Supercritical carbon dioxide cooling fluctuation pressurization fracturing device and method

Abstract

The application discloses a supercritical carbon dioxide cooling fluctuation pressurization fracturing device and method, and relates to the field of fracturing devices.The fracturing device comprises a pipe body, a thickened sleeve arranged outside the pipe body, a correction sieve bowl arranged in the pipe body from top to bottom, a cooling leakage bucket and a disturber.The top end of the pipe body is connected with a fracturing oil pipe.The top end of the correction sieve bowl is open, and the bottom end is connected with the cooling leakage bucket.A mesh hole is arranged on the side wall of the correction sieve bowl.The continuous oil pipe is connected with the cooling leakage bucket.The disturber is arranged in the middle part of the pipe body and comprises two magnetic block fixing rings and a rotating impeller.A plurality of strong magnetic blocks are arranged on the magnetic block fixing ring.The rotating impeller is arranged in a containing space formed by the two magnetic block fixing rings and the inner wall of the pipe body.An eccentric magnetic block for driving the eccentric movement of the rotating impeller is arranged on the roller of the rotating impeller.Lateral injection holes and pressure relief injection holes are arranged at the bottom of the pipe body.The application combines the impact force of the fracturing device and the impact force of the fluid, and uses liquid nitrogen to cool and fracture the reservoir while burying CO2, so that the problem of difficult fracturing construction of deep reservoirs is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of deep oil and gas reservoir stimulation technology, specifically to a supercritical carbon dioxide cooling fluctuation pressurization fracturing device and method. Background Technology

[0002] With the continuous increase in global energy demand, the focus of oil and gas exploration and development has inevitably shifted from shallow to deep reservoirs. However, as oil and gas resources become deeper, the development environment is increasingly characterized by high temperature, high pressure, and high stress, making development more difficult. Therefore, effective methods are needed to modify oil and gas reservoirs to achieve ideal production levels and improve the economic efficiency of oilfield development.

[0003] Reservoir fracturing, a commonly used reservoir stimulation technique in oil and gas fields, involves injecting water or gas into the reservoir to fracture the rock mass, creating a complex network of highly permeable fractures that facilitates the flow of oil and gas from the reservoir to the wellbore. During injection, the flow of fluid or gas within the fractures promotes fracture propagation and extension, increasing the porosity and permeability of the reservoir rock, thereby improving oil and gas production. However, traditional large-scale hydraulic fracturing suffers from problems such as water consumption, environmental pollution, and formation damage, increasing the risks of reservoir stimulation and drawing increasing criticism in recent years. To address the issues associated with traditional large-scale hydraulic fracturing, waterless fracturing methods such as carbon dioxide fracturing have been proposed.

[0004] However, due to the influence of high temperature, high pressure and high stress environment, fracturing construction in deep reservoirs often brings more technical problems and challenges. Because rocks exhibit different mechanical properties under high temperature, high pressure and high stress environment, the mechanical behavior of rocks changes significantly, which seriously affects the fracturing construction of deep reservoirs.

[0005] Therefore, there is an urgent need to propose a supercritical carbon dioxide cooling fluctuation pressurization fracturing device and method to solve the problem of difficult fracturing operations using waterless fracturing methods under high temperature, high pressure, and high stress environments in deep reservoirs, and to improve the development efficiency of deep oil and gas resources. Summary of the Invention

[0006] This invention aims to solve the above-mentioned problems and provides a supercritical carbon dioxide cooling fluctuation pressurization fracturing device and method, which solves the problem of difficult fracturing construction in deep high-temperature environments. By providing impact stress and liquid impact stress to the formation to be fractured to form a fracture network, the cost of reservoir stimulation is reduced, laying the foundation for the safe and efficient development of deep oil and gas resources.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A supercritical carbon dioxide cooling fluctuation pressurization fracturing device includes a tube body and a correction sieve, a cooling leak tank and a disturbance arranged sequentially from top to bottom inside the tube body.

[0009] The top of the pipe is open and the bottom is closed. The top of the inner wall of the pipe is provided with a connecting thread for connecting to the fracturing tubing. The outer wall of the pipe is fitted with a thickened sleeve.

[0010] The corrective sieve bowl is fixed below the connecting thread and located at the top of the tube. The corrective sieve bowl has an inverted conical structure with an open top and the bottom end is connected to the cooling sieve barrel. Multiple mesh holes are provided on the side wall.

[0011] The cooling leak barrel is drumstick shaped. The top of the cooling leak barrel is provided with an internal pipe thread for connecting a continuous oil pipe. The bottom is closed. The top is connected to the correction sieve bowl to form a flow channel. Multiple leak holes are provided on the side wall.

[0012] The disturbance is located below the cooling barrel, in the middle of the tube body, and includes a first magnetic block fixing ring, a second magnetic block fixing ring, and a rotating impeller. A pair of limiting grooves are symmetrically arranged on the inner wall of the tube body. The first magnetic block fixing ring and the second magnetic block fixing ring are fixed in the limiting grooves. Multiple strong magnetic blocks are fixed on both the first magnetic block fixing ring and the second magnetic block fixing ring. The first magnetic block fixing ring, the second magnetic block fixing ring, and the inner wall of the tube body together form an accommodating space, and the rotating impeller is arranged in the accommodating space.

[0013] The rotating impeller is provided with a roller and a plurality of blades evenly arranged along the circumference of the roller. A pair of eccentric magnetic blocks with opposite magnetic properties are staggered on the roller on both sides of the blade. The two ends of the roller are placed in the limiting groove. One end of the blade is fixedly connected to the roller, and the other end extends out from the accommodating space.

[0014] The bottom of the disturbance device has multiple lateral spray holes on the side wall of the tube body, and multiple pressure relief spray holes on the bottom surface of the tube body. Both the lateral spray holes and the pressure relief spray holes are used to connect the inside of the tube body with the well to be fractured.

[0015] Preferably, a first strong magnetic block, a second strong magnetic block, a third strong magnetic block, and a fourth strong magnetic block are equally spaced on the top surface of the first magnetic block fixing ring and the bottom surface of the second magnetic block fixing ring. The first strong magnetic block and the third strong magnetic block are symmetrically arranged and have the same magnetism, the second strong magnetic block and the fourth strong magnetic block are symmetrically arranged and have the same magnetism, and the first strong magnetic block and the second strong magnetic block have opposite magnetism.

[0016] Preferably, the mesh openings are arranged in an array on the sidewall of the correcting screen.

[0017] Preferably, the eccentric magnetic block is configured as a fan-shaped structure, and the central angle of the fan-shaped structure is fixed on the roller of the rotating impeller.

[0018] Preferably, the angle between the blade axis and the roller axis in the rotating impeller is set to 15°.

[0019] Preferably, both the lateral spray orifice and the pressure relief spray orifice are configured as conical spray orifices, with the inner diameter of the conical spray orifice gradually decreasing from the top to the bottom, and the diameter of the pressure relief spray orifice being larger than the diameter of the lateral spray orifice.

[0020] A supercritical carbon dioxide cooling and fluctuating pressurization fracturing method, employing the supercritical carbon dioxide cooling and fluctuating pressurization fracturing device described above, specifically includes the following steps:

[0021] Step 1: Connect the pipe body of the supercritical carbon dioxide cooling and pressure boosting fracturing device to the fracturing tubing via connecting threads. Then, based on the fracturing design scheme of the well to be fracturing, determine the fracturing zone, the formation pressure of the fracturing zone, and the pre-fracturing fluid injection volume. After lowering the pipe body to the fracturing zone from the wellhead of the well to be fracturing, lower the coiled tubing from the fracturing tubing to the fracturing zone and connect it to the cooling leak bucket via the internal pipe thread to complete the installation of the supercritical carbon dioxide cooling and pressure boosting fracturing device.

[0022] The fracturing tubing is equipped with a fracturing tubing injection pump and a fracturing tubing pressure gauge, and the coiled tubing is equipped with a coiled tubing injection pump and a coiled tubing pressure gauge. The fracturing tubing injection pump, the fracturing tubing pressure gauge, the coiled tubing injection pump, and the coiled tubing pressure gauge are all located on the ground surface and close to the wellhead of the well to be fractured.

[0023] Step 2: Start the fracturing tubing injection pump and inject the pre-flush fluid into the supercritical carbon dioxide cooling and pressure boosting fracturing device through the fracturing tubing according to the preset pre-flush injection volume. At the same time, start the coiled tubing injection pump and inject air into the supercritical carbon dioxide cooling and pressure boosting fracturing device through the coiled tubing. Observe the readings of the fracturing tubing pressure gauge and the coiled tubing pressure gauge in real time, and control the pumping pressure of the fracturing tubing injection pump and the coiled tubing injection pump to make the injection pressure of the pre-flush fluid and air the same.

[0024] Step 3: After the pre-flush fluid injection is completed, the fracturing operation begins. Supercritical carbon dioxide fracturing fluid is injected into the pipe of the supercritical carbon dioxide cooling and undulating pressure boosting fracturing device through the fracturing tubing. At the same time, liquid nitrogen is injected into the pipe of the supercritical carbon dioxide cooling and undulating pressure boosting fracturing device through the coiled tubing. The readings of the fracturing tubing pressure gauge and the coiled tubing pressure gauge are monitored in real time, and the pumping pressure of the fracturing tubing injection pump and the coiled tubing injection pump are controlled to ensure that the injection pressure of the supercritical carbon dioxide fracturing fluid and the liquid nitrogen are the same.

[0025] Supercritical carbon dioxide fracturing fluid flows through the fracturing tubing into the correction sieve bowl of the supercritical carbon dioxide cooling and pressure boosting fracturing device. It then flows into the pipe body through the mesh holes set on the side wall of the correction sieve bowl. Liquid nitrogen flows through the continuous tubing into the cooling leak tank of the supercritical carbon dioxide cooling and pressure boosting fracturing device and then flows into the pipe body through the leak holes set on the cooling leak tank. Liquid nitrogen is used to lower the temperature of the supercritical carbon dioxide fracturing fluid. Liquid nitrogen and supercritical carbon dioxide fracturing fluid are mixed to form a fracturing mixture.

[0026] Step 4: The fracturing mixture flows downwards within the pipe, impacting the disruptor and converting the hydrodynamic force of the fracturing mixture into the rotational force of the rotating impeller. This causes the rotating impeller of the disruptor to rotate in a circular motion under the impact of the fracturing mixture. Simultaneously, the eccentric magnetic block on the rotating impeller roller is attracted and repelled by the strong magnetic blocks on the first and second magnetic block fixing rings, causing the roller to move eccentrically within the accommodating space. The disruptor drives the supercritical carbon dioxide cooling and pressure boosting fracturing device to impact the well wall. At the same time as the supercritical carbon dioxide cooling and pressure boosting fracturing device impacts the well wall, the fracturing mixture is ejected from the pipe of the supercritical carbon dioxide cooling and pressure boosting fracturing device through the lateral nozzles and pressure relief nozzles, impacting the formation and fracturing it.

[0027] Step 5: Under the dual action of the hydraulic stress of the fracturing mixture and the impact stress of the supercritical carbon dioxide cooling and pressure boosting fracturing device, the rock at the fracturing site fractures to form a fracture network, the reservoir fracturing operation is completed, the fracturing tubing injection pump and the coiled tubing injection pump are shut down, the formation pressure at the fracturing site decreases, causing the liquid nitrogen in the fracturing mixture to decompose into nitrogen gas, which is used to replenish the formation pressure.

[0028] Preferably, in step 2, during the pre-flush injection process, the fracturing tubing injection pump is adjusted in real time according to the reading of the fracturing tubing pressure gauge, so that the reading of the fracturing tubing pressure gauge is always less than the formation pressure at the fracturing site.

[0029] The beneficial technical effects brought about by this invention are as follows:

[0030] 1. This invention proposes a supercritical carbon dioxide cooling and pressure-boosting fracturing device and method. It employs a continuous tubing system within the fracturing tubing to separate supercritical carbon dioxide fracturing fluid from liquid nitrogen. The internal structure is compact. During injection, liquid nitrogen is used to cool the supercritical carbon dioxide fracturing fluid. After being injected into the tubing of the supercritical carbon dioxide cooling and pressure-boosting fracturing device, the fluid mixes with the fluid flowing from the mesh of the correction sieve and the leaks of the cooling funnel to form a fracturing mixture. This fracturing mixture impacts the rotating impeller of the disturbance device, causing it to rotate. Combined with the magnetic force of a strong magnetic block on the eccentric magnetic block on the impeller's roller, the supercritical carbon dioxide cooling and pressure-boosting fracturing device oscillates and impacts the reservoir within the well to be fractured. Simultaneously, the fracturing mixture within the device is ejected through lateral and pressure-relief nozzles, impacting the reservoir. The combined effect of the fluid impact and the swaying impact of the disturbance device disrupts the stress environment of the reservoir rock, forming a fracture network and thus achieving reservoir modification.

[0031] 2. When the supercritical carbon dioxide cooling and pressure-boosting fracturing device proposed in this invention is applied to fracturing operations, it uses liquid nitrogen injected through a separate cooling injection method to reduce the temperature of the supercritical carbon dioxide fracturing fluid and reservoir rock. Combined with the impact of the supercritical carbon dioxide cooling and pressure-boosting fracturing device and the injection of low-temperature high-pressure jets, it reduces the rock fracturing initiation pressure while realizing fracturing operations on the reservoir. This enhances the expandability of the fracture network formed by fracturing operations and significantly improves the fracturing effect.

[0032] 3. The supercritical carbon dioxide cooling fluctuation pressure boosting fracturing method proposed in this invention utilizes supercritical carbon dioxide to perform fracturing operations on reservoirs. It not only uses supercritical carbon dioxide to create impact fractures in the reservoir rocks and replenish formation pressure after fracturing operations, but also achieves carbon dioxide sequestration by injecting supercritical carbon dioxide into the reservoir, thus realizing the efficient utilization of energy. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a supercritical carbon dioxide cooling fluctuation pressurization fracturing device according to the present invention.

[0034] Figure 2 This is a front view of the disturbance device of the present invention.

[0035] Figure 3 This is a top view of the disturbance device of the present invention.

[0036] In the diagram, 1. Pipe body, 2. Correcting sieve bowl, 3. Cooling leaking barrel, 4. Disturber, 5. Thickened sleeve, 6. Mesh, 7. Leakage hole, 8. Strong magnetic block, 9. Rotating impeller, 10. Roller, 11. Blade, 12. Eccentric magnetic block, 13. Side spray hole, 14. Pressure relief spray hole, 15. Limiting groove. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0038] Example 1

[0039] This invention proposes a supercritical carbon dioxide cooling fluctuation pressurization fracturing device, such as... Figure 1 As shown, it includes a tube body 1 and, from top to bottom, a correction sieve bowl 2, a cooling sieve barrel 3, and a disturbance device 4 arranged inside the tube body 1.

[0040] The top of the pipe body 1 is open and the bottom is closed. The top of the inner wall of the pipe body is provided with connecting threads for connecting to the fracturing tubing.

[0041] The corrective sieve bowl 2 is fixed below the connecting thread and located at the top of the pipe body. The corrective sieve bowl has an inverted conical structure with an open top and its bottom end is connected to the cooling leak 3. Multiple mesh holes 6 arranged in an array are provided on the side wall so that the fluid injected into the corrective sieve bowl by the fracturing oil pipe flows into the pipe body.

[0042] The cooling leak barrel 3 has a drumstick-shaped barrel body. The top of the cooling leak barrel is provided with an internal pipe thread for connecting the continuous oil pipe directly to the cooling leak barrel, so that the fluid in the continuous oil pipe is directly injected into the cooling leak barrel. The bottom of the cooling leak barrel is closed, and the top is fixed on the correction sieve bowl and connected to the bottom of the correction sieve bowl to form a flow channel. Multiple leak holes 7 are provided on the side wall of the cooling leak barrel body for connecting the inside of the cooling leak barrel with the inside of the pipe body, so that the fluid in the continuous oil pipe flows into the pipe body through the leak holes.

[0043] The disturbance 4 is located below the cooling leak tank, in the middle of the pipe body, such as... Figure 2 and Figure 3 As shown, it includes a first magnetic block fixing ring, a second magnetic block fixing ring, and a rotating impeller 9; a pair of limiting grooves 15 are symmetrically arranged on the inner wall of the tube, the first magnetic block fixing ring and the second magnetic block fixing ring are fixed on the limiting grooves 15, the first magnetic block fixing ring, the second magnetic block fixing ring and the inner wall of the tube together form an accommodating space, and the rotating impeller 9 is arranged in the accommodating space.

[0044] In this embodiment, four strong magnetic blocks 8 are equally spaced on the top surface of the first magnetic block fixing ring and the bottom surface of the second magnetic block fixing ring. These are the first strong magnetic block, the second strong magnetic block, the third strong magnetic block, and the fourth strong magnetic block. The first and third strong magnetic blocks are symmetrically arranged and both have N poles. The second and fourth strong magnetic blocks are symmetrically arranged and have the same magnetism, both having S poles.

[0045] The rotating impeller 9 is provided with a roller 10 and a plurality of blades 11 evenly arranged along the circumference of the roller. The blades are at a certain angle to the roller support. In this embodiment, the angle between the blade axis and the roller axis is 15°. When the fluid in the tube flows downward, it impacts the blades of the rotating impeller, causing the blades to drive the rotating impeller to rotate in a circular motion. A pair of eccentric magnetic blocks 12 with opposite magnetic properties are staggered on the rollers on both sides of the blades. The eccentric magnetic blocks are configured as a fan-shaped structure. The central angle of the fan-shaped structure is fixed on the roller of the rotating impeller. Under the magnetic force of the strong magnetic blocks, the roller drives the disturbance to make eccentric motion in the accommodating space, so that the tube swings and impacts the well wall of the fracturing well under the action of eccentric force.

[0046] Both ends of the roller are placed in the limiting groove. The limiting groove is used to limit the position of the rotating impeller roller, ensuring that the movement of the roller is always limited within the limiting groove when the rotating impeller is impacted by the fluid in the pipe and attracted and repelled by the strong magnetic block. One end of the blade of the rotating impeller is fixedly connected to the roller, and the other end extends out from the accommodating space.

[0047] The bottom of the pipe is fitted with a thickened sleeve 5. The thickened sleeve is used to protect the pipe and prevent damage to the pipe when the supercritical carbon dioxide cooling fluctuation pressure boosting fracturing device hits the well wall. It is also used to increase the stress when the supercritical carbon dioxide cooling fluctuation pressure boosting fracturing device hits the formation.

[0048] In this embodiment, a plurality of lateral spray holes 13 are provided on the thickened sleeve at the bottom of the disturbance device, and four pressure relief spray holes 14 are arranged in an array on the bottom surface of the pipe body. The diameter of the pressure relief spray holes is larger than the diameter of the lateral spray holes, connecting the inside of the pipe body with the outside of the pipe body. This is used to spray the fluid inside the pipe body to the reservoir of the fracturing layer. The hydraulic pressure of the fluid flowing out of the pipe body impacts the rock surface, and in conjunction with the impact of the pipe body on the rock of the fracturing layer, a fracture network is generated in the rock of the fracturing layer.

[0049] In order to obtain greater fluid impact force during fracturing, both the lateral nozzles and the pressure relief nozzles in this embodiment are set as conical nozzles, and the inner diameter of the conical nozzles gradually decreases from the top to the bottom. This is used to provide greater impact force for the fracturing operation of the reservoir, form a fracture network in the rock, and improve the quality of the fracturing operation.

[0050] Example 2

[0051] This invention proposes a supercritical carbon dioxide cooling and fluctuating pressure fracturing method, employing the supercritical carbon dioxide cooling and fluctuating pressure fracturing device described in Example 1, specifically including the following steps:

[0052] Step 1: Connect the supercritical carbon dioxide cooling and pressure-boosting fracturing device to the fracturing tubing via connecting threads. Then, based on the fracturing design scheme of the well to be fractured, determine the fracturing zone, the formation pressure at the fracturing zone, and the pre-fracturing fluid injection volume. After lowering the supercritical carbon dioxide cooling and pressure-boosting fracturing device from the wellhead to the fracturing zone, lower the coiled tubing from the fracturing tubing to the fracturing zone and connect it to the cooling leak bucket via the internal tubing thread to complete the installation of the supercritical carbon dioxide cooling and pressure-boosting fracturing device.

[0053] The fracturing tubing is equipped with a fracturing tubing injection pump and a fracturing tubing pressure gauge, and the coiled tubing is equipped with a coiled tubing injection pump and a coiled tubing pressure gauge. The fracturing tubing injection pump, fracturing tubing pressure gauge, coiled tubing injection pump, and coiled tubing pressure gauge are all located on the surface, close to the wellhead of the well to be fractured. The fracturing tubing pressure gauge and the coiled tubing pressure gauge are used to monitor the internal pressure of the supercritical carbon dioxide cooling fluctuation pressurization fracturing device to ensure the pressure balance inside the supercritical carbon dioxide cooling fluctuation pressurization fracturing device.

[0054] Step 2: Start the fracturing tubing injection pump and inject the pre-flush fluid into the supercritical carbon dioxide cooling and pressurizing fracturing device through the fracturing tubing according to the preset injection volume. Observe the reading of the fracturing tubing pressure gauge, ensuring that the reading of the fracturing tubing pressure gauge is always lower than the formation pressure at the fracturing site. At the same time, start the coiled tubing injection pump and inject air into the supercritical carbon dioxide cooling and pressurizing fracturing device through the coiled tubing. Observe the readings of the fracturing tubing pressure gauge and the coiled tubing pressure gauge in real time, and control the pumping pressure of the fracturing tubing injection pump and the coiled tubing injection pump to ensure that the injection pressure of the pre-flush fluid and the air are the same. The air injection not only ensures the stability of the formation pressure at the fracturing site, but also discharges the fluid in the correction sieve and cooling leak tank.

[0055] Step 3: After the pre-flush fluid injection is completed, the fracturing operation begins. Supercritical carbon dioxide fracturing fluid is injected into the supercritical carbon dioxide cooling and pressurizing fracturing device through the fracturing tubing. Simultaneously, liquid nitrogen is injected into the supercritical carbon dioxide cooling and pressurizing fracturing device through the coiled tubing. The readings of the fracturing tubing pressure gauge and the coiled tubing pressure gauge are monitored in real time, and the pumping pressures of the fracturing tubing injection pump and the coiled tubing injection pump are controlled to ensure that the injection pressures of the supercritical carbon dioxide fracturing fluid and liquid nitrogen are the same. This prevents the supercritical carbon dioxide fracturing fluid from flowing back from the mesh into the cooling leak tank due to excessive injection pressure during the injection process, which could cause blockage of the coiled tubing.

[0056] Supercritical carbon dioxide fracturing fluid flows through the fracturing tubing into the correction sieve bowl of the supercritical carbon dioxide cooling and pressure boosting fracturing device. It then flows into the pipe body through the mesh holes on the side wall of the correction sieve bowl. Liquid nitrogen flows through the coiled tubing into the cooling leak tank of the supercritical carbon dioxide cooling and pressure boosting fracturing device, and then flows into the pipe body through the leak holes on the cooling leak tank. This lowers the temperature of the supercritical carbon dioxide fracturing fluid and mixes with it to form a fracturing mixture. At this time, due to the injection of supercritical carbon dioxide fracturing fluid and liquid nitrogen, the inside of the pipe body of the supercritical carbon dioxide cooling and pressure boosting fracturing device is under high pressure. The temperature and pressure inside the pipe body keep the injected liquid nitrogen in a critical equilibrium state and maintain its liquid state.

[0057] Step 4: The fracturing mixture flows downwards within the pipe, impacting the agitator and driving the blades of the rotating impeller to rotate its rollers. This converts the hydrodynamic force of the fracturing mixture into the rotational force of the impeller, causing the impeller to rotate in a circular motion under the impact of the fracturing mixture. Simultaneously, the eccentric magnetic block on the impeller roller is attracted and repelled by the strong magnetic blocks on the first and second magnetic block fixing rings, causing the impeller roller to move eccentrically within the accommodating space. Under the influence of the impact force and strong magnetic force, the impeller swings within the accommodating space. The movement drives the supercritical carbon dioxide cooling and pressure boosting fracturing device to impact the well wall. Simultaneously, the fracturing mixture is ejected from the pipe of the supercritical carbon dioxide cooling and pressure boosting fracturing device through lateral nozzles and pressure relief nozzles, impacting the formation to fracture it. The lateral nozzles and pressure relief nozzles eject the fracturing mixture inside the pipe, transferring the high pressure of the fracturing mixture to the formation. This not only unloads the internal pressure of the pipe but also uses the liquid impact of the fracturing mixture to provide stress to break the rock and create fractures, achieving the effect of pressurized fracturing of the formation.

[0058] Step 5: Under the dual action of the hydraulic stress of the fracturing mixture and the impact stress of the supercritical carbon dioxide cooling and pressure boosting fracturing device, the stress balance condition of the rock at the reservoir pressure layer is disrupted, causing the reservoir rock at the fracturing layer to fracture and form a fracture network, thus completing the fracturing operation. The fracturing tubing injection pump and the coiled tubing injection pump are then shut down. The formation pressure at the fracturing layer decreases, breaking the critical equilibrium state of liquid nitrogen in the fracturing mixture. The liquid nitrogen is converted from liquid to gaseous nitrogen and injected into the formation through the fracture network generated by fracturing, replenishing the formation pressure and ensuring the stability of the formation pressure after the fracturing operation. This is beneficial to improving the reservoir production in the subsequent production stage.

[0059] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," "link," and "fix" 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 communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0060] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A supercritical carbon dioxide chill down surge boost fracturing apparatus, characterized by, The pipe body and a correction sieve bowl, a cooling leakage bucket and a disturber arranged in sequence from top to bottom inside the pipe body; The pipe body is open at the top end and closed at the bottom end, a connecting thread for connecting a fracturing oil pipe is arranged on the inner wall of the pipe body, and a thickened sleeve is arranged on the outer wall of the pipe body; The correction sieve bowl is fixed below the connecting thread and located at the top of the pipe body, the correction sieve bowl is a reverse conical structure with an open top end, the bottom end is communicated with the cooling leakage bucket, and a plurality of mesh holes are arranged on the side wall; The barrel of the cooling leakage bucket is in the shape of a mallet, an inner pipe thread for connecting a coiled tubing is arranged on the top end of the cooling leakage bucket, the bottom end is closed, the top end is communicated with the correction sieve bowl to form a flow passage, and a plurality of leakage holes are arranged on the side wall; The disturber is arranged below the cooling leakage bucket and located at the middle of the pipe body, and comprises a first magnetic block fixing ring, a second magnetic block fixing ring and a rotating impeller; a pair of limiting grooves are symmetrically arranged on the inner wall of the pipe body, the first magnetic block fixing ring and the second magnetic block fixing ring are fixed on the limiting grooves, a plurality of strong magnetic blocks are fixed on the first magnetic block fixing ring and the second magnetic block fixing ring, the first magnetic block fixing ring, the second magnetic block fixing ring and the inner wall of the pipe body jointly form a containing space, and the rotating impeller is arranged in the containing space; The rotating impeller is provided with a roller and a plurality of blades arranged uniformly in the circumferential direction of the roller, a pair of eccentric magnetic blocks with opposite magnetic properties are arranged in opposite directions on the roller at both sides of the blades, both ends of the roller are arranged in the limiting grooves, one end of the blade is fixedly connected with the roller, and the other end extends out of the containing space; A plurality of lateral injection holes are arranged on the side wall of the pipe body at the bottom of the disturber, and a plurality of pressure relief injection holes are arranged on the bottom surface of the pipe body, the lateral injection holes and the pressure relief injection holes are used to communicate the inside of the pipe body with a well to be fractured; First, second, third and fourth strong magnetic blocks are equally and spacedly arranged on the top surface of the first magnetic block fixing ring and the bottom surface of the second magnetic block fixing ring, wherein the first and third strong magnetic blocks are symmetrically arranged and have the same magnetic property, the second and fourth strong magnetic blocks are symmetrically arranged and have the same magnetic property, and the first and second strong magnetic blocks have opposite magnetic properties.

2. The supercritical carbon dioxide chill-down surge pressure fracturing apparatus of claim 1, wherein, The mesh holes are arranged in an array on the side wall of the correction sieve bowl.

3. The supercritical carbon dioxide chill-down surge pressure fracturing apparatus of claim 1, wherein, The eccentric magnetic blocks are arranged in a fan-shaped structure, and the central angle of the fan-shaped structure is fixed on the roller of the rotating impeller.

4. The supercritical carbon dioxide chill-down surge fracturing device of claim 1, wherein, The included angle between the blade axis and the roller axis of the rotating impeller is 15°.

5. The supercritical carbon dioxide chill-down surge pressure fracturing apparatus of claim 1, wherein, The lateral injection holes and the pressure relief injection holes are arranged in a conical shape, the inner diameter of the conical injection hole gradually decreases from the top end to the bottom end, and the diameter of the pressure relief injection hole is larger than that of the lateral injection hole.

6. A supercritical carbon dioxide temperature swing surge fracturing method, characterized by, The supercritical carbon dioxide cooling fluctuation pressure fracturing device is used to perform the following steps: Step 1, the pipe body of the supercritical carbon dioxide cooling fluctuation pressure fracturing device is connected with the fracturing oil pipe through the connecting thread, then according to the fracturing design scheme of the well to be fractured, the fracturing layer position, the formation pressure of the fracturing layer position and the injection amount of the preflush are determined, the pipe body is lowered to the fracturing layer position from the wellhead of the well to be fractured, the coiled tubing is lowered to the fracturing layer position from the fracturing oil pipe, and the coiled tubing is connected with the cooling leakage bucket through the inner pipe thread, so that the installation of the supercritical carbon dioxide cooling fluctuation pressure fracturing device is completed; The fracturing oil pipe is provided with a fracturing oil pipe injection pump and a fracturring oil pipe pressure gauge, and the coiled tubing is provided with a coiled tubing injection pump and a coiled tubing pressure gauge, the fracturing oil pipe injection pump, the fracturring oil pipe pressure gauge, the coiled tubing injection pump and the coiled tubing pressure gauge are arranged on the ground and close to the wellhead of the well to be fractured; Step 2, the fracturing oil pipe injection pump is started, the preflush is injected into the pipe body of the supercritical carbon dioxide cooling fluctuation pressurization fracturing device through the fracturing oil pipe according to the preset preflush injection amount, the coiled tubing injection pump is started at the same time, the air is injected into the pipe body of the supercritical carbon dioxide cooling fluctuation pressurization fracturing device through the coiled tubing, the readings of the fracturing oil pipe pressure gauge and the coiled tubing pressure gauge are observed in real time, and the injection pressures of the fracturing oil pipe injection pump and the coiled tubing injection pump are controlled so that the injection pressures of the preflush and the air are the same; Step 3, after the preflush injection is completed, the fracturing operation is started, the supercritical carbon dioxide fracturing fluid is injected into the pipe body of the supercritical carbon dioxide cooling fluctuation pressurization fracturing device through the fracturing oil pipe, and the liquid nitrogen is injected into the pipe body of the supercritical carbon dioxide cooling fluctuation pressurization fracturing device through the coiled tubing, the readings of the fracturing oil pipe pressure gauge and the coiled tubing pressure gauge are observed in real time, and the injection pressures of the fracturing oil pipe injection pump and the coiled tubing injection pump are controlled so that the injection pressures of the supercritical carbon dioxide fracturing fluid and the liquid nitrogen are the same; The supercritical carbon dioxide fracturing fluid flows into the rectification screen bowl of the supercritical carbon dioxide cooling fluctuation pressurization fracturing device through the fracturing oil pipe, flows into the pipe body through the mesh holes arranged on the sidewall of the rectification screen bowl, the liquid nitrogen flows into the cooling leakage barrel of the supercritical carbon dioxide cooling fluctuation pressurization fracturing device through the coiled tubing, and then flows into the pipe body through the leakage holes arranged on the cooling leakage barrel, the temperature of the supercritical carbon dioxide fracturing fluid is lowered by the liquid nitrogen, and the liquid nitrogen and the supercritical carbon dioxide fracturing fluid are mixed to form a fracturing mixed fluid; Step 4, the fracturing mixed fluid flows downward in the pipe body and impacts the disturber, the fluid power of the fracturing mixed fluid is converted into the rotating force of the rotating impeller, the rotating impeller of the disturber rotates and does circular motion under the impact of the fracturing mixed fluid, at the same time, the eccentric magnetic block on the rolling shaft is attracted and repelled by the strong magnetic blocks on the first magnetic block fixing ring and the second magnetic block fixing ring, so that the rolling shaft moves and does eccentric motion in the accommodating space, the disturber drives the supercritical carbon dioxide cooling fluctuation pressurization fracturing device to impact the well wall, at the same time, the fracturing mixed fluid is sprayed from the pipe body of the supercritical carbon dioxide cooling fluctuation pressurization fracturing device through the lateral injection holes and the pressure relief injection holes, and the stratum is fractured by the impact; Step 5, under the dual action of the liquid force stress of the fracturing mixed fluid and the impact stress of the supercritical carbon dioxide cooling fluctuation pressurization fracturing device, the rock at the fracturing layer position is broken to form a crack network, the reservoir fracturing operation is completed, the fracturing oil pipe injection pump and the coiled tubing injection pump are closed, and the nitrogen gas in the fracturing mixed fluid is used to supplement the formation pressure due to the decrease of the formation pressure at the fracturing layer position.

7. The supercritical carbon dioxide cooldown surge pressure fracturing method of claim 6, wherein, In the step 2, the fracturing tubing injection pump is adjusted in real time according to the reading of the fracturing tubing pressure gauge during the preflush injection, so that the reading of the fracturing tubing pressure gauge is always less than the formation pressure of the fracturing layer.

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