Coal seam multistage pulse unstable convergent hydraulic fracturing tool nipple

Abstract

The present application relates to a kind of coal seam multistage pulse unstable convergent flow hydraulic fracturing tool nipple, including external casing and internal convergent flow device, convergent flow device is located in the inside of external casing, device upper and lower ends are fixed, there is an annular flow channel in the middle, convergent flow channel has convergent flow channel in the inside of convergent flow device, and convergent flow channel is composed of multistage flow channel and a convergent flow cavity, and high discharge fracturing fluid is formed high pressure pulse by convergent flow cavity oscillation.Set the toothed flow channel in the lower half of casing inner wall, it is convenient to form turbulent resonance, disturb casing outside contact coal seam, reduce the difficulty of cracking, while crushing large particle coal powder, prevent perforation blockage.There are multiple perforations on the upper half of casing outer wall, and the perforation is around casing outer, and it is multiple rows annular array, and there are two flow channels in the inside of perforation:the multistage pulse unstable jet hydraulic fracturing tool nipple can realize coalbed methane efficient production and cost reduction and efficiency improvement, overcome the problem of the complexity of coal seam hydraulic fracturing fracture limited degree and coal powder blockage perforation.

Description

TECHNICAL FIELD

[0001] The present application relates to a coal seam multi-stage pulse unstable convergent flow hydraulic fracturing tool sub, belonging to the field of oil and gas drilling, mainly applied to the hydraulic fracturing of coal bed methane in the oil field. BACKGROUND

[0002] Coal bed methane has the characteristics of low pressure, low permeability, low gas saturation and strong heterogeneity, and hydraulic fracturing is the most commonly used permeability improvement technology for current coal bed methane development. Conventional hydraulic fracturing increases the permeation channel and improves the permeation capacity by pumping a large amount of liquid and proppant into low-permeability oil and gas reservoirs, but the permeation capacity is limited, the process steps are more and the development is more mature, so that the space for cost reduction is limited. Although China has carried out large-scale coal bed methane resource exploration and development work, for local coal bed methane reservoirs with low gas content, due to the low rock permeability, the efficient utilization and development of local coal bed methane is limited. Therefore, it is necessary to explore a reservoir reconstruction tool and method which can effectively increase the permeability and reduce the cost to increase the permeability of coal rock, so as to improve the gas production and gas production efficiency of coal bed methane. Pulse hydraulic fracturing is a process with better production effect than conventional hydraulic fracturing, and accordingly, a pulse hydraulic fracturing tool and method suitable for coal seams are needed.

[0003] The prior art mainly changes the continuous high-speed jet into intermittent pulse high-speed jet by intermittently disconnecting the connection between the nozzle and the flow channel of the rotor. It has good application effect in many formations, but for coal seams which are easy to be damaged, the jet flow may be blocked by coal powder during the intermittent period, affecting the fracturing effect. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide a coal seam multi-stage pulse unstable convergent flow hydraulic fracturing tool sub, which can realize efficient production of coal bed methane and cost reduction and efficiency improvement, and overcome the problems of limited complexity of coal seam hydraulic fracturing cracks and coal powder blocking perforation.

[0005] To achieve the above purpose, the present application adopts the following technical scheme:

[0006] The present application provides a coal seam multi-stage pulse unstable convergent flow hydraulic fracturing tool sub, comprising an external casing and a convergent flow device, the convergent flow device is sleeved in the external casing, and an annular flow channel is formed between the convergent flow device and the external casing;

[0007] The convergent flow device has a convergent flow channel in the center, the convergent flow channel comprises a multi-stage convergent flow port, a flow expansion port and a convergent flow cavity, and the multi-stage convergent flow port, the flow expansion port and the convergent flow cavity are connected in sequence along the axial direction;

[0008] The bottom of the flow converging device is further provided with a flow distribution port, fluid flows into the flow converging flow channel and then passes through the multi-stage flow converging ports, the flow expanding ports and the flow converging cavities in sequence and enters into the annular flow channel through the flow distribution port;

[0009] The top of the outer sleeve is provided with a plurality of perforating holes, the annular flow channel comprises a turning flow channel at the bottom and a toothed flow channel in the middle, the perforating holes are arranged above the toothed flow channel, the inner wall of the flow converging device and the inner wall of the outer sleeve are both formed with toothed structures, and the toothed flow channel is formed between the toothed structures on both sides.

[0010] Preferably, the toothed flow channel continues upward to the position where the perforating holes are located, and the toothed structures on both sides are staggered.

[0011] Preferably, the flow distribution port is formed in an arc shape, and the diameter of the flow distribution port gradually increases from top to bottom.

[0012] Preferably, the plurality of perforating holes are formed in a plurality of rows, the rows are arranged at intervals along the length direction of the outer sleeve, and each row of perforating holes is arranged in an annular array.

[0013] Preferably, a nozzle is connected to the perforating hole, the nozzle comprises an outer sleeve and an inner sleeve, the inner sleeve is sleeved in the outer sleeve, a straight flow channel is formed between the outer sleeve and the inner sleeve, a flow converging channel is formed in the inner sleeve, and the straight flow channel and the flow converging channel are both in communication with the toothed flow channel.

[0014] Preferably, the inner sleeve is fixed in the outer sleeve by a fixing beam.

[0015] Preferably, the fixing beam comprises a plurality of fixing beams, and the plurality of fixing beams are uniformly and circumferentially arranged at intervals.

[0016] Preferably, the cross section of the fixing beam is in an inverted triangular shape.

[0017] Preferably, the perforating hole flow converging port at the outlet of the straight flow channel is inwardly curved in an arc structure.

[0018] Preferably, the plurality of perforating holes comprise a first-stage flow converging port and a second-stage flow converging port, and the first-stage flow converging port and the second-stage flow converging port are both in an inverted conical shape.

[0019] The present application has the following advantages due to the above technical scheme:

[0020] 1. The multi-stage pulse unstable jet hydraulic fracturing tool sub of the present application has multi-stage pulse flow converging function and turbulent resonance function; the cross toothed structure of the toothed flow channel forms high-pressure high-speed turbulent flow, and at the same time, the tool resonates, which is beneficial to disturb the external contact coal seam, reduce the difficulty of cracking, crush large particle coal powder and prevent perforating hole blockage;

[0021] 2. The shunt structure of the direct current channel and the convergent channel in the perforation is beneficial to form multi-flow convergence for jet fracturing at the perforation, and is more beneficial to the formation of hydraulic fractures.

[0022] 3. The fixed beam inside the perforation is in an inverted triangular structure, which further strengthens the convergent capacity after temporary flow expansion.

[0023] 4. The perforation multi-row annular array, multi-stage convergent flow channel, perforation internal structure and perforation convergent port arc can be freely configured according to different requirements, have high flexibility and wide application range. BRIEF DESCRIPTION OF DRAWINGS

[0024] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the application. Throughout the drawings, like reference numerals will be used to refer to like components. In the drawings:

[0025] Figure 1 is a cross-sectional view of an embodiment of the coal seam multi-stage pulse unstable convergent hydraulic fracturing tool sub provided by the present application;

[0026] Figure 2 Figure 1 is a top view of the perforation;

[0027] Figure 3 is a cross-sectional view of the nozzle and a cross-sectional view of the fixed beam;

[0028] Figure 4 I, Figure 4 II, Figure 4 III and Figure 4 IV are four different embodiments of the cross-sectional view of the nozzle, respectively;

[0029] The various signs in the drawings represent the following:

[0030] 1 - convergent device, 2 - convergent flow channel, 3 - first-stage convergent port, 4 - second-stage convergent port, 5 - flow expansion port, 6 - convergent cavity, 7 - shunt port, 8 - external sleeve, 9 - annular flow channel, 10 - nozzle, 11 - tooth-shaped flow channel, 12 - tooth-shaped structure, 13 - turning flow channel, 101 - outer sleeve, 102 - inner sleeve, 103 - direct current channel, 104 - perforation convergent port, 105 - convergent channel, 106 - fixed beam. DETAILED DESCRIPTION

[0031] Exemplary embodiments of the present application will be described herein below with reference to the accompanying drawings. While exemplary embodiments of the present application are illustrated, it is to be understood that the application is not to be limited to the embodiments described herein, which are presented as examples of the present application. Rather, the present application is to cover all modifications and alternatives arising from the teachings of the present application.

[0032] The coal seam multi-stage pulse unstable convergent flow hydraulic fracturing tool sub provided by the present application comprises an outer sleeve and a convergent flow device, the convergent flow device is sleeved in the outer sleeve, and an annular flow channel is formed between the convergent flow device and the outer sleeve. A convergent flow passage is formed in the center of the convergent flow device, the convergent flow passage comprises a multi-stage convergent flow port, a divergent flow port and a convergent flow cavity, and the multi-stage convergent flow port, the divergent flow port and the convergent flow cavity are connected in sequence along the axial direction. A flow distribution port is further arranged at the bottom of the convergent flow device, fluid flows into the convergent flow passage and then passes through the multi-stage convergent flow port, the divergent flow port and the convergent flow cavity in sequence, and then enters the annular flow channel through the flow distribution port. A plurality of perforations are arranged at the top of the outer sleeve, the annular flow channel comprises a turning flow channel at the bottom and a tooth-shaped flow channel in the middle, and the perforations are arranged above the tooth-shaped flow channel. The multi-stage pulse unstable jet hydraulic fracturing tool sub of the present application can realize efficient production increase and cost reduction and efficiency increase of coal seam gas, and overcome the problems of limited complexity of coal seam hydraulic fracturing cracks and coal powder blocking perforations.

[0033] As shown in Figure 1 and Figure 2 An embodiment of the present application provides a coal seam multi-stage pulse unstable convergent flow hydraulic fracturing tool sub, which comprises an outer sleeve 8 and a convergent flow device 1, the convergent flow device 1 is sleeved in the outer sleeve 8, and an annular flow channel 9 is formed between the convergent flow device 1 and the outer sleeve 8. A convergent flow passage 2 is formed in the center of the convergent flow device 1, the convergent flow passage 2 comprises a first-stage convergent flow port 3, a second-stage convergent flow port 4, a divergent flow port 5 and a convergent flow cavity 6, and the first-stage convergent flow port 3, the second-stage convergent flow port 4, the divergent flow port 5 and the convergent flow cavity 6 are connected in sequence along the axial direction. A flow distribution port 7 is further arranged at the bottom of the convergent flow device 1, fluid flows into the convergent flow passage 2 and then passes through the first-stage convergent flow port 3, the second-stage convergent flow port 4, the divergent flow port 5 and the convergent flow cavity 6 in sequence, and then enters the annular flow channel 9 through the flow distribution port 7. A plurality of perforations are arranged at the top of the outer sleeve 8, the annular flow channel comprises a turning flow channel 13 at the bottom and a tooth-shaped flow channel 11 in the middle, the perforations are arranged above the tooth-shaped flow channel 11, the inner wall of the convergent flow device 1 and the inner wall of the outer sleeve are both formed with tooth-shaped structures 12, and the tooth-shaped flow channel 11 is formed between the tooth-shaped structures on both sides.

[0034] The tool short section comprises an external sleeve 8 and an internal flow converging device 1, the flow converging device 1 is located inside the external sleeve 8, the device is fixed at both ends, and a ring space flow channel 9 is arranged in the middle, the flow converging device 1 is internally provided with a flow converging flow channel 2, the flow converging flow channel 2 is composed of a plurality of flow channels and a flow converging cavity 6, and high-displacement fracturing fluid is oscillated in the flow converging cavity 6 to form a high-pressure pulse. The lower half of the inner wall surface of the external sleeve 8 is provided with a tooth-shaped flow channel 11, so that turbulent resonance is formed, the external sleeve 8 is disturbed, the external contact coal seam is reduced, the difficulty of cracking is reduced, and large-particle coal powder is broken to prevent the perforation from being blocked.

[0035] The central flow converging device 1 is finally reduced in diameter due to the existence of a small-diameter first flow converging port 3 and a second flow converging port 4 in the inside.

[0036] Preferably, the lengths of the first flow converging port 3 and the second flow converging port 4 gradually increase from top to bottom in the inside of the flow converging device 1, and the lengths increase by 30%-50% successively.

[0037] The flow converging port is not limited to two levels, but can be three levels or more than three levels, or only one level, and the design mode is within the protection scope of the present application.

[0038] The plurality of perforations are formed to comprise a plurality of rows, the plurality of rows are arranged at intervals along the length direction of the external sleeve 8, and each row of the perforations is arranged along a ring array.

[0039] The tooth-shaped flow channel 11 is continued upward to the position where the perforation is located.

[0040] The tooth-shaped structures on the two walls of the tooth-shaped flow channel 11 are arranged in cross opposition, and the teeth and grooves of the tooth-shaped structures on the two sides are arranged in cross opposition, so that turbulence is formed while the resistance is reduced.

[0041] The flow dividing port 7 is formed in an arc shape, and the diameter of the flow dividing port 7 gradually increases from top to bottom. The end of the flow converging device 1 is provided with the flow dividing port 7, so that the resistance is reduced and the fluid is diffused to the annular outer flow channel.

[0042] The perforation is connected with a nozzle 10, the nozzle 10 comprises an outer sleeve 101 and an inner sleeve 102, the inner sleeve 102 is sleeved in the outer sleeve 101, a straight flow channel 103 is formed between the outer sleeve 101 and the inner sleeve 102, a flow converging channel 105 is formed in the inner sleeve 102, and the straight flow channel 103 and the flow converging channel 105 are in communication with the tooth-shaped flow channel 11.

[0043] The outer sleeve 8 has a plurality of perforations on the outer wall of the upper half, the perforations are arranged around the outer sleeve 8, and the perforations are arranged in a plurality of annular arrays, and there are two flow channels inside the perforations: a straight flow channel 103 and a converging flow channel 105, the outer wall of the straight flow channel 103 and the outlet of the converging flow channel 105 are arc-shaped structures inside, so that the jet flow forms a multi-flow convergence at the perforation outlet, and the hydraulic fracturing expansion capability is improved. The angle of the arc-shaped structure of the perforation converging port 104 can be changed, and the radian can be increased or decreased without affecting the jet flow intensity.

[0044] The inner sleeve 102 is fixed in the outer sleeve 101 by a fixing beam. The fixing beam 106 includes a plurality of fixing beams 106, and the plurality of fixing beams 106 are uniformly spaced along the circumference.

[0045] The cross section of the fixing beam 106 is inverted triangular. The fixing beam 106 inside the perforation is inverted triangular, so that the jet flow in the perforation is dispersed and expanded and then converges, further strengthening the converging flow capability and forming a high-pressure high-speed jet flow. The structure of the fixing beam 106 and the straight flow channel 103 can be customized: one is to change the number of fixing beams 106, the other is to change the diameter of the perforation straight flow channel 103, and the third is to change both.

[0046] The use method of the coal seam multi-stage pulse unstable converging flow hydraulic fracturing tool nipple includes the following steps:

[0047] When drilling a coal seam gas, the above-mentioned multi-stage pulse unstable jet flow hydraulic fracturing tool is connected by a tubing, a pump pumps high-displacement fracturing into the pulse hydraulic fracturing tool through the tubing, the high-displacement fracturing fluid flows into the converging flow device 1 inside,

[0048] The fracturing fluid forms a jet flow through the first converging flow port 3 and the second converging flow port 4, and finally expands to the converging flow cavity 6 through the flow expansion port 5 to form a high-frequency high-pressure pulse liquid, and the high-frequency high-pressure pulse liquid formed by the converging flow cavity 6 outlet through the flow distribution port 7 is diffused at high speed into the annular flow channel 9 between the outer sleeve 8 and the converging flow device 1;

[0049] The flow passes through the tooth-shaped flow channel 11, and the tooth-shaped structure of the tooth-shaped flow channel wall surface is cross arranged, forming an unstable jet flow, so that the tool itself resonates continuously, disturbs the easily damaged coal seam, reduces the difficulty of cracking, and can also crush large particle coal powder to prevent the perforation from being blocked.

[0050] Finally, the unstable jet flow flows to each nozzle 10, respectively flows to the converging flow channel 105 and the perforation straight flow channel 103 inside the nozzle 10, the liquid of the perforation converging flow channel 105 is expanded by the fixing beam 106, and then converges through the perforation converging port 104 at the perforation outlet, the liquid of the perforation converging flow channel 105 converges with the liquid of the perforation straight flow channel, forming a high-pressure high-speed jet flow, which is convenient for forming a wider and longer hydraulic fracture.

[0051] The short section can be multiple in parallel, the internal structure of the perforation, the number of perforations outside the casing and the radian of the perforation flow gathering port can be flexibly customized, and the application range is wide.

[0052] The short section of the multi-pulse unstable jet hydraulic fracturing tool forms high-pressure high-speed pulses through the multi-stage flow gathering port and the oscillation of the flow gathering cavity 6, improves the fracturing efficiency; the cross-toothed structure of the tooth-shaped flow channel 11 forms high-pressure high-speed turbulent flow at the same time, and makes the tool resonate, which is beneficial to disturb the external contact coal seam, reduces the difficulty of cracking, at the same time, crushes large particle coal powder, prevents perforation blockage; the shunt structure inside the perforation is beneficial to form multi-flow convergence for jetting and fracturing at the perforation, and is more beneficial to the formation of hydraulic fractures; the self-defined configuration of the internal structure of the perforation can change the flow gathering effect, increasing the number of fixed beams 106 can improve the multi-flow convergence ability, further reduce the cracking difficulty, and is beneficial to form a fracture network; increasing the diameter of the straight flow channel of the perforation can improve the main fracture extension capacity. In summary, the tool can improve the fracturing efficiency by forming pulses, reduce the cracking difficulty and be beneficial to form a fracture network by forming turbulent flow resonance to disturb the coal seam, and improve the length and width of the hydraulic fracture by multi-flow convergence at the perforation.

[0053] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A coal seam multistage pulse unstable cluster hydraulic fracturing tool sub, characterized in that, The device comprises an outer sleeve and a flow converging device, the flow converging device is sleeved in the outer sleeve, and an annular flow channel is formed between the flow converging device and the outer sleeve; The flow converging device is centrally provided with a flow converging flow channel, the flow converging flow channel comprises a plurality of flow converging ports, a flow expanding port and a flow converging cavity connected in sequence; The flow converging device is further provided with a flow dividing port at the bottom, fluid flows into the flow converging flow channel, sequentially passes through the plurality of flow converging ports, the flow expanding port and the flow converging cavity, and then enters the annular flow channel through the flow dividing port; The outer sleeve is provided with a plurality of perforations at the top, the annular flow channel comprises a turning flow channel at the bottom and a tooth-shaped flow channel in the middle, the perforations are arranged above the tooth-shaped flow channel, the inner wall of the flow converging device and the inner wall of the outer sleeve are both formed with tooth-shaped structures, and the tooth-shaped structures on both sides form the tooth-shaped flow channel.

2. The coal seam multistage pulse unstable converging hydraulic fracturing tool nipple according to claim 1, characterized in that, The tooth-shaped flow channel continues upward to the position where the perforations are located, and the tooth-shaped structures on both sides are staggered.

3. The coal seam multistage pulse unstable converging hydraulic fracturing tool nipple of claim 1, characterized in that, The flow dividing port is formed in an arc shape, and the diameter of the flow dividing port gradually increases from top to bottom.

4. The coal seam multistage pulse unsteady convergent hydraulic fracturing tool nipple of claim 1, characterized in that, The plurality of perforations are formed in a plurality of rows, the rows are arranged at intervals along the length direction of the outer sleeve, and the perforations in each row are arranged in a circular array.

5. The coalbed multistage pulse unsteady convergent hydraulic fracturing tool sub of claim 1, characterized in that, A nozzle is connected to the perforation, the nozzle comprises an outer sleeve and an inner sleeve, the inner sleeve is sleeved in the outer sleeve, a straight flow channel is formed between the outer sleeve and the inner sleeve, a flow converging channel is formed in the inner sleeve, and the straight flow channel and the flow converging channel are both in communication with the tooth-shaped flow channel.

6. The coal seam multistage pulse unsteady convergent hydraulic fracturing tool nipple of claim 5, characterized in that, The inner sleeve is fixed in the outer sleeve by a fixing beam.

7. The coal seam multistage pulse unsteady converging hydraulic fracturing tool nipple according to claim 6, characterized in that, The fixing beam comprises a plurality of fixing beams, and the fixing beams are uniformly and circumferentially arranged at intervals.

8. The coal seam multistage pulse unsteady converging hydraulic fracturing tool sub according to claim 6 or 7, characterized in that, The cross section of the fixing beam is in the shape of an inverted triangle.

9. The coalbed multistage pulsing unpropped hydraulic fracturing tool sub of claim 6, wherein, The perforation flow converging port at the outlet of the straight flow channel is inwardly curved in an arc shape.

10. The coalbed multistage pulsing unpropped hydraulic fracturing tool segment of claim 1, wherein, The plurality of flow converging ports comprise a primary flow converging port and a secondary flow converging port, and the primary flow converging port and the secondary flow converging port are both in the shape of an inverted cone.

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