 120 is used to pump the fracturing fluid in the liquid storage tank 110 into the first cylinder 130.

[0030] As Figure 2 shown, the hydraulic rotary drive mechanism can be a turbine and vortex fan 140. The turbine and vortex fan 140 is rotationally connected to the first cylinder 130, and the rotation axis is collinear with the axis of the first cylinder 130. When the fracturing fluid passes through the turbine and vortex fan 140, the fracturing fluid drives the turbine and vortex fan 140 to rotate.

[0031] The drive sleeve 150 is rotationally and sealingly connected to the bottom end of the first cylinder 130 and is in transmission connection with the turbine and vortex fan 140. When the fracturing fluid drives the turbine and vortex fan 140 to rotate, it drives the drive sleeve 150 to rotate.

[0032] There is no specific limitation on the material of the first cylinder 130. The function of the first cylinder 130 is to protect the turbine and vortex fan 140 and the liquid pump 120 from the influence of factors such as formation pressure and temperature, and to avoid the situation that the turbine and vortex fan 140 and the liquid pump 120 are damaged due to high coal seam temperature and large pressure during the fracturing process.

[0033] The frequency modulation and speed reduction pipe section 200 includes a second cylinder body 210, a first load-bearing water conduit 220, a frequency modulation and speed reduction mechanism, and a driven sleeve 250. The upstream end of the second cylinder body 210 is connected to the driving sleeve 150, and the driven sleeve 250 is connected to the downstream end of the second cylinder body 210. The first load-bearing water conduit 220 is arranged inside the second cylinder body 210, and the upstream end of the first load-bearing water conduit 220 is internally connected to the first cylinder body 130 through the driving sleeve 150. The downstream end of the first load-bearing water conduit 220 is connected to the driven sleeve 250, and the frequency modulation and speed reduction mechanism is connected to the first load-bearing water conduit 220.

[0034] Specifically, as Figure 1 shown, the top end of the second cylinder body 210 is connected to the bottom end of the driving sleeve 150, and the driven sleeve 250 is connected to the bottom end of the second cylinder body 210.

[0035] The first load-bearing water conduit 220 is arranged inside the second cylinder body 210, and the top end of the first load-bearing water conduit 220 is connected to the driving sleeve 150 and is connected to the first cylinder body 130 through the driving sleeve 150, so that the fracturing fluid can directly enter the first load-bearing water conduit 220 after passing through the turbine and turbofan 140. The bottom end of the first load-bearing water conduit 220 is connected to the driven sleeve 250.

[0036] The frequency modulation and speed reduction mechanism is arranged on the first load-bearing water conduit 220. When the fracturing fluid passes through the frequency modulation and speed reduction mechanism, the frequency and flow rate of the fracturing fluid can be adjusted.

[0037] Furthermore, a check valve 230 is also arranged inside the first load-bearing water conduit 220. The check valve 230 is arranged upstream of the frequency modulation and speed reduction mechanism, and its function is to prevent the fracturing fluid from flowing back.

[0038] The function of the second cylinder body 210 is the same as that of the first cylinder body 130. The second cylinder body 210 can protect the first load-bearing water conduit 220, the frequency modulation and speed reduction mechanism, and the check valve 230 from the influence of factors such as formation pressure and temperature, and avoid the situation that the first load-bearing water conduit 220, the frequency modulation and speed reduction mechanism, and the check valve 230 are damaged due to high coal seam temperature and large pressure during the fracturing process.

[0039] The pulse boosting pipe section 300 includes a third cylinder body 310, a second load-bearing water conduit 320, a boosting pump 330, a pulse generator 340, and a sealing baffle 400. The upstream end of the third cylinder body 310 is connected to the driven sleeve 250, and the sealing baffle 400 is sealingly connected to the downstream end of the third cylinder body 310. The second load-bearing water conduit 320 is arranged inside the third cylinder body 310, and the upstream end of the second load-bearing water conduit 320 is communicated with the first load-bearing water conduit 220 through the driven sleeve 250. The downstream end of the second load-bearing water conduit 320 is sealingly connected to the sealing baffle 400. The boosting pump 330 is arranged inside the second load-bearing water conduit 320, and the pulse generator 340 is arranged inside the boosting pump 330. A plurality of fracturing fluid outlets 350 communicating the inside and outside of the second load-bearing water conduit 320 are arranged on the third cylinder body 310 and the second load-bearing water conduit 320. The plurality of fracturing fluid outlets 350 are distributed along the axial direction of the third cylinder body 310, and the distance between two adjacent fracturing fluid outlets 350 is equal to the distance between two adjacent perforations on the wellbore casing.

[0040] Specifically, referring to Figure 1 , the top end of the third cylinder body 310 is connected to the driven sleeve 250, so that the third cylinder body 310 rotates synchronously with the driven sleeve 250. The sealing baffle 400 is arranged at the bottom end of the third cylinder body 310 for sealing the bottom of the third cylinder body 310.

[0041] The second load-bearing water conduit 320 is arranged through the third cylinder body 310. The top of the second load-bearing water conduit 320 is communicated with the first load-bearing water conduit 220 through the driven sleeve 250, and the bottom end of the second load-bearing water conduit 320 is closed by the sealing baffle 400.

[0042] The boosting pump 330 is arranged inside the second load-bearing water conduit 320, and the pulse generator 340 is arranged inside the boosting pump 330. A plurality of fracturing fluid outlets 350 are arranged on the second load-bearing water conduit 320 and the third cylinder body 310. The plurality of fracturing fluid outlets 350 are distributed along the axial direction of the third cylinder body 310 and penetrate through the second load-bearing water conduit 320 and the third cylinder body 310 in the radial direction of the third cylinder body 310 to communicate the second load-bearing water conduit 320 and the wellbore casing. The number of the fracturing fluid outlets 350 is the same as the number of a group of perforations, and the distance between two adjacent fracturing fluid outlets 350 is the same as the distance between two adjacent perforations in the same group of perforations.

[0043] The third cylinder body 310 has the same effect as the first cylinder body and the second cylinder body. The third cylinder body 310 can protect the boosting pump 330 and the pulse generator 340 from the influence of factors such as formation pressure and temperature, and avoid the situation that the boosting pump 330 and the pulse generator 340 are damaged due to high coal seam temperature and large pressure during the fracturing process.

[0044] In some embodiments, referring to Figure 3, the frequency modulation and speed reduction mechanism includes a housing 241 and a gear 246.

[0045] A main flow channel 242 is provided on the housing 241 in the direction from the upstream end to the downstream end of the first load-carrying water conduit 220, and the main flow channel 242 penetrates through the housing 241. A first bypass flow channel 243 and a second bypass flow channel 244 are symmetrically arranged on the left and right parts of the housing 241 respectively, and accommodation grooves 245 are symmetrically arranged on the left and right parts of the housing 241.

[0046] The main flow channel 242 is arranged in the middle, and the accommodation grooves 245 on both sides of the main flow channel 242 are both communicated with the main flow channel 242. The accommodation grooves 245 can be arc-shaped grooves, and their inner diameters are equal to the pitch circle diameter of the gear 246. A gear 246 is rotatably connected in each accommodation groove 245, and the two gears 246 are meshed in the main flow channel 242.

[0047] The top end of the first bypass flow channel 243 on the left side is communicated with the upstream end of the main flow channel 242, and the bottom end is communicated with the lower half part on the left side of the accommodation groove 245 on the left side. The bottom end of the second bypass flow channel 244 on the left side is communicated with the downstream end of the main flow channel 242, and the top end is communicated with the upper half part on the left side of the accommodation groove 245 on the left side.

[0048] Similarly, the structures of the first bypass flow channel 243, the second bypass flow channel 244 and the accommodation groove 245 on the right side are the same as those on the left side, and only the structures on the left side need to be symmetrically arranged to the right.

[0049] In this way, when fracturing fluid flows through the main flow channel 242, the pressure of the fracturing fluid before passing through the gear 246 is greater than the pressure of the fracturing fluid after passing through the gear 246. Through the first bypass flow channel 243 and the second bypass flow channel 244, a rotational driving force can be applied to the gear 246. The gear 246 on the left side rotates counterclockwise, and the gear 246 on the right side rotates clockwise. In this way, resistance can be provided for the fracturing fluid flowing in the main flow channel 242, and thus the effect of frequency modulation and speed reduction can be achieved.

[0050] In some embodiments, a guide shoe 500 is further provided on the side of the sealing baffle 400 away from the third cylinder 310, which mainly plays a guiding role when the coal seam gas fracturing device is inserted into the wellbore casing. For example, the guide shoe 500 can be hemispherical or semi-ellipsoidal.

[0051] The specific working process of the coal seam gas fracturing device provided by the present invention is as follows; After the fracturing fluid source is connected to the fracturing fluid inlet of the liquid storage tank 110, fracturing fluid is supplied into the liquid storage tank 110. The liquid pump 120 pumps the fracturing fluid in the liquid storage tank 110 into the first cylinder 130. The fracturing fluid flows through the turbine and vortex fan 140, thereby driving the turbine and vortex fan 140 to rotate, and further driving the driving sleeve 150, the frequency modulation and speed reduction pipe section 200 and the pulse boosting pipe section 300 to rotate.

[0052] Then, the fracturing fluid enters the first load-bearing water conduit 220. When passing through the frequency modulation and speed reduction mechanism, the frequency of the fracturing fluid is adjusted and its flow rate is reduced.

[0053] Then, the fracturing fluid enters the second load-bearing water conduit 320. The booster pump 330 and the pulse generator 340 in the second load-bearing water conduit 320 are used to boost the pressure of the fracturing fluid a second time. Moreover, during the rotation of the pulse boosting pipe section 300, the fracturing fluid outlet 350 is periodically aligned with the perforations on the wellbore casing. When they are aligned, high-pressure fracturing fluid is ejected to form a pulsed water hammer pressure fluctuation, thereby realizing strong pulsed hydraulic fracturing.

[0054] An embodiment of the present invention further provides a fracturing system. Since the coalbed methane fracturing device as described above is provided, it has the same advantages as described above.

[0055] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various embodiments of the present application, and they should all be covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any manner. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A coalbed methane fracturing device, characterized in that Comprising: A rotary drive pipe section (100), including a fracturing fluid pumping assembly, a first cylinder body (130), a hydraulic rotary drive mechanism, and a drive sleeve (150). The fracturing fluid pumping assembly is arranged at the upstream end of the first cylinder body (130) for delivering fracturing fluid into the first cylinder body (130). The drive sleeve (150) is arranged at the downstream end of the first cylinder body (130) and is rotationally and sealingly connected to the first cylinder body (130). The hydraulic rotary drive mechanism is arranged inside the first cylinder body (130) and is in transmission connection with the drive sleeve (150); A frequency modulation and speed reduction pipe section (200), including a second cylinder body (210), a first load-bearing water conduit (220), a frequency modulation and speed reduction mechanism, and a driven sleeve (250). The upstream end of the second cylinder body (210) is connected to the drive sleeve (150). The driven sleeve (250) is connected to the downstream end of the second cylinder body (210). The first load-bearing water conduit (220) is arranged inside the second cylinder body (210), and the upstream end of the first load-bearing water conduit (220) is in communication with the inside of the first cylinder body (130) through the drive sleeve (150). The downstream end of the first load-bearing water conduit (220) is connected to the driven sleeve (250). The frequency modulation and speed reduction mechanism is connected to the first load-bearing water conduit (220); A pulse boosting pipe section (300), including a third cylinder body (310), a second load-bearing water conduit (320), a booster pump (330), a pulse generator (340), and a sealing baffle (400). The upstream end of the third cylinder body (310) is connected to the driven sleeve (250). The sealing baffle (400) is sealingly connected to the downstream end of the third cylinder body (310). The second load-bearing water conduit (320) is arranged inside the third cylinder body (310), and the upstream end of the second load-bearing water conduit (320) is in communication with the first load-bearing water conduit (220) through the driven sleeve (250). The downstream end of the second load-bearing water conduit (320) is sealingly connected to the sealing baffle (400). The booster pump (330) is arranged inside the second load-bearing water conduit (320). The pulse generator (340) is arranged inside the booster pump (330). A plurality of fracturing fluid outlets (350) communicating the inside and outside of the second load-bearing water conduit (320) are arranged on the third cylinder body (310) and the second load-bearing water conduit (320). The plurality of fracturing fluid outlets (350) are distributed along the axial direction of the third cylinder body (310), and the distance between two adjacent fracturing fluid outlets (350) is equal to the distance between two adjacent perforations on the wellbore casing.

2. The coal seam gas fracturing device according to claim 1, wherein The fracturing fluid pumping assembly includes a liquid storage tank (110) and a liquid pump (120). The first side of the liquid storage tank (110) is sealingly connected to the upstream end of the first cylinder (130), and the second side of the liquid storage tank (110) is used to connect to a fracturing fluid source. The liquid pump (120) is arranged inside the first cylinder (130) and is connected to the first side of the liquid storage tank (110).

3. The coal seam gas fracturing device according to claim 1, characterized in that, The hydraulic rotary drive mechanism includes a turbine and fan (140).

4. The coal seam gas fracturing device according to claim 1, characterized in that A check valve (230) is further arranged inside the first load-carrying water conduit (220), and the check valve (230) is arranged on the upstream side of the frequency modulation and speed reduction mechanism.

5. The coal seam gas fracturing device according to claim 1 or 4, characterized in that, The frequency modulation and speed reduction mechanism includes: A housing (241) with a main flow channel (242), a pair of receiving grooves (245), a pair of first bypass flow channels (243) and a pair of second bypass flow channels (244) arranged inside. The main flow channel (242) is connected to the first load-carrying water conduit (220). The pair of receiving grooves (245) are symmetrically arranged on both sides of the main flow channel (242) and are connected to the main flow channel (242). One end of the first bypass flow channel (243) is connected to the upstream end of the main flow channel (242), and the other end is connected to the lower half of the side of the same-side receiving groove (245) away from the main flow channel (242). One end of the second bypass flow channel (244) is connected to the downstream end of the main flow channel (242), and the other end is connected to the upper half of the side of the same-side receiving groove (245) away from the main flow channel (242). Gears (246), including two gears (246) respectively arranged inside the two receiving grooves (245), rotatably connected to the housing (241) with parallel rotation axes along the horizontal direction. The two gears (246) are meshed inside the main flow channel (242), and the pitch circle diameter of the gears (246) is equal to the inner diameter of the receiving groove (245).

6. The coal seam gas fracturing device according to claim 1, wherein, A guiding shoe (500) is further included, and the guiding shoe (500) is arranged on the side of the sealing baffle (400) away from the third cylinder (310).

7. The coal seam gas fracturing device according to claim 6, characterized in that, The guiding shoe (500) is hemispherical or semi-ellipsoidal.

8. A fracturing system, characterized in that, It includes the coal seam gas fracturing device according to any one of claims 1 to 7.

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