Hydraulic fracturing and burning explosion permeability increasing system and method for extracting unconventional natural gas

Abstract

The system comprises a plurality of sections of screen pipes, a pushing rod extends into the screen pipes, one end of the pushing rod is connected with a fracturing and burning explosion integrated device, the other end of the pushing rod extends to a wellhead, a conveying oil pipe, a conveying gas pipe and a liquid discharging pipe penetrate into the pushing rod, and the liquid discharging pipe is connected with the pushing rod. Screen holes are formed in the multiple sections of screen pipes at intervals, and energy-gathered perforators are installed at the positions of the screen holes. Hydraulic fracturing is firstly carried out in the first section of screen pipe of the horizontal well, then the pushing rod is moved to enable the blasting gas punching holes to be aligned with the screen holes, compressed mixed combustible gas in the blasting device module is ignited, secondary fracture forming can be carried out on fractures through generated impact, the low-permeability rock stratum is further damaged, and the shale gas yield is increased. In addition, gas impact generated by burning explosion can push the proppant in the crack to a farther position and a newly generated crack, and the crack is prevented from being closed. And finally, the modularized integrated design system not only is simple to operate, but also greatly reduces the engineering cost.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of hydraulic fracturing and combustion penetration system and method of extraction of unconventional natural gas, belong to shale gas exploitation technical field. BACKGROUND

[0002] At present, unconventional natural gas development mostly adopts horizontal well segmented fracturing exploitation technology.Due to geological conditions are mostly dense sandstone or shale, only rely on hydraulic fracture seam making difficulty is usually greater, this technology often exists the problem of high initial production, mid-term production gradually reduces.In order to improve production, the technology needs to be strengthened. SUMMARY

[0003] The purpose of the present application is to provide a kind of hydraulic fracturing and combustion penetration system and method of extraction of unconventional natural gas.Through the system and method, the shock wave generated by igniting compressed combustible gas can be applied to secondary seam making on the basis of original hydraulic fracture seam making, and the proppant in the fracturing fluid can be pushed into further cracks or newly generated cracks, effectively improving the percolation of the reservoir, and bringing substantial progress to the exploitation of unconventional natural gas.

[0004] The technical scheme of the present application: a kind of hydraulic fracturing and combustion penetration system of extraction of unconventional natural gas, comprising multiple screen pipes installed in horizontal well, hollow push rod is inserted into multiple screen pipes, one end of push rod is connected with fracturing and combustion integrated device, the other end extends to wellhead, fracturing and combustion integrated device is composed of fracturing module and combustion device module, push rod is penetrated by delivery tubing, gas delivery pipe and liquid discharge pipe, wherein one end of delivery tubing and liquid discharge pipe is connected with fracturing module, the other end is connected with fracturing fluid pump station, one end of gas delivery pipe is connected with combustion device module, the other end is connected with mixed combustible gas pump station;A group of screen holes are arranged at intervals on multiple screen pipes, and concentrator perforator is installed at screen hole.

[0005] In the foregoing hydraulic fracturing and combustion penetration system of extraction of unconventional natural gas, the fracturing module is in communication with the outside through the fracturing fluid injection hole, and a sealer is installed at the hole mouth of the fracturing fluid injection hole.

[0006] In the foregoing hydraulic fracturing and combustion penetration system of extraction of unconventional natural gas, the combustion device module is provided with a spark plug and a gas pressure detection device inside, and the combustion device module is in communication with the outside through the combustion gas hole, and a bursting disc and a holder are installed at the hole mouth of the combustion device module;A sealing valve and a second control valve are arranged on the gas delivery pipe.

[0007] In the foregoing hydraulic fracturing and combustion penetration system for extracting unconventional natural gas, a screen groove is arranged on the inner wall of the multi-section screen pipe behind each group of screen holes, and a telescopic sealing wall is movably connected to the push rod, and a limiting block is arranged on the outer wall of the push rod in front of and behind the telescopic sealing wall.

[0008] In the foregoing hydraulic fracturing and combustion penetration system for extracting unconventional natural gas, a first control valve and a pressure gauge are arranged on the conveying oil pipe.

[0009] In the foregoing hydraulic fracturing and combustion penetration system for extracting unconventional natural gas, the system further comprises an extraction pipe extending into the horizontal well, and one end of the extraction pipe is connected to the shale gas storage chamber.

[0010] A method for hydraulic fracturing and combustion penetration for extracting unconventional natural gas, which is implemented by the foregoing system and specifically comprises the following steps:

[0011] S1: determining a shale gas reservoir to be extracted and constructing a horizontal well;

[0012] S2: lowering the hydraulic fracturing and combustion penetration device system into the wellbore;

[0013] S3: expanding the telescopic sealing wall to make it engage with the screen groove; firing the shaped charge at the screen hole to make a perforation, controlling the push rod to inject fracturing fluid into the perforation and the screen hole; opening the fracturing fluid pump station, injecting fracturing fluid into the fracturing module in the horizontal well through the conveying oil pipe, performing hydraulic fracturing, and after completion, pumping the fracturing fluid back to the fracturing fluid pump station through the drainage pipe in the reverse direction;

[0014] S4: controlling the push rod to retreat towards the wellhead, so that the combustion gas perforation is aligned with the screen hole, opening the mixed combustible gas pump station, and conveying the mixed gas of methane and air to the combustor module through the conveying gas pipe, checking the gas pressure detection device, igniting the mixed gas by the spark plug when the explosion condition is reached, and performing secondary fracture creation on the fractures generated by hydraulic fracturing;

[0015] S5: retracting the telescopic sealing wall, controlling the push rod to move the fracturing and combustion integrated device to the next section of screen pipe, and repeating steps 1 to 4 until all screen pipes are operated;

[0016] S6: controlling the push rod to return to the wellhead of the extraction derrick, recovering the fracturing and combustion integrated device, and installing the extraction pipe to extract the shale gas storage.

[0017] The beneficial effects of the present application: compared with the prior art, the present application is provided with fracturing and explosion integrated device, push rod and other structures, in the horizontal well screen pipe, first hydraulic fracturing, then move the push rod to punch the hole aiming at the screen hole, by igniting the compressed mixed combustible gas in the explosion device module, the impact generated can make the fracture secondary fracture, further damage the low permeability rock layer, improve the shale gas production. Moreover, the gas impact generated by the explosion can also push the proppant in the fracture to a farther and newly generated fracture, preventing the fracture from closing. Finally, the modular integrated design system not only has simple operation, but also greatly reduces the engineering cost. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structural schematic diagram of the present application;

[0019] Figure 2 is a structural schematic diagram of the fracturing and explosion integrated device;

[0020] Figure 3 is a cross-sectional schematic diagram of the fracturing and explosion integrated device.

[0021] The drawing shows: 1-overburden, 2-shale gas reservoir, 3-underburden, 4-horizontal well, 5-multistage screen pipe, 6-push rod, 7-delivery gas pipe, 8-delivery oil pipe, 9-drainage pipe, 10-screen pipe groove, 11-retractable sealing wall, 12- shaped charge, 13-fracturing and explosion integrated device, 14-fracture network, 15-extraction derrick, 16-extraction pipe, 17-pressure gauge, 18-first control valve, 19-fracturing fluid pump station, 20-second control valve, 21-mixed combustible gas pump station, 22-shale gas storage chamber, 23-fracturing module, 24-fracturing fluid injection hole, 25-sealer, 26-explosion device module, 27-spark plug, 28-gas pressure detection device, 29-explosion gas punch, 30-bursting disc and holder, 31-sealing valve, 32-limiting block. DETAILED DESCRIPTION

[0022] The present application will be further described below in conjunction with the drawings and examples, but not as the basis for limiting the present application.

[0023] Embodiment of the present application: a hydraulic fracturing and combustion penetration system for extracting unconventional natural gas, the system is suitable for geological conditions of dense sandstone or shale, the system comprises a plurality of screen pipes 5 installed in a horizontal well 4, the plurality of screen pipes 5 are sequentially connected, a hollow push rod 6 extends into the plurality of screen pipes 5, one end of the push rod 6 is connected with the center of a fracturing and combustion integrated device 13, and the other end extends to the well mouth and is connected with a ground extraction derrick 15, the push rod 6 is movable in the plurality of screen pipes 5, the fracturing and combustion integrated device 13 is integrally composed of a fracturing module 23 and a combustor module 25, so as to facilitate downhole operation. The push rod 6 is penetrated by a delivery oil pipe 8, a delivery gas pipe 7 and a liquid discharge pipe 9, one end of the delivery oil pipe 8 and the liquid discharge pipe 9 is connected with the fracturing module 23, and the other end is connected with a fracturing fluid pump station 19 located on the ground, one end of the delivery gas pipe 7 is connected with the combustor module 26, and the other end is connected with a mixed combustible gas pump station 21 on the ground. Each screen pipe of the plurality of screen pipes 5 is provided with a group of screen holes, and each group of screen holes is composed of two screen holes located at the top and bottom, and an energy-gathering perforator 12 is installed at each screen hole of the outer wall of the screen pipe.

[0024] In use, first, one group of energy-gathering perforators 12 on the plurality of screen pipes 5 is ignited, and a metal jet is used to punch a hole, then the push rod 6 is moved to make the fracturing module 23 align with the screen hole on the screen pipe, then the fracturing fluid pump station 19 inputs fracturing fluid into the delivery oil pipe 8, the fracturing fluid is discharged from the fracturing module 23 and is pressed out of the screen hole to be injected into the rock stratum, and hydraulic fracturing is performed on the perforation formed by the previous energy-gathering perforator 12. After fracturing is completed, part of the fracturing fluid will flow into the horizontal well 4, and then the fracturing fluid pump station 19 is reversely pumped to make the fracturing fluid enter the fracturing module 23 through the screen hole on the screen pipe from the horizontal well 4, and finally return to the fracturing fluid pump station 19 through the liquid discharge pipe 9. The fracturing fluid can be recycled after being treated. Then the push rod 6 is moved to make the combustor module 26 correspond to the screen hole, and the mixed combustible gas pump station 21 is started to deliver mixed combustible gas to the combustor module 26 through the delivery gas pipe 7, when the mixed combustible gas reaches the set pressure, it is ignited, at this time, the high-temperature and high-pressure shock wave and gas generated by combustion can be directed to the rock stratum through the channel, to realize the effect of punching or penetration, and to expand the fracture of the hydraulic fracturing. Then the push rod 6 is moved to the well mouth, and the above operation is repeated.

[0025] The fracturing module 23 is in communication with the outside through two fracturing fluid injection holes 24, the orifices of which are provided with sealers 25, which are matched in size with the screen holes on the multi-section screen pipe 5. The sealers 25 are specially used to prevent the fracturing fluid from seeping into the screen pipe, which can not only lock the required fracturing pressure and avoid pressure relief, but also prevent fracturing fluid leakage during the flowback stage, ensuring that the fracturing and flowback links meet the process requirements.

[0026] The combustor module 26 has a spark plug 27 inside for igniting the combustible gas, and a gas pressure detection device 28 is installed inside to check the optimal pressure of the combustible gas reaching the combustion condition at any time. The combustor module 26 is externally provided with combustible gas injection holes 29 radially distributed and matched with the size and position of the screen holes, and a bursting disc and holder 30 are installed at the orifices of each combustible gas injection hole 29. The delivery gas pipe 7 is provided with a sealing valve 31 and a second control valve 20.

[0027] When the combustible gas is injected into the combustor module 26, the bursting disc tightly covers the combustible gas injection hole 29 under the fixation of the holder, at this time the bursting disc as a sealing element can reliably block the fluid exchange between the inside and outside of the channel, ensuring that the combustible gas can stably accumulate in the combustor module 26, providing a sealed pressure environment for subsequent combustion. When the combustible gas in the combustor module 26 is ignited, the instantaneous explosion will cause the pressure in the cavity to rise sharply, and when the pressure reaches the "rupture pressure threshold" designed in advance by the bursting disc, the bursting disc will be instantaneously broken, and the originally sealed combustible gas injection hole 29 channel will be opened. At this time, the high-temperature and high-pressure shock wave and gas generated by combustion can act on the rock layer through the channel, realizing the effect of perforation or permeability increase. During the process of injecting mixed combustible gas into the combustor module 26, the sealing valve 31 and the second control valve 20 on the delivery gas pipe 7 need to be opened, and after reaching the set pressure, the second control valve 20 and the sealing valve 31 are closed to avoid the high-pressure shock wave generated from entering the delivery gas pipe 7 in the opposite direction. The combustion process not only performs secondary fracturing on the fracture, but also pushes the proppant in the fracturing fluid to a farther fracture or newly generated fracture through the gas impact.

[0028] A screen groove 10 is arranged on the inner wall of one screen pipe of the multi-section screen pipe 5 behind each screen hole. A telescopic sealing wall 11 is movably connected to the push rod 6. A limiting block 32 is arranged on the outer wall of the push rod 6 in front of and behind the telescopic sealing wall 11. The distance between the two limiting blocks 32 is the length between the fracturing fluid injection hole 24 and the explosion gas punching hole 29. When hydraulic fracturing and explosion penetration are performed on the innermost screen pipe of the multi-section screen pipe 5, the push rod 6 is pushed inward, the left limiting block 32 abuts against the telescopic sealing wall 11, and the telescopic sealing wall 11 is moved inward together. A monitoring device is installed on the outer wall of the push rod 6. When the telescopic sealing wall 11 reaches the innermost screen groove 10, the telescopic sealing wall 11 is controlled to be extended and clamped into the screen groove 10. At this time, the fracturing fluid injection hole 24 on the fracturing module 23 is aligned with the screen hole of the innermost screen pipe. After hydraulic fracturing and fracturing fluid pumping, the push rod 6 is pulled to the wellhead. When the right limiting block 32 abuts against the telescopic sealing wall 11, the push rod 6 cannot be pulled out any more, and the explosion gas punching hole 29 is aligned with the screen hole. After hydraulic fracturing and explosion penetration are performed on one screen pipe, the telescopic sealing wall 11 is controlled to be retracted, so that the push rod 6 can be pulled out. During the process of pulling out the push rod 6, the telescopic sealing wall 11 is moved outward together under the action of the right limiting block 32. When the telescopic sealing wall 11 reaches the second screen groove 10 from inside to outside, the telescopic sealing wall 11 is controlled to be extended and clamped into the screen groove 10 again. At this time, the telescopic sealing wall 11 abuts against the right limiting block 32, so the explosion gas punching hole 29 is aligned with the screen hole. Therefore, the push rod 6 needs to be pushed inward. When the left limiting block 32 abuts against the telescopic sealing wall 11, the fracturing fluid injection hole 24 is aligned with the screen hole.

[0029] The conveying oil pipe 8 is provided with a first control valve 18 and a pressure gauge 17. The first control valve 18 is used to control the opening and closing of the conveying oil pipe 8, and the pressure gauge 17 is used to display the pressure of the conveyed fracturing fluid.

[0030] The system further comprises a pumping pipe 16 extending into the horizontal well 4, and one end of the pumping pipe 16 is connected with the shale gas storage chamber 22. After hydraulic fracturing and explosion penetration are performed on the entire multi-section screen pipe 5, the shale gas will overflow through the formed fracture network 14. At this time, the pumping pipe 16 can be installed to pump and store the shale gas.

[0031] A hydraulic fracturing and explosion penetration system and method for pumping unconventional natural gas, the method is realized by the above system, and specifically includes the following steps.

[0032] First, a shale gas reservoir 2 to be mined is determined, a pumping derrick 15 is installed on the ground, and a horizontal well 4 is constructed by a directional drill bit. A multi-section screen pipe 5 is installed in the horizontal well, and a concentrative perforator 12 is installed at each screen hole of each screen pipe.

[0033] Then, the fracturing and explosion integrated device 13 is sent to the innermost part of the multi-section screen pipe 5 by using the push rod 6. The telescopic sealing wall 11 is unfolded and engaged with the screen pipe groove 10 to prevent the fracturing or explosion process from affecting the next stage screen pipe. The electric detonator inside the shaped charge gun 12 is fired to perforate, the push rod 6 is adjusted, i.e. the left limiting block 32 is tightly close to the telescopic sealing wall 11, the fracturing fluid injection hole 24 is aligned with the screen hole, the fracturing fluid pump station 19 is started, the first control valve 18 is opened, the pressure is adjusted to 20 MPa according to the reading shown by the pressure gauge 17, the fracturing fluid enters the fracturing module 23 through the delivery tubing 8, and then is injected into the rock formation through the fracturing fluid injection hole 24 to perform hydraulic fracturing. The fracturing lasts for 40 minutes, the first control valve 18 is closed, and the fracturing fluid is returned and discharged to the fracturing fluid pump station 19 through the discharge pipe 9.

[0034] Secondly, the push rod 6 is moved to the wellhead direction, so that the right limiting block 32 is tightly close to the telescopic sealing wall 11, the explosion gas hole 29 outside the exploder module 26 is aligned with the screen hole, the combustible gas pump station 21 is started, the second control valve 20 and the sealing valve 31 are opened, and the mixed combustible gas is continuously injected into the exploder module 26 in the horizontal well through the delivery gas pipe 7. When the gas pressure detection device 28 detects that the inside of the exploder module 26 reaches a predetermined pressure of 6 MPa, the second control valve 20 and the sealing valve 31 are closed, and the combustible gas is ignited by the spark plug 27. The sharp rise of the pressure of the exploder module 26 will instantaneously destroy the bursting disc, at this time, the high-temperature and high-pressure shock wave and gas generated by the explosion enter the rock formation fracture through the explosion gas hole 29 to perform secondary expansion of the fracture after the hydraulic fracturing.

[0035] Finally, the telescopic sealing wall 11 is contracted, the push rod 6 is controlled to move the fracturing and explosion integrated device 13 to the next section screen pipe, and the above operation steps are repeated until all the screen pipe operations are completed. The push rod 6 is controlled to return to the wellhead of the extraction derrick 15, the fracturing and explosion integrated device 13 is recovered, and the extraction pipe 16 is installed to extract the shale gas storage. The penetration improvement of the horizontal well 4 is completed.

[0036] The above-mentioned method can not only realize the improvement of the penetration of the horizontal well 4, but also has a more simple and clear extraction system method compared with the known scheme, and maximally reduces the complexity of the downhole process. Meanwhile, the above-mentioned method is only the optimal implementation manner of the present application, and the protection scope of the present application is not limited to this. Any adjustment or change within the technical framework disclosed in the present application and easily realized by the person skilled in the art belongs to the protection scope of the present application. Therefore, when the protection scope of the present application is determined, the protection scope stated in the claims should be used as the criterion.

Claims

1. A hydraulic fracturing and combustion induced permeability enhancement system for extraction of unconventional natural gas, characterized by: The system comprises a plurality of screen pipes (5) installed in the horizontal well (4), a hollow push rod (6) extending into the screen pipes (5), one end of the push rod (6) being connected with a fracturing and blasting integrated device (13), the other end of the push rod (6) extending to the well mouth, the fracturing and blasting integrated device (13) being integrally composed of a fracturing module (23) and a burner module (25), the push rod (6) being penetrated by a delivery oil pipe (8), a delivery gas pipe (7) and a liquid discharge pipe (9), one end of the delivery oil pipe (8) and the liquid discharge pipe (9) being connected with the fracturing module (23), the other end of the delivery oil pipe (8) and the liquid discharge pipe (9) being connected with a fracturing fluid pump station (19), one end of the delivery gas pipe (7) being connected with the burner module (26), the other end of the delivery gas pipe (7) being connected with a mixed combustible gas pump station (21), a plurality of screen holes being arranged at intervals on the screen pipes (5), and a set of energy focusing perforators (12) being installed at the screen holes.

2. The hydraulic fracturing and combustion induced permeability enhancement system for extracting unconventional natural gas by drainage according to claim 1, characterized in that: The fracturing module (23) is communicated with the outside through a fracturing fluid injection hole (24), and a sealer (25) is installed at the hole mouth of the fracturing fluid injection hole (24).

3. The hydraulic fracturing and combustion induced permeability enhancement system for extracting unconventional natural gas according to claim 1, wherein: The burner module (26) is internally provided with a spark plug (27) and a gas pressure detection device (28), and the burner module (26) is communicated with the outside through a blasting gas punching hole (29), and a bursting disc and holder (30) is installed at the hole mouth of the blasting gas punching hole (29); the delivery gas pipe (7) is provided with a sealing valve (31) and a second control valve (20).

4. The hydraulic fracturing and combustion induced permeability enhancement system for extracting unconventional natural gas according to claim 1, wherein: A screen pipe groove (10) is arranged on the inner wall of the screen pipe (5) behind each set of screen holes, and a telescopic sealing wall (11) is movably sleeved on the push rod (6), and a limiting block (32) is arranged on the outer wall of the push rod (6) before and after the telescopic sealing wall (11).

5. The hydraulic fracturing and combustion induced permeability enhancement system for extracting unconventional natural gas according to claim 1, wherein: The delivery oil pipe (8) is provided with a first control valve (18) and a pressure gauge (17).

6. The hydraulic fracturing and combustion induced permeability enhancement system for extracting unconventional natural gas according to claim 1, wherein: The system further comprises a pumping pipe (16) extending into the horizontal well (4), one end of the pumping pipe (16) being connected with a shale gas storage chamber (22).

7. A hydraulic fracturing and combustion induced permeability method for extraction of unconventional natural gas, characterized by: The method is implemented by means of the system according to any one of claims 1-6, and specifically comprises the following steps: S1: determining a shale gas reservoir (2) to be exploited, and constructing a horizontal well (4); S2: lowering the horizontal well hydraulic fracturing and blasting permeability enhancement device system into the wellbore; S3: unfolding the telescopic sealing wall (11) to make it engage with the screen pipe groove (10); exciting the energy focusing perforators (12) at the screen holes to punch holes, and aligning the fracturing fluid injection hole (24) with the screen holes by means of the push rod (6); opening the fracturing fluid pump station (19), and injecting fracturing fluid into the fracturing module (23) in the horizontal well (4) through the delivery oil pipe (8) to perform hydraulic fracturing, and after completion, the fracturing fluid is reversely pumped back to the fracturing fluid pump station (19) through the liquid discharge pipe (9); S4: retracting the push rod (6) towards the well mouth to make the blasting gas punching hole (29) align with the screen holes, opening the mixed combustible gas pump station (21), and delivering the methane and air mixed gas to the burner module (26) through the delivery gas pipe (7), checking the gas pressure detection device (28), igniting the mixed gas by means of the spark plug (27) when the explosive condition is reached, and performing secondary fracture creation on the fractures generated by the hydraulic fracturing. S5: shrinkage of the scalable sealing wall (11), control the push rod (6) to move the fracturing and combustion integrated device (13) to the next section of the screen pipe, repeat the above steps one to four operations until all the screen pipe operation is completed; S6: control the push rod (6) to return to the extraction derrick (15) wellhead, recycle the fracturing and combustion integrated device (13), install the extraction pipe (16) to extract the shale gas storage.

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