A gradient combustion and explosion layered targeted pulse fracturing device and method for liquid energetic materials

Abstract

A gradient combustion and explosion stratified targeted pulse fracturing device and method using liquid energetic materials relates to the field of oil and gas reservoir fracturing and production enhancement technology. The technical solution includes multiple reaction chambers connected to adjacent chambers via a reaction chamber connector. Each reaction chamber includes a pressure relief screen. The beneficial effects of this technical solution are: by setting up multiple sets of independent sealed reaction chambers in the same fracturing section, and by configuring shear pins with different pressure resistance thresholds, step-by-step shearing and time-division pressure relief are achieved under synchronous ignition conditions, forming a continuous multi-stage pulse pressure superposition field. This effectively prolongs the duration of high-pressure fluid action on the reservoir, continuously driving fracture extension, diameter expansion, and penetration.

Description

Technical Field

[0001] This invention relates to the field of oil and gas reservoir fracturing and production enhancement technology, and in particular to a liquid energetic material gradient combustion stratified targeted pulse fracturing device and method. Background Technology

[0002] High-energy gas fracturing relies on the instantaneous combustion and explosion of energetic agents to generate high-pressure shock waves and high-temperature, high-pressure gases to create fractures in the reservoir. It offers advantages such as no fracturing fluid damage, short construction period, low operating cost, and adaptability to different well completion methods and small-diameter well conditions, and is widely used in low-permeability oil and gas reservoir production enhancement and old well re-clogging and stimulation projects. Currently, existing high-energy fracturing technologies mostly use solid explosives, solid propellants, and gel energetic bodies as energy carriers, employing fixed charge structures to complete reservoir fracturing and stimulation.

[0003] Existing deflagration fracturing technologies mostly employ a fixed energy output operation mode, which cannot adapt to the differences in physical properties of vertically heterogeneous thin interbedded reservoirs. Different reservoir sections vary significantly in compressive strength, elastic modulus, porosity, and permeability. Conventional "one-size-fits-all" fixed-energy fracturing methods have significant drawbacks. They are prone to insufficient energy in tight, hard reservoirs, resulting in shallow fracture depth and small fracture size. At the same time, they are prone to overpressure impacts on loose, soft reservoirs, leading to formation collapse, casing damage, and microfracture compaction and closure. Overall, the ability to target and stimulate different layers is poor, and the stimulation effect of heterogeneous reservoirs is uneven.

[0004] Furthermore, traditional deflagration fracturing currently involves single-layer synchronous instantaneous deflagration, a single pressure impact mode, and an extremely short pressure duration. The high-pressure energy decays rapidly, only forming short micro-fractures near the wellbore, unable to continuously drive fractures to extend deeper into the reservoir. This results in a small effective stimulation radius and poor fracture connectivity. Existing pulse fracturing technologies rely on mechanical and chemical delays to achieve pulse output, but these are structurally complex, have a high failure rate, and poor timing accuracy, making it impossible to achieve controllable multi-stage pulse superposition fracturing within the same layer. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of current deflagration fracturing methods, which involve single-layer synchronous instantaneous deflagration, single pressure impact mode, extremely short pressure action time, rapid decay of high-pressure energy, small effective modification radius, and poor fracture connectivity. In response, this invention proposes a gradient deflagration layered targeted pulse fracturing device and method for liquid energetic materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A gradient combustion and detonation stratified targeted pulse fracturing device for liquid energetic materials includes multiple reaction chambers. Adjacent reaction chambers are connected by reaction chamber connectors. Each reaction chamber includes a pressure relief screen pipe, and a sealing screen pipe is provided on the inner wall of the pressure relief screen pipe. Liquid energetic materials are placed inside the sealing screen pipe. A sealing joint is connected to the upper end of the sealing screen pipe. An upper joint is threadedly connected to the inner wall of the pressure relief screen pipe. The upper joint is located above the sealing joint and is connected to the sealing joint. An ignition component is provided on the sealing joint. A piston is connected to the lower part of the sealing screen pipe, and the piston is connected to the pressure relief screen pipe by a pin.

[0008] Preferably, the pressure relief screen pipe and the sealing screen pipe are respectively provided with a plurality of first through holes and a plurality of second through holes, and the first through holes and the second through holes are staggered.

[0009] Preferably, the initial axial distance between the uppermost end of the second through hole and the uppermost end of the first through hole is H1, and the distance between the bottom of the piston and the top of the reaction chamber connector is H2.

[0010] Preferably, the bottom of the upper connector is provided with a connecting hole, the upper end of the sealing connector is connected with a limiting post, the upper end of the limiting post extends through the connecting hole into the upper connector, the outer wall of the limiting post is provided with an external thread, and a nut is connected to the external thread.

[0011] Preferably, the ignition assembly includes a sealed plug-type detonator disposed on a sealing joint. The sealing joint and the limiting post are integrally formed. The sealing joint and the limiting post are both provided with a coaxial stepped hole. The sealed plug-type detonator is located in the stepped hole. A sealing pin is disposed in the stepped hole of the sealing joint located in the inlet reaction chamber. The sealing pin is located above the corresponding sealed plug-type detonator. A firing pin is disposed through the reaction chamber connector. A placement hole is provided at the lower part of the reaction chamber connector. A flash cap is connected to the side wall of the placement hole. The lower part of the stepped hole is connected to the sealing screen tube. The upper part of the stepped hole is corresponding to the firing pin. The flash cap is located between the firing pin and the upper connector. The firing pin is corresponding to the piston in the upper reaction chamber.

[0012] Preferably, the outer wall of the reaction chamber connector is provided with a limiting groove, the inner wall of the pressure relief screen pipe of the upper reaction chamber is threaded to the groove wall of the limiting groove, the outer wall of the upper connector on the lower pressure relief screen pipe is provided with an installation groove, and the inner wall of the reaction chamber connector is threaded to the groove wall of the installation groove.

[0013] Preferably, a sealing groove is provided between two adjacent second through holes on the sealing screen tube, and a sealing ring is installed in the sealing groove.

[0014] Preferably, the diameter of the first through hole on the pressure relief screen tube is 20 mm, the diameter of the second through hole on the sealing screen tube is 15 mm, and the hole density of both the first and second through holes is 16 holes / meter.

[0015] A method for a gradient combustion and explosion layered targeted pulse fracturing device for liquid energetic materials, employing the layered targeted pulse fracturing device as described above, includes the following steps: S1: The reservoir is divided into different reservoirs based on its physical properties; S2: Formulate gradient liquid energetic materials according to reservoir properties, and fill the corresponding gradient liquid energetic materials into the reaction chambers of the corresponding reservoir section respectively; S3: Multiple independent sealed reaction chambers are connected in series to form a fracturing unit, and the fracturing unit corresponds to a single target reservoir section; multiple such fracturing units constitute a multi-level layered operation structure, and each reaction chamber in the same fracturing unit is equipped with pins with different pressure resistance thresholds. S4: Assemble multiple fracturing units into an integrated downhole fracturing string; S5: The fracturing string is lowered into the target layer so that each fracturing unit precisely corresponds to the target reservoir and the interlayer is sealed and isolated by the packer; S6: Longitudinal series detonation propagation, igniting each stage, so that the liquid energetic material burns and detonates in the corresponding reaction chamber in a sealed manner and pressurizes. S7: Multiple fracturing units within the same section are ignited simultaneously. The sealing pin on the same fracturing unit controls the sealing plug-type detonator to detonate the liquid energetic material. The pin on the piston breaks and moves downward. The piston drives the sealing screen tube to move downward until the bottom of the piston touches the top of the reaction chamber connector. Since H2=H1, the second through hole aligns with the first through hole to form a pressure relief channel. The pins with different pressure resistance thresholds in the reaction chamber below break in sequence, realizing time-sequential graded pressure relief and forming a multi-stage pulse pressure field. S8: High-pressure gas is directed to impact the reservoir through the pressure relief channel to create fractures.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. In the initial state, the sealing screen tube is coaxially fitted inside the pressure relief screen tube. The first and second through holes on the side walls of the two are misaligned, and together with the piston and pin, a locking structure is formed, making the whole a sealed cavity. During the combustion and explosion stage, it can prevent premature leakage of high-pressure gas inside, allowing the energetic medium to react fully and the energy to be highly concentrated, significantly improving the energy utilization rate. After the combustion and explosion, the pressure can be rigidly unlocked when it reaches the set value. The action is stable and reliable, and there will be no sealing failure problem. The overall energy concentration and gap-making efficiency is excellent. 2. A single-layer, multi-unit reaction chamber is synchronously ignited, relying on pins with different pressure resistance thresholds to achieve time-sharing pressure relief, forming a continuous multi-stage pulse pressure field. When the internal pressure of the sealed screen tube rises to the set threshold, the pin breaks, driving the piston and the sealed screen tube to descend synchronously. Utilizing the time-series pulse superposition effect formed by the differentiated pins in multiple chambers, the duration of high pressure on the formation is effectively extended, continuously driving fractures to extend and penetrate deeper into the reservoir. Attached Figure Description

[0017] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a structural schematic diagram of a specific embodiment of the present invention.

[0019] Figure 2 for Figure 1 Enlarged view at point A.

[0020] Figure 3 This is a schematic diagram of the connection between the pressure relief screen pipe and the reaction chamber connector in a specific embodiment of the present invention.

[0021] Figure 4 This is a schematic diagram of the pressure relief screen tube in a specific embodiment of the present invention.

[0022] Figure 5 This is a schematic diagram of the structure of the sealed screen tube in a specific embodiment of the present invention.

[0023] Figure 6 This is a schematic diagram of the piston structure in a specific embodiment of the present invention.

[0024] Figure 7 This is a schematic diagram of the upper connector in a specific embodiment of the present invention.

[0025] Figure 8 This is a schematic diagram of the sealing joint in a specific embodiment of the present invention.

[0026] In the diagram: 1. Upper connector; 2. Sealing pin; 3. Sealing joint; 4. Sealing screen tube; 5. Pressure relief screen tube; 6. Sealing groove; 7. Second through hole; 8. First through hole; 9. Piston; 10. Pin; 11. Strike pin; 12. Reaction chamber connector; 13. Fire cap; 14. Limiting groove; 15. Sealing plug-type detonator; 16. Limiting post; 17. Stepped hole; 18. Limiting plug; 19. Connecting hole; 20. Nut. Detailed Implementation

[0027] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the specific embodiments. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0028] Reference Figures 1-8 A gradient combustion and explosion stratified targeted pulse fracturing device for liquid energetic materials includes multiple reaction chambers, which form a fracturing unit. Each fracturing unit is correspondingly positioned to a reservoir. Adjacent reaction chambers are connected via reaction chamber connectors 12. The outer wall of the reaction chamber connector 12 is provided with a limiting groove 14. The inner wall of the pressure relief screen pipe 5 of the upper reaction chamber is threaded to the groove wall of the limiting groove 14. The outer wall of the limiting groove 14 is provided with external threads, and the lower part of the pressure relief screen pipe 5 is provided with internal threads. The inner wall of the pressure relief screen pipe 5 is threadedly connected to the outer wall of the reaction chamber connector 12. The outer wall of the upper connector 1 on the lower pressure relief screen pipe 5 is provided with an installation groove. The inner wall of the reaction chamber connector 12 is threadedly connected to the groove wall of the installation groove. The outer wall of the reaction chamber connector 12 is provided with a limiting groove 14, which engages with the threaded inner wall of the upper pressure relief screen pipe 5. The inner wall of the reaction chamber connector 12 is threadedly connected to the installation groove on the outer wall of the upper connector 1 of the lower pressure relief screen pipe 5, achieving a rigid, sealed series connection between the upper and lower chambers. The reaction chamber includes a pressure relief screen pipe 5. The inner wall of the pressure relief screen 5 is provided with a sealing screen tube 4, and a liquid energetic material is placed inside the sealing screen tube 4. The upper end of the sealing screen tube 4 is connected to a sealing joint 3. The inner wall of the pressure relief screen tube 5 is threaded with an upper joint 1, which is located above the sealing joint 3. The sealing joint 3 is connected to the upper joint 1. The bottom of the upper joint 1 is provided with a connecting hole 19. The upper end of the sealing joint 3 is connected to a limiting post 16. The limiting post 16 and the sealing joint 3 are integrally formed. The upper end of the limiting post 16 extends through the connecting hole 19 into the upper joint 1. The outer wall of the limiting post 16 is provided with external threads, and a nut 20 is threaded onto the external threads. The limiting post 16 passes through the connecting hole 19 and extends into the upper connector 1. It is locked by the nut 20 thread, realizing the axial fixation and radial positioning of the upper connector 1 and the sealing connector 3. The upper connector 1 is threadedly connected to the inner wall of the pressure relief screen pipe 5, which completely seals the liquid energetic material and prevents leakage. In the event of an explosion of the liquid energetic material, it can resist high pressure impact, does not loosen or leak, and at the same time ensures the coaxiality of the ignition assembly installation. An ignition assembly is installed on the sealing joint 3. A piston 9 is connected below the sealing screen tube 4. The piston 9 is connected to the pressure relief screen tube 5 by pins 10. The number of pins 10 in each reaction chamber is different. Since the number of pins 10 in multiple reaction chambers in the same section is different, the pins 10 are made of copper. The threshold values ​​of the pins 10 are 4MPa, 8MPa, 12MPa and 16MPa from top to bottom. When the liquid energetic material in the first reaction chamber explodes, the sealing screen tube 4 drives the piston 9 to move downward together. When the pin 10 on piston 9 in the reaction chamber breaks, the pins 10 in the reaction chamber below break sequentially from low to high pressure threshold, thereby achieving single-layer synchronous ignition, time-sharing pressure relief, and multi-stage pressure superposition. This effectively prolongs the duration of high formation pressure and continuously drives the fractures to extend and penetrate deeper into the reservoir. Compared with traditional single instantaneous deflagration, the fracture extension length, modification radius, and fracture connectivity are significantly improved. It can efficiently construct a large-scale three-dimensional fracture network and realize a modular, series-connected, and independently sealed reaction chamber structure, ensuring complete sealing and energy accumulation before the explosion. In use, multiple independent sealed reaction chambers are connected in series. Adjacent chambers are connected by reaction chamber connector 12. Each reaction chamber has a pressure relief screen pipe 5 as the outer cylinder and a sealing screen pipe 4 as the inner cylinder. Liquid energetic material is placed inside the sealing screen pipe 4. The upper end of the sealing screen pipe 4 is sealed by a sealing joint 3. The upper end of the pressure relief screen pipe 5 is threaded to the upper joint 1. The upper joint 1 and the sealing joint 3 are fixed together. An ignition component is installed in the sealing joint 3. The lower end of the sealing screen pipe 4 is connected to the piston 9 by bolts. The piston 9 is locked to the pressure relief screen pipe 5 by a pin 10 to form an initial sealed structure. The bolt threshold is greater than the pin 10 threshold. When the pin 10 breaks, the piston 9 and the sealing screen pipe 4 remain in a fixed state, ensuring that the piston 9 moves downward.

[0029] Reference Figure 1 and Figures 3-5Multiple first through holes 8 and multiple second through holes 7 are respectively provided on the side walls of the pressure relief screen pipe 5 and the sealing screen pipe 4. The diameter of the first through hole 8 on the pressure relief screen pipe 5 is 20mm, and the diameter of the second through hole 7 on the sealing screen pipe 4 is 15mm. The pore density of both the first through hole 8 and the second through hole 7 is 16 holes / meter. The pore diameter and pore density match the high-pressure gas flow and directional injection requirements, ensuring sufficient pressure relief flow, concentrated directional injection, and high fracture formation efficiency. It adapts to the reservoir fracture formation pressure requirements, avoiding poor pressure relief due to excessively small pore diameter or energy dispersion due to excessively large pore diameter. The first through hole 8 and the second through hole 7 are staggered. In the initial state, the first through hole 8 is 20mm in diameter, and the second through hole 7 is 15mm in diameter. The first through hole 8 and the second through hole 7 are radially misaligned, blocking the pressure relief channel. A sealing groove 6 is provided between each pair of adjacent second through holes 7 on the sealing screen tube 4, and a sealing ring is installed inside the sealing groove 6. The sealing ring prevents the liquid energetic material from flowing out of the first through hole 8 on the pressure relief screen tube 5, thus preventing leakage of the liquid energetic material. Before ignition, a seal is ensured, and there is no leakage of the liquid energetic material. When the piston 9 moves the sealing screen tube 4 to its position, the first through hole 8 and the second through hole 7 align and connect, forming a pressure relief channel, thereby releasing high-pressure gas and shock waves. Due to the arrangement of pins 10 in multiple reaction chambers, the time-sharing... High-pressure gas and shock waves are released to form a continuous multi-stage pulse pressure superposition field, which continuously acts on the reservoir. Tight reservoirs rely on high-energy pulse superposition to achieve deep fracture initiation and propagation, medium-quality reservoirs achieve balanced fracture creation and expansion, and loose reservoirs achieve low-energy and mild unblocking and protective layering. The initial axial distance between the uppermost point of the second through-hole 7 and the uppermost point of the first through-hole 8 is H1, and the distance between the bottom of the piston 9 and the top of the reaction chamber connector 12 is H2. The design ensures that H2=H1. When the piston 9 moves down to the reaction chamber connector 12, the first through-hole 8 and the second through-hole 7 are exactly aligned. When the piston 9 is in position, the through-holes are fully aligned. When the first through hole 8 and the second through hole 7 are fully connected, the high-pressure gas and shock wave inside the sealed screen tube 4 can be directionally injected into the reservoir through the aligned first through hole 8 and the second through hole 7, ensuring energy concentration, avoiding random spraying and side leakage, improving the fracture initiation and extension effect, and completing fracture creation. Moreover, the first through hole 8 and the second through hole 7 are only aligned when the piston 9 moves down to the position, which is synchronized with the shearing sequence of the pin 10. The first through hole 8 and the second through hole 7 in different reaction chambers are aligned in sequence to form a multi-level, time-division and superimposed pulse pressure field. The depressurization sequence and opening degree are controllable, and there is no problem of insufficient or excessive depressurization.

[0030] Reference Figure 1 , Figure 2 and Figure 8The ignition assembly includes a sealed plug-type detonator 15 mounted on a sealed joint 3. The sealed joint 3 and the limiting post 16 are integrally formed. Both the sealed joint 3 and the limiting post 16 have a coaxial stepped hole 17. The sealed plug-type detonator 15 is located in the stepped hole 17. A sealed pin 2 is installed in the stepped hole 17 of the sealed joint 3 in the inlet reaction chamber. The sealed pin 2 is located above the corresponding sealed plug-type detonator 15 and is a conductive conductor. The sealed pin 2 is connected to the sealed plug-type detonator 15 below it by a wire. During ignition, the sealed pin 2 is energized to trigger the sealed plug-type detonator 15. In the first stage chamber, the sealed pin 2 triggers the sealed plug-type detonator 15. When the sealed plug-type detonator 15 explodes, it ignites the energetic liquid. Materials; A firing pin 11 is installed through the reaction chamber connector 12. A placement hole is provided at the lower part of the reaction chamber connector 12. A burner cap 13 is connected to the side wall of the placement hole. The lower part of the stepped hole 17 is connected to the sealing screen tube 4. The upper part of the stepped hole 17 is correspondingly set to the firing pin 11. The burner cap 13 is located between the firing pin 11 and the upper connector 1. The burner cap 13 is located above the upper connector 1. The firing pin 11 is correspondingly set to the piston 9 in the upper reaction chamber. The lower reaction chamber drives the firing pin 11 to strike the burner cap 13 below through the downward movement of the piston 9, realizing step-by-step ignition from top to bottom. It can realize independent ignition of layers and stable inter-stage detonation, which is suitable for multi-stage layered fracturing sequence requirements. The inner wall of the pressure relief screen tube 5 of the lowest reaction chamber is threadedly connected to the limiting plug 18.

[0031] A method for a gradient combustion and explosion layered targeted pulse fracturing device for liquid energetic materials, employing the layered targeted pulse fracturing device as described above, includes the following steps: S1: Based on reservoir properties, the reservoir is divided into different reservoirs. First, the compressive strength, elastic modulus, porosity and permeability parameters of each reservoir corresponding to the perforation section of the target well are collected. Based on the density and hardness of the reservoir, it is divided into three types of sections: loose soft reservoir, medium-quality conventional reservoir and tight hard reservoir. S2: Based on reservoir properties, gradient liquid energetic materials are formulated. Following the principle of positive correlation between reservoir density and the concentration and density of energetic materials, liquid energetic propellants with gradient parameters are independently configured for different reservoir sections. The corresponding gradient liquid energetic materials are then loaded into the reaction chambers of the corresponding reservoir sections. Specifically, loose and soft reservoirs are matched with low-energy liquid materials with a density of 1.1–1.2 g / cm³; medium-quality conventional reservoirs are matched with medium-energy liquid materials with a density of 1.3–1.4 g / cm³; and tight and hard reservoirs are matched with high-energy liquid materials with a mass density of 1.5–1.6 g / cm³. S3: Multiple independent sealed reaction chambers are connected in series to form a fracturing unit. Each fracturing unit corresponds to a single target reservoir section. Multiple such fracturing units constitute a multi-level layered operation structure. Different reaction chambers are filled with gradient liquid energetic materials that are suitable for the corresponding reservoir properties. At the same time, each reaction chamber in the same fracturing unit is equipped with pins 10 with different pressure resistance thresholds. S4: Multiple fracturing units, intelligent layered ignition control modules and centralizing positioning mechanisms are connected in series and assembled into an integrated downhole fracturing string. The fracturing string is equipped with corresponding layered packers for different sections. At the same time, the fracturing string is also equipped with... S5: The fracturing string is lowered into the target layer so that each fracturing unit is precisely aligned with the target reservoir. The layered packers expand radially to fit the inner wall of the wellbore, achieving vertical isolation of each reservoir section and forming a layered targeted fracturing space that is independent between layers, does not cross pressure, and does not interfere with each other. S6: Longitudinal series-sequential explosion transmission, igniting each layer, so that the liquid energetic material burns and explodes in the corresponding reaction chamber in a sealed manner and pressurizes. Different layers output differentiated gradient combustion and explosion pressure, which can be accurately adapted to the fracture creation requirements of the corresponding reservoir. S7: Multiple fracturing units in the same layer are ignited simultaneously. The sealing pin 2 on the same fracturing unit controls the sealing plug-type detonator 15 to detonate the liquid energetic material. The piston 9 will move downward under the action of high pressure gas and shock wave. In this way, the piston 9 drives the sealing screen tube 4 to move downward until the bottom of the piston 9 touches the top of the reaction chamber connector 12. Since H2=H1, the second through hole 7 is aligned with the first through hole 8 to form a pressure relief channel. Since the pressure resistance threshold of the pins 10 in each reaction chamber is different, the pressure in the chamber reaches the shear condition step by step. The pins 10 will break in sequence to achieve time-sequential pressure relief and form a multi-level pulse pressure field. Multiple reaction chambers release high pressure gas and shock wave in time, forming a continuous multi-level pulse pressure superposition field in the single-layer reservoir, prolonging the high pressure action time, continuously driving the fracture extension, diameter expansion and penetration, and constructing a large-scale three-dimensional fracture network. S8: High-pressure gas is directed to impact the reservoir through the pressure relief channel to create fractures. After the operation is completed, the layered packer is unsealed, and the entire downhole tubing is retrieved without any solid residue or downhole debris, thus completing the layered adaptive gradient targeted pulse fracturing operation.

[0032] The liquid energetic material formulation mainly consists of 50%~60% ammonium nitrate solution (85% concentration), 5%~10% glycerol, 3%~5% urea, 0.6% thickener, 3%~5% lead-2, and 15%~20% water. The ammonium nitrate solution, glycerol, urea, and water are mixed in a certain proportion and stirred at a low speed of 100 rpm for 10 minutes using an electric stirrer. The thickener is then added to the solution, and stirring is continued at the same speed for 3 minutes. Finally, lead-2 is added to the solution and stirred for 5 minutes.

[0033] Depending on the reservoir, liquid energetic materials of different densities are set. When the density of the liquid energetic material is reduced, the proportion of water is increased and the proportions of ammonium nitrate solution and glycerol are appropriately reduced. To increase density by adding liquid energetic materials: increase the proportion of ammonium nitrate solution or glycerol, and decrease the proportion of water.

[0034] Low-energy liquid energetic material with a density of 1.1–1.2 g / cm³, containing 50% ammonium nitrate solution, 5% glycerol, 3% urea, 0.6% thickener, 3% lead-2, and 20% water. The medium-energy liquid energetic material has a density of 1.3–1.4 g / cm³, contains 55% ammonium nitrate solution, 8% glycerol, 5% urea, 0.6% thickener, 5% lead-2, and 15% water. High-energy liquid energetic material with a density of 1.5–1.6 g / cm³, containing 60% ammonium nitrate solution, 10% glycerol, 5% urea, 0.6% thickener, 5% lead-2, and 15% water. By using liquid energetic materials with gradient controllable concentration and density, precise energy distribution can be achieved for reservoirs with different physical properties, completely solving the technical drawbacks of the traditional fixed-energy fracturing "one-size-fits-all" approach. This enables layered and targeted transformation of loose reservoirs by removing protective layers and creating high-energy deep fractures in dense reservoirs, significantly improving the uniformity and success rate of transformation of heterogeneous thin interbedded reservoirs.

[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A gradient combustion and explosion stratified targeted pulse fracturing device for liquid energetic materials, characterized in that: It includes multiple reaction chambers, and two adjacent reaction chambers are connected by a reaction chamber connector (12). The reaction chamber includes a pressure relief screen pipe (5). A sealing screen pipe (4) is provided on the inner wall of the pressure relief screen pipe (5). Liquid energetic material is placed inside the sealing screen pipe (4). A sealing joint (3) is connected to the upper end of the sealing screen pipe (4). An upper joint (1) is threaded on the inner wall of the pressure relief screen pipe (5). The upper joint (1) is located above the sealing joint (3). The sealing joint (3) is connected to the upper joint (1). An ignition component is provided on the sealing joint (3). A piston (9) is connected to the lower part of the sealing screen pipe (4). The piston (9) is connected to the pressure relief screen pipe (5) by a pin (10). The number of pins (10) in each reaction chamber is different. Multiple first through holes (8) are provided on the side wall of the pressure relief screen pipe (5), and multiple second through holes (7) are provided on the side wall of the sealing screen pipe (4). The first through holes (8) and the second through holes (7) are staggered. The initial axial distance between the uppermost end of the second through hole (7) and the uppermost end of the first through hole (8) is H1, and the distance between the bottom of the piston (9) and the top of the reaction chamber connector (12) is H2. The ignition assembly includes a sealed plug-type detonator (15) mounted on a sealing joint (3). The sealing joint (3) and the limiting post (16) are integrally formed. Both the sealing joint (3) and the limiting post (16) have coaxial stepped holes (17). The sealed plug-type detonator (15) is located in the stepped hole (17). A sealing pin (2) is provided in the stepped hole (17) of the sealing joint (3) located in the inlet reaction chamber. The sealing pin (2) is located in the corresponding sealed plug-type detonator. Above the tube (15); a striker (11) is provided through the reaction chamber connector (12), a placement hole is provided at the lower part of the reaction chamber connector (12), a flame cap (13) is connected to the side wall inside the placement hole, the lower part of the stepped hole (17) is connected to the sealing screen tube (4), the upper part of the stepped hole (17) is corresponding to the striker (11), the flame cap (13) is located between the striker (11) and the upper connector (1), and the striker (11) is corresponding to the piston (9) in the upper reaction chamber; Multiple independent sealed reaction chambers are connected in series to form a fracturing unit, and each fracturing unit corresponds to a single target reservoir section; multiple such fracturing units constitute a multi-level layered operation structure, and each reaction chamber in the same fracturing unit is equipped with pins (10) with different pressure resistance thresholds. Multiple fracturing units in the same section are ignited simultaneously. The sealing pin (2) on the same fracturing unit controls the sealing plug-type detonator (15) to detonate the liquid energetic material. The pin (10) on the piston (9) breaks and moves downward. The piston (9) drives the sealing screen tube (4) to move downward until the bottom of the piston (9) touches the top of the reaction chamber connector (12). Since H2=H1, the second through hole (7) is aligned with the first through hole (8) to form a pressure relief channel. The pins (10) with different pressure resistance thresholds in the reaction chamber below break in sequence to achieve time-sequential graded pressure relief and form a multi-level pulse pressure field.

2. The liquid energetic material gradient combustion layered targeted pulse fracturing device according to claim 1, characterized in that: The bottom of the upper connector (1) is provided with a connecting hole (19), and the upper end of the sealing connector (3) is connected to a limiting post (16). The upper end of the limiting post (16) extends through the connecting hole (19) into the upper connector (1). The outer wall of the limiting post (16) is provided with an external thread, and a nut (20) is connected to the external thread.

3. The liquid energetic material gradient combustion layered targeted pulse fracturing device according to claim 1, characterized in that: The outer wall of the reaction chamber connector (12) is provided with a limiting groove (14). The inner wall of the pressure relief screen pipe (5) of the upper reaction chamber is threaded to the groove wall of the limiting groove (14). The outer wall of the upper connector (1) on the lower pressure relief screen pipe (5) is provided with an installation groove. The inner wall of the reaction chamber connector (12) is threaded to the groove wall of the installation groove.

4. The gradient combustion and explosion layered targeted pulse fracturing device for liquid energetic materials according to claim 1, characterized in that: A sealing groove (6) is provided between two adjacent second through holes (7) on the sealing screen tube (4), and a sealing ring is installed in the sealing groove (6).

5. The gradient combustion and explosion layered targeted pulse fracturing device for liquid energetic materials according to claim 1, characterized in that: The diameter of the first through hole (8) on the pressure relief screen pipe (5) is 20 mm, the diameter of the second through hole (7) on the sealing screen pipe (4) is 15 mm, and the hole density of the first through hole (8) and the second through hole (7) is 16 holes / meter.

6. A method for a gradient combustion and explosion stratified targeted pulse fracturing device for liquid energetic materials, characterized in that, The layered targeted pulse fracturing device according to claim 1 includes the following steps: S1: The reservoir is divided into different reservoirs based on its physical properties; S2: Formulate gradient liquid energetic materials according to reservoir properties, and fill the corresponding gradient liquid energetic materials into each reaction chamber of the corresponding reservoir section respectively; S3: Multiple independent sealed reaction chambers are connected in series to form a fracturing unit, and each fracturing unit corresponds to a single target reservoir section; multiple such fracturing units constitute a multi-level layered operation structure, and each reaction chamber in the same fracturing unit is equipped with pins (10) with different pressure resistance thresholds. S4: Assemble multiple fracturing units into an integrated downhole fracturing string; S5: The fracturing string is lowered into the target layer so that each fracturing unit precisely corresponds to the target reservoir and the interlayer is sealed and isolated by the packer; S6: Ignite each section to make the liquid energetic material burn and explode in the corresponding reaction chamber in a sealed manner and increase the pressure; S7: Multiple fracturing units in the same section are ignited simultaneously. The sealing pin (2) on the same fracturing unit controls the sealing plug-type detonator (15) to detonate the liquid energetic material. The pin (10) on the piston (9) breaks and moves downward. The piston (9) drives the sealing screen tube (4) to move downward until the bottom of the piston (9) touches the top of the reaction chamber connector (12). Since H2=H1, the second through hole (7) is aligned with the first through hole (8) to form a pressure relief channel. The pins (10) with different pressure resistance thresholds in the reaction chamber below break in sequence to achieve time-sequential pressure relief and form a multi-level pulse pressure field. S8: High-pressure gas is directed to impact the reservoir through the pressure relief channel to create fractures.

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