A storable projectile perforation fracturing device and method thereof

Abstract

This invention belongs to the field of energy extraction equipment technology, and relates to a storable shot perforation fracturing device and method, including a tubing, a perforation fracturing tool string, a casing, and a cement sheath; the lower end of the tubing is connected to the upper end of the perforation fracturing tool string, which is installed in a cylindrical casing. A cement sheath is fitted on the outside of the casing, and the cement sheath is formed in the rock containing an oil and gas reservoir. The storable shot perforation fracturing device uses compressible gas for perforation fracturing; the device accelerates the shot through pressure differential and a long acceleration tube, increasing the jet destructive force, and the shot penetration can form a deeper perforation; during the fracturing process, pulse-induced low temperature and turbulence are used, which can increase the apparent viscosity of the fluid and reduce the proppant holding effect under the filtration pressure differential, thereby helping to solve the proppant carrying problem.

Description

Technical fields:

[0001] This invention belongs to the field of energy extraction equipment technology, and relates to a device and method for shot perforation and fracturing using the elastic energy storage characteristics of compressible fluids, particularly a storage-type shot perforation and fracturing device and method. Background technology:

[0002] As the world's energy mix shifts from solid (firewood and coal) and liquid (oil) to gaseous (natural gas), the proportion of natural gas in primary energy consumption is increasing year by year. It is predicted that by 2030, natural gas consumption will surpass coal and oil to become the primary energy source. In recent years, natural gas imports have continued to grow, and trend analysis predicts that the dependence on foreign natural gas will reach 44% in 2020 and 64% in 2030. Therefore, improving the competitiveness of natural gas is a key issue in optimizing China's energy structure.

[0003] According to the national oil and gas resource assessment, excluding natural gas hydrates which have not yet been commercially exploited, my country's geological resources of shale gas, conventional gas, tight gas, and coalbed methane are 80 × 10⁻⁶ respectively. 12 m 3 78×10 12 m 3 22×10 12 m 3 and 30×10 12 m 3 Shale gas accounts for more than 38% of my country's natural gas resources. Shale gas extraction has become the main driving force for the growth of natural gas production. Research on its extraction technology is of great significance to my country's energy transformation and energy security.

[0004] Shale gas reservoirs contain both adsorbed and free gas, and have low permeability and porosity, meaning they cannot be produced spontaneously after drilling. Extraction typically employs techniques such as extended reach horizontal wells, cluster wells, and hydraulic fracturing. Hydraulic fracturing is the primary extraction method and spearheaded the shale gas revolution in the United States. However, hydraulic fracturing has several drawbacks: it consumes significant amounts of water, and the backflow of wastewater poses a major risk of surface water pollution. Furthermore, China's shale gas resources are mostly located in mountainous areas, deserts, and loess plateaus, where surface conditions are even more challenging and water resources are scarcer. Many shale gas reservoirs have even lower permeability and higher clay content. Factors such as clay swelling upon contact with water in water-based fracturing fluids, water-locking effects, incomplete flowback, and additives in the fracturing fluid all contribute to greater damage to the reservoir.

[0005] Driven by the goals of reducing environmental risks, minimizing reservoir damage, and minimizing water consumption, anhydrous fracturing technologies such as CO2 dry fracturing, LPG / LNG fracturing, and high-energy gas fracturing have gradually become research focuses. Among these, supercritical CO2 fracturing technology has become a major development direction for shale gas extraction due to its advantages: low friction and low formation initiation pressure; enhanced shale gas recovery through strong adsorption and displacement between CO2 and CH4; and the ability to achieve geological CO2 storage. However, supercritical CO2 fracturing also presents several key challenges: low viscosity and poor proppant carrying capacity; high compressibility and slow pressurization; and low CO2 viscosity and high diffusion coefficient, resulting in high formation filtration loss. Viscosifiers and low-density proppants are two methods to increase CO2 proppant carrying capacity, but viscosifiers can trap in the formation, damage the reservoir, and increase friction, while low-density proppants have low strength and high cost. The common solution to the above problems is to increase the pump's displacement and pressure, thereby generating greater turbulence and proppant-carrying capacity, enabling rapid pressurization and fracturing in a short time, and reducing filtration time. However, this significantly increases fluid friction loss, thus placing high demands on the pressure resistance and displacement of the construction equipment. Furthermore, currently, high-pressure, high-flow-rate booster equipment for supercritical CO2 fracturing is mainly imported. Statistics from 2018 show that there are fewer than 10 sets of such equipment in China, severely restricting the development and application of supercritical CO2 fracturing technology. In addition, shale gas resources in formations below 3500m account for more than 65% of my country's total resources, and related fracturing technologies and equipment have not yet achieved breakthroughs. Under high formation closure pressure conditions, increasing reservoir stimulation volume and improving the long-term conductivity of the fracture network are particularly crucial, which also places higher demands on the displacement and pressure of CO2 booster pumps. Summary of the Invention:

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and address the dependence of existing supercritical CO2 fracturing technology on high-pressure, high-flow-rate booster equipment. This invention designs an energy-storage-type shot perforation fracturing device and method, which increases the sand-carrying capacity and fracturing ability of supercritical CO2 through induced pulses. It utilizes the compressive energy storage characteristics of supercritical CO2 for shot perforation and fracturing, reducing formation fracturing initiation pressure and decreasing the dependence of supercritical CO2 fracturing on high-pressure, high-flow-rate equipment.

[0007] To achieve the above objectives, the present invention relates to a storable shot perforation fracturing device, comprising a tubing, a perforation fracturing tool string, a casing, and a cement sheath; the lower end of the tubing is connected to the upper end of the perforation fracturing tool string, which is installed in the cylindrical casing, and a cement sheath is fitted on the outside of the casing; the cement sheath is formed in the rock, and the rock contains an oil and gas reservoir; the storable shot perforation fracturing device uses compressible gas for perforation fracturing; wherein the perforation fracturing tool string includes a tubing adapter, a pulse oscillator, a hydraulic anchor, a packer, a shot delivery device, a shot acceleration device, a main channel, and a guide head; the tubing adapter is provided at the upper end of the perforation fracturing tool string to connect the tubing to the perforation fracturing tool string; the lower end of the tubing adapter is connected to the pulse oscillator, which generates pressure and flow pulsations; symmetrically arranged or uniformly arrayed hydraulic anchors are installed below the pulse oscillator. The hydraulic anchor is used to secure the perforation fracturing tool string. Below the hydraulic anchor is a packer, which seals the fracturing fluid within the perforation fracturing tool string against the annular groove in the casing. Below the packer is a projectile projectile launcher, which controls the frequency of projectile launch. Below the projectile launcher is a projectile acceleration device, which accelerates, steers, and ejects the projectiles. Below the projectile acceleration device are another set of packers and hydraulic anchors. A main channel is located at the center of the perforation fracturing tool string, connecting the fluid within the tubing and serving as a pressure testing channel. The upper end of the main channel connects to the lower end of the pulse oscillator, and is also connected to the hydraulic anchor, packer, and projectile acceleration device. The lower end of the main channel connects to the upper end of the guide head. The guide head is located at the lower end of the perforation fracturing tool string, controlling its movement within the tubing and facilitating the transition between pressure testing and pressure build-up during fracturing.

[0008] The pulse oscillator of this invention includes an oscillation inlet, a primary oscillation chamber, guide columns, a secondary oscillation chamber, a sealing shell, and an inner frame. The inner frame is housed within the sealing shell, and a cylindrical oscillation inlet is located at the upper end of the inner frame. The upper end of the oscillation inlet connects to the lower end of an oil pipe adapter. The oscillation inlet is used to convert fluid pressure energy into fluid kinetic energy. The lower end of the oscillation inlet connects to the primary oscillation chamber, which has a vertical cross-section resembling a frustum of a cone. Four guide columns are located at the connection between the central cylindrical cavity and the side frustum of a cone cavity of the primary oscillation chamber, arranged in a circumferential array. The lower end of the primary oscillation chamber connects to the secondary oscillation chamber, which has the same structure. Both the primary and secondary oscillation chambers are used to absorb fluid kinetic energy and generate pulsed flow.

[0009] The hydraulic anchor of this invention includes an anchor sealing ring, a piston anchor claw, an anti-detachment elastic partition, an anchor cylinder sleeve, and an anchor pressure guide port. The anchor cylinder sleeve is fixedly connected to the housing of the perforation fracturing tool string. An anchor pressure guide port is opened on the inner end of the anchor cylinder sleeve and is connected to the main channel. A piston anchor claw is installed in the anchor cylinder sleeve. The piston anchor claw is composed of an anchor piston on the inner end and an anchor claw on the outer end. An anchor sealing rings are provided on the upper and lower sides of the anchor piston. The piston anchor claw extends outward under the action of fluid pressure and can abut against the sleeve to fix the perforation fracturing tool string. An anti-detachment elastic partition is embedded in the outer end of the anchor claw. The two ends of the anti-detachment elastic partition are fixedly connected to the anchor cylinder sleeve. The anti-detachment elastic partition prevents the piston anchor claw from detaching from the anchor cylinder sleeve.

[0010] The packer of this invention includes a sealing strip, a sealing ring, an elastic sleeve, a packer piston, a packer cylinder liner, and a packer pressure guide port. The annular packer is embedded in the perforation fracturing tool string housing. The packer cylinder liner is fixedly connected to the perforation fracturing tool string housing. A packer pressure guide port is opened on the inner end of the packer cylinder liner, and the packer pressure guide port is connected to the main flow channel. The packer piston is installed in the packer cylinder liner. A packer sealing strip is installed on the upper and lower sides of the packer piston. An elastic sleeve is installed on the outer end of the packer piston. A sealing ring is installed on the outer end of the elastic sleeve. The upper and lower ends of the sealing ring are connected to the packer cylinder liner. When the packer piston extends outward under fluid pressure, the packer piston squeezes the sealing ring outward, and the sealing ring abuts against the sleeve. The sealing ring at the upper end of the perforation fracturing tool string, the perforation fracturing tool string housing itself, the sealing ring at the lower end of the perforation fracturing tool string, and the sleeve together constitute an annular sealed cavity.

[0011] The projectile launching device of the present invention includes a projectile outer cavity, a projectile cavity cover, a thrust piston, a projectile, a housing, a baffle, a launching thrust hole, a launching hole, a torsion spring, and a rotating shaft fixing plate; wherein, four projectile outer cavities are evenly arranged in a circular array at the upper end of the projectile launching device, the upper end of each projectile outer cavity is connected to the main channel through an inverted "L"-shaped projectile connecting pipe, the lower end of each projectile outer cavity is provided with a projectile cavity cover, the lower end of each projectile cavity cover is provided with a projectile cavity, a thrust piston is installed in the projectile cavity, and a projectile is installed in the projectile cavity below the thrust piston. The projectile, propelled by a thrust piston, moves the projectile within the projectile chamber. Both the projectile chamber cap and the thrust piston have small through holes, allowing fluid to be introduced from the outer cavity of the projectile into the inner cavity, generating the thrusting force that propels the piston forward. The thrust piston pushes the projectile downward, ensuring the projectiles remain in contact. The projectile is made of tungsten steel. An "L"-shaped connecting pipe connects to the lower end of the projectile chamber. This connecting pipe consists of an upper vertical pipe and a lower horizontal pipe. The end of the horizontal pipe connects to the upper end of the projection hole, which in turn connects to the lower end of an inverted "L"-shaped projection thrust hole. The upper end is connected to the main channel; a baffle is installed at the lower end of the projection hole, and a rotating shaft is installed at one end of the baffle. Torsion springs are symmetrically mounted on the rotating shaft, and both ends of the rotating shaft are connected to a rotating shaft fixing plate, which is fixed to the housing of the projectile projection device. When the pressure difference between the upper and lower parts of the baffle is small, the baffle and the torsion springs work together to prevent the projectile from being ejected. When the pressure difference between the upper and lower parts of the baffle is large, the projection thrust hole introduces fluid from the main channel, generating a thrust that propels the projectile out of the projection hole. When the thrust is greater than the reaction torque of the torsion spring, the projectile is ejected from the projection hole. The torsion spring and the projection... The torque generated by the fluid in the thrust orifice on the baffle satisfies the following conditions: when the static pressure below the baffle is less than 1 / 2 of the static pressure in the main channel, the baffle will open completely and the projectile will be projected. When the static pressure below the baffle is not less than 1 / 2 of the static pressure in the main channel, no projectile will be projected, thereby controlling the projectile projection frequency and ensuring that each projectile has enough energy for acceleration. The diameter of the projection orifice is 2-3 mm larger than the diameter of the projectile to ensure that the fluid ejected from the thrust orifice can generate sufficient thrust on the projectile in the projection orifice when the pressure difference is large.

[0012] The projectile acceleration device of this invention consists of four identical parts arranged in a circular array. Each part includes a fluid inlet, a jet acceleration tube, a rupture disc fixing cap, a projectile outlet, and a reverse-arching rupture disc. The uppermost end of the jet acceleration tube is connected to the lower end of the projection hole. The jet acceleration tube is connected to the main flow channel through the fluid inlet, which is a tubular structure that slopes downwards from the inside to the outside. The equivalent flow area of ​​the fluid inlet is more than eight times that of the projection thrust hole, serving as the main fluid source for projectile acceleration. The jet acceleration tube consists of a long straight pipe at the top and a short curved pipe at the bottom. The long straight pipe accelerates the projectile using fluid energy, while the short curved pipe... The curved pipe redirects the projectile velocity by 90 degrees outwards. A projectile outlet is located at the outer end of the short curved pipe, and an anti-arching rupture disc is installed at the outlet. The anti-arching rupture disc protrudes inwards, and a rupture disc fixing cap is installed at the outer end of the anti-arching rupture disc, which fixes the anti-arching rupture disc at the projectile outlet. The burst pressure of the anti-arching rupture disc is lower than the maximum pressure resistance of the booster pump and tubing. When the pressure of the tubing and the perforation fracturing tool string exceeds the burst pressure of the anti-arching rupture disc, the anti-arching rupture disc bursts, converting static pressure energy into dynamic pressure energy. The flow velocity at the fluid inlet is higher than the flow velocity in the main channel, thus creating a pressure difference between the upper and lower baffles, initiating the projectile projection and acceleration process.

[0013] The guide head of this invention includes an end shell, a fracturing ball, a constricted flow channel, and an end connecting groove. The end shell has an end connecting groove at its upper end, which connects to the lower end of the main body of the perforated fracturing tool string. The lower middle part of the end connecting groove communicates with the constricted flow channel of a tubular structure. The upper end of the constricted flow channel communicates with the lower end of the main flow channel. The diameter of the constricted flow channel decreases from top to bottom, and the constricted flow channel can be connected to the fracturing ball via a slotted connection. After the device pressure test is completed, the fracturing ball is inserted from the wellhead into the main flow channel. After the fracturing ball contacts the constricted flow channel, it can cut off the flow in the main flow channel, realizing the transformation from the device pressure test to the pressure holding process during fracturing.

[0014] The energy storage type shot perforation fracturing device of the present invention achieves shot perforation and fracturing through a method comprising: device pressure testing and pressure build-up, high-pressure energy storage, shot acceleration and injection, shot perforation, water hammer pressure fracturing, pulse sand carrying and fracturing, and fluid drainage. The specific process steps are as follows:

[0015] (1) Pressure testing and pressure holding: After well cleaning and flushing at the oil and gas extraction site, the perforation and fracturing tool string is placed into the well, and the tubing is connected to the upper end of the perforation and fracturing tool string. CO2 is pumped into the perforation and fracturing tool string for pressure testing. After the pressure test, fracturing balls are placed in for pressure holding. The pressure holding adopts the following scheme:

[0016] As a preferred option, a burst valve is placed at the pressure port of the packer, with a burst pressure slightly greater than the test pressure. The packer is closed during the test, and a fracturing ball is placed after the test. Then, the annulus of the device is depressurized to atmospheric pressure, thereby generating a larger jet pressure differential.

[0017] (2) High pressure energy storage: Utilizing the strong compressibility of supercritical CO2, the long oil pipe is used as an energy storage device. CO2 is stored and pressurized through long-term small-displacement pressurization and wellbore heat exchange, and finally the CO2 in the main channel is modulated into a high-pressure supercritical state.

[0018] (3) Projectile acceleration and ejection: After reaching a predetermined pressure of 40MPa or more, the anti-arch rupture fragment bursts, the projectile acceleration device forms a high-pressure ejection, the projectile projection device is opened, and the projectile in the projectile cavity is carried into the ejection acceleration tube by the fluid. The difference between the diameter of the projectile and the diameter of the ejection acceleration tube is controlled to be within 1mm, so that the projectile is accelerated to near the highest pressure difference velocity of the fluid under the fluid pressure difference.

[0019] (4) Shot perforation: After the shot changes direction by 90 degrees through the bend of the jet acceleration tube, it is ejected horizontally from the shot outlet and penetrates the casing, cement sheath and reservoir in sequence, forming shot perforation and complex fractures. At the same time, the low temperature generated by the expansion of CO2 jet will cause the rock to shrink and the stress around the perforation to decrease. The fractures will further expand under CO2 pressure and temperature difference.

[0020] (5) Water hammer pressure fracturing: During the high-speed jet process, the fluid in the tubing and the shot acceleration device generates a large flow inertia, and the upper and lower sets of hydraulic anchors and packers have extended under the pressure difference inside and outside the main channel, forming a closed environment. Therefore, water hammer pressure will be generated after the shot is perforated. The water hammer pressure further communicates and expands the fracture through the high permeability of supercritical CO2, and carries some of the shot into the depth of the fracture, forming effective support for the newly expanded fracture.

[0021] (6) Pulse-carrying and fracturing: CO2 is pumped into the perforation fracturing tool string at a conventional flow rate to continue the propagation of the fracture. Then, CO2-carrying fluid is pumped in. At this time, the flow rate and fluid density are relatively reduced. The pulse oscillation chamber of the pulse oscillator begins to generate pressure and temperature fluctuations and turbulence of 10-100Hz, which brings two beneficial effects. First, it increases the molecular viscosity and apparent viscosity to effectively carry sand. Second, the instantaneous high pressure and alternating temperature stress generated by the pulse are more likely to induce the generation of new fractures.

[0022] (7) Fluid drainage: After fracturing, shut in the well and drain the fluid after a period of time.

[0023] The energy storage projectile perforation fracturing device or packer capable of removing perforation fracturing tool strings described in this invention.

[0024] The projectile exit of the present invention uses a constant diameter nozzle or a Laval nozzle.

[0025] The energy storage projectile perforation fracturing device described in this invention may use nitrogen gas for perforation fracturing.

[0026] Compared with the prior art, the energy storage projectile perforation fracturing device and method designed in this invention have a reasonable main structure and the following beneficial effects:

[0027] (1) This method mainly accelerates the projectile through pressure difference and long acceleration tube, which can ensure the transfer of sufficient energy;

[0028] (2) The projectile is made of tungsten steel balls, and its density is more than 700 times that of the annular fluid. Even if the projectile speed is only accelerated to half the speed of the fluid, the impact force generated by the projectile can reach 350 times that of the fluid, thereby greatly increasing the destructive force of the jet. The projectile can form a deep perforation hole under penetration.

[0029] (3) Because supercritical CO2 is highly compressible, it can form a high-pressure jet for tens of minutes, which can ensure that there is enough energy and projectiles to accelerate the jet and break the solid.

[0030] (4) Compared with particle jets, tungsten steel projectiles have a larger mass and diameter. The impact crater and cracks are positively correlated with the diameter and density of the steel ball. The projectile can cause deeper damage to the impacting object, and the collision stress wave can also induce the generation of microcracks deep in the rock layer.

[0031] (5) Due to water hammer pressure, static pressure several times that of the tubing pressure will be generated in the perforation. The water wedge action will expand the existing cracks. This is different from the cracking mechanism of the projectile, thus forming a complex crack network.

[0032] (6) Under the pressure of shot perforation and water hammer, pores and initial fractures are formed in the near-well formation, which can reduce the flow resistance and initiation pressure of subsequent conventional fracturing, thereby reducing the requirements for pump displacement and pressure.

[0033] (7) The tubing energy storage pressurization reduces the pressurization time from low density to high density in the wellbore, thereby reducing fluid loss time and loss amount;

[0034] (8) In the later stage of conventional fracturing, pulse-induced low temperature and turbulence are used, which can increase the apparent viscosity of the fluid and reduce the pressure holding effect of the proppant under the pressure difference, thus helping to solve the sand carrying problem. Attached image description:

[0035] Figure 1 This is a schematic diagram of the structural principle of the energy storage projectile perforation fracturing device according to the present invention, with a vertical cross-section.

[0036] Figure 2 This is a schematic diagram of the structural principle of the perforation fracturing tool string with a vertical cross-section according to the present invention.

[0037] Figure 3 This is a schematic diagram of the structural principle of the pulse oscillator with a vertical cross-section according to the present invention.

[0038] Figure 4 The invention relates to the following: Figure 3 A schematic diagram of the structural principle of the cross-section cut at point AA along the middle.

[0039] Figure 5 This is a schematic diagram of the structural principle of the vertical cross-section of the hydraulic anchor involved in this invention.

[0040] Figure 6 This is a schematic diagram of the structural principle of the packer with a vertical cross-section according to the present invention.

[0041] Figure 7 This is a schematic diagram of the structural principle of the connection between the packer and the projectile projection device involved in this invention, with a vertical cross-section.

[0042] Figure 8 This is a schematic diagram of the structural principle of the projectile launching device according to the present invention, with a vertical cross-section.

[0043] Figure 9 The invention relates to the following: Figure 8 A schematic diagram of the structural principle of the cross-section at point BB.

[0044] Figure 10 The invention relates to the following: Figure 8 A schematic diagram of the structural principle of the cross-section at the CC point.

[0045] Figure 11 The invention relates to the following: Figure 8 A schematic diagram of the structural principle of the cross-section at point DD.

[0046] Figure 12 This is a schematic diagram of the structural principle of the projectile acceleration device according to the present invention, with a vertical cross-section.

[0047] Figure 13 This is a schematic diagram of the structural principle of the guide head with a vertical cross-section according to the present invention.

[0048] Figure 14 This is a schematic diagram illustrating the structural principle of the projectile acceleration and ejection process involved in this invention.

[0049] Figure 15 This is a schematic diagram illustrating the structural principle of the projectile perforation process involved in this invention.

[0050] Figure 16 This is a schematic diagram illustrating the structural principle of the water hammer pressure fracturing process involved in this invention.

[0051] Figure 17 This is a schematic diagram illustrating the structural principle of the pulse sand-carrying and fracturing process involved in the present invention. Detailed implementation method:

[0052] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0053] Example 1:

[0054] This embodiment relates to a storable projectile perforation fracturing device, such as... Figure 1 As shown, the main structure includes a tubing 1, a perforation fracturing tool string 2, a casing 3, and a cement sheath 4. The lower end of the tubing 1 is connected to the upper end of the perforation fracturing tool string 2, which is installed in the cylindrical casing 3. A cement sheath 4 is fitted on the outside of the casing 3. The cement sheath 4 is formed in rock 6, where an oil and gas reservoir 5 is buried. The perforation fracturing tool string 2 includes a tubing adapter 21, a pulse oscillator 22, a hydraulic anchor 23, a packer 24, a projectile delivery device 25, and a projectile delivery system. The perforation fracturing tool string 2 includes a pellet acceleration device 26, a main channel 27, and a guide head 28. A tubing adapter 21 is installed at the upper end of the perforation fracturing tool string 2, connecting the tubing 1 to the perforation fracturing tool string 2. The lower end of the tubing adapter 21 is connected to a pulse oscillator 22, which generates pressure and flow pulsations. Symmetrically arranged hydraulic anchors 23 are installed below the pulse oscillator 22 to secure the perforation fracturing tool string 2. A packer 24 is installed below the hydraulic anchors 23. Packer 24 is used to seal the fracturing fluid in the perforation fracturing tool string 2 with the annular cavity groove in the casing 3; below packer 24 is shot projection device 25, which is used to control the frequency of shot projection; below shot projection device 25 is shot acceleration device 26, which is used to accelerate, steer, and eject the shot; below shot acceleration device 26 is another set of packers 24 and hydraulic anchor 23 installed in sequence; the center of perforation fracturing tool string 2 is set with a main The main flow channel 27 is used to connect the fluid in the tubing and serve as a pressure testing flow channel. The upper end of the main flow channel 27 is connected to the lower end of the pulse oscillator 22. The main flow channel 27 is connected to the hydraulic anchor 23, the packer 24, and the shot acceleration device 26. The lower end of the main flow channel 27 is connected to the upper end of the guide head 28. The guide head 28 is located at the lower end of the perforation fracturing tool string 2. The guide head 28 is used to control the movement of the perforation fracturing tool string 2 in the tubing and to realize the transformation between the pressure testing and pressure holding processes during fracturing.

[0055] like Figure 3As shown, the pulse oscillator 22 involved in this embodiment includes an oscillation inlet 221, a primary oscillation chamber 222, a guide post 223, a secondary oscillation chamber 224, a sealing shell 225, and an inner frame 226. The inner frame 226 is disposed inside the sealing shell 225, and a cylindrical oscillation inlet 221 is disposed at the upper end of the inner frame 226. The upper end of the oscillation inlet 221 is connected to the lower end of the oil pipe adapter 21. The oscillation inlet 221 is used to convert fluid pressure energy into fluid kinetic energy. The lower end of the oscillation inlet 221 is connected to the primary oscillation chamber 222. The primary oscillation chamber 222 has an overall structure of a frustum-shaped annular groove with a vertical cross-section resembling the number "8". Figure 3 , 4 As shown, four guide pillars 223 are provided at the connection between the central cylindrical cavity and the side frustum annular cavity of the primary oscillation cavity 222. The guide pillars 223 are arranged in a circumferential array. The lower end of the primary oscillation cavity 222 is connected to the secondary oscillation cavity 224. The primary oscillation cavity 222 and the secondary oscillation cavity 224 have the same structure. The primary oscillation cavity 222 and the secondary oscillation cavity 224 are used to absorb fluid kinetic energy and generate pulse flow.

[0056] like Figure 5 As shown, the hydraulic anchor 23 involved in this embodiment includes an anchor sealing ring 231, a piston anchor claw 232, an anti-detachment elastic diaphragm 233, an anchor cylinder sleeve 234, and an anchor pressure guide port 235. The anchor cylinder sleeve 234 is fixedly connected to the housing of the perforation fracturing tool string 2. An anchor pressure guide port 235 is opened on the inner end of the anchor cylinder sleeve 234, and the anchor pressure guide port 235 is connected to the main channel 27. A piston anchor claw 232 is installed in the anchor cylinder sleeve 234, and the piston anchor claw 232 is anchored from the inner end of the anchor. The piston and the outer end of the anchor claw are combined. Anchor sealing rings 231 are provided on the upper and lower sides of the anchor piston. The piston anchor claw 232 extends outward under the action of fluid pressure. The anchor claw can abut against the sleeve 3 to fix the perforation fracturing tool string 2. An anti-detachment elastic partition 233 is embedded in the outer end of the anchor claw. The two ends of the anti-detachment elastic partition 233 are fixedly connected to the anchor cylinder sleeve 234. The anti-detachment elastic partition 233 prevents the piston anchor claw 232 from detaching from the anchor cylinder sleeve 234.

[0057] like Figure 6As shown, the packer 24 involved in this embodiment includes a sealing strip 241, a sealing ring 242, an elastic sleeve 243, a piston 244, a cylinder liner 245, and a pressure guide port 246. The annular packer 24 is embedded in the housing of the perforation fracturing tool string 2. The cylinder liner 245 is fixedly connected to the housing of the perforation fracturing tool string 2. The pressure guide port 246 is opened on the inner end of the cylinder liner 245 and communicates with the main channel 27. The piston 244 is installed in the cylinder liner 245, and the sealing strip is installed on the upper and lower sides of the piston 244. 241. An elastic sleeve 243 is installed on the outer end of the piston 244. A sealing ring 242 is installed on the outer end of the elastic sleeve 243. The upper and lower ends of the sealing ring 242 are connected to the cylinder liner 245. When the piston 244 extends outward under the action of fluid pressure, the piston 244 pushes the sealing ring 242 outward, and the sealing ring 242 abuts against the sleeve 3. The sealing ring 242 at the upper end of the perforation fracturing tool string 2, the housing of the perforation fracturing tool string 2, the sealing ring 242 at the lower end of the perforation fracturing tool string 2, and the sleeve 3 together constitute an annular sealed cavity.

[0058] like Figure 7 , Figure 8 As shown, the projectile launching device 25 involved in this embodiment includes a projectile outer connecting cavity 30, a projectile cavity cover 251, a thrust piston 252, a projectile 253, a housing 254, a baffle 255, a projection thrust hole 256, a projection hole 257, a torsion spring 258, and a rotating shaft fixing plate 259; wherein, four projectile outer connecting cavities 30 are evenly arranged in a circular array on the upper end of the projectile launching device 25, the upper end of each projectile outer connecting cavity 30 is connected to the main channel 27 through an inverted "L"-shaped projectile connecting pipe 29, the lower end of each projectile outer connecting cavity 30 is provided with a projectile cavity cover 251, and the lower end of each projectile cavity cover 251 is provided with a projectile cavity, such as Figure 8-10 As shown, a thrust piston 252 is installed in the projectile cavity, and a projectile 253 is installed in the projectile cavity below the thrust piston 252. The thrust piston 252 is used to push the projectile 253 in the projectile cavity. Both the projectile cavity cover 251 and the thrust piston 252 have small through holes, which allow fluid to be introduced from the outer cavity 250 of the projectile into the projectile cavity to generate the thrust force that propels the thrust piston 252 forward. The thrust piston 252 pushes the projectile 253 downward, keeping the projectile 253 in a constant state of mutual contact. Contact state; the projectile 253 is made of tungsten steel balls with high density and hardness; the lower end of the projectile cavity is connected to an "L"-shaped connecting pipe 250, which is composed of an upper vertical pipe and a lower horizontal pipe. The end of the horizontal pipe is connected to the upper end of the projection hole 257, and the upper end of the projection hole 257 is also connected to the lower end of the inverted "L"-shaped projection thrust hole 256. The upper end of the projection thrust hole 256 is connected to the main channel 27; a baffle 255 is provided at the lower end of the projection hole 257, such as... Figure 11As shown, a rotating shaft is installed at one end of the baffle 255, and torsion springs 258 are symmetrically mounted on the rotating shaft. Both ends of the rotating shaft are connected to a rotating shaft fixing plate 259, which is fixed to the housing 254 of the projectile projection device 25. When the pressure difference between the upper and lower parts of the baffle 255 is small, the baffle 255 and the torsion springs 258 work together to prevent the projectile 253 from being ejected. When the pressure difference between the upper and lower parts of the baffle 255 is large, the projection thrust hole 256 introduces fluid from the main channel 27, generating a thrust that propels the projectile 253 out of the projection hole 257. When the thrust is greater than the reaction torque of the torsion springs 258, the projectile 253 is ejected from the projection hole 257. The torsion springs 258 and the projection thrust hole 256... The torque generated by the fluid inside the 6th channel on the baffle 255 satisfies the following conditions: when the static pressure below the baffle 255 is less than 1 / 2 of the static pressure inside the main channel 27, the baffle 255 will be fully opened and the projectile 253 will be projected. When the static pressure below the baffle 255 is not less than 1 / 2 of the static pressure inside the main channel 27, no projectile 253 will be projected, thereby controlling the projection frequency of the projectile 253 and ensuring that each projectile 253 has enough energy for acceleration. The diameter of the projection hole 257 is 2-3 mm larger than the diameter of the projectile 253 to ensure that the fluid ejected from the projection thrust hole 256 can generate sufficient thrust on the projectile 253 inside the projection hole 257 when the pressure difference is large.

[0059] like Figure 12As shown, the projectile acceleration device 26 involved in this embodiment consists of four identical parts arranged in a circular array. Each part includes a fluid inlet 261, a jet acceleration pipe 262, a rupture disc fixing cap 263, a projectile outlet 264, and a reverse-arching rupture disc 265. The uppermost end of the jet acceleration pipe 262 is connected to the lower end of the projection hole 257. The jet acceleration pipe 262 is connected to the main channel 27 through the fluid inlet 261. The tubular fluid inlet 261 slopes downward from the inside to the outside. The equivalent flow area of ​​the fluid inlet 261 is more than 8 times that of the projection thrust hole 256, serving as the main fluid source for accelerating the projectile 253. The jet acceleration pipe 262 consists of a long straight pipe at the top and a short curved pipe at the bottom. The long straight pipe accelerates the projectile 253 using fluid energy, while the short curved pipe... The curved pipe turns the velocity of the projectile 253 outward by 90 degrees. A projectile outlet 264 is set at the outer end of the short curved pipe. An anti-arching rupture disc 265 is installed at the output port of the projectile outlet 264. The anti-arching rupture disc 265 protrudes inward. A rupture disc fixing cap 263 is set at the outer end of the anti-arching rupture disc 265, which fixes the anti-arching rupture disc 265 to the projectile outlet 264. The burst pressure of the anti-arching rupture disc 265 is lower than the maximum pressure resistance of the booster pump and the oil pipe 1. When the pressure of the oil pipe 1 and the perforation fracturing tool string 2 exceeds the burst pressure of the anti-arching rupture disc 265, the anti-arching rupture disc 265 bursts, and the static pressure energy is converted into dynamic pressure energy. The flow velocity of the fluid inlet 261 is higher than the flow velocity in the main channel 27, thereby creating a pressure difference above and below the baffle 255, and the projectile 253 is launched and accelerated.

[0060] like Figure 13 As shown, the guide head 28 involved in this embodiment includes an end housing 281, a fracturing ball 282, a constricted flow channel 283, and an end connecting groove 284. The end housing 281 has an end connecting groove 284 at its upper end, which is connected to the lower end of the main body of the perforated fracturing tool string 2. The lower middle part of the end connecting groove 284 is connected to the constricted flow channel 283 of the tubular structure. The upper end of the constricted flow channel 283 is connected to the lower end of the main flow channel 27. The diameter of the constricted flow channel 283 decreases from top to bottom, and the constricted flow channel 283 can be connected to the fracturing ball 282 in a slotted manner. After the device pressure test is completed, the fracturing ball 282 is dropped from the wellhead into the main flow channel 27. After the fracturing ball 282 contacts the constricted flow channel 283, it can cut off the flow in the main flow channel 27, realizing the transformation of the device pressure test and pressure holding process during fracturing.

[0061] The energy storage type shot perforation fracturing device involved in this embodiment achieves shot perforation and fracturing, including device pressure testing and pressure build-up, high-pressure energy storage, shot acceleration and injection, shot perforation, water hammer pressure fracturing, pulse sand carrying and fracturing, and fluid drainage. The specific process steps are as follows:

[0062] (1) Pressure testing and pressure holding: After well cleaning and flushing at the oil and gas extraction site, the perforation and fracturing tool string 2 is placed into the well, and the tubing 1 is connected to the upper end of the perforation and fracturing tool string 2. CO2 is pumped into the perforation and fracturing tool string 2 for pressure testing. After the pressure test, the fracturing ball 282 is placed in for pressure holding. The pressure holding adopts the following scheme:

[0063] As a preferred option, a burst valve is placed at the pressure port 246 of the packer 24, with a burst pressure slightly greater than the test pressure. The packer 24 is closed during the test, and after the test, the fracturing ball 282 is placed in. Then, the annulus of the device is depressurized to atmospheric pressure, thereby generating a larger jet pressure differential.

[0064] (2) High pressure energy storage: Utilizing the strong compressibility of supercritical CO2, the long oil pipe 1 is used as an energy storage device. Through long-term small-displacement pressurization and wellbore heat exchange, CO2 is stored and pressurized, and finally the CO2 in the main channel 27 is modulated into a high-pressure supercritical state.

[0065] (3) Projectile Acceleration and Ejection: After reaching the predetermined pressure (above 40MPa), the anti-arch rupture disc 265 ruptures, the projectile acceleration device 26 forms a high-pressure jet, the projectile projection device 25 is activated, and the projectile 253 in the projectile cavity is carried by the fluid into the jet acceleration tube 262. The diameter difference between the projectile 253 and the jet acceleration tube 262 is controlled to be within 1mm, so that the projectile 253 is accelerated to near the highest pressure difference velocity of the fluid under the fluid pressure difference. The ejection process is as follows: Figure 14 As shown;

[0066] (4) Projectile perforation: After passing through the bend in the jet acceleration tube 262, the projectile 253 is horizontally ejected from the projectile outlet 264, sequentially penetrating the casing 3, cement sheath 4, and reservoir 5, forming a projectile perforation and complex fractures. Simultaneously, the low temperature generated by the expansion of the CO2 jet causes rock contraction and reduces the stress around the perforation, further expanding the fractures under CO2 pressure and temperature difference. The process of projectile perforation is as follows: Figure 15 As shown;

[0067] (5) Water hammer pressure fracturing: During the high-speed jet process, the fluid in the tubing 1 and the shot acceleration device 26 generates a large flow inertia, and the hydraulic anchor 23 and packer 24 have extended under the pressure difference inside and outside the main channel 27, forming a closed environment. Therefore, water hammer pressure will be generated after the shot is perforated. The water hammer pressure further connects and expands the fracture through the high permeability of supercritical CO2, and carries some of the shot 253 into the depth of the fracture, forming effective support for the newly expanded fracture; the water hammer pressure fracturing process is as follows: Figure 16 As shown;

[0068] (6) Pulse-driven propagation and fracturing: CO2 is pumped into the perforation fracturing tool string 2 at a conventional flow rate to continue propagating the fracture. Subsequently, CO2 propagating fluid is pumped in. At this point, the flow rate and fluid density are relatively reduced, and the pulse oscillation chamber of the pulse oscillator 22 begins to generate pressure and temperature fluctuations and turbulence at 10-100Hz, bringing two beneficial effects: firstly, it increases molecular viscosity and apparent viscosity to effectively carry propagation; secondly, the instantaneous high pressure and alternating temperature stress generated by the pulse make it easier to induce the formation of new fractures. The pulse-driven propagation and fracturing process is as follows: Figure 17 As shown;

[0069] (7) Fluid drainage: After fracturing, shut in the well and drain the fluid after a period of time.

[0070] This embodiment relates to an energy storage projectile perforation fracturing device or a packer 24 that can remove the perforation fracturing tool string 2.

[0071] The working principle of the energy storage projectile perforation fracturing device involved in this embodiment is as follows:

[0072] (1) During the shot injection process, the carbon dioxide density in the tubing is more than 400 times the gas density in the annulus between the perforation fracturing tool string 2 and the casing 3, as shown in Table 1. When the space between the upper and lower packers 24 of the perforation fracturing tool string 2 and the casing 3 is large or no packers are used, a high-pressure differential injection can be formed for a long time (more than 20 minutes), as shown in Table 2. For example, for a 5000m deep well, when the initial pressure in the tubing 1 is 50MPa and the initial pressure in the annulus between the perforation fracturing tool string 2 and the casing 3 is 0.1MPa, a high-pressure injection with a pressure difference of more than 40MPa, a flow rate of 60L / min and a duration of more than 40 minutes can be generated (as shown in Table 2). In addition, when the annular pressure is low, due to the characteristics of the jet, the pressure inside the jet orifice is close to that inside the tubing, and is in a high-pressure state, but the density is similar to that of the annular fluid. As a result, the fluid will expand and absorb heat, and the temperature inside the jet orifice can drop by tens of degrees. This can reduce the ground stress in the orifice and is conducive to the formation of cracks.

[0073] Table 1. CO2 density variation with temperature and pressure

[0074]

[0075]

[0076] Table 2. Statistics of CO2 High-Pressure Jet Time

[0077] Flow rate (L / s) 60 60 60 60 Well depth(m) 3000 3000 4000 5000 Oil pipe inner diameter (mm) 76 76 76 76 Oil pipe outer diameter (mm) 95 95 95 95 <![CDATA[Volume of tubing (m 3 )]]> 13.61 13.61 18.15 22.68 Annular inner diameter (mm) 123 123 123 123 Annular outer diameter (mm) 132 132 132 132 <![CDATA[Annular volume (m 3 )]]> 14.38 14.38 19.18 23.97 Pre-injection oil line pressure (MPa) 50 50 50 50 <![CDATA[Density of oil pipe before injection (kg / m -3 )]]> 899 899 899 899 Post-injection oil line pressure (MPa) 30 40 40 40 <![CDATA[Density of the oil pipe after injection (kg / m -3 )]]> 780 850 850 850 Pre-injection casing pressure (MPa) 0.1 0.1 0.1 0.1 <![CDATA[Casing density before injection (kg / m -3 )]]> 1.5 1.5 1.5 1.5 Post-spray casing pressure (MPa) 1 1 1 1 <![CDATA[Casing density after injection (kg / m -3 )]]> 15 15 15 15 Spray mass (kg) 1620 667 889 1111 Spraying time (min) 60 25 33 41

[0078] (2) During the injection process, the density of the fluid in the annular space is less than 20 kg / m³. 3The density of tungsten pellets is 15630 kg / m³. 3 The latter has a density more than 700 times that of the former. Even if the projectile velocity is only accelerated to half the velocity of the fluid, the impact force generated by the projectile 253 can reach 350 times that of the fluid, thus greatly increasing the destructive force of the jet. For example, when the projectile exit 264 uses a constant diameter nozzle, the upper limit of the fluid velocity is determined by the pressure difference, the outlet fluid density, and the speed of sound. The maximum velocity of the projectile 253 is more than 250 m / s, and three 15 mm projectiles 253 can penetrate the sleeve 3 (as shown in Table 3). If the projectile exit 264 uses a Laval nozzle, the fluid velocity can reach 7-8 times the speed of sound, and the maximum velocity of the projectile can reach more than 1800 m / s. One 15 mm projectile can penetrate three layers of sleeve 3 (as shown in Table 4).

[0079] Table 3. Statistics on the maximum penetration depth of a single CO2 projectile under conventional nozzle conditions.

[0080] Oil pressure in the injection line (MPa) 50 50 50 50 50 50 Injection casing pressure (MPa) 0.1 1 5 10 15 20 <![CDATA[Outlet density (kg / m 3 )]]> 1.7 19.5 116 638 783 841 Carbon dioxide flow rate (m / s) 7662 2242 881 354 299 267 Speed ​​of sound of carbon dioxide (m / s) 274 268 234 277 230 515 Projectile velocity (m / s) 274 268 234 277 230 267 Projectile diameter (mm) 15 15 15 15 15 15 <![CDATA[Tungsten pellet density (kg / m 3 )]]> 15630 15630 15630 15630 15630 15630 <![CDATA[Casing density (kg / m 3 )]]> 7900 7900 7900 7900 7900 7900 Casing strength (MPa) 900 900 900 900 900 900 Penetration depth (mm) 3.18 3.10 2.64 3.22 2.58 3.08

[0081] Table 4. Statistics on the maximum penetration depth of a single CO2 projectile under Laval nozzles.

[0082] Oil pressure in the injection line (MPa) 50 50 50 50 50 50 Injection casing pressure (MPa) 0.1 1 5 10 15 20 <![CDATA[Outlet density (kg / m 3 )]]> 1.7 19.5 116 638 783 841 Carbon dioxide flow rate (m / s) 7662 2242 881 354 299 267 Speed ​​of sound of carbon dioxide (m / s) 274 268 234 277 230 515 Projectile velocity (m / s) 1918 1876 881 354 299 267 Projectile diameter (mm) 15 15 15 15 15 15 <![CDATA[Tungsten pellet density (kg / m 3 )]]> 15630 15630 15630 15630 15630 15630 <![CDATA[Casing density (kg / m 3 )]]> 7900 7900 7900 7900 7900 7900 Casing strength (MPa) 800 800 800 800 800 800 Impact pressure (MPa) 28749 27504 6066 979 699 557 Penetration depth (mm) 32.25 31.41 12.77 4.31 3.53 3.08

[0083] (3) The shot acceleration injection is a process from high pressure difference to low pressure difference, and at the same time, the flow velocity in the tubing and the injection undergoes a process from high speed to low speed. Because the flow velocity in the injection decreases earlier than the flow velocity change in the tubing, the fluid in the pipeline will generate a large water hammer pressure at the inlet of the injection acceleration tube due to inertia. In addition, the annulus and the formation are relatively closed spaces, which can also generate a large water hammer pressure under the injection. Both of these factors are conducive to the further expansion of formation fractures after perforation.

[0084] (4) The energy storage of the shot perforation and water hammer pressure produced three beneficial effects: first, it formed erosion holes and fractures; second, it reduced the seepage resistance around the wellbore; and third, it reduced the pressurization time from low density to high density in the wellbore, thereby reducing the formation fracturing pressure, fluid flow resistance and fluid loss time, reducing the requirements of fracturing on pump discharge and pressure, which is conducive to the subsequent sand fracturing.

[0085] (5) In the later stage of conventional fracturing, pulse-induced low temperature and turbulence can increase the apparent viscosity of the fluid and reduce the pressure holding effect of the proppant under the filtration pressure difference, thus helping to solve the sand carrying problem. In addition, the instantaneous high pressure and alternating temperature stress generated by the pulse are more likely to induce the generation of new cracks, which helps the crack generation and propagation.

[0086] Example 2:

[0087] The energy storage projectile perforation fracturing device involved in this embodiment is also applicable to fracturing of compressible gases such as nitrogen. As shown in Tables 5-7, compared with using supercritical CO2 for perforation fracturing, using nitrogen for projectile perforation can maintain a larger pressure differential injection time and produce a deeper projectile penetration depth.

[0088] Table 5. Statistics of Nitrogen High-Pressure Jet Time

[0089]

[0090]

[0091] Table 6. Statistics on the maximum penetration depth of a single projectile injected with nitrogen under conventional nozzle conditions.

[0092] Oil pressure in the injection line (MPa) 50 50 50 50 50 50 Injection casing pressure (MPa) 0.1 1 5 10 15 20 <![CDATA[Outlet density (kg / m 3 )]]> 0.98 10.8 49.7 96.8 141.38 182.9 Nitrogen flow rate (m / s) 10091 3012 1346 909 704 573 Speed ​​of sound of nitrogen (m / s) 377 380 390 406 425 447 Projectile velocity (m / s) 377 380 390 406 425 447 Projectile diameter (mm) 15 15 15 15 15 15 <![CDATA[Tungsten pellet density (kg / m 3 )]]> 15630 15630 15630 15630 15630 15630 <![CDATA[Casing density (kg / m 3 )]]> 7900 7900 7900 7900 7900 7900 Casing strength (MPa) 800 800 800 800 800 800 Penetration depth (mm) 4.65 4.69 4.84 5.08 5.36 5.69

[0093] Table 7. Statistics on the maximum penetration depth of a single projectile injected with nitrogen under Laval nozzles.

[0094] Oil pressure in the injection line (MPa) 50 50 50 50 50 50 Injection casing pressure (MPa) 0.1 1 5 10 15 20 <![CDATA[Export density (kg / m 3 )]]> 0.98 10.8 49.7 96.8 141.38 182.9 Nitrogen flow rate (m / s) 10091 3012 1346 909 704 573 Speed ​​of sound of nitrogen (m / s) 377 380 390 406 425 447 Projectile velocity (m / s) 2639 3012 1346 909 704 573 Projectile diameter (mm) 15 15 15 15 15 15 <![CDATA[Tungsten pellet density (kg / m 3 )]]> 15630 15630 15630 15630 15630 15630 <![CDATA[Casing density (kg / m 3 )]]> 7900 7900 7900 7900 7900 7900 Casing strength (MPa) 800 800 800 800 800 800 Penetration depth (mm) 47.15 55.18 21.15 13.26 9.78 7.65

Claims

1. A storable projectile perforation fracturing device, characterized in that: The system includes tubing, a perforation fracturing tool string, casing, and a cement sheath. The lower end of the tubing is connected to the upper end of the perforation fracturing tool string, which is installed inside the cylindrical casing. A cement sheath is fitted on the outside of the casing. The cement sheath is formed in the rock, where an oil and gas reservoir is buried. The energy storage projectile perforation fracturing device uses compressible gas for perforation fracturing. The perforation fracturing tool string includes a tubing adapter, a pulse oscillator, a hydraulic anchor, a packer, a projectile delivery device, a projectile acceleration device, a main channel, and a guide head. The projectile launching device includes a projectile outer cavity, a projectile cavity cover, a thrust piston, a projectile, a housing, a baffle, a launching thrust hole, a launching hole, a torsion spring, and a rotating shaft fixing plate. Four projectile outer cavities are evenly arranged in a circular array at the upper end of the projectile launching device. The upper end of each projectile outer cavity is connected to the main channel via an inverted "L"-shaped projectile connecting pipe. A projectile cavity cover is located at the lower end of each projectile outer cavity, and a projectile cavity is located below each projectile cavity cover. A thrust piston is installed in each projectile cavity, and a projectile is loaded in the projectile cavity below the thrust piston. The thrust piston is used to push the projectile inside the projectile chamber. Both the projectile chamber cap and the thrust piston have small through holes, allowing fluid to be introduced from the outer cavity of the projectile into the projectile chamber to generate the thrust piston's forward force. The thrust piston pushes the projectile downwards, ensuring the projectiles remain in contact. The projectile is made of tungsten steel balls. An "L"-shaped connecting pipe is connected to the lower end of the projectile chamber. This connecting pipe consists of an upper vertical pipe and a lower horizontal pipe. The end of the horizontal pipe connects to the upper end of the projection hole, and the upper end of the projection hole also connects to the lower end of the inverted "L"-shaped projection thrust hole. The projectile is connected to the main channel at one end; a baffle is installed at the lower end of the projection hole, and a rotating shaft is installed at one end of the baffle. Torsion springs are symmetrically mounted on the rotating shaft, and both ends of the rotating shaft are connected to a rotating shaft fixing plate, which is fixed to the housing of the projectile projection device. When the pressure difference between the upper and lower parts of the baffle is small, the baffle and the torsion spring work together to prevent the projectile from being ejected. When the pressure difference between the upper and lower parts of the baffle is large, the projection thrust hole introduces fluid from the main channel, generating a thrust that propels the projectile out of the projection hole. When the thrust is greater than the reaction torque of the torsion spring, the projectile is ejected from the projection hole. The torsion spring and the projection thrust... The torque generated by the fluid in the thrust orifice on the baffle satisfies the following conditions: when the static pressure below the baffle is less than 1 / 2 of the static pressure in the main channel, the baffle will open completely and the projectile will be launched. When the static pressure below the baffle is not less than 1 / 2 of the static pressure in the main channel, no projectile will be launched, thereby controlling the projectile launch frequency and ensuring that each projectile has enough energy for acceleration. The diameter of the projection orifice is 2-3 mm larger than the diameter of the projectile to ensure that the fluid ejected from the thrust orifice can generate sufficient thrust on the projectile in the projection orifice when the pressure difference is large.

2. The energy storage projectile perforation fracturing device according to claim 1, characterized in that: The perforation fracturing tool string is equipped with a tubing adapter at its upper end, which connects the tubing to the tool string. The lower end of the tubing adapter is connected to a pulse oscillator, which generates pressure and flow pulsations. Below the pulse oscillator are symmetrically arranged or evenly distributed circumferential hydraulic anchors, which secure the perforation fracturing tool string. Below the hydraulic anchors is a packer, which seals the fracturing fluid within the perforation fracturing tool string against the annular cavity in the casing. Below the packer is a projectile projectile launcher, which controls the frequency of projectile launch. Below the projectile projectile launcher is a connection... There is a projectile acceleration device, which is used to accelerate, steer, and eject the projectile. Below the projectile acceleration device, another set of packers and hydraulic anchors are installed in sequence. A main channel is set in the center of the perforation fracturing tool string, which is used to connect the fluid in the tubing and serve as a pressure test channel. The upper end of the main channel is connected to the lower end of the pulse oscillator, and the main channel is connected to the hydraulic anchor, packer, and projectile acceleration device. The lower end of the main channel is connected to the upper end of the guide head. The guide head is set at the lower end of the perforation fracturing tool string and is used to control the movement of the perforation fracturing tool string in the tubing and to realize the conversion between pressure testing and pressure holding during fracturing.

3. The energy storage projectile perforation fracturing device according to claim 2, characterized in that: The pulse oscillator includes an oscillation inlet, a primary oscillation chamber, guide columns, a secondary oscillation chamber, a sealing shell, and an inner frame. The inner frame is housed within the sealing shell, and a cylindrical oscillation inlet is located at the upper end of the inner frame. The upper end of the oscillation inlet connects to the lower end of the oil pipe adapter. The oscillation inlet converts fluid pressure energy into fluid kinetic energy. The lower end of the oscillation inlet connects to the primary oscillation chamber, which has a vertical cross-section resembling a frustum of a cone. Four guide columns are arranged in a circular array at the connection between the central cylindrical cavity and the side frustum of a cone cavity of the primary oscillation chamber. The lower end of the primary oscillation chamber connects to the secondary oscillation chamber, which has the same structure. Both the primary and secondary oscillation chambers absorb fluid kinetic energy and generate pulsed flow.

4. The energy storage projectile perforation fracturing device according to claim 3, characterized in that: The hydraulic anchor includes an anchor sealing ring, a piston anchor claw, an anti-detachment elastic baffle, an anchor cylinder sleeve, and an anchor pressure guide port. The anchor cylinder sleeve is fixedly connected to the housing of the perforation fracturing tool string. An anchor pressure guide port is opened on the inner end of the anchor cylinder sleeve, and the anchor pressure guide port is connected to the main channel. A piston anchor claw is installed in the anchor cylinder sleeve. The piston anchor claw is composed of an anchor piston on the inner end and an anchor claw on the outer end. An anchor sealing rings are provided on the upper and lower sides of the anchor piston. The piston anchor claw extends outward under the action of fluid pressure. The anchor claw can abut against the sleeve to fix the perforation fracturing tool string. An anti-detachment elastic baffle is embedded in the outer end of the anchor claw. The two ends of the anti-detachment elastic baffle are fixedly connected to the anchor cylinder sleeve. The anti-detachment elastic baffle prevents the piston anchor claw from detaching from the anchor cylinder sleeve.

5. The energy storage projectile perforation fracturing device according to claim 4, characterized in that: The packer includes a sealing strip, a sealing ring, an elastic sleeve, a piston, a cylinder liner, and a pressure guide port. The annular packer is embedded in the perforation fracturing tool string housing. The cylinder liner is fixedly connected to the perforation fracturing tool string housing. A pressure guide port is opened on the inner end of the cylinder liner and communicates with the main flow channel. The piston is installed in the cylinder liner. A sealing strip is installed on the upper and lower sides of the piston. An elastic sleeve is installed on the outer end of the piston. A sealing ring is installed on the outer end of the elastic sleeve. The upper and lower ends of the sealing ring are connected to the cylinder liner. When the piston extends outward under fluid pressure, it squeezes the sealing ring outward, and the sealing ring abuts against the casing. The sealing ring at the upper end of the perforation fracturing tool string, the housing of the perforation fracturing tool string itself, the sealing ring at the lower end of the perforation fracturing tool string, and the casing together constitute an annular sealed cavity.

6. The energy storage projectile perforation fracturing device according to claim 5, characterized in that: The projectile acceleration device consists of four identical parts arranged in a circular array. Each part includes a fluid inlet, a jet acceleration tube, a rupture disc fixing cap, a projectile outlet, and a reverse-arching rupture disc. The uppermost end of the jet acceleration tube is connected to the lower end of the projection hole. The jet acceleration tube is connected to the main flow channel through the fluid inlet, which is a tubular structure that slopes downwards from the inside out. The equivalent flow area of ​​the fluid inlet is more than eight times that of the projection thrust hole, serving as the main fluid source for projectile acceleration. The jet acceleration tube consists of a long straight pipe at the top and a short curved pipe at the bottom. The long straight pipe accelerates the projectile using fluid energy, while the short curved pipe... The projectile velocity is turned 90 degrees outwards by the short, curved pipe. A projectile outlet is located at the outer end of the short, curved pipe. An anti-arching rupture disc is installed at the outlet of the projectile. The anti-arching rupture disc protrudes inwards, and a rupture disc fixing cap is installed at the outer end of the anti-arching rupture disc, which fixes the anti-arching rupture disc at the projectile outlet. The burst pressure of the anti-arching rupture disc is lower than the maximum pressure resistance of the booster pump and the tubing. When the pressure of the tubing and the perforation fracturing tool string exceeds the burst pressure of the anti-arching rupture disc, the anti-arching rupture disc bursts, and static pressure energy is converted into dynamic pressure energy. The flow velocity at the fluid inlet is higher than the flow velocity in the main channel, thereby creating a pressure difference between the upper and lower baffles, and the projectile projection and acceleration process begins.

7. The energy storage projectile perforation fracturing device according to claim 6, characterized in that: The guide head includes an end shell, a fracturing ball, a constricted flow channel, and an end connecting groove. The end shell has an end connecting groove at its upper end, which connects to the lower end of the main body of the perforated fracturing tool string. The lower middle part of the end connecting groove communicates with the constricted flow channel of the tubular structure. The upper end of the constricted flow channel communicates with the lower end of the main flow channel. The diameter of the constricted flow channel decreases from top to bottom, and the constricted flow channel can be connected to the fracturing ball via a slotted connection. After the device pressure test is completed, the fracturing ball is inserted into the main flow channel from the wellhead. After the fracturing ball contacts the constricted flow channel, it can cut off the flow in the main flow channel, realizing the transformation from the device pressure test to the pressure holding process during fracturing.

8. The energy storage projectile perforation fracturing device according to claim 7, characterized in that: The energy storage type shot perforation fracturing device achieves shot perforation and fracturing through a method including device pressure testing and pressure buildup, high-pressure energy storage, shot acceleration and injection, shot perforation, water hammer pressure fracturing, pulse sand carrying and fracturing, and fluid drainage. The specific process steps are as follows: (1) Pressure testing and pressure holding: After well cleaning and flushing at the oil and gas extraction site, the perforation and fracturing tool string is placed into the well, and the tubing is connected to the upper end of the perforation and fracturing tool string. CO2 is pumped into the perforation and fracturing tool string for pressure testing. After the pressure test, fracturing balls are placed in for pressure holding. The pressure holding adopts the following scheme: As a preferred option, a burst valve is placed at the pressure port of the packer, with a burst pressure slightly greater than the test pressure. The packer is closed during the test, and a fracturing ball is placed after the test. Then, the annulus of the device is depressurized to atmospheric pressure, thereby generating a larger jet pressure differential. (2) High pressure energy storage: Utilizing the strong compressibility of supercritical CO2, the long oil pipe is used as an energy storage device. CO2 is stored and pressurized through long-term small-displacement pressurization and wellbore heat exchange, and finally the CO2 in the main channel is modulated into a high-pressure supercritical state. (3) Projectile acceleration and ejection: After reaching a predetermined pressure of 40MPa or more, the anti-arch rupture fragment bursts, the projectile acceleration device forms a high-pressure ejection, the projectile projection device is opened, and the projectile in the projectile cavity is carried into the ejection acceleration tube by the fluid. The difference between the diameter of the projectile and the diameter of the ejection acceleration tube is controlled to be within 1mm, so that the projectile is accelerated to near the highest pressure difference velocity of the fluid under the fluid pressure difference. (4) Shot perforation: After the shot changes direction by 90 degrees through the bend of the jet acceleration tube, it is ejected horizontally from the shot outlet and penetrates the casing, cement sheath and reservoir in sequence, forming shot perforation and complex fractures. At the same time, the low temperature generated by the expansion of CO2 jet will cause the rock to shrink and the stress around the perforation to decrease. The fractures will further expand under CO2 pressure and temperature difference. (5) Water hammer pressure fracturing: During the high-speed jet process, the fluid in the tubing and the shot acceleration device generates a large flow inertia, and the upper and lower sets of hydraulic anchors and packers have extended under the pressure difference inside and outside the main channel, forming a closed environment. Therefore, water hammer pressure will be generated after the shot is perforated. The water hammer pressure further communicates and expands the fracture through the high permeability of supercritical CO2, and carries some of the shot into the depth of the fracture, forming effective support for the newly expanded fracture. (6) Pulse-carrying and fracturing: CO2 is pumped into the perforation fracturing tool string at a conventional flow rate to continue the propagation of the fracture. Then, CO2-carrying fluid is pumped in. At this time, the flow rate and fluid density are relatively reduced. The pulse oscillation chamber of the pulse oscillator begins to generate pressure and temperature fluctuations and turbulence of 10-100Hz, which brings two beneficial effects. First, it increases the molecular viscosity and apparent viscosity to effectively carry sand. Second, the instantaneous high pressure and alternating temperature stress generated by the pulse are more likely to induce the generation of new fractures. (7) Fluid drainage: After fracturing, shut in the well and drain the fluid after a period of time.

9. The energy storage projectile perforation fracturing device according to claim 6, characterized in that: The energy-storing shot perforation fracturing device may have a packer that can be removed from the perforation fracturing tool string; the shot outlet adopts a constant diameter nozzle or a Laval nozzle; the energy-storing shot perforation fracturing device may use nitrogen for perforation fracturing.

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