Device and method for horizontal well methane in-situ explosion multistage fracturing packing and ignition

Abstract

A downhole fracking and packing device includes fusible metal packing plates which contact a borehole wall. Distanced from the plates is an ignition mechanism for igniting a methane gas mix expelled v

Description

The application belongs to the technical field of shale gas exploitation, and in particular relates to a device and a method for horizontal well methane in-situ explosion multistage fracturing packing and ignition. Shale gas is an unconventional natural gas, which is contained in reservoir rock series and has great development potential. Methane in-situ explosion fracturing is a method that uses methane gas adsorbed in the reservoir to impact and fracture shale reservoir through high temperature and high-pressure gas circulation generated by combustion improver explosion, forming a complex three-dimensional fracture network in the reservoir and obtaining shale gas efficiently. However, existing in-situ explosion fracturing methods need to use cables to control the underground ignition device. Sometimes the existing in-situ explosion fracturing methods need cable control for up to thousands of meters, and the cable is difficult to control underground, which is easy to cause construction failure. At the same time, the existing in-situ explosion fracturing methods also negatively affect the packing of horizontal wells, leading to gas leakage during fracturing and reducing the fracturing effect. Therefore, the application designs a device and a method for horizontal well methane in-situ explosion multistage fracturing packing and ignition. In order to solve the above technical problems, the application provides a device and a method for horizontal well methane in-situ explosion multistage fracturing packing and ignition. In order to achieve the above purpose, the application provides a device for horizontal well methane in-situ explosion multistage fracturing packing and ignition, including following steps: a packing mechanism is arranged in the horizontal well, and an ignition mechanism is arranged at one end of the packing mechanism far away from the packing mechanism; the ignition mechanism includes a fixed shell arranged on the packing mechanism, a fuel assembly and an ignition assembly are arranged in the fixed shell, and the fuel assembly is communicated with the horizontal well; the packing mechanism includes a packing assembly in limited contact with the inner wall of the horizontal well, a ventilation assembly is arranged at one end of the packing assembly facing the fixed shell, and the ventilation assembly is communicated with the ground surface; and the packing assembly includes a fusible metal packing plate, two ends of the fusible metal packing plate are respectively provided with a first metal packing plate and a second metal packing plate, and the fixed shell is fixed on the second metal packing plate. Optionally, the fuel assembly includes a container arranged in the fixed shell, and the container is filled with combustion improver and flammable agent stored separately; one side of the container far away from the second metal packing plate is communicated with a gas transmission valve, and the gas transmission valve extends out of the fixed shell to communicate with the horizontal well. Optionally, the inner cavity of the side wall of the container is filled with ultra-low temperature freezing liquid; the inner cavity of the container is provided with a packing membrane, and the combustion improver and the flammable agent are located at two sides of the packing membrane respectively. Optionally, the flammable agent and the combustion improver are in a low-temperature liquefaction state in the container. Optionally, the ignition assembly includes a methane concentration sensor arranged outside the fixed shell, and the methane concentration sensor is in signal connection with the container and the gas transmission valve. Optionally, the ignition assembly includes an induction igniter arranged outside the fixed shell, and the induction igniter is in signal connection with a signal collector arranged inside the fixed shell. Optionally, the ventilation assembly includes a gas transportation channel arranged on the second metal packing plate, and the gas transportation channel is arranged around the outer wall of the fixed shell; the gas transportation channel is connected with a first gas delivery pipeline and a second gas delivery pipeline fixedly connected to the first metal packing plate, one end of the first gas delivery pipeline and the second gas delivery pipeline is communicated with the gas transportation channel, and the other end of the first gas delivery pipeline and the second gas delivery pipeline extends to the ground surface. A method for horizontal well methane in-situ explosion multistage fracturing packing and ignition includes following steps: constructing from the ground surface, forming the horizontal well in a target reservoir, and pre-drilling holes in the horizontal well; installing a packing and ignition device to the designated position in the level, and preliminarily fixing the device by concrete; ventilating the space between the end of the horizontal well and the packing and ignition device through the ventilation assembly; injecting mixed gas into the space between the end of the horizontal well and the packing and ignition device through the fuel assembly; the ignition assembly monitors the gas composition and realizes automatic ignition, thus forming explosion fracturing and forming a complex fracture network, and at the same time, the residual mixed gas is discharged through the ventilation assembly; and after multiple explosion fracturing are carried out in the deepest part of the horizontal well, multistage explosion fracturing operations are repeatedly carried out in the new horizontal well area from inside and outside to form a fracture network. Optionally, in the step of explosion fracturing, the high temperature generated by explosion melts the fusible metal packing plate, strengthens the first metal packing plate and the second metal packing plate, and simultaneously packs the fracture between the first metal packing plate and the second metal packing plate and the side wall of the horizontal well. Compared with the prior art, the application has following advantages and technical effects: the application provides a device and method for horizontal well methane in-situ explosion multistage fracturing packing and ignition, which combines the packing assembly and the ignition assembly, thus significantly reducing unnecessary waste and damage to the environment; the explosion welding technology is applied in the packing assembly, which effectively utilizes the high-temperature and high-pressure environment generated by explosion fracturing under the high-temperature condition generated by explosion, and improves an effective utilization rate of explosion fracturing. Compared with the conventional cement plugging method, the combination of metal and cement has better improved the plugging effect and prevented the gas from flowing out through the cement fracture on the outer wall of the packer after explosion fracturing. The ignition assembly is arranged in the underground fixed shell, which improves the protection and reduces the error caused by ground ignition and the inconvenience caused by a high length cable; by combining with an actual engineering background and facing defects of shale gas hydraulic fracturing at present, the method of the application puts forward several ideas and changes of the device system. The fusible metal packing plate melts at high temperature and produces explosion welding reaction under the impact of high temperature and high pressure, so the first metal packing plate and the second metal packing plate are reinforced with the horizontal well, and are able to be tightly attached to or even embedded in the horizontal well wall, which has the characteristics of high reliability, low risk and low investment. The application has the advantages of simple structure, convenient use and strong integration, is suitable for deep shale gas well in-situ explosion multistage fracturing to efficiently prepare shale gas, avoids wasting resources as much as possible, maximally improves the mining efficiency, realizes the utilization of clean and efficient new energy, and is beneficial to the exploitation and utilization of shale gas. The accompanying drawings, which constitute a part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and descriptions are used to explain this application, and do not constitute an improper limitation of this application. In the accompanying drawings: Figure 1 is a schematic structural diagram of a device for horizontal well methane in-situ explosion multistage fracturing packing and ignition. Figure 2 is a schematic diagram of a method for horizontal well methane in-situ explosion multistage fracturing packing and ignition. In the figures: 1. ground surface; 2. vertical well; 3. other reservoirs; 4. target reservoir; 5. horizontal well; 6. prefabricated hole; 7. first gas delivery pipeline; 8. second gas delivery pipeline; 9. fracture; 10. packing and ignition device; 1011. methane concentration sensor; 1012. signal transmitter; 1021. induction igniter; 1022. signal collector; 1031. container; 1032. combustion improver; 1033. flammable agent; 104. sensing line; 105. storage battery; 1061. first metal packing plate; 1062. fusible metal packing plate; 1063. second metal packing plate; 107. gas transmission valve; 11. horizontal shaft wall; 12. gas transportation channel. In the following, the technical schemes in the embodiments of the present application will be clearly and completely described with reference to the accompanying drawings. Apparently, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative effort belong to the protection scope of the present application. In order to make the above objects, features and advantages of the present application more obvious and easier to understand, the present application will be further described in detail with the accompanying drawings and specific embodiments. Referring to Figure 1- Figure 2, this embodiment provides a device for horizontal well methane in-situ explosion multistage fracturing packing and ignition, including following steps: a packing mechanism is arranged in the horizontal well 5, and an ignition mechanism is arranged at one end of the packing mechanism far away from the packing mechanism; the ignition mechanism includes a fixed shell arranged on the packing mechanism, a fuel assembly and an ignition assembly are arranged in the fixed shell, and the fuel assembly is communicated with the horizontal well 5; the packing mechanism includes a packing assembly in limited contact with the inner wall of the horizontal well 5, a ventilation assembly is arranged at one end of the packing assembly facing the fixed shell, and the ventilation assembly is communicated with the ground surface 1; and the packing assembly includes a fusible metal packing plate 1062, two ends of the fusible metal packing plate 1062 are respectively provided with a first metal packing plate 1061 and a second metal packing plate 1063, and the fixed shell is fixed on the second metal packing plate 1063. The application provides a device and method for horizontal well methane in-situ explosion multistage fracturing packing and ignition, which combines the packing assembly and the ignition assembly, thus significantly reducing unnecessary waste and environmental damage; the explosion welding technology is applied in the packing assembly, which effectively utilizes the high-temperature and high-pressure environment generated by explosion fracturing under the high-temperature condition generated by explosion fracturing, and improves the effective utilization rate of explosion fracturing. Compared with the conventional cement plugging method, the combination of metal and cement has better improved the plugging effect and prevented the gas from flowing out through the cement fracture on the outer wall of the packer after explosion fracturing. The ignition assembly is arranged in the underground fixed shell, which improves the protection and reduces the error caused by ground ignition and the inconvenience caused by a high length cable; by combining with an actual engineering background and facing defects of shale gas hydraulic fracturing at present, the method of the application puts forward several ideas and changes of the device system. The fusible metal packing plate 1062 melts at high temperature and produces explosion welding reaction under the impact of high temperature and high pressure, so the first metal packing plate 1061 and the second metal packing plate 1063 are reinforced with the horizontal well 5, and are able to be tightly attached to or even embedded in the horizontal well wall 11, which has the characteristics of high reliability, low risk and low investment. The application has the advantages of simple structure, convenient use and strong integration, is suitable for deep shale gas well in-situ explosion multistage fracturing to efficiently prepare shale gas, avoids wasting resources as much as possible, maximally improves the mining efficiency, realizes the utilization of clean and efficient new energy, and is beneficial to the exploitation and utilization of shale gas. Further, the fusible metal packing plate 1062 of this embodiment has a melting point of 100°C-300°C, and may be melted during combustion to produce a welding effect. Further, the whole packing assembly has a bearing ability of not less than 300 MPa. In a further optimization scheme, the fuel assembly includes a container 1031 arranged in the fixed shell, and the container 1031 is filled with combustion improver 1032 and flammable agent 1033 stored separately; one side of the container 1031 far away from the second metal packing plate 1063 is communicated with a gas transmission valve 107, and the gas transmission valve 107 extends out of the fixed shell to communicate with the horizontal well 5. The container 1031 is fixed in the fixed shell, so as to prevent the combustion improver 1032 and the flammable agent 1033 from being affected by shaking during the propulsion in the horizontal well 5, so the container 1031 may be pre-filled and released conveniently; in actual use, the ignition assembly monitors the methane concentration in the horizontal well 5 in real time, and after the combustion improver 1032 and flammable agent 1033 are put in at a set time, the ignition assembly ignites to generate explosion, and the prefabricated hole 6 on the side wall of the horizontal well 5 is fractured by huge pressure. Further, the combustion improver 1032 in this embodiment is liquid oxygen, and the flammable agent 1033 is methane. Further, the target concentration of methane gas in the horizontal well 5 in this embodiment is 5-10MPa. In a further optimization scheme, the inner cavity of the side wall of the container 1031 is filled with ultra-low temperature freezing liquid; the inner cavity of the container 1031 is provided with a packing membrane, and the combustion improver 1032 and the flammable agent 1033 are located at two sides of the packing membrane respectively; the flammable agent 1033 and the combustion improver 1032 are in a low-temperature liquefaction state in the container 1031. In order to facilitate the filling of the flammable agent 1033 and the combustion improver 1032 in the container 1031, both of the flammable agent 1033 and the combustion improver 1032 are filled in liquid form, so the cavity of the inner wall of the container 1031 is filled with ultra-low temperature freezing liquid to realize the low-temperature liquefaction and preservation of the flammable agent 1033 and the combustion improver 1032. The combustion improver 1032 and the flammable agent 1033 in the container 1031 are separated by the packing membrane, so the combustion improver 1032 and the flammable agent 1033 are separated during storage. Further, when the flammable agent 1033 and the combustion improver 1032 are released, liquid oxygen and liquid methane vaporize to burst the packing membrane, which is convenient for release. Further, liquid oxygen is light blue liquid with a total expansion ratio as high as 860:1. The storage environment of the liquid oxygen is ultra-low temperature and high pressure, and the temperature is not higher than -200°C to prevent liquid oxygen from vaporizing and expanding in volume. Further, liquid oxygen, as the combustion improver 1032, may also fracture a target reservoir 4 at low temperature. The research shows that mechanical properties of shale change significantly with the increase of temperature, and the stress and strain decrease with the increase of temperature, indicating that shale is more likely to produce fractures 9 with the support of ground temperature. In a further optimization scheme, the ignition assembly includes a methane concentration sensor 1011 arranged outside the fixed shell, and the methane concentration sensor 1011 is in signal connection with the container 1031 and the gas transmission valve 107; the ignition assembly includes an induction igniter 1021 arranged outside the fixed shell, and the induction igniter 1021 is in signal connection with a signal collector 1022 arranged inside the fixed shell. The ignition assembly consists of an induction igniter nozzle, the signal collector 1022, the methane concentration sensor 1011 and a signal transmitter 1012, where the methane concentration sensor is used for measuring the methane concentration in the horizontal well 5, so as to conveniently control the release of the flammable agent 1033 and the combustion improver 1032; when the methane concentration reaches the standard, the methane concentration sensor 1011 transmits the ignition signal to the signal collector 1022 of the induction igniter through sensing lines 104 and the signal transmitter, and then conducting ignition through the induction igniter nozzle, so the mixed flammable agent 1033 and combustion improver 1032 are deflagrated. Further, a storage battery 105 is arranged in the fixed shell for supplying power to the ignition assembly. Further, the ignition assembly except the methane concentration sensor 1011 and the signal transmitter 1012 are all located in the fixed shell, which may effectively play a protective role. Further, all devices such as the storage battery 105, the sensing lines 104 and signal collector 1022 may resist high temperature up to 500°C to prevent the devices from being damaged by high temperature explosion. In a further optimization scheme, the ventilation assembly includes a gas transportation channel 12 arranged on the second metal packing plate 1063, and the gas transportation channel 12 is arranged around the outer wall of the fixed shell; the gas transportation channel 12 is connected with a first gas delivery pipeline 7 and a second gas delivery pipeline 8 fixedly connected to the first metal packing plate 1061, one end of the first gas delivery pipeline 7 and the second gas delivery pipeline 8 is communicated with the gas transportation channel 12, and the other end of the first gas delivery pipeline 7 and the second gas delivery pipeline 8 extends to the ground surface 1. The first gas delivery pipeline 7 and the second gas delivery pipeline 8 communicate with the gas transportation channel 12. Before the flammable agent 1033 and the combustion improver 1032 are released, impurity gas in the well is pumped out through the first gas delivery pipeline 7 and the gas transportation channel 12, and the gas is screened to avoid waste and environmental pollution, and then the combustion improver 1032 and the flammable agent 1033 are delivered into the target hole through the gas transmission valve 107. The application relates to a method for horizontal well methane in-situ explosion multistage fracturing packing and ignition, which includes the following steps: construction is carried out from the ground surface 1, after passing through other reservoirs 3, the horizontal well 5 is formed in the target reservoir 4, and holes are pre-drilled in the horizontal well 5; exploring and drilling from the ground surface 1 to the target reservoir 4, and after reaching the target reservoir 4, selecting the suitable horizontal well 5 that may work for a long time according to geological conditions; using a shaped charge perforation gun in the horizontal well 5, shaped charge perforation is performed at the target position to form a three-dimensional hole and a prefabricated fracture 9, and after the shaped charge perforation device completes the perforation work from inside to outside in the well, the perforation device is pulled out to form a preliminary exploitation well; installing a packing and ignition device 10 to the designated position in the level, and preliminarily fixing the device by concrete; installing the improved packing and ignition device 10, and using cement for initial packing; the impurity gas in the well is pumped out through the first gas delivery pipeline 7 and the gas transportation channel 12 of the ventilation assembly, and the gas is screened to avoid waste and environmental pollution; ventilating the space between the end of the horizontal well 5 and the packing and ignition device 10 through the ventilation assembly; the impurity gas in the well is pumped out through the first gas delivery pipeline 7 and the gas transportation channel 12 of the ventilation assembly, and the gas is screened to avoid waste and environmental pollution; injecting mixed gas into the space between the end of the horizontal well 5 and the packing and ignition device 10 through the fuel assembly; opening the gas transmission valve 107, and discharging the combustion improver 1032 and flammable agent 1033 in the container 1031 into the horizontal well 5. After the liquid oxygen in the hole expands, the liquid oxygen will be mixed with methane gas in the well to form flammable and mixed gas. the ignition assembly monitors the gas composition and realizes automatic ignition, thus forming explosion fracturing and forming a complex fracture 9 network, and at the same time, the residual mixed gas is discharged through the ventilation assembly; when the target concentration is reached and the ignition signal is transmitted by the methane concentration sensor 1011 to the signal collector 1022 of the induction igniter through the sensing lines 104 and the signal transmitter, ignition is carried outby the induction igniter 1021. After ignition, the mixed gas of oxygen and methane quickly reacts to produce a large amount of high-temperature and high-pressure gas; at the same time, the fusible metal packing plate 1062 is melted, so the first metal packing plate 1061 and the second metal packing plate 1063 are explosively welded to play a connecting role; at the same time, the cement is matched to plug the small space, so the plugging effect is better; and among a large number of gases produced by the primary explosion, carbon dioxide gas is the majority, and the mixed gas in the well is discharged through the gas transportation channel 12 and the second gas delivery pipeline 8 for screening and transportation; after multiple explosion fracturing are carried out in the deepest part of the horizontal well 5, multistage explosion fracturing operations are repeatedly carried out in the new horizontal well 5 area from inside and outside to form a fracture network; after the horizontal well 5 and the hole are re-prepared, the plugging and ignition explosion are repeated, and the explosion fracturing is carried out for many times, so the fracture 9 in the target reservoir 4 are highly developed and a three-dimensional complex fracture 9 network is formed; and after explosion fracturing for many times in the deepest hole in the horizontal well 5, the multistage explosion fracturing work is repeated in the new hole from the inside and outside. In the description of the present application, it should be understood that the terms “longitudinal” , “transverse” , “up” , “down” , “front” , “back” , “left” , “right” , “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, etc. indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, only for the convenience of describing the present application, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present application. The above-mentioned embodiments only describe the preferred mode of the present application, and do not limit the scope of the present application. Under the premise of not departing from the design spirit of the present application, various modifications and improvements made by ordinary technicians in the field to the technical schemes of the present application should fall within the protection scope of the present application.

Claims

1. A device for horizontal well methane in-situ explosion multistage fracturing packing and ignition, wherein a packing mechanism is arranged in the horizontal well (5), and an ignition mechanism is arranged at one end of the packing mechanism far away from the packing mechanism;the ignition mechanism comprises a fixed shell arranged on the packing mechanism, wherein a fuel assembly and an ignition assembly are arranged in the fixed shell, and the fuel assembly is communicated with the horizontal well (5);the packing mechanism comprises a packing assembly in limited contact with the inner wall of the horizontal well (5), wherein a ventilation assembly is arranged at one end of the packing assembly facing the fixed shell, and the ventilation assembly is communicated with the ground surface (1); andthe packing assembly comprises a fusible metal packing plate (1062), wherein two ends of the fusible metal packing plate (1062) are respectively provided with a first metal packing plate (1061) and a second metal packing plate (1063), and the fixed shell is fixed on the second metal packing plate (1063).

2. The device for horizontal well methane in-situ explosion multistage fracturing packing and ignition according to claim 1, wherein the fuel assembly comprises a container (1031) arranged in the fixed shell, wherein the container (1031) is filled with combustion improver (1032) and flammable agent (1033) stored separately; and one side of the container (1031) far away from the second metal packing plate (1063) is communicated with a gas transmission valve (107), and the gas transmission valve (107) extends out of the fixed shell to communicate with the horizontal well (5).

3. The device for horizontal well methane in-situ explosion multistage fracturing packing and ignition according to claim 2, wherein the inner cavity of the side wall of the container (1031) is filled with ultra-low temperature freezing liquid; and the inner cavity of the container (1031) is provided with a packing membrane, and the combustion improver (1032) and the flammable agent (1033) are located at two sides of the packing membrane respectively.

4. The device for horizontal well methane in-situ explosion multistage fracturing packing and ignition according to claim 2, wherein the flammable agent (1033) and the combustion improver(1032) are in a low-temperature liquefaction state in the container (1031).

5. The device for horizontal well methane in-situ explosion multistage fracturing packing and ignition according to claim 2, wherein the ignition assembly comprises a methane concentration sensor (1011) arranged outside the fixed shell, wherein the methane concentration sensor (1011) is in signal connection with the container (1031) and the gas transmission valve (107).

6. The device for horizontal well methane in-situ explosion multistage fracturing packing and ignition according to claim 5, wherein the ignition assembly comprises an induction igniter (1021) arranged outside the fixed shell, wherein the induction igniter (1021) is in signal connection with a signal collector (1022) arranged inside the fixed shell.

7. The device for horizontal well methane in-situ explosion multistage fracturing packing and ignition according to claim 1, wherein the ventilation assembly comprises a gas transportation channel (12) arranged on the second metal packing plate (1063), wherein the gas transportation channel (12) is arranged around the outer wall of the fixed shell; and the gas transportation channel (12) is connected with a first gas delivery pipeline (7) and a second gas delivery pipeline (8) fixedly connected to the first metal packing plate (1061), one end of the first gas delivery pipeline (7) and the second gas delivery pipeline (8) is communicated with the gas transportation channel (12), and the other end of the first gas delivery pipeline (7) and the second gas delivery pipeline (8) extends to the ground surface (1).

8. A method for horizontal well methane in-situ explosion multistage fracturing packing and ignition, the device for horizontal well methane in-situ explosion multistage fracturing packing and ignition according to any one of claims 1 to 7 comprises following steps:constructing from the ground surface (1), forming the horizontal well (5) in a target reservoir (4), and pre-drilling holes in the horizontal well (5);installing a packing and ignition device (10) to the designated position in the level, and preliminarily fixing the device by concrete;ventilating the space between the end of the horizontal well (5) and the packing and ignition device (10) through the ventilation assembly;injecting mixed gas into the space between the end of the horizontal well (5) and the packing and ignition device (10) through the fuel assembly;the ignition assembly monitors the gas composition and realizes automatic ignition, thus formingexplosion fracturing and forming a complex fracture (9) network, and at the same time, the residual mixed gas is discharged through the ventilation assembly; andafter multiple explosion fracturing are carried out in the deepest part of the horizontal well (5), multistage explosion fracturing operations are repeatedly carried out in the new horizontal well 5 (5) area from inside and outside to form a fracture network.

9. The method for horizontal well methane in-situ explosion multistage fracturing packing and ignition according to claim 8, wherein in the step of explosion fracturing, the high temperature generated by explosion melts the fusible metal packing plate (1062), strengthens the first metal packing plate (1061) and the second metal packing plate (1063), and simultaneously packs the 10 fracture between the first metal packing plate (1061) and the second metal packing plate (1063) and the side wall of the horizontal well (5).

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