A multi-stage delivery tool and method for methane in-situ explosion fracturing combustion aid

Abstract

A tool and method for multi-stage delivery of combustion aid for in-situ explosion fracturing of methane, the tool: an outer guide tube is coaxially sleeved on the outside of an inner gas cylinder, and its upper end is connected to the upper part of the inner gas cylinder through an annular connecting plate; a central tube is coaxially arranged in the inner gas cylinder, and its lower end passes through the bottom plate of the inner gas cylinder and the bottom plate of the outer guide tube in sequence, and its upper end is connected to a plugging funnel; a constant pressure spray hole is provided on the bottom plate of the inner gas cylinder, and a constant pressure plug is installed; a lateral opening is provided on the outer guide tube; the method: gaseous combustion aid is respectively filled into a plurality of delivery tools in required amounts; each level of packer is set; a steel ball is introduced to seal the central tube, and the annular piston is pushed downward by high-pressure nitrogen to press the gaseous combustion aid into the sealed delivery section; the combustion aid delivery operation of each sealed delivery section is carried out sequentially from bottom to top. The tool and method can perform segmented quantitative delivery of combustion aid according to the space requirements of each methane reservoir section.

Description

Technical Field

[0001] The present invention belongs to the technical field of transformation and exploitation of unconventional natural gas reservoirs, and in particular relates to a tool and method for multi-stage delivery of a methane in-situ explosion fracturing combustion aid. Background Art

[0002] At present, most unconventional natural gas exploitation uses hydraulic fracturing technology. Hydraulic fracturing can promote the formation of fracturing cracks in unconventional natural gas reservoirs, achieve the effect of increasing the permeability of unconventional natural gas reservoirs, and thus complete the exploitation of unconventional natural gas. However, hydraulic fracturing has a series of problems such as groundwater pollution, fresh water depletion, and easy migration of hydraulic fracturing chemicals to the surface. In order to effectively avoid the various problems of hydraulic fracturing, a new reservoir fracturing method that "takes materials locally" has emerged in recent years, namely the methane in-situ explosion fracturing method. This method uses reservoir methane as fuel, and forms a methane-combustion-aid mixed gas at the bottom of the well or in the reservoir by artificially adding an accelerant, and then detonates the methane-combustion-aid mixed gas to produce instantaneous explosion high pressure, causing the reservoir to form impact cracks, thereby forming a complex three-dimensional fracture network, and finally achieving the increase in production and permeability of unconventional natural gas reservoirs. Methane in-situ explosion fracturing technology uses the high-pressure conditions generated by methane explosion to perform fracturing. Compared with hydraulic fracturing, it can produce greater fracturing pressure and will not have a series of problems existing in hydraulic fracturing, such as groundwater pollution and fresh water depletion.

[0003] Usually, the depth of natural gas reservoirs is thousands of meters, and the diameter of underground wells is only about 120mm. There are various problems with the placement of combustion aids in the bottom space of the well, such as long placement distance and small working space. At the same time, since methane explosion has specific requirements for the concentration of various gases, it is necessary to quantitatively control the amount of combustion aids according to the actual operation situation. Due to the lack of professional placement tools, it is extremely difficult to quantitatively and evenly place combustion aids in underground spaces. Therefore, there is an urgent need to provide a tool and method that can achieve the placement of combustion aids in the narrow space at the bottom of the well. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a tool and method for multi-stage delivery of combustion aid for methane in-situ explosive fracturing. The tool has a simple structure and diverse functions. It can use the gas storage space to pre-store gaseous combustion aid. At the same time, it can play the role of connecting pipelines when the central tube is not blocked, and can also conveniently realize the quantitative delivery of gaseous combustion aid when the central tube is blocked. This method can not only carry out segmented and quantitative delivery of combustion aid according to the size of each methane reservoir space, but also can make the combustion aid fully mixed with the in-situ methane in the reservoir space during delivery, which is helpful to realize the multi-stage delivery of methane in-situ explosive fracturing, and can solve the problem that only single-stage tools can be put in during traditional delivery, but multi-stage tools cannot be put in, and thus the demand for multi-stage delivery of combustion aid cannot be met.

[0005] In order to achieve the above-mentioned invention object, the present invention provides a methane in-situ explosion fracturing combustion aid multi-stage delivery tool, the delivery tool comprises an inner gas storage cylinder, an outer guide cylinder, a center cylinder and an annular piston;

[0006] The top center of the inner gas storage cylinder is fixedly connected with a feed pipeline communicating with its inner cavity, and the bottom thereof is provided with a gas storage bottom plate; an upper through hole is opened in the central area of ​​the gas storage bottom plate, and a plurality of constant pressure nozzles are evenly opened in the circumferential direction around the outer periphery of the upper through hole, and a constant pressure plug is installed in the constant pressure nozzle;

[0007] The top of the outer guide tube is an open structure, and a plurality of lateral openings are opened upwards. The bottom of the guide tube has a guide bottom plate, and a lower through hole is opened in the central area of ​​the guide bottom plate. The outer guide tube is coaxially sleeved on the outer side of the inner air storage cylinder, and the top of the outer guide tube is fixedly connected to the top of the inner air storage cylinder through an annular connecting plate.

[0008] The outer diameter of the central tube matches the inner diameter of the upper through hole and the lower through hole. The central tube is coaxially arranged inside the inner air storage cylinder. The lower end of the central tube sequentially passes through the upper through hole and the lower through hole and extends to the outside of the bottom of the outer guide tube. The upper end of the central tube stops below the top of the inner air storage cylinder and is fixedly connected with a plugging funnel. The plugging funnel is clearance-matched with the inner air storage cylinder.

[0009] The outer diameter of the annular piston is matched with the inner diameter of the inner gas storage cylinder, and the diameter of the center hole is matched with the outer diameter of the center tube; the annular piston is axially slidably assembled inside the inner gas storage cylinder, and axially slidably sleeved on the outer side of the center tube through its center hole;

[0010] A flow guide annulus is formed between the outer flow guide cylinder, the center cylinder and the inner air storage cylinder, and an air storage space is formed between the annular piston, the center cylinder and the air storage bottom plate.

[0011] Furthermore, in order to facilitate the rapid plugging of the center tube by throwing, it also includes a steel ball, the outer diameter of which is compatible with the inner diameter of the plugging funnel. The steel ball is installed in the plugging funnel to plug the inlet end of the center tube.

[0012] As a preferred embodiment, the body of the inner gas storage cylinder consists of a funnel section and a cylindrical section, and the funnel section is arranged inverted and transitionally connects the lower end of the feed pipeline and the upper end of the cylindrical section.

[0013] Furthermore, in order to ensure that the steel ball passing through the feed pipeline can accurately fall into the blocking funnel, and at the same time, to prevent the steel ball from slipping out of the blocking funnel from the gap between the large diameter end of the blocking funnel and the feed pipeline, the size of the large diameter end of the blocking funnel is adapted to the size of the feed pipeline, and the gap between the large diameter end and the lower end of the feed pipeline is matched.

[0014] Furthermore, in order to improve the fracturing efficiency and the fracturing effect, the plurality of lateral openings are evenly distributed circumferentially and are divided into three layers from top to bottom.

[0015] Furthermore, in order to more efficiently guide the gas flowing out of the gas storage space to the lateral openings so as to quickly complete the combustion-aiding agent delivery work in the sealed delivery section, the guide bottom plate is funnel-shaped.

[0016] In the present invention, the outer guide tube is coaxially mounted on the outer side of the inner gas storage tube, and at the same time, the upper end of the outer guide tube is fixedly connected to the top of the inner gas storage tube through an annular connecting plate, and then the lower end of the center tube placed at the axis of the inner gas storage tube passes through the upper through hole on the gas storage bottom plate and the lower through hole of the guide bottom plate to the outer side of the bottom of the outer guide tube in turn, so that a guide annulus can be formed between the inner gas storage tube, the center tube and the outer guide tube. An annular piston that is slidably sealed with the center tube and the inner gas storage tube is assembled between the center tube and the inner gas storage tube, so that a gas storage space can be formed between the annular piston, the center tube and the inner gas storage tube, and then the gas storage space can be used to pre-store gaseous combustion-supporting agents. A gap is left between the plugging funnel at the upper end of the center tube and the inner gas storage tube, so that it can be ensured that the high-pressure nitrogen pumped in by the feed pipeline can act on the upper end surface of the annular piston. A plurality of constant-pressure nozzles are provided on the gas storage bottom plate, so that the gas storage space and the guide annulus can be connected by using the plurality of constant-pressure nozzles. A plurality of lateral openings are provided on the body of the outer guide tube, which can ensure that the gaseous combustion-supporting agent entering the guide annulus can flow out through the plurality of lateral openings and act on the target reservoir efficiently and accurately. By fixing the plugging funnel at the upper end of the central tube, on the one hand, the plugging body can be conveniently installed in the plugging funnel, and then the plugging body can be used to realize the quick plugging operation of the central tube, and on the other hand, the plugging funnel with an outer diameter larger than the outer diameter of the central tube can be used to form an upper limit position for the annular piston, thereby avoiding the situation where the annular piston is separated from the central tube. A constant pressure plug is installed in the constant pressure nozzle, and the constant pressure nozzle can be plugged under normal conditions. In this way, under normal conditions, not only the air tightness of the gas storage space can be effectively maintained, but also the gap between the inner gas storage cylinder and the central tube can be plugged by the annular piston under normal conditions, so that the high-pressure nitrogen entering the feed pipeline can be directly discharged through the lower end of the central tube under normal conditions, thereby playing the role of connecting the pipeline. In addition, after placing the plugging body in the plugging funnel at the upper end of the central tube, the high-pressure nitrogen pumped in by the feed pipeline can directly act on the upper end surface of the annular piston. In this way, the pumped high-pressure nitrogen can be used to push the annular piston downward, thereby facilitating the pressurization of the gaseous combustion aid in the gas storage space. In this way, the pressurized gaseous combustion aid can be used to quickly press the constant pressure plug out of the constant pressure nozzle, and then the gaseous combustion aid pre-stored in the gas storage space can quickly enter the diversion annulus and flow into the wellbore through the lateral openings. In this way, the gaseous combustion aid can be continuously and quantitatively delivered to the target reservoir, and then it can be fully mixed with the in-situ methane in the target reservoir space, which helps to efficiently realize the fracturing operation of the target reservoir.

[0017] The present invention has a simple structure and diverse functions. It can use the gas storage space to pre-store the gaseous combustion aid. At the same time, it can play a role in connecting pipelines when the central tube is not blocked, and can also conveniently realize the quantitative delivery of the gaseous combustion aid when the central tube is blocked.

[0018] The present invention also provides a method for multi-stage delivery of a methane in-situ explosion fracturing combustion aid, which uses a multi-stage delivery tool for a methane in-situ explosion fracturing combustion aid, and comprises the following steps:

[0019] Step 1: Determine the number of required delivery tools, the number of sections and the length of the required tubing according to the predetermined fracturing position; at the same time, ensure that the models and sizes of the multiple delivery tools are reduced step by step, prepare multiple steel balls that are compatible with the multiple delivery tools, and ensure that the steel balls corresponding to the previous delivery tools can pass through the center tube of the next delivery tool;

[0020] Step 2: According to the combustion-supporting amount required by each level of target reservoir, the required amount of gaseous combustion-supporting agent is respectively charged into the gas storage space of multiple delivery tools;

[0021] Step 3: First, multiple sections of oil pipes are arranged in sequence from top to bottom, and one or more packers are installed on the outside of each section of oil pipe; then, multiple delivery tools with gradually decreasing models and sizes are placed in the space between two adjacent sections of oil pipes, and the upper end of the feed pipeline in the delivery tool is connected to the lower end of the oil pipe at the corresponding position, and the lower end of the center tube in the delivery tool is connected to the upper end of the oil pipe at the corresponding position, thereby forming an integrated delivery assembly;

[0022] Step 4: First, a fracturing truck is arranged on the ground at one side of the wellbore where the fracturing operation is to be performed; then, the integrated delivery assembly is lowered through the wellbore to the location of the target reservoir, and the upper end of the uppermost section of the oil pipe is connected to the output pipeline of the fracturing truck;

[0023] Step 5: Pump high-pressure nitrogen into the oil pipe through the fracturing truck, use the high-pressure nitrogen to seal the packers at each level, and use the two packers distributed on the upper and lower sides of the delivery tool to form a sealed delivery section at the location of the delivery tool;

[0024] Step 6: Determine the sealing delivery section of the target level one according to the principle of from bottom to top; drop a steel ball that matches the target level one delivery tool through the oil pipe, and the steel ball passes through the center tubes of the delivery tools at all levels above the target level one in turn, and reaches the plugging funnel in the center tube of the delivery tool at this level, so as to achieve the plugging operation of the center tube on the delivery tool at this level;

[0025] Step 7: Continue to pump high-pressure nitrogen into the oil pipe through the fracturing truck, and use the high-pressure nitrogen with increasing pressure to act on the upper end surface of the annular piston in the target first-level delivery tool to move the annular piston of the target first level downward; use the compression effect of the annular piston to continuously increase the pressure in the gas storage space, and when the pressure in the gas storage space reaches the opening pressure of the constant pressure plug, the gaseous combustion-supporting agent in the gas storage space enters the guide annulus through the opened multiple constant-pressure nozzles, and then flows out through multiple lateral openings and enters the sealed delivery section of the target first level, until the gaseous combustion-supporting agent in the gas storage space is completely filled into the sealed delivery section, completing the combustion-supporting agent delivery work of the target first-level target reservoir;

[0026] Step 8: Repeat steps 6 and 7 several times until the combustion aid placement work is completed in all sealed placement sections.

[0027] In the present invention, multiple delivery tools of decreasing models and sizes are connected by multiple sections of oil pipes to form an integrated delivery assembly, so that multiple delivery tools can be lowered to the location of the target reservoir in the wellbore by using the oil pipes. A packer is set on the outside of each section of the oil pipe, and the packer can be set by pumping high-pressure nitrogen. In this way, a sealed delivery section can be formed between the two packers on the upper and lower sides of the same delivery tool, so that the gaseous combustion-supporting agent released by the delivery tool can fully act on the sealed delivery area, which is further conducive to promoting the full mixing of the charged combustion-supporting agent with the in-situ methane in the reservoir space. According to the principle of from bottom to top, the sealing delivery section of the target level is determined, and then the corresponding steel balls are dropped through the oil pipe, so that the steel balls can pass through each section of the oil pipe and each center tube in turn into the sealing funnel of the center tube in the target level one delivery tool. The sealing funnel has a limiting effect on the steel ball, and the high-pressure nitrogen gas pumped in can reliably seal the center tube of the target level one. In this way, the high-pressure nitrogen gas pumped in later can be used to push the annular piston to move in the direction of the bottom of the gas storage cylinder, and the pressurization process of the gaseous combustion aid in the gas storage space is realized. During the pressurization process, the constant pressure plug will automatically detach from the constant pressure nozzle, and then the pre-stored gaseous combustion aid can enter the sealing delivery section through multiple directional nozzles, the guide annulus and multiple lateral openings. In this way, the delivery operation of the first-level sealing delivery section can be completed. On this basis, an integrated delivery assembly formed by a multi-stage delivery tool, multiple sections of oil pipes and multiple packers is used in series. In combination with pre-charging of combustion aid, the sequential delivery of multi-stage steel balls to plug the multi-stage central tubes and the sequential use of multi-stage piston compression can achieve quantitative, uniform and multi-stage delivery of combustion aids in deep methane reservoir spaces. In this process, the delivery processes in each level of the reservoir do not affect each other, thus meeting the needs of continuous multi-stage operations of in-situ methane explosion fracturing.

[0028] This method can not only carry out segmented and quantitative delivery of the combustion aid according to the size of each methane reservoir space, but also fully mix the combustion aid with the in-situ methane in the reservoir space during delivery, which helps to realize continuous multi-stage operation of methane in-situ explosion fracturing, and solves the problem that only single-stage tools can be put in during the traditional delivery process, and multi-stage tools cannot be put in, thus failing to meet the demand for multi-stage delivery of the combustion aid. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a longitudinal cross-sectional view of the delivery tool of the present invention;

[0030] Figure 2 It is a three-dimensional structural schematic diagram of the delivery tool in the present invention;

[0031] Figure 3 It is a quarter cross-sectional view of the delivery tool of the present invention;

[0032] Figure 4 It is a schematic diagram of the workflow of the delivery method of the present invention;

[0033] Figure 5 It is a structural schematic diagram of the integrated delivery component in the present invention.

[0034] In the figure: 1, center tube, 2, inner gas storage cylinder, 3, annular piston, 4, outer guide tube, 5, plugging funnel, 6, oil pipe, 7, funnel section, 8, constant pressure nozzle, 9, gas storage space, 10, gaseous combustion aid, 11, lateral opening, 12, diversion annulus, 13, wellbore, 14, target reservoir, 15, delivery tool, 16, fracturing truck, 17, high-pressure nitrogen, 18, steel ball, 19, packer, 20, sealing delivery section, 21, feed pipeline, 22, cylindrical section, 23, gas storage bottom plate, 24, diversion bottom plate, 25, annular connecting plate, 26, constant pressure plug. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings.

[0036] like Figures 1 to 3 As shown, the present invention provides a multi-stage delivery tool for methane in-situ explosion fracturing combustion aid, the delivery tool 15 comprises an inner gas storage cylinder 2, an outer guide cylinder 4, a central cylinder 1 and an annular piston 3;

[0037] The top center of the inner gas storage cylinder 2 is fixedly connected with a feed pipeline 21 communicating with its inner cavity, and the bottom thereof is provided with a gas storage bottom plate 23; an upper through hole is opened in the central area of ​​the gas storage bottom plate 23, and a plurality of constant pressure nozzles 8 are evenly opened in the circumferential direction of the outer periphery of the upper through hole, and a constant pressure plug 26 is installed in the constant pressure nozzle 8, and the constant pressure plug 26 automatically detaches from the constant pressure nozzle 8 after the applied pressure reaches the opening pressure, thereby opening the constant pressure nozzle 8;

[0038] The top of the outer guide tube 4 is an open structure, and a plurality of lateral openings 11 are opened upwardly, and a guide bottom plate 24 is provided at the bottom, and a lower through hole is provided in the central area of ​​the guide bottom plate 24; the outer guide tube 4 is coaxially sleeved on the outer side of the inner gas storage cylinder 2, and the top of the outer guide tube 4 is fixedly connected to the top of the inner gas storage cylinder 2 through an annular connecting plate 25, and the annular connecting plate 25 is sealedly connected to the outer surface of the inner gas storage cylinder 2 and the top of the outer guide tube 4 to ensure the air tightness of the guide annulus 12 formed subsequently; as a preferred embodiment, the number of the lateral openings 11 is six;

[0039] The outer diameter of the central tube 1 is adapted to the size of the inner diameter of the upper through hole and the lower through hole. The central tube 1 is coaxially arranged inside the inner air storage cylinder 2, and its lower end sequentially passes through the upper through hole and the lower through hole and extends to the outside of the bottom of the outer guide tube 4, and its upper end stops below the top of the inner air storage cylinder 2 and is fixedly connected with a plugging funnel 5; the small diameter end of the plugging funnel 5 is adapted to the size of the central tube 1 and is connected to the central tube 1, and the top end of the plugging funnel 5 is gap-matched with the inner air storage cylinder 2; wherein, the central tube 1 and the upper through hole and the lower through hole are sealed and connected;

[0040] The outer diameter of the annular piston 3 is adapted to the inner diameter of the inner gas cylinder 2, and the diameter of the center hole thereof is adapted to the outer diameter of the center cylinder 1; the annular piston 3 is axially slidably assembled inside the inner gas cylinder 2, and is axially slidably mounted on the outer side of the center cylinder 1 through its center hole;

[0041] A flow guide annulus 12 is formed between the outer flow guide cylinder 4 , the center cylinder 1 and the inner gas storage cylinder 2 , and a gas storage space 9 is formed between the annular piston 3 , the center cylinder 1 and the gas storage bottom plate 23 .

[0042] In order to facilitate the rapid plugging of the center tube by throwing, a steel ball 18 is also included. The outer diameter of the steel ball 18 is compatible with the inner diameter of the plugging funnel 5. The steel ball 18 is installed in the plugging funnel 5 to plug the inlet end of the center tube 1.

[0043] As a preferred embodiment, in order to facilitate the filling of the gaseous combustion aid 10 into the gas storage space 9, an inflation pipeline connected to the gas storage space 9 can be connected to the gas storage bottom plate 23, and the air inlet end of the inflation pipeline extends to the outside of the bottom of the outer guide tube 4 through the mounting hole reserved on the guide bottom plate 24. At the same time, a one-way valve is installed at the air inlet end of the inflation pipeline, so as to facilitate the filling operation of the gaseous combustion aid 10.

[0044] As a preferred embodiment, the body of the inner gas storage cylinder 2 is composed of a funnel section 7 and a cylindrical section 22 , and the funnel section 7 is arranged inverted and transitionally connects the lower end of the feed pipeline 21 and the upper end of the cylindrical section 22 .

[0045] In order to ensure that the steel ball passing through the feed pipeline can accurately fall into the blocking funnel, and at the same time, to prevent the steel ball from slipping out of the blocking funnel from the gap between the large diameter end of the blocking funnel and the feed pipeline, the size of the large diameter end of the blocking funnel 5 is adapted to the size of the feed pipeline 21, and the gap between the large diameter end and the lower end of the feed pipeline 21 is matched.

[0046] In order to improve the fracturing efficiency and effect, the plurality of lateral openings 11 are evenly distributed circumferentially and are divided into three layers from top to bottom.

[0047] In order to more efficiently guide the gas flowing out of the gas storage space to the lateral openings so as to quickly complete the combustion-supporting agent delivery work in the sealed delivery section, the guide bottom plate 24 is funnel-shaped.

[0048] In the present invention, the outer guide tube is coaxially mounted on the outer side of the inner gas storage tube, and at the same time, the upper end of the outer guide tube is fixedly connected to the top of the inner gas storage tube through an annular connecting plate, and then the lower end of the center tube placed at the axis of the inner gas storage tube passes through the upper through hole on the gas storage bottom plate and the lower through hole of the guide bottom plate to the outer side of the bottom of the outer guide tube in turn, so that a guide annulus can be formed between the inner gas storage tube, the center tube and the outer guide tube. An annular piston that is slidably sealed with the center tube and the inner gas storage tube is assembled between the center tube and the inner gas storage tube, so that a gas storage space can be formed between the annular piston, the center tube and the inner gas storage tube, and then the gas storage space can be used to pre-store gaseous combustion-supporting agents. A gap is left between the plugging funnel at the upper end of the center tube and the inner gas storage tube, so that it can be ensured that the high-pressure nitrogen pumped in by the feed pipeline can act on the upper end surface of the annular piston. A plurality of constant-pressure nozzles are provided on the gas storage bottom plate, so that the gas storage space and the guide annulus can be connected by using the plurality of constant-pressure nozzles. A plurality of lateral openings are provided on the body of the outer guide tube, which can ensure that the gaseous combustion-supporting agent entering the guide annulus can flow out through the plurality of lateral openings and act on the target reservoir efficiently and accurately. By fixing the plugging funnel at the upper end of the central tube, on the one hand, the plugging body can be conveniently installed in the plugging funnel, and then the plugging body can be used to realize the quick plugging operation of the central tube, and on the other hand, the plugging funnel with an outer diameter larger than the outer diameter of the central tube can be used to form an upper limit position for the annular piston, thereby avoiding the situation where the annular piston is separated from the central tube. A constant pressure plug is installed in the constant pressure nozzle, and the constant pressure nozzle can be plugged under normal conditions. In this way, under normal conditions, not only the air tightness of the gas storage space can be effectively maintained, but also the gap between the inner gas storage cylinder and the central tube can be plugged by the annular piston under normal conditions, so that the high-pressure nitrogen entering the feed pipeline can be directly discharged through the lower end of the central tube under normal conditions, thereby playing the role of connecting the pipeline. In addition, after placing the plugging body in the plugging funnel at the upper end of the central tube, the high-pressure nitrogen pumped in by the feed pipeline can directly act on the upper end surface of the annular piston. In this way, the pumped high-pressure nitrogen can be used to push the annular piston downward, thereby facilitating the pressurization of the gaseous combustion aid in the gas storage space. In this way, the pressurized gaseous combustion aid can be used to quickly press the constant pressure plug out of the constant pressure nozzle, and then the gaseous combustion aid pre-stored in the gas storage space can quickly enter the diversion annulus and flow into the wellbore through the lateral openings. In this way, the gaseous combustion aid can be continuously and quantitatively delivered to the target reservoir, and then it can be fully mixed with the in-situ methane in the target reservoir space, which helps to efficiently realize the fracturing operation of the target reservoir.

[0049] like Figures 4 to 5 As shown, the present invention also provides a method for multi-stage delivery of a methane in-situ explosion fracturing combustion aid, using a methane in-situ explosion fracturing combustion aid multi-stage delivery tool, comprising the following steps:

[0050] Step 1: Determine the number of required delivery tools 15, the number of sections and the length of the required oil pipe 6 according to the predetermined fracturing position; at the same time, ensure that the models and sizes of the multiple delivery tools 15 are gradually reduced, and prepare multiple steel balls 18 compatible with the multiple delivery tools 15, and ensure that the steel balls 18 corresponding to the previous delivery tools 15 can pass through the central tube 1 in the next delivery tool 15;

[0051] The inner diameters of the central tubes 1 in the various levels of the delivery tools 15 decrease in sequence. The delivery tool 15 corresponding to the central tube 1 with the smallest inner diameter is the uppermost level, and the delivery tool 15 corresponding to the central tube 1 with the largest inner diameter is the lowermost level. During the installation process, the delivery tool 15 of the upper level is located below the delivery tool 15 of the lower level.

[0052] As a preferred embodiment, the inner diameter of the central tube 1 in the next-level delivery tool 15 is 5 mm larger than the inner diameter of the central tube 1 in the previous-level delivery tool 15. At the same time, the diameter of the steel ball 18 in the next-level delivery tool 15 is the median of the inner diameters of the two central tubes 1 in the two adjacent delivery tools 15.

[0053] Step 2: According to the combustion-supporting amount required by each level of target reservoir 14, the required amount of gaseous combustion-supporting agent 10 is respectively filled into the gas storage spaces 9 in the multiple delivery tools 15;

[0054] Step 3: First, multiple sections of oil pipes 6 are arranged in sequence from top to bottom, and one or more packers 19 are installed on the outside of each section of oil pipe 6; then, multiple delivery tools 15 with gradually decreasing models and sizes are respectively placed in the space between two adjacent sections of oil pipe 6, and the upper end of the feed pipeline 21 in the delivery tool 15 is connected to the lower end of the oil pipe 6 at the corresponding position, and the lower end of the central tube 1 in the delivery tool 15 is connected to the upper end of the oil pipe 6 at the corresponding position, thereby forming an integrated delivery assembly;

[0055] Step 4: First, a fracturing vehicle 16 is arranged on the ground at one side of the wellbore 13 where the fracturing operation is to be performed; then, the integrated delivery assembly is lowered through the wellbore 13 to the location of the target reservoir 14, and the upper end of the uppermost section of the oil pipe 6 is connected to the output pipeline of the fracturing vehicle 16;

[0056] Step 5: Pump high-pressure nitrogen 17 into the oil pipe 6 through the fracturing truck 16, use the high-pressure nitrogen 17 to seal the various levels of packers 19, and use the two packers 19 distributed on the upper and lower sides of the delivery tool 15 to form a sealed delivery section 20 at the location of the delivery tool 15;

[0057] Step 6: Determine the sealing delivery section 20 of the target level one according to the principle of from bottom to top; drop the steel ball 18 matched with the target level one delivery tool 15 through the oil pipe 6, and the steel ball 18 passes through the central cylinder 1 in the delivery tools 15 of the target level and above in turn, and reaches the plugging funnel 5 in the central cylinder 1 on the delivery tool 15 of the current level, so as to realize the plugging operation of the central cylinder 1 on the delivery tool 15 of the current level;

[0058] Step 7: Continue to pump high-pressure nitrogen 17 into the oil pipe 6 through the fracturing vehicle 16, and use the high-pressure nitrogen 17 with increasing pressure to act on the upper end surface of the annular piston 3 in the target first-level delivery tool 15, so that the annular piston 3 of the target first level moves downward; use the compression effect of the annular piston 3 to continuously increase the pressure in the gas storage space 9. When the pressure in the gas storage space 9 reaches the opening pressure of the constant pressure plug 26, the gaseous combustion-supporting agent 10 in the gas storage space 9 enters the guide annulus 12 through the opened multiple constant pressure nozzles 8, and then flows out through the multiple lateral openings 11 and enters the sealed delivery section 20 of the target first level, until the gaseous combustion-supporting agent 10 in the gas storage space 9 is completely filled into the sealed delivery section 20, and the combustion-supporting agent delivery work of the target first-level target reservoir 14 is completed;

[0059] Step 8: Repeat steps 6 and 7 several times until the combustion aid placement work is completed in all sealed placement sections.

[0060] In the present invention, multiple delivery tools of decreasing models and sizes are connected by multiple sections of oil pipes to form an integrated delivery assembly, so that multiple delivery tools can be lowered to the location of the target reservoir in the wellbore by using the oil pipes. A packer is set on the outside of each section of the oil pipe, and the packer can be set by pumping high-pressure nitrogen. In this way, a sealed delivery section can be formed between the two packers on the upper and lower sides of the same delivery tool, so that the gaseous combustion-supporting agent released by the delivery tool can fully act on the sealed delivery area, which is further conducive to promoting the full mixing of the charged combustion-supporting agent with the in-situ methane in the reservoir space. According to the principle of from bottom to top, the sealing delivery section of the target level is determined, and then the corresponding steel balls are dropped through the oil pipe, so that the steel balls can pass through each section of the oil pipe and each center tube in turn into the sealing funnel of the center tube in the target level one delivery tool. The sealing funnel has a limiting effect on the steel ball, and the high-pressure nitrogen gas pumped in can reliably seal the center tube of the target level one. In this way, the high-pressure nitrogen gas pumped in later can be used to push the annular piston to move in the direction of the bottom of the gas storage cylinder, and the pressurization process of the gaseous combustion aid in the gas storage space is realized. During the pressurization process, the constant pressure plug will automatically detach from the constant pressure nozzle, and then the pre-stored gaseous combustion aid can enter the sealing delivery section through multiple directional nozzles, the guide annulus and multiple lateral openings. In this way, the delivery operation of the first-level sealing delivery section can be completed. On this basis, an integrated delivery assembly formed by a multi-stage delivery tool, multiple sections of oil pipes and multiple packers is used in series. In combination with pre-charging of combustion aid, the sequential delivery of multi-stage steel balls to plug the multi-stage central tubes and the sequential use of multi-stage piston compression can achieve quantitative, uniform and multi-stage delivery of combustion aids in deep methane reservoir spaces. In this process, the delivery processes in each level of the reservoir do not affect each other, thus meeting the needs of continuous multi-stage operations of in-situ methane explosion fracturing.

[0061] This method can not only carry out segmented and quantitative delivery of the combustion aid according to the size of each methane reservoir space, but also fully mix the combustion aid with the in-situ methane in the reservoir space during delivery, which helps to realize continuous multi-stage operation of methane in-situ explosion fracturing, and solves the problem that only single-stage tools can be put in during the traditional delivery process, and multi-stage tools cannot be put in, thus failing to meet the demand for multi-stage delivery of the combustion aid.

Claims

1. A methane in-situ explosive fracturing combustion aid multi-stage delivery tool, the delivery tool (15) comprising an inner gas storage cylinder (2), characterized in that: It also includes an outer guide tube (4), a center tube (1) and an annular piston (3); The top center of the inner gas storage cylinder (2) is fixedly connected to a feed pipeline (21) communicating with its inner cavity, and the bottom thereof is provided with a gas storage bottom plate (23); an upper through hole is provided in the central area of ​​the gas storage bottom plate (23), and a plurality of constant pressure nozzles (8) are uniformly provided in an annular direction around the outer periphery of the upper through hole, and a constant pressure plug (26) is installed in the constant pressure nozzle (8); The top end of the outer guide tube (4) is an open structure, and a plurality of lateral openings (11) are formed upwardly thereon, and the bottom end has a guide bottom plate (24), and a lower through hole is formed in the central area of ​​the guide bottom plate (24); the outer guide tube (4) is coaxially sleeved on the outside of the inner gas storage cylinder (2), and the top end of the outer guide tube is fixedly connected to the top of the inner gas storage cylinder (2) via an annular connecting plate (25); The outer diameter of the central tube (1) matches the size of the inner diameters of the upper through hole and the lower through hole. The central tube (1) is coaxially arranged inside the inner gas storage cylinder (2). Its lower end sequentially passes through the upper through hole and the lower through hole and extends to the outside of the bottom of the outer guide tube (4). Its upper end stops below the top of the inner gas storage cylinder (2) and is fixedly connected to a plugging funnel (5). The plugging funnel (5) is clearance-matched with the inner gas storage cylinder (2). The outer diameter of the annular piston (3) is matched to the inner diameter of the inner gas storage cylinder (2), and the diameter of the center hole thereof is matched to the outer diameter of the center cylinder (1); the annular piston (3) is axially slidably mounted inside the inner gas storage cylinder (2), and is axially slidably mounted on the outer side of the center cylinder (1) through its center hole; A flow guide annulus (12) is formed between the outer flow guide cylinder (4), the center cylinder (1) and the inner gas storage cylinder (2), and a gas storage space (9) is formed between the annular piston (3), the center cylinder (1) and the gas storage bottom plate (23); It also comprises a steel ball (18), the outer diameter of the steel ball (18) being matched to the inner diameter of the plugging funnel (5), and the steel ball (18) being thrown into the plugging funnel (5) to plug the inlet end of the central tube (1).

2. A methane in-situ explosion fracturing combustion aid multi-stage delivery tool according to claim 1, characterized in that: The body of the inner gas storage cylinder (2) is composed of a funnel section (7) and a cylindrical section (22); the funnel section (7) is arranged inverted and transitionally connects the lower end of the feed pipeline (21) and the upper end of the cylindrical section (22).

3. A methane in-situ explosion fracturing combustion aid multi-stage delivery tool according to claim 2, characterized in that: The size of the large diameter end of the plugging funnel (5) is adapted to the size of the feed pipeline (21), and the clearance between the large diameter end and the lower end of the feed pipeline (21) is matched.

4. A methane in-situ explosion fracturing combustion aid multi-stage delivery tool according to claim 3, characterized in that: The plurality of lateral openings (11) are evenly distributed in the circumferential direction and are divided into three layers from top to bottom.

5. A methane in-situ explosion fracturing combustion aid multi-stage delivery tool according to claim 4, characterized in that: The guide bottom plate (24) is funnel-shaped.

6. A method for multi-stage delivery of a methane in-situ explosion fracturing combustion aid, using a multi-stage delivery tool for a methane in-situ explosion fracturing combustion aid as claimed in claim 5, characterized in that: The following steps are involved: Step 1: Determine the number of required delivery tools (15), the number of sections and the length of the required oil pipe (6) according to the predetermined fracturing position; at the same time, ensure that the models and sizes of the multiple delivery tools (15) are gradually reduced, prepare multiple steel balls (18) compatible with the multiple delivery tools (15), and ensure that the steel balls (18) corresponding to the previous delivery tools (15) can pass through the central tube (1) in the next delivery tool (15); Step 2: According to the combustion-aiding agent dosage required by each level of target reservoir (14), the required amount of gaseous combustion-aiding agent (10) is respectively charged into the gas storage spaces (9) in the plurality of delivery tools (15); Step 3: First, multiple sections of oil pipe (6) are arranged in sequence from top to bottom, and one or more packers (19) are mounted on the outside of each section of oil pipe (6); then, multiple delivery tools (15) of gradually decreasing size are respectively placed in the space between two adjacent sections of oil pipe (6), and the upper end of the feed pipeline (21) in the delivery tool (15) is connected to the lower end of the oil pipe (6) at the corresponding position, and the lower end of the central tube (1) in the delivery tool (15) is connected to the upper end of the oil pipe (6) at the corresponding position, thereby forming an integrated delivery assembly; Step 4: firstly, a fracturing vehicle (16) is arranged on the ground at one side of the wellbore (13) where the fracturing operation is to be performed; then, the integrated delivery assembly is lowered through the wellbore (13) to the location of the target reservoir (14), and the upper end of the uppermost section of the oil pipe (6) is connected to the output pipeline of the fracturing vehicle (16); Step 5: high-pressure nitrogen (17) is pumped into the oil pipe (6) by the fracturing vehicle (16), and the high-pressure nitrogen (17) is used to seal the various packers (19), and two packers (19) distributed on the upper and lower sides of the delivery tool (15) are used to form a sealed delivery section (20) at the location of the delivery tool (15); Step 6: Determine the sealing delivery section (20) of the target level one according to the principle of going from bottom to top; drop a steel ball (18) that matches the target level one delivery tool (15) through the oil pipe (6); the steel ball (18) passes through the central cylinder (1) of each level of delivery tools (15) above the target level one in turn, and reaches the plugging funnel (5) in the upper central cylinder (1) of the delivery tool (15) of the current level, thereby completing the plugging operation of the upper central cylinder (1) of the delivery tool (15) of the current level; Step 7: Continue to pump high-pressure nitrogen (17) into the oil pipe (6) through the fracturing vehicle (16), and use the high-pressure nitrogen (17) with increasing pressure to act on the upper end surface of the annular piston (3) in the target first-level delivery tool (15), so that the annular piston (3) of the target first level moves downward; use the compression effect of the annular piston (3) to continuously increase the pressure in the gas storage space (9), and when the pressure in the gas storage space (9) reaches the opening pressure of the constant pressure plug (26), the gaseous combustion-supporting agent (10) in the gas storage space (9) enters the guide annulus (12) through the opened multiple constant pressure nozzles (8), and then flows out through the multiple lateral openings (11) and enters the sealed delivery section (20) of the target first level, until the gaseous combustion-supporting agent (10) in the gas storage space (9) is completely filled into the sealed delivery section (20), and the combustion-supporting agent delivery work of the target first-level target reservoir (14) is completed; Step 8: Repeat steps 6 and 7 several times until the combustion aid placement work is completed in all sealed placement sections.

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