A pulse generator and a polymer pulse injection method

Abstract

This invention provides a pulse generating device, comprising: a housing; a piston disposed within the housing, the piston dividing the inner cavity of the housing into an upper energy storage chamber and a lower discharge chamber; a first elastic element disposed within the discharge chamber; and a switching valve disposed on the piston. The piston is configured to move downwards in response to the pressure of the upper fluid, thereby compressing the first elastic element. The switching valve is configured to open after the piston moves downwards, thereby allowing fluid to flow from the energy storage chamber to the discharge chamber. The first elastic element is configured to overcome the reduced pressure of the upper fluid and push the piston upwards after the fluid flows from the energy storage chamber to the discharge chamber, thereby forming a pulse motion for fluid injection. This invention utilizes the interaction of the piston, valve core, and elastic element to generate pressure pulse waves as a polymer passes through the interior of the pulse generating device. This invention also provides a corresponding polymer pulse injection method capable of realizing polymer pulse injection.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas extraction technology, specifically relating to a pulse generator and a polymer pulse injection method. Background Technology

[0002] my country has abundant low-permeability oil reservoirs. Waterflooding is a common production method for low-permeability oil reservoirs, but the recovery rate is typically only around 20%. The main reason for this low recovery rate is that low-permeability reservoirs often exhibit heterogeneity, resulting in poor sweep efficiency.

[0003] Currently, polymer flooding is commonly used in my country to enhance sweep efficiency. However, polymers have poor injection capacity and tend to remain near the wellbore, making deep-level flooding difficult. Improving the injection capacity of polymers is of great significance for the widespread application of polymer flooding technology in low-permeability reservoirs.

[0004] Pressure pulse waves can reduce polymer viscosity, thereby enhancing polymer injection capability in the near-wellbore zone. Simultaneously, as the pressure pulse wave energy rapidly attenuates away from the injection well, the polymer viscosity gradually recovers, achieving the goal of deep polymer flow control. Pressure pulse technology, with its advantages of convenient construction and economic reliability, shows promising application prospects.

[0005] Common pulse wave generating tools are classified into external excitation tools, self-excited tools, and hydraulic oscillation tools according to the principle of wave generation. (1) External excitation tools require external work to generate pulse waves, including wellhead and downhole tools. Wellhead equipment requires mechanical power from the wellhead, which is costly, and the pulse wave is lost during transmission within the wellbore. Downhole tools generate pulse waves by controlling mechanical pistons, valves, screws, etc., which is relatively complex and costly. (2) Self-excited tools use injected energy to store and release energy to generate pulse waves, including rotary tools and accumulator valve tools. Rotary tools generate pulse waves by rotating a rotor. For example, Halliburton's Pulsonix tool uses a rotor to separate the tubing string. The injected displacement fluid drives the rotor to rotate. When the rotor rotates to a specific position, the tubing string is connected, and energy is stored in other positions. The stored pressure is periodically released to generate pulse waves. When polymers are injected into this type of tool, the polymer will wrap around the rotor, causing the polymer to mechanically shear, reducing the polymer molecular weight and affecting the polymer flooding effect. Accumulator valve tools also use injected energy to generate pulse waves. For example, the Powerwave tool developed by Wavefront Energy and Environmental Services in Canada releases energy and generates pulse waves by accumulating pressure in the energy storage chamber and reaching a certain pressure. Conventional energy storage valve tools also mechanically shear the polymer, affecting the polymer flooding effect. (3) Hydraulic oscillation tools are mainly jet-type tools that generate hydraulic oscillations by changing the direction of the liquid flow, but they are not suitable for high molecular weight polymers. The polymers are connected together, which is not conducive to the direction of the liquid flow. The wedge of the hydraulic oscillation tool will also exert a strong shearing force on the polymer, reducing the molecular weight of the polymer. When used for polymer injection, the polymer will also accumulate in the feedback flow path of the hydraulic oscillation tool, and may even block the feedback flow path. In addition, there are other types of devices that can only generate a limited number of pressure pulses and are generally used for unblocking, but are not suitable for pulse polymer injection.

[0006] Comparative analysis suggests that screw-type excitation tools and self-excited tools exhibit the weakest shearing effect on polymers. However, screw-type tools are relatively complex and require significant power, typically necessitating external energy supply. Therefore, this invention improves upon traditional self-excited tools by proposing a pressure pulse generator suitable for polymer injection modulation. This invention reduces polymer shearing, improves polymer flooding efficiency, and is suitable for pulsed polymer injection. The device is simple to operate, low in cost, and shows promising application prospects. Summary of the Invention

[0007] In view of the technical problems mentioned above, the present invention aims to provide a pulse generator that is applicable to polymer injection, providing pulse power for polymer injection, thereby solving the problem of poor polymer injection capability.

[0008] The present invention also proposes a polymer pulse injection method, which can improve the injection capacity of polymer and improve reservoir recovery.

[0009] According to the present invention, a pulse generating device is provided, comprising: a housing; a piston disposed within the housing, the piston dividing the inner cavity of the housing into an upper energy storage chamber and a lower discharge chamber; a first elastic member disposed within the discharge chamber; and a switching valve disposed on the piston, wherein the piston is configured to move downward in response to the pressure of an upper fluid, thereby compressing the first elastic member, the switching valve is configured to open after the piston moves downward, thereby allowing fluid to flow from the energy storage chamber to the discharge chamber, and to close after the piston returns to its original position, the first elastic member being configured to push the piston upward against the reduced pressure of the upper fluid after the fluid flows from the energy storage chamber to the discharge chamber, thereby forming a pulse motion of fluid injection.

[0010] In one embodiment, the piston includes a central through-hole, and the switching valve includes: a valve core movable within the central through-hole to selectively open or close the central through-hole; and a striker disposed within the drainage chamber and capable of engaging the valve core to push the valve core to open the central through-hole.

[0011] In one embodiment, a first baffle is provided in the drainage chamber, the first baffle is provided with a first through hole that allows fluid to pass through, and the first elastic element is provided between the first baffle and the piston.

[0012] In one embodiment, the valve core includes: a valve pad abutting against the central through hole; a valve stem disposed on the lower end face of the valve pad; and a needle seat disposed at the lower end of the valve stem, the needle seat being used to abut against the striking pin; wherein, a second partition is further disposed within the central through hole, the valve stem is slidably disposed through the second partition, an elastic stabilizer is disposed between the second partition and the needle seat, the elastic stabilizer is sleeved on the valve stem, and a second through hole is disposed on the second partition to allow fluid to pass through.

[0013] In one embodiment, the valve pad is made of an elastic material, such as rubber, and the side of the valve pad that abuts against the central through hole is configured as a conical surface.

[0014] In one embodiment, a sealing assembly is provided between the piston and the housing.

[0015] In one embodiment, the sealing assembly includes an O-ring disposed on the contact surface between the piston and the housing.

[0016] In one embodiment, both the upper and lower ends of the housing are provided with threads for connection with the tubing of other downhole tools.

[0017] According to the present invention, a polymer pulse injection method is also provided, using a pulse generating device, comprising the following steps: The initial state of the pressure pulse generating device is that the first elastic element is in a relaxed state, and the piston's switching valve is in a closed state. Fluid is injected from the top of the pressure pulse generating device. As the fluid is continuously injected, the pressure in the energy storage chamber at the top of the piston continuously increases, pushing the piston downwards and compressing the first elastic element, converting the pressure potential energy in the energy storage chamber into the elastic potential energy of the first elastic element and the kinetic energy of the piston. When the piston moves downwards to a specific position, the striking pin inserts into the groove of the switching valve striking pin seat. The piston continues to move downwards, and the striking pin opens the switching valve, connecting the energy storage chamber and the discharge chamber. The pressure potential energy in the energy storage chamber is rapidly released, forming a pressure pulse. The lower the piston position, the greater the polymer flow rate. As the polymer enters the discharge chamber from the energy storage chamber and releases its pressure potential energy, the piston's kinetic energy is gradually converted into the elastic potential energy of the first elastic element, causing the piston to gradually stop moving downwards. Subsequently, the first elastic element pushes the piston upwards. When it reaches the specific position, the striking pin separates from the groove of the switching valve striking pin seat, and simultaneously, the rubber valve pad adheres to the piston, closing the piston's switching valve. Subsequently, the first elastic element pushes the piston upward at a slower speed, and the pressure in the energy storage chamber gradually increases. As fluid is injected, the pressure potential energy in the energy storage chamber increases again until the piston stops moving upward, completing one pulse cycle. By periodically repeating the above process, pressure pulse injection of polymer can be achieved.

[0018] The frequency of the pulse wave can also be adjusted by changing the polymer injection speed.

[0019] According to the present invention, another polymer pulse injection method is also provided, using a pulse generating device, comprising the following steps: connecting the bottom of the pressure pulse generating device to a water injection string, and connecting the top of the pressure pulse generating device and the bottom of the water injection string to an oil tubing; lowering the pressure pulse generating device, the water injection string, and the oil tubing together into a pre-arranged casing inside the wellbore, and fixing the oil tubing with a packer; injecting the polymer from the wellhead into the oil tubing, thereby realizing the pressure pulse injection of the polymer.

[0020] According to the present invention, another polymer pulse injection method is also provided, using a pulse generating device, comprising the following steps: connecting the bottom of the pressure pulse generating device to a water injection string, and connecting the top of the pressure pulse generating device and the bottom of the water injection string to an oil pipe; lowering the pressure pulse generating device, the water injection string, and the oil pipe together into a pre-arranged casing inside the wellbore, and fixing the oil pipe below the water injection string with a packer; injecting polymer from the wellhead into the annular space between the oil pipe and the casing, while simultaneously injecting water from the wellhead into the oil pipe, thereby achieving pressure pulse injection of polymer.

[0021] Compared with the prior art, the advantages of this application are:

[0022] This invention utilizes the interaction of a piston, valve core, and elastic element to generate pressure pulse waves as the polymer passes through the inner casing. These pressure pulse waves reduce the polymer's viscosity, thereby improving its injection capability. Simultaneously, as the polymer moves further away from the injection well, the pressure pulse wave energy rapidly attenuates, and the polymer's viscosity gradually recovers, achieving the goal of deep polymer displacement. This invention, with its advantages of convenient construction and economic reliability, has promising application prospects.

[0023] Furthermore, the valve gasket in the valve core of this invention is made of an elastic material, which, in conjunction with the central through-hole, reduces the shearing effect on the polymer during movement, and the piston movement reduces the mechanical stress on the polymer, preventing polymer breakage. By reducing polymer molecular weight loss, the invention achieves increased polymer injection capacity in low-permeability reservoirs and enables deep-drainage. Attached Figure Description

[0024] The present invention will now be described with reference to the accompanying drawings.

[0025] Figure 1 A schematic diagram of one embodiment of the pulse generating apparatus according to the present invention is shown;

[0026] Figure 2 A schematic diagram of a first embodiment of the pulse generation method according to the present invention is shown;

[0027] Figure 3 A schematic diagram of a second embodiment of the pulse generation method according to the present invention is shown.

[0028] The annotations in the attached figures are explained as follows:

[0029] 1: Outer shell; 2: Piston; 3: First elastic element; 4: First partition; 5: First through hole; 6: Impact pin; 7: Valve gasket; 8: Valve stem; 9: Second partition; 10: Needle seat; 11: Elastic centralizer; 12: Accumulator chamber; 13: Drain chamber; 14: Oil pipe; 16: Second through hole; 17: Central through hole; 18: Sleeve; 19: Packer; 20: Switch valve; 21: Water injection string; 25: O-ring seal.

[0030] In this application, all drawings are schematic and are used only to illustrate the principles of the invention, and are not drawn to scale. Detailed Implementation

[0031] The invention will now be described with reference to the accompanying drawings.

[0032] In this application, it should be noted that the direction in which the energy storage cavity is provided in the housing according to the present invention is described as "upper" or similar term, while the direction in which the drain cavity is provided in the housing is described as "lower" or similar term.

[0033] Figure 1 A schematic diagram of one embodiment of the pulse generator 100 according to the present invention is shown. Figure 1 As shown, the pulse generator 100 includes a housing 1, a piston 2, a first elastic element 3, and a switching valve 20.

[0034] In one specific embodiment, the outer casing 1 is cylindrical in shape, and threads are provided at both the upper and lower ends of the outer casing 1. In this embodiment, the pulse generator 100 is configured with threads at both the upper and lower ends of the outer casing 1 for connection with the tubing of other downhole tools. The material, inner diameter, and threads of the outer casing 1 are all manufactured strictly according to the specifications of standard tubing, conforming to the standard GB / T19830. The piston 2 is cylindrical in shape and is sealed and slidably disposed inside the outer casing 1. The piston 2 divides the inner cavity of the outer casing 1 into two parts, wherein the upper part is the energy storage chamber 12 and the lower part is the drainage chamber 13. According to the present invention, during use, fluid flows from the upper part to the lower part, and the fluid accumulates pressure in the energy storage chamber 12, pushing the piston 2 to move downward. A central through hole 17 is provided along the axial direction of the piston 2, and a switching valve 20 is movably disposed in the central through hole 17. When the piston 2 moves downward, the switching valve 20 can open, thereby allowing the fluid in the energy storage chamber 12 to flow from the central through hole 17 to the drainage chamber 13, reducing the fluid pressure in the energy storage chamber 12. A first partition 4 is fixedly installed inside the outer casing 1, located within the drain chamber 13. The first partition 4 has a first through hole 5 for fluid passage. A first elastic element 3 is installed between the first partition 4 and the piston 2 to provide the piston 2 with the power to reset. The first elastic element 3 is preferably a spring. With this arrangement, when the fluid flowing into the energy storage chamber 12 generates pressure, the fluid will push the piston 2 downwards and compress the first elastic element 3. After the piston 2 moves downwards, the valve core moves upwards relative to the piston 2, opening the central through hole 17, thus allowing fluid to flow from the energy storage chamber 12 to the drain chamber 13. The flow of fluid from the energy storage chamber 12 to the drain chamber 13 causes a sudden drop in pressure within the energy storage chamber 12. At this time, the elastic force stored in the first elastic element 3 is greater than the fluid pressure within the energy storage chamber 12, and the first elastic element 3 pushes the piston 2 upwards. During the upward reset of the piston 2, the valve core also begins to reset, closing the central through hole 17 again. Afterwards, the energy storage chamber 12 begins to accumulate fluid pressure. The above movements are then repeated to generate pulses.

[0035] In a preferred embodiment, a sealing assembly is provided between the piston 2 and the outer casing 1, preferably an O-ring 25. A groove for placing the O-ring 25 is provided on the contact surface between the piston 2 and the outer casing 1. By placing the O-ring 25 in the groove, the O-ring 25 is fixed to the piston 2, enhancing the sealing effect. The sealing assembly may also include a centering ring, which is disposed on the contact surface between the piston 2 and the outer casing 1. It is readily understood that the centering ring is a type of sealing ring and is existing technology, so it will not be described in detail here.

[0036] In one specific embodiment, the switching valve 20 includes a valve core and a striking pin 6. The valve core is slidably disposed within the central through-hole 17. When the valve core moves upward, the central through-hole 17 is opened. The striking pin 6 is fixedly disposed within the drain chamber 13 and can engage with the valve core. Preferably, it is disposed on the first partition 4 and passes through the first elastic member 3. With this arrangement, when the piston 2 moves downward, the valve core located within the central through-hole 17 can move downward along with the piston 2. After the valve core moves to engage with the striking pin 6, it continues to move downward. At this time, the striking pin 6 can hold the valve core in place, while the piston 2 continues to move downward, thereby causing the valve core to move upward relative to the piston 2, opening the central through-hole 17.

[0037] In one specific embodiment, the valve core includes a valve pad 7, a valve stem 8, and a needle seat 10. The valve pad 7 abuts against the central through hole 17 from above and downwards. The valve stem 8 is disposed at the lower part of the valve pad 7 and passes through the central through hole 17. The needle seat 10 is fixedly disposed at the lower end of the valve stem 8 for engaging with the striking pin 6. A second partition 9 is also disposed within the central through hole 17. The valve stem 8 passes through the second partition 9 and slides with it. A second through hole 16 for fluid passage is also provided on the second partition 9. An elastic stabilizer 11 is disposed between the needle seat 10 and the second partition 9. The elastic stabilizer 11 is preferably a spring and is sleeved on the valve stem 8. With this arrangement, when the valve core moves downwards along with the piston 2, the needle seat 10 engages with the striking pin 6 first, thereby causing both the valve stem 8 and the valve pad 7 to stop moving downwards. Then, piston 2 continues to move downwards, opening the central through-hole 17, allowing fluid to flow from the accumulator chamber 12 through the central through-hole 17 to the drain chamber 13. When piston 2 returns to its original position, valve pad 7, valve stem 8, and needle seat 10 also return to their original positions under the action of the elastic stabilizer 11. The elastic stabilizer 11 can be a spring.

[0038] In a preferred embodiment, the valve gasket 7 is made of an elastic material, such as rubber. This arrangement minimizes the shearing effect of the valve gasket 7 on the fluid.

[0039] In a preferred embodiment, the contact surface between the valve gasket 7 and the central through-hole 17 on the piston 2 is configured as a conical surface. Similarly, the surface at the upper end of the central through-hole 17 that mates with the valve gasket 7 is also configured as a conical surface with the same taper. This configuration further reduces the shearing effect of the valve gasket 7 on the fluid.

[0040] According to the present invention, the initial state of the pressure pulse generating device 100 is that the first elastic element 3 is in a relaxed state and the switching valve 20 of the piston 2 is in a closed state. Fluid is injected from the top of the pressure pulse generating device 100. As the fluid is continuously injected, the pressure in the energy storage chamber 12 at the top of the piston 2 continuously increases, pushing the piston 2 downwards and compressing the first elastic element 3, converting the pressure potential energy in the energy storage chamber 12 into the elastic potential energy of the first elastic element 3 and the kinetic energy of the piston 2. Subsequently, the striking pin 6 is inserted into the groove of the needle seat 10 of the switching valve 20, and the piston 2 continues to move downwards. The striking pin 6 pushes open the valve pad 7 of the switching valve 20, connecting the energy storage chamber 12 with the discharge chamber 13. The pressure potential energy in the energy storage chamber 12 is rapidly released, forming a pressure pulse. The lower the position of the piston 2, the greater the polymer flow rate. As the polymer enters the discharge chamber 13 from the energy storage chamber 12 and releases its pressure potential energy, the kinetic energy of the piston 2 is gradually converted into the elastic potential energy of the first elastic element 3, causing the piston 2 to gradually stop moving downwards. Subsequently, the first elastic element 3 pushes the piston 2 upward, causing the striking pin 6 to separate from the groove of the needle seat 10 of the switching valve 20. Simultaneously, the valve pad 7 engages with the piston 2, closing the switching valve 20. The upward movement of the piston 2, driven by the first elastic element 3, then begins to slow down, and the pressure within the energy storage chamber 12 gradually increases. As fluid is injected, the pressure potential energy within the energy storage chamber 12 increases again until the piston 2 stops moving upward, completing one pulse cycle. By periodically repeating the above process, pressure pulse injection of fluid can be achieved.

[0041] The frequency of the pulse wave can also be adjusted by changing the fluid injection rate.

[0042] Figure 2 A polymer pulse injection method according to the present invention is shown, using the pulse generator 100 of the present invention, which is installed between oil pipes 14. Figure 2 As shown, according to the present invention, in combination Figure 1 The pulse generator 100 is positioned with the energy storage chamber 12 facing upwards. Its upper end is threaded to the tubing 14, and its lower end is threaded to the water injection string 21, the lower end of which is connected to the tubing 14. The pulse generator 100 is then lowered into the casing 18 along with the tubing 14. Next, a packer 19 is used to secure the tubing 14 to the inner wall of the casing 18. Polymer is then injected into the tubing 14 from the tubing inlet 22 at the wellhead at a constant speed. The pulse generator 100 generates pressure pulse waves, which then pass through the injector and nozzle on the water injection string 21 into the annular space between the tubing 14 and the casing 18. Finally, the polymer enters the formation through the water injection section on the casing 18, thus achieving pressure pulsed injection of the polymer.

[0043] Figure 3 Another polymer pulse injection method according to the present invention is shown. Casing 18 is a device used in existing waterflooding oil recovery technology. Figure 3 As shown, according to the present invention, the pulse generator 100 is positioned with the energy storage chamber 12 facing upwards, its upper end connected to the tubing 14 via a thread, and its lower end connected to the water injection string 21 via a thread. The lower end of the water injection string 21 is connected to the tubing 14. The pulse generator 100 is then inserted into the casing 18 along with the tubing 14. Afterwards, a packer 19 is used to seal and fix the tubing 14 below the pulse generator 100, and the annular space between the casing 18 and the tubing 14 above the packer 19 is completely filled with water, allowing the gas inside to escape from the wellhead. Polymer mother liquor is injected into the annular space from the casing inlet 23 at the wellhead of the polymer injection well at a constant rate. Simultaneously, water is injected into the tubing 14 from the tubing inlet 22 at the wellhead of the polymer injection well at a corresponding rate. This causes the water to pass through the pulse generator 100 to generate pressure pulse waves, which then enter the annular space through the injector and nozzle on the water injection string 21. This dilutes the polymer mother liquor injected from the casing inlet 23 to form a polymer solution, which is then injected into the formation through the water injection section on the casing 18. This achieves pressure pulsed injection of the polymer. The injection rate of the polymer mother liquor and the water injection rate can be adjusted in different ratios according to the usage requirements to prepare the polymer solution.

[0044] As is easy to understand, casing 18, tubing 14, packer 19, water injection string 21, and the injector and nozzle included in water injection string 21 are all commonly used equipment in water-driven oil production in the existing technology, and will not be described in detail here.

[0045] This invention utilizes the interaction of piston 2, valve core, and elastic element to generate pressure pulse waves as the polymer passes through the outer shell. These pressure pulse waves reduce the polymer's viscosity, thereby improving its injection capacity. Simultaneously, as the polymer moves away from the injection wellhead, the pressure pulse wave energy rapidly attenuates, and the polymer's viscosity gradually recovers, thus achieving the purpose of polymer depth regulation. This invention, with its advantages of convenient construction and economic reliability, has promising application prospects.

[0046] Furthermore, the valve pad 7 in the valve core of this invention is made of an elastic material and is fitted with a tapered central through-hole 17. By setting the valve pad 7 into a tapered shape that mates with the central through-hole 17, the shearing effect on the polymer can be reduced during movement, and the piston movement can reduce the mechanical stress on the polymer, preventing polymer breakage. By reducing polymer molecular weight loss, the goal of increasing the injection capacity of polymers in low-permeability reservoirs and enabling deep-drainage is achieved.

[0047] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0048] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0050] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pulse generating device for pulsed injection of polymer, comprising: Outer shell (1); A piston (2) disposed inside the outer casing (1) divides the inner cavity of the outer casing (1) into an upper energy storage chamber (12) and a lower liquid discharge chamber (13). The piston (2) includes a central through hole (17). The first elastic element (3) is disposed in the drainage chamber (13); And a switching valve (20) disposed on the piston (2), the switching valve (20) including a valve core and a striker (6), the valve core being movable within the central through hole (17) to selectively open or close the central through hole (17); the striker (6) being disposed within the drain chamber (13) and being able to engage with the valve core to push the valve core to open the central through hole (17); The piston (2) is configured to move downward in response to the pressure of the upper fluid, thereby compressing the first elastic element (3). The switching valve (20) is configured to open by the engagement of the striker (6) with the valve core after the piston (2) moves downward, thereby allowing fluid to flow from the accumulator chamber (12) to the drain chamber (13), and to close after the piston (2) returns to its original position. The first elastic element (3) is configured to push the piston (2) upward after the fluid flows from the energy storage chamber (12) to the discharge chamber (13), overcoming the reduced pressure of the upper fluid, thereby forming a pulse motion of fluid injection.

2. The pulse generating device according to claim 1, characterized in that, The drain chamber (13) is provided with a first partition (4), and the first partition (4) is provided with a first through hole (5) that allows fluid to pass through. The first elastic element (3) is provided between the first partition (4) and the piston (2).

3. The pulse generating device according to claim 2, characterized in that, The valve core includes: Valve gasket (7) abutting against the central through hole (17); The valve stem (8) is disposed on the lower end face of the valve pad (7); A needle seat (10) is provided at the lower end of the valve stem (8), and the needle seat (10) is used to abut against the firing pin (6); The central through hole (17) is provided with a second partition (9), the valve stem (8) is slidably inserted on the second partition (9), an elastic stabilizer (11) is provided between the second partition (9) and the needle seat (10), the elastic stabilizer (11) is sleeved on the valve stem (8), and the second partition (9) is provided with a second through hole (16) that allows fluid to pass through.

4. The pulse generating device according to claim 3, characterized in that, The valve pad (7) is made of elastic material, and the side of the valve pad (7) that abuts against the central through hole (17) is set as a conical surface.

5. The pulse generating device according to claim 4, characterized in that, A sealing assembly is provided between the piston (2) and the outer shell (1). The sealing assembly includes an O-ring (25) and the O-ring (25) is disposed on the contact surface between the piston (2) and the outer shell (1).

6. The pulse generating device according to claim 5, characterized in that, Both ends of the outer casing (1) are provided with threads, which are used to connect with the tubing of other downhole tools.

7. A polymer pulse injection method, characterized in that, Using the pulse generator according to any one of claims 1 to 6 includes the following steps: The initial state of the pulse generator (100) is that the first elastic element (3) is in a relaxed state and the switching valve (20) of the piston (2) is in a closed state. Fluid is injected from the top of the pulse generator (100). As the fluid is continuously injected, the pressure in the energy storage chamber at the top of the piston (2) increases continuously, pushing the piston (2) downward and compressing the first elastic element (3) at the same time, converting the pressure potential in the energy storage chamber into the elastic potential energy of the first elastic element (3) and the kinetic energy of the piston (2). When the piston (2) moves downward to a specific position, the striking pin is inserted into the striking pin seat groove of the switching valve (20). The piston (2) continues to move downward, and the striking pin pushes open the switching valve (20), so that the energy storage chamber is connected to the discharge chamber. The pressure potential energy in the energy storage chamber is quickly released to form a pressure pulse. The lower the position of the piston (2), the better. The greater the flow rate of the polymer, the more the kinetic energy of the piston (2) is gradually converted into the elastic potential energy of the first elastic element (3) as the polymer releases pressure potential energy from the storage chamber into the discharge chamber, causing the piston (2) to gradually stop moving downwards. Subsequently, the first elastic element (3) pushes the piston (2) upwards. When it reaches the specific position, the striker separates from the striker seat groove of the switch valve (20), and at the same time, the rubber valve pad adheres to the piston (2), closing the switch valve (20) of the piston (2). Subsequently, the speed at which the first elastic element (3) pushes the piston (2) upwards begins to slow down, and the pressure in the storage chamber begins to gradually increase. As fluid is injected, the pressure potential energy in the storage chamber increases again until the piston (2) stops moving upwards, completing one pulse cycle. By periodically repeating the above process, the pressure pulse injection of the polymer can be achieved. The frequency of the pulse wave can also be adjusted by changing the polymer injection speed.

8. A polymer pulse injection method, characterized in that, Using the pulse generator according to any one of claims 1 to 6 includes the following steps: Connect the bottom of the pulse generator to the water injection pipe, and connect the top of the pulse generator and the bottom of the water injection pipe to the oil pipe. The pulse generator, water injection string, and tubing are lowered together into the pre-arranged casing inside the wellbore, and the tubing is secured using a packer. By injecting the polymer into the tubing from the wellhead, pressure pulse injection of the polymer can be achieved.

9. A polymer pulse injection method, characterized in that, Using the pulse generator according to any one of claims 1 to 6 includes the following steps: Connect the bottom of the pulse generator to the water injection pipe, and connect the top of the pulse generator and the bottom of the water injection pipe to the oil pipe. The pulse generator, water injection string, and tubing are lowered together into the casing that has been pre-arranged inside the wellbore, and the tubing below the water injection string is fixed with a packer. By injecting polymer into the annular space between the tubing and casing from the wellhead, and simultaneously injecting water into the tubing from the wellhead, pressure pulse injection of polymer can be achieved.

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