In-situ gas fracturing method in reservoir

Abstract

The in-situ gas fracturing method in the reservoir comprises the steps that a horizontal section of a horizontal well is sequentially divided into a plurality of sections from the toe end to the heel end, and perforation holes are formed in each section; the continuous oil pipe column is put down, fracturing fluid is pumped into the continuous oil pipe column after the continuous oil pipe column is dragged upwards, and hydraulic seams are formed in the first section to the last section of the horizontal section of the horizontal well in sequence till fracturing seam forming of all the sections is completed; the continuous oil pipe column is put down again, the liquid high-energy material is injected into the continuous oil pipe column to replace original fracturing fluid in the continuous oil pipe column and the casing pipe of the horizontal section, the continuous oil pipe column is dragged upwards, then the liquid high-energy material is injected, and the liquid high-energy material enters the hydraulic seams of all the sections of the horizontal section; and the coiled tubing string is lifted out, an ignition bridge plug is arranged in the contact area of the liquid high-energy material in the horizontal well casing and the fracturing fluid, the liquid high-energy material in the horizontal well casing and the hydraulic seam is detonated by exciting an ignition head on the lower portion of the ignition bridge plug, and reservoir transformation is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of high-energy gas fracturing, and in particular to an in-situ gas fracturing method within a reservoir. Background Art

[0002] Fracturing is an effective means to transform reservoirs and increase production and injection. Drawing on the successful experience of shale gas in the United States, volume fracturing is currently the main means of increasing production for the efficient development of unconventional oil and gas resources. Especially for shale gas and deep coalbed methane, the extreme volume horizontal well staged fracturing technology system of "dense cutting + large displacement + combined proppant + pre-acid + sticky and slippery water" is mainly used.

[0003] However, conventional fracturing operations require a large amount of water resources, and China faces the following problems: (1) Water resources are scarce, and large-scale hydraulic fracturing is unsustainable. my country's per capita water resources are only 2,100 cubic meters, less than 1 / 10 of the United States. In the northwestern mountainous areas, water resources are even scarcer, and water supply is difficult, which seriously restricts the progress of operations and makes economic development difficult. (2) Large-scale fracturing fluid entering the formation is prone to cause problems such as coal powder, water sensitivity, water lock, and scaling, which affects the pore conductivity and causes great damage to the reservoir. In addition, the large amount of liquid leads to a long drainage time, and the initial liquid volume is large and the later liquid volume is small, which requires a high wide-range operating capacity of the drainage equipment, and the pressure of well repair and pump replacement is high, making drainage difficult. (3) The return fluid and production waste liquid have a large amount of water and complex composition. The liquid contains solid particles, metal ions, and chemical agents of different components, which can easily cause potential harm to the environment. In addition, it is difficult to treat production water. Although the return fluid has been partially compounded, there are still process and cost problems.

[0004] High-energy gas fracturing technology relies on the pulse energy generated by high-energy gas and high-energy particles, or the pulse energy generated by mechanical structures to achieve fracturing. It is one of the strong dynamic load reservoir transformation technologies. It mainly includes three processes: one is to lower the cable into the high-energy gas generator and ignite it through the ground power supply; the second is to lower the oil pipe into the generator and use the casting rod to impact and ignite; the third is the process of solid charge igniting liquid charge. The advantages of this type of technology are that it does not require large equipment, does not require sand and water sources, does not require drainage after compression, and the process is simple and low in cost. The disadvantages are that the charge is mainly limited to the wellbore, the amount of charge is limited, and the crack length is relatively short; the cementing quality requirements are high, which limits the application in certain well conditions; the technical operation is relatively difficult, and safety needs to be focused on.

[0005] In short, there is currently a lack of in-situ gas fracturing methods within reservoirs that can be applied to large-scale reservoir transformation using high-energy gas fracturing technology and are safe and easy to operate. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide an in-situ gas fracturing method in a reservoir, which is used to solve the problem that there is currently a lack of an in-situ gas fracturing method in a reservoir that can apply high-energy gas fracturing technology to large-scale reservoir transformation and is safe and easy to operate.

[0007] To achieve the above object, the present invention adopts the following technical solutions: The invention discloses an in-situ gas fracturing method in a reservoir, comprising: Step A: The horizontal section of the horizontal well is divided into several sections from the toe end to the heel end, and a perforation hole is formed in each section; Step B: lowering the coiled tubing string, dragging the coiled tubing string upwards and pumping in fracturing fluid, so that hydraulic fractures are formed in the first to last sections of the horizontal section of the horizontal well in sequence, and the hydraulic fractures extend into the reservoir until the fracturing and fracture formation of all sections are completed; Step C: lowering the coiled tubing string again, injecting liquid high-energy material into the coiled tubing string, replacing the original fracturing fluid in the coiled tubing string and the casing of the horizontal section, and injecting liquid high-energy material after dragging the coiled tubing string upward, so that the liquid high-energy material enters the hydraulic fractures of each section of the horizontal section respectively; Step D: The coiled tubing string is brought out, and an ignition bridge plug is set in the contact area between the liquid high-energy material and the fracturing fluid in the horizontal well casing. The liquid high-energy material in the horizontal well casing and the hydraulic fracture is detonated by stimulating the ignition head at the bottom of the ignition bridge plug, thereby realizing reservoir transformation.

[0008] Wherein, the step A comprises the following specific steps: Step A1: dividing the horizontal section of the horizontal well from the toe end to the heel end into a plurality of sections, namely the first section, the second section, ..., the Nth section, wherein N is a natural number greater than 1; Step A2: Scrape and clean the horizontal well; Step A3: Use a tubing-transported perforating gun string to perform segmented perforation on the casing of the horizontal section of the horizontal well and its surrounding formations, and form perforation holes in each section so that the liquid in the casing can flow into the surrounding formations through the perforation holes.

[0009] In step B, the method for forming a hydraulic fracture in one section of the reservoir comprises the following specific steps: First, two packers are pre-configured on the coiled tubing string, and at least one liquid outlet is provided on the coiled tubing string between the two packers; Second, lowering the coiled tubing string and positioning it to ensure that the perforation holes of the reservoir section are located between the two packers on the coiled tubing string; Third: inject fracturing fluid into the coiled tubing string from the wellhead and perform pressure pumping. The fracturing fluid fills the inside of the coiled tubing string. The fracturing fluid in the coiled tubing string compresses the two packers outwards. The outer walls of the two packers gradually press against the inner wall of the casing until the two packers are seated between the outer wall of the coiled tubing string and the inner wall of the casing, so that the two packers, the inner wall of the casing, and the outer wall of the coiled tubing string form a closed annular space. The closed annular space is not only connected to the interior of the coiled tubing string through the liquid outlet hole, but also connected to the hydraulic fracture through the perforation hole, thereby realizing that the interior of the coiled tubing string, the liquid outlet hole, the closed annular space, the perforation hole of the reservoir section and the hydraulic fracture are connected in sequence to form a liquid flow channel; Fourth: Continue to pump the fluid, the fracturing fluid flows out from the outlet hole, enters the closed annular space, and finally enters the formation through the perforation holes to form hydraulic fractures.

[0010] The step B comprises the following specific steps: Step B1: lowering the coiled tubing string and positioning it to ensure that the perforation holes of the first section of the reservoir are located between two packers on the coiled tubing string; Step B2: injecting fracturing fluid into the coiled tubing string and pressurizing it until two packers are seated between the outer wall of the coiled tubing string and the inner wall of the casing to form a closed annular space; Step B3: Continue to pump the fracturing fluid, the fracturing fluid flows out from the outlet hole, enters the closed annular space, and finally enters the formation through the perforation holes to form hydraulic fractures; Step B4: drag the coiled tubing string upward so that the perforation holes of the next section are located between two packers on the coiled tubing string, and repeat steps B2 to B3 to form hydraulic fractures in the next section of the reservoir; Step B5: Repeat step B4 until all segments of the reservoir are fractured.

[0011] Specifically, the fracturing fluid is slick water.

[0012] The step C comprises the following specific steps: Step C1: lowering the coiled tubing string again and positioning it to ensure that the perforation holes of the first section of the reservoir are located between the two packers on the coiled tubing string, and injecting liquid high-energy material into the coiled tubing string from the wellhead to replace the original fracturing fluid in the coiled tubing and the casing of the horizontal section; Step C2: the coiled tubing string is pressurized, and the liquid high-energy material fills the interior of the casing until two packers are set between the outer wall of the coiled tubing string and the inner wall of the casing to form a closed annular space; Step C3: Continue to pressurize, and the liquid high-energy material flows out from the outlet hole of the coiled tubing string, enters the closed annular space, and finally enters the hydraulic fracture through the perforation hole; Step C4: drag the coiled tubing string upwards so that the perforation holes of the next section of the reservoir are located between the two packers on the coiled tubing string, and repeat steps C2 to C3 to allow the liquid high-energy material to enter the hydraulic fracture of the next section of the reservoir; Step C5: Repeat step C4 until the liquid high-energy material is squeezed into the hydraulic fractures of all sections of the reservoir.

[0013] The step D comprises the following specific steps: Step D1: taking out the coiled tubing string; Step D2: lowering the ignition bridge plug through the cable, so that the ignition bridge plug is located in the contact area between the liquid high-energy material and the fracturing fluid in the deflection section at the upper part of the horizontal section, and ensuring that the ignition head of the ignition bridge plug is located on one side of the liquid high-energy material and is in direct contact with the liquid high-energy material; Step D3: energizing the setting tool of the ignition bridge plug to set the bridge plug of the ignition bridge plug, thereby separating the fracturing fluid located above from the liquid high-energy material located below; Step D4: Take out the cable and the setting tool of the ignition bridge plug; Step D5: The fracturing fluid in the casing is pressurized at the wellhead to stimulate the ignition head at the bottom of the ignition bridge plug, thereby detonating the liquid high-energy material in the horizontal well casing and the hydraulic fracture. The explosion of the liquid high-energy material transforms the formation around the hydraulic fracture to form a self-supporting complex fracture network.

[0014] When liquid high-energy materials explode, a large amount of high-energy gas is generated in the hydraulic fractures in a short period of time, which fully transforms the strata around the hydraulic fractures and forms a self-supporting complex fracture network.

[0015] In order to ensure the safety of the wellhead, the bridge plug of the ignition bridge plug seals off the high-energy gas during combustion and explosion.

[0016] The step D5 also includes a step D6: drilling out the ignition bridge plug by lowering a drilling tool to clear the horizontal well.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses an in-situ gas fracturing method in a reservoir, comprising: step A: dividing the reservoir of a horizontal section of a horizontal well into a plurality of sections from the toe end to the heel end, and forming perforations in each section of the reservoir; step B: lowering a coiled tubing string, After the continuous tubing string is pulled upward, the fracturing fluid is pumped in, so that hydraulic fractures are formed in the first to the last section of the horizontal section of the horizontal well, and the hydraulic fractures extend into the reservoir until the fracturing and fracture formation of all sections are completed; Step C: Liquid high-energy material is injected into the continuous tubing string to replace the original fracturing fluid in the continuous tubing string, the continuous tubing string is lowered again, and the continuous tubing string is pulled upward and the liquid high-energy material is injected, so that the liquid high-energy material enters the hydraulic fracture of each section of the reservoir respectively; Step D: The continuous tubing string is raised, and an ignition bridge plug is set in the contact area between the liquid high-energy material and the fracturing fluid in the casing of the horizontal well, and the ignition head at the bottom of the ignition bridge plug is stimulated to detonate the liquid high-energy material in the casing of the horizontal well and in the hydraulic fracture, thereby realizing the reservoir transformation. The in-situ gas fracturing method in the reservoir disclosed by the present invention can realize the purpose of manufacturing a large-scale complex fracture network in the reservoir for full transformation in a safe and simple manner using only a small amount of water and liquid high-energy material. The invention can be used for multi-stage fracturing reformation of well types such as directional wells or horizontal wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of scraping pipe and washing wells provided in Example 2 of the present invention; Figure 2 is a schematic diagram of forming a perforation hole provided in Example 2 of the present invention; Figure 3 is a schematic diagram of injecting slick water to form a hydraulic joint provided in Example 2 of the present invention; Figure 4 is a schematic diagram of injecting liquid high-energy material to fill the interior of the casing provided by Example 2 of the present invention; Figure 5 It is a schematic diagram of the liquid high-energy material provided in Example 2 of the present invention entering the hydraulic fracture from the perforated hole; Figure 6 Schematic diagram of the liquid high-energy material provided in Example 2 of the present invention being squeezed into hydraulic fractures in all sections of the reservoir; Figure 7 It is a schematic diagram of an ignition bridge plug provided by Example 2 of the present invention being located in the contact area between the liquid high-energy material and the fracturing fluid in the deflection section at the upper part of the horizontal section, and ensuring that the ignition head of the ignition bridge plug is located on one side of the liquid high-energy material and in direct contact with the liquid high-energy material; Figure 8 This is a schematic diagram of the ignition bridge plug provided in Example 2 of the present invention, which isolates high-energy gas during combustion and explosion to ensure the safety of the wellhead; Fig. 9It is a schematic diagram of a horizontal well and hydraulic fracture after drilling plug and well drilling provided by Example 2 of the present invention. DETAILED DESCRIPTION

[0019] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0020] In order to solve the problem of the lack of an in-situ gas fracturing method in a reservoir that can apply high-energy gas fracturing technology to large-scale reservoir transformation and is safe and easy to operate, the present invention discloses an in-situ gas fracturing method in a reservoir, comprising: step A: dividing the reservoir of the horizontal section of the horizontal well into a plurality of sections from the toe end to the heel end, and forming perforations in each section of the reservoir; step B: lowering a coiled tubing string, After the coiled tubing strings are respectively dragged upward, fracturing fluid is pumped in, so that hydraulic fractures are formed in the first to the last sections of the horizontal section of the horizontal well in sequence, and the hydraulic fractures extend into the reservoir until the fracturing and fracture formation of all sections are completed; Step C: Liquid high-energy material is injected into the coiled tubing string to replace the original fracturing fluid in the coiled tubing string, the coiled tubing string is lowered again, and the coiled tubing strings are respectively dragged upward and then injected with liquid high-energy material, so that the liquid high-energy material enters the hydraulic fracture of each section of the reservoir; Step D: The coiled tubing string is raised, and an ignition bridge plug is set in the contact area between the liquid high-energy material and the fracturing fluid in the casing of the horizontal well, and the liquid high-energy material in the casing of the horizontal well and the hydraulic fracture is detonated by stimulating the ignition head at the bottom of the ignition bridge plug, thereby realizing reservoir transformation.

[0021] Example 1: An in-situ gas fracturing device in a reservoir Embodiment 1 of the present invention provides an in-situ gas fracturing device in a reservoir, and its structure is described in detail below with reference to the accompanying drawings.

[0022] refer to Figures 1 to 9 The in-situ gas fracturing device in the reservoir includes a horizontal well, a tubing-transported perforating gun string (TCP), a coiled tubing string and an ignition bridge plug.

[0023] The horizontal well comprises a vertical well section, a deflection section and a horizontal section. The vertical well section and the horizontal section are connected via the deflection section, and the horizontal section is located in a reservoir to be mined.

[0024] A casing is arranged in the horizontal well. The casing is sequentially lowered into the horizontal well from top to bottom, and the casing runs through the horizontal section of the horizontal well.

[0025] The horizontal section of the horizontal well is divided into several sections from the toe end to the heel end, namely the first section, the second section, ..., the Nth section, wherein N is a natural number greater than 1.

[0026] In order to facilitate the liquid in the casing to flow into the reservoir surrounding the horizontal section, perforation holes are respectively arranged from the first section to the last section of the horizontal section of the horizontal well.

[0027] Specifically, the oil pipe-transported perforating gun string can be lowered into the casing, and can perform segmented perforation on the casing and surrounding formations of several reservoir sections in the horizontal section of the horizontal well, and form perforation holes in each section of the reservoir.

[0028] Before the fracturing fluid is pressurized to form hydraulic fractures in the reservoir segments, a coiled tubing string needs to be run into the casing.

[0029] The coiled tubing string can be lowered into the casing, and two packers are arranged on the coiled tubing string, and at least one liquid outlet is arranged on the coiled tubing string between the two packers.

[0030] By dragging the coiled tubing string, the perforation holes from the first section to the last section of the horizontal section of the horizontal well can be located between the two packers on the coiled tubing string respectively.

[0031] The ignition bridge plug is equipped with a setting tool, and the setting tool is equipped with a cable connector. A cable is inserted into the cable connector. The setting tool is lowered by moving the cable, and the ignition bridge plug is then transported to the liquid high-energy material.

[0032] Specifically, the setting tool is transported by a cable to transport and set the bridge plug of the ignition bridge plug in the contact area between the liquid high-energy material and the fracturing fluid in the deflection section above the horizontal section.

[0033] Specifically, the ignition bridge plug comprises a bridge plug body and an ignition head, and the ignition head is arranged on the bridge plug body.

[0034] Specifically, the bridge plug body is provided with a central flow channel, a piston housing is fixed to the bottom end thereof, and the inside of the piston housing is in communication with the central flow channel; The ignition head includes a piston, a firing pin and a detonator, the piston housing includes a cavity, and the piston is temporarily restrained at the upper part of the cavity of the piston housing by two shear pins; The firing pin is fixed to the lower part of the piston; The detonator is fixed at the bottom of the piston housing and directly faces the firing pin; The central flow channel is provided with a one-way valve, which only allows pressure to be transmitted in one direction from top to bottom, and is used as a channel for the circulation of pressurized medium to impact the piston and move it forward, and at the same time serves as a barrier to isolate the wellbore pressure below the bridge plug; When the piston is impacted by the pressurized medium, the shear pin is first cut off to get rid of the temporary restraint, and then the firing pin is driven to move forward; the firing pin moves forward until it hits the detonator; after the detonator is hit, sparks are generated, and the sparks extend forward into the liquid high-energy material to achieve ignition.

[0035] The bridge plug body is arranged in the contact area between the liquid high-energy material and the fracturing fluid in the deflection section at the upper part of the horizontal section, and ensures that the ignition head of the ignition bridge plug is located on one side of the liquid high-energy material and is in direct contact with the liquid high-energy material.

[0036] Specifically, the liquid high-energy material is liquid explosive.

[0037] In order to ensure that the sparks generated by the detonator after impact can smoothly extend into the liquid high-energy material, the detonator runs through the bottom of the piston shell.

[0038] Example 2: A method for in-situ gas fracturing in a reservoir Embodiment 2 of the present invention provides an in-situ gas fracturing method in a reservoir, using the in-situ gas fracturing device in the reservoir of Embodiment 1, and the method comprises the following steps: Step A: The horizontal section of the horizontal well is divided into several sections from the toe end to the heel end, and a perforation hole is formed in each section, including the following specific steps: Step A1: dividing the horizontal section of the horizontal well from the toe end to the heel end into a plurality of sections, namely the first section, the second section, ..., the Nth section, wherein N is a natural number greater than 1; Step A2: Scrape and clean the horizontal well, such as Figure 1 As shown, Specifically, the pipe used for scraping and well washing is a casing.

[0039] Step A3: Use a tubing-transported perforating gun string to perform segmented perforation of the casing and surrounding formations in the horizontal section of the horizontal well, and form perforation holes in each section, such as Figure 2 As shown, the liquid in the casing can flow into the surrounding formation through the perforations.

[0040] Step B: lowering the coiled tubing string, dragging the coiled tubing string upwards and pumping in fracturing fluid, so that hydraulic fractures are formed in the first to last sections of the horizontal well in sequence, and the hydraulic fractures extend into the reservoir until all sections are fractured.

[0041] The method for forming a hydraulic fracture in a section of a reservoir comprises the following specific steps: First, two packers are pre-configured on the coiled tubing string, and at least one liquid outlet is provided on the coiled tubing string between the two packers; Second, lower the coiled tubing string and position it to ensure that the perforation holes in this section of the reservoir are located between the two packers on the coiled tubing string, such as Figure 3 As shown; Third: inject fracturing fluid into the coiled tubing string from the wellhead and perform pressure pumping. The fracturing fluid fills the inside of the coiled tubing string. The fracturing fluid in the coiled tubing string compresses the two packers outwards. The outer walls of the two packers gradually press against the inner wall of the casing until the two packers are seated between the outer wall of the coiled tubing string and the inner wall of the casing, so that the two packers, the inner wall of the casing, and the outer wall of the coiled tubing string form a closed annular space. The closed annular space is not only connected to the interior of the coiled tubing string through the liquid outlet hole, but also connected to the hydraulic fracture through the perforation hole, thereby realizing that the interior of the coiled tubing string, the liquid outlet hole, the closed annular space, the perforation hole of the reservoir section and the hydraulic fracture are connected in sequence to form a liquid flow channel; Specifically, the fracturing fluid is slick water.

[0042] Fourth: Continue to pump the fracturing fluid, the fracturing fluid flows out from the outlet hole, enters the closed annular space, and finally enters the formation through the perforation holes to form hydraulic fractures. Figure 3 shown.

[0043] Specifically, step B includes the following specific steps: Step B1: lowering the coiled tubing string and positioning it to ensure that the perforation holes of the first section of the reservoir are located between two packers on the coiled tubing string; Step B2: injecting fracturing fluid into the coiled tubing string and pressurizing it until two packers are seated between the outer wall of the coiled tubing string and the inner wall of the casing to form a closed annular space, thereby connecting the interior of the coiled tubing string, the liquid outlet hole, the closed annular space, the perforated holes of the reservoir section and the hydraulic fractures in sequence to form a liquid circulation channel; Step B3: Continue to pump the fracturing fluid, the fracturing fluid flows out from the outlet hole, enters the closed annular space, and finally enters the formation through the perforation holes to form hydraulic fractures; Step B4: Drag the coiled tubing string upward so that the perforation holes of the next section are located between the two packers on the coiled tubing string, and repeat steps B2 to B3 to form hydraulic fractures in the next section of the reservoir. Figure 3 As shown; Step B5: Repeat step B4 until all segments of the reservoir are fractured.

[0044] Step C: lowering the coiled tubing string again, injecting liquid high-energy material into the coiled tubing string, replacing the original fracturing fluid in the coiled tubing string and the casing of the horizontal section, and injecting liquid high-energy material after dragging the coiled tubing string upward, so that the liquid high-energy material enters the hydraulic fractures of each section of the horizontal section respectively, including the following specific steps: Step C1: lowering the coiled tubing string again and positioning it to ensure that the perforation holes of the first section of the reservoir are located between the two packers on the coiled tubing string, and injecting liquid high-energy material into the coiled tubing string from the wellhead to replace the original fracturing fluid in the coiled tubing and the casing of the horizontal section; Step C2: Pressurize the coiled tubing string, and the liquid high-energy material fills the inside of the casing, such as Figure 4 As shown, until two packers are set between the outer wall of the coiled tubing string and the inner wall of the casing to form a closed annular space; Step C3: Continue to pressurize, the liquid high-energy material flows out from the outlet hole of the coiled tubing string, enters the closed annular space, and finally enters the hydraulic fracture through the perforation hole. Figure 5 As shown; Step C4: drag the coiled tubing string upwards so that the perforation holes of the next section of the reservoir are located between the two packers on the coiled tubing string, and repeat steps C2 to C3 to allow the liquid high-energy material to enter the hydraulic fracture of the next section of the reservoir; Step C5: Repeat step C4 until the liquid high-energy material is squeezed into the hydraulic fractures of all sections of the reservoir. Figure 6 shown.

[0045] Step D: taking out the coiled tubing string, setting an ignition bridge plug in the contact area between the liquid high-energy material and the fracturing fluid in the horizontal well casing, and igniting the ignition head at the bottom of the ignition bridge plug to detonate the liquid high-energy material in the horizontal well casing and the hydraulic fracture, thereby realizing the transformation of the formation around the hydraulic fracture, including the following specific steps: Step D1: taking out the coiled tubing string; Step D2: lower the ignition bridge plug through the cable, so that the ignition bridge plug is located in the contact area between the liquid high-energy material and the fracturing fluid in the deflection section above the horizontal section, and ensure that the ignition head of the ignition bridge plug is located on one side of the liquid high-energy material and is in direct contact with the liquid high-energy material, such as Figure 7 As shown; Step D3: energizing the setting tool of the ignition bridge plug to set the bridge plug of the ignition bridge plug, thereby separating the fracturing fluid located above from the liquid high-energy material located below; Step D4: Take out the cable and the setting tool of the ignition bridge plug; Step D5: The fracturing fluid in the casing is pressurized at the wellhead to stimulate the ignition head at the bottom of the ignition bridge plug, thereby detonating the liquid high-energy material in the horizontal well casing and the hydraulic fracture. The explosion of the liquid high-energy material transforms the formation around the hydraulic fracture to form a self-supporting complex fracture network.

[0046] When liquid high-energy materials explode, a large amount of high-energy gas is generated in the hydraulic fractures in a short period of time, which fully transforms the strata around the hydraulic fractures and forms a self-supporting complex fracture network.

[0047] Specifically, the liquid energetic material is liquid explosive.

[0048] Among them, the bridge plug of the ignition bridge plug isolates high-energy gas during combustion and explosion to ensure the safety of the wellhead, such as Figure 8 shown.

[0049] Specifically, in order to prevent the high-energy and high-pressure gas from returning to the upper part of the casing after the explosion of the liquid high-energy material below the ignition bridge plug, two protective barriers are designed.

[0050] Design of the first protective barrier: the inner diameter of the cavity of the piston shell is larger than the inner diameter of the central flow channel of the center tube, and a step is provided at the junction of the cavity of the piston shell and the central flow channel of the center tube to prevent the piston from entering the central flow channel of the center tube from the cavity of the piston shell.

[0051] Design of the second protective barrier: A one-way valve is provided at the connection between the butt end of the sealing tool and the central flow channel of the central tube, and the one-way valve is used to only allow the medium to be transmitted from top to bottom, but not from bottom to top.

[0052] The second protective barrier can isolate the high-energy and high-pressure gas under the ignition bridge plug, thereby isolating the high-energy gas.

[0053] Step D6: Drill out the ignition bridge plug by running the drilling tool to clear the horizontal well. Fig. 9 shown.

[0054] Specifically, the running drilling tool includes a drill bit and a drill rod.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for in-situ gas fracturing in a reservoir, characterized in that: include Step A: The horizontal section of the horizontal well is divided into several sections from the toe end to the heel end, and a perforation hole is formed in each section; Step B: lowering the coiled tubing string, dragging the coiled tubing string upwards and pumping in fracturing fluid, so that hydraulic fractures are formed in the first to last sections of the horizontal section of the horizontal well in sequence, and the hydraulic fractures extend into the reservoir until the fracturing and fracture formation of all sections are completed; Step C: lowering the coiled tubing string again, injecting liquid high-energy material into the coiled tubing string, replacing the original fracturing fluid in the coiled tubing string and the casing of the horizontal section, and injecting liquid high-energy material after dragging the coiled tubing string upward, so that the liquid high-energy material enters the hydraulic fractures of each section of the horizontal section respectively; Step D: The coiled tubing string is brought out, and an ignition bridge plug is set in the contact area between the liquid high-energy material and the fracturing fluid in the horizontal well casing. The liquid high-energy material in the horizontal well casing and the hydraulic fracture is detonated by stimulating the ignition head at the bottom of the ignition bridge plug, thereby realizing reservoir transformation.

2. The in-situ gas fracturing method in a reservoir according to claim 1, characterized in that: The step A comprises the following specific steps: Step A1: dividing the horizontal section of the horizontal well from the toe end to the heel end into a plurality of sections, namely the first section, the second section, ..., the Nth section, wherein N is a natural number greater than 1; Step A2: Scrape and clean the horizontal well; Step A3: Use a tubing-transported perforating gun string to perform segmented perforation on the casing of the horizontal section of the horizontal well and its surrounding formations, and form perforation holes in each section so that the liquid in the casing can flow into the surrounding formations through the perforation holes.

3. The in-situ gas fracturing method in a reservoir according to claim 2, characterized in that: In step B, the method for forming a hydraulic fracture in one section of the reservoir comprises the following specific steps: First, two packers are pre-configured on the coiled tubing string, and at least one liquid outlet is provided on the coiled tubing string between the two packers; Second, lowering the coiled tubing string and positioning it to ensure that the perforation holes of the reservoir section are located between the two packers on the coiled tubing string; Third: inject fracturing fluid into the coiled tubing string from the wellhead and perform pressure pumping. The fracturing fluid fills the inside of the coiled tubing string. The fracturing fluid in the coiled tubing string compresses the two packers outwards. The outer walls of the two packers gradually press against the inner wall of the casing until the two packers are seated between the outer wall of the coiled tubing string and the inner wall of the casing, so that the two packers, the inner wall of the casing, and the outer wall of the coiled tubing string form a closed annular space. The closed annular space is not only connected to the interior of the coiled tubing string through the liquid outlet hole, but also connected to the hydraulic fracture through the perforation hole, thereby realizing that the interior of the coiled tubing string, the liquid outlet hole, the closed annular space, the perforation hole of the reservoir section and the hydraulic fracture are connected in sequence to form a liquid flow channel; Fourth: Continue to pump the fluid, the fracturing fluid flows out from the outlet hole, enters the closed annular space, and finally enters the formation through the perforation holes to form hydraulic fractures.

4. The in-situ gas fracturing method in a reservoir according to claim 1, characterized in that: The step B comprises the following specific steps: Step B1: lowering the coiled tubing string and positioning it to ensure that the perforation holes of the first section of the reservoir are located between two packers on the coiled tubing string; Step B2: injecting fracturing fluid into the coiled tubing string and pressurizing it until two packers are seated between the outer wall of the coiled tubing string and the inner wall of the casing to form a closed annular space; Step B3: Continue to pump the fracturing fluid, the fracturing fluid flows out from the outlet hole, enters the closed annular space, and finally enters the formation through the perforation holes to form hydraulic fractures; Step B4: drag the coiled tubing string upward so that the perforation holes of the next section are located between two packers on the coiled tubing string, and repeat steps B2 to B3 to form hydraulic fractures in the next section of the reservoir; Step B5: Repeat step B4 until all segments of the reservoir are fractured.

5. The in-situ gas fracturing method in a reservoir according to claim 3 or 4, characterized in that: The fracturing fluid is slick water.

6. The in-situ gas fracturing method in a reservoir according to claim 1, characterized in that: The step C comprises the following specific steps: Step C1: lowering the coiled tubing string again and positioning it to ensure that the perforation holes of the first section of the reservoir are located between the two packers on the coiled tubing string, and injecting liquid high-energy material into the coiled tubing string from the wellhead to replace the original fracturing fluid in the coiled tubing and the casing of the horizontal section; Step C2: the coiled tubing string is pressurized, and the liquid high-energy material fills the interior of the casing until two packers are set between the outer wall of the coiled tubing string and the inner wall of the casing to form a closed annular space; Step C3: Continue to pressurize, and the liquid high-energy material flows out from the outlet hole of the coiled tubing string, enters the closed annular space, and finally enters the hydraulic fracture through the perforation hole; Step C4: drag the coiled tubing string upwards so that the perforation holes of the next section of the reservoir are located between the two packers on the coiled tubing string, and repeat steps C2 to C3 to allow the liquid high-energy material to enter the hydraulic fracture of the next section of the reservoir; Step C5: Repeat step C4 until the liquid high-energy material is squeezed into the hydraulic fractures of all sections of the reservoir.

7. The in-situ gas fracturing method in a reservoir according to claim 1, characterized in that: The step D comprises the following specific steps: Step D1: taking out the coiled tubing string; Step D2: lowering the ignition bridge plug through the cable, so that the ignition bridge plug is located in the contact area between the liquid high-energy material and the fracturing fluid in the deflection section at the upper part of the horizontal section, and ensuring that the ignition head of the ignition bridge plug is located on one side of the liquid high-energy material and is in direct contact with the liquid high-energy material; Step D3: energizing the setting tool of the ignition bridge plug to set the bridge plug of the ignition bridge plug, thereby separating the fracturing fluid located above from the liquid high-energy material located below; Step D4: Take out the cable and the setting tool of the ignition bridge plug; Step D5: The fracturing fluid in the casing is pressurized at the wellhead to stimulate the ignition head at the bottom of the ignition bridge plug, thereby detonating the liquid high-energy material in the horizontal well casing and the hydraulic fracture. The explosion of the liquid high-energy material transforms the formation around the hydraulic fracture to form a self-supporting complex fracture network.

8. The in-situ gas fracturing method in a reservoir according to claim 7, characterized in that: When liquid high-energy materials explode, a large amount of high-energy gas is generated in the hydraulic fractures in a short period of time, which fully transforms the strata around the hydraulic fractures and forms a self-supporting complex fracture network.

9. The in-situ gas fracturing method in a reservoir according to claim 8, characterized in that: The bridge plug of the ignition bridge plug seals off high-energy gas during combustion and explosion to ensure the safety of the wellhead.

10. The in-situ gas fracturing method in a reservoir according to claim 7, characterized in that: The step D5 also includes Step D6: Drill out the ignition bridge plug by lowering the drilling tool to clear the horizontal well.

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