Micro-nano bubble liquid oil displacement device and oil displacement method

Abstract

The application provides a kind of micro-nano bubble liquid oil displacement device and oil displacement method, including valve body, valve body is provided with one-stage generation channel along axis, and the both ends of one-stage generation channel are respectively provided with air inlet and liquid inlet.The check valve cover is sealingly connected at air inlet.One-stage generation channel is connected with gas generating device.Valve body side wall is provided with first outlet and second outlet communicated with one-stage generation channel, and the first outlet is sealingly connected with gas-liquid mixing device, and the second outlet is provided with gas-liquid mixing device along axis in two-stage mixing channel, and the second outlet is provided with gas-liquid mixer in two-stage mixing channel, and the end of gas-liquid mixing device away from valve body is provided with spray hole.The application avoids direct impact of gas on pressure detection element, prolongs the service life of pressure detection element, and generates uniform micro-nano bubbles by combining three-stage static mixing with gas-liquid reverse hedging, to improve oil production efficiency.

Description

[0001] This invention belongs to the technical field of carbon dioxide flooding for enhanced oil recovery, specifically relating to a micro / nano bubble liquid flooding device and method. Background Technology

[0002] In the middle and later stages of oilfield development, water injection or gas injection is typically used to replenish formation energy and improve oil recovery. Carbon dioxide flooding is an important enhanced oil recovery technology: CO2 is highly miscible with crude oil, which can significantly reduce crude oil viscosity, cause crude oil volume expansion, and make it easier to diffuse into micropores under supercritical conditions; at the same time, CO2 dissolves in water to form carbonic acid, which can improve the oil-water mobility ratio and increase oil displacement efficiency.

[0003] Currently, most micro-nano bubble generators used for CO2-driven oil recovery employ a straight-through air inlet structure, where the injection pressure directly acts on the pressure detection element. Long-term use can easily damage the pressure gauge. In addition, gas and liquid are usually injected from the same end, resulting in a short mixing path, insufficient bubble cutting, and large bubble size with poor uniformity. Furthermore, under high pressure, liquid can easily backflow into the injection system, affecting the stable operation of the device.

[0004] More importantly, the equipment is in a complex environment of mineral scale and oil scale in the well for a long time, which makes it very easy for micropores to become blocked, resulting in a sharp drop in bubble generation efficiency or even complete failure. Existing equipment lacks effective self-cleaning means and requires frequent disassembly, maintenance or replacement of diffusers, which seriously affects the continuity and economy of CO2 oil recovery operations. Summary of the Invention

[0005] Purpose of the invention: In order to overcome the above shortcomings, the present invention provides a micro-nano bubble liquid oil displacement device and oil displacement method, which can generate CO2 micro-nano bubbles with uniform particle size and high concentration, and can automatically or manually trigger backwashing when the microporous diffuser is blocked, thereby achieving self-cleaning, extending the continuous operation cycle of the device, and improving the CO2 oil displacement efficiency.

[0006] Technical Solution: To achieve the above objectives, this invention provides a micro / nano bubble liquid-driven oil device, comprising a valve body with a primary generation channel along its axis, and an air inlet and a liquid inlet at each end of the primary generation channel. A check valve cover is sealed to the air inlet, which is connected to the gas injection system via the check valve cover. A gas generator is connected within the primary generation channel and extends towards the liquid inlet. The gas generator includes a sealing assembly, a microporous diffuser fixedly connected to the sealing assembly, and a flushing assembly fitted around the microporous diffuser. The flushing assembly has a passive flushing mode and an active flushing mode. In the passive flushing mode, backflushing is triggered when the internal pressure of the microporous diffuser increases due to blockage. In the active flushing mode, backflushing is triggered by increasing the gas supply pressure of the gas injection system. The side wall of the valve body has a first outlet and a second outlet communicating with the primary generation channel. A gas-liquid mixing device is sealed to the first outlet, and a secondary mixing channel is provided along its axis within the gas-liquid mixing device, containing a gas-liquid mixer. The first outlet is connected to the downhole gas injection string via a gas-liquid mixing device, which injects the generated CO2 micro-nano bubble liquid into the formation for oil displacement.

[0007] Furthermore, in the aforementioned micro / nano bubble liquid-driven oil device, the flushing assembly includes an inner protective sleeve and an outer protective sleeve, with the outer protective sleeve fitted around the outer periphery of the inner protective sleeve. The inner protective sleeve has an inner guide groove on its sidewall, and the outer protective sleeve has an outer guide groove on its sidewall, with the inner and outer guide grooves corresponding to each other. An annular space is defined between the inner sidewall of the inner protective sleeve and the outer sidewall of the microporous diffuser. When the inner and outer guide grooves are misaligned and closed, the annular space forms a closed chamber. A ratchet assembly is connected to the end of the microporous diffuser furthest from the sealing assembly. The ratchet assembly includes a floating element, the outer peripheral surface of which slides against the inner sidewall of the outer protective sleeve, and the ratchet assembly is driven to connect with the inner protective sleeve. A clearance exists between the sliding surfaces of the inner and outer protective sleeves, which provides a drainage channel connecting the closed chamber to the primary generation channel when the inner and outer guide grooves are misaligned and closed. The clearance is configured to allow backwash pressure to build up in the closed chamber during flushing, and to allow the pressure in the closed chamber to drop to a level comparable to the pressure in the primary generation channel after a predetermined time following flushing.

[0008] Furthermore, in the aforementioned micro / nano bubble liquid-driven oil device, a conical guide head is connected to the end of the outer protective sleeve furthest from the sealing assembly. The ratchet assembly includes: an upper ratchet, fixedly connected to the microporous diffuser; a lower ratchet, fixedly connected to the conical guide head and positioned opposite the upper ratchet, with the vertical surfaces of their ratchet teeth on the same plane; a floating ratchet, i.e., a floating component, located between the upper and lower ratchets, with a central boss, an annular pressure-bearing surface, and upper ratchet teeth sequentially arranged from the inside out at the upper end of the floating ratchet; the central boss is a conical boss, and a sealing seat is provided at the end where the microporous diffuser connects to the upper ratchet, with a conical hole that mates with the outer circumference of the central boss; a lower ratchet tooth is provided at the lower end of the floating ratchet, with the vertical surfaces of the upper and lower ratchet teeth circumferentially offset; and a thrust spring is located between the lower ratchet and the floating ratchet. The thrust spring applies a thrust toward the upper end face ratchet to the floating ratchet, causing the upper ratchet teeth to mesh with the upper end face ratchet.

[0009] Furthermore, in the aforementioned micro / nano bubble liquid-driven oil device, the sealing assembly includes a sealing head and a first check valve disposed between the sealing head and the microporous diffuser. One end of the sealing head is threadedly sealed to the inner wall of the air inlet, and the end of the sealing head away from the microporous diffuser is sealed to the check valve cover. The sealing head has a first air inlet channel along its axis, and the inner wall of the first air inlet channel has a spiral drainage groove.

[0010] Furthermore, in the aforementioned micro / nano bubble liquid-driven oil device, the trigger pressure of the floating ratchet action is lower than the gas supply pressure of the gas injection system. When the internal pressure of the microporous diffuser rises to the trigger pressure, the first check valve remains open, and the gas injection system continues to supply gas to maintain the internal pressure of the microporous diffuser, driving the floating ratchet to complete the movement to the flushing position.

[0011] Furthermore, in the aforementioned micro / nano bubble liquid-driven oil device, the check valve cover is provided with a through groove and an air inlet groove, the through groove being arranged along the axis of the check valve cover. The air inlet groove is located on the side wall of the check valve cover and communicates with the through groove. The end of the air inlet groove furthest from the through groove has an interface for connecting to an air injection system, the end of the through groove furthest from the valve body is used to connect a pressure detection element, and the end of the through groove closest to the valve body is sealed to the sealing head via a sealing ring. A second check valve is installed inside the air inlet groove.

[0012] Furthermore, in the aforementioned micro-nano bubble liquid-driven oil device, at least two first sealing grooves are provided at intervals along the axial direction of the through groove on the inner side wall of the end of the through groove near the valve body, and a sealing ring is provided in the first sealing groove.

[0013] Furthermore, in the aforementioned micro / nano bubble liquid-driven oil device, a connector for connecting a sampling mechanism is provided at the second outlet. The gas-liquid mixer consists of an SK static mixer, an SX static mixer, and an SV static mixer, which are arranged sequentially in the direction away from the valve body.

[0014] A CO2-based oil displacement method, applied to the aforementioned micro / nano bubble liquid oil displacement device, includes: S1. The gas injection system injects gas into the microporous diffuser through the air inlet of the check valve cover. The gas overflows from the micropores of the microporous diffuser to form initial bubbles. At the same time, liquid enters the primary generation channel from the liquid inlet. The gas and liquid flow in opposite directions to form a counter-current mixing. After being sheared by the spiral flow channel formed by the inner and outer guide channels, the gas-liquid mixture enters the gas-liquid mixing device from the first outlet. The gas-liquid mixer further refines the mixture into micro-nano bubble liquid. The CO2 micro-nano bubble liquid is injected into the oil well through the gas injection string to displace the crude oil in the reservoir and improve the recovery rate.

[0015] S2: The internal pressure of the microporous diffuser increases due to blockage.

[0016] S3: The floating ratchet is pressed and separates from the upper end ratchet to form a gap. The central boss is separated from the sealing seat of the microporous diffuser. The side of the central boss and the annular pressure surface are exposed to the internal air pressure, which increases the effective pressure area.

[0017] S4: The floating ratchet continues to move towards the lower end face ratchet. The lower ratchet tooth of the floating ratchet slides along the inclined surface of the ratchet tooth of the lower end face ratchet. While moving axially, it generates circumferential rotation, driving the inner protective sleeve to rotate. This causes the inner guide groove and the outer guide groove to be misaligned circumferentially, trapping the liquid in the annular space between the protective sleeve and the microporous diffuser in a closed chamber between the inner side wall of the inner protective sleeve and the outer side wall of the microporous diffuser, until the lower ratchet tooth of the floating ratchet engages with the lower end face ratchet.

[0018] S5: The high-pressure gas inside the microporous diffuser is introduced into the closed chamber through the gap between the floating ratchet and the upper end ratchet, which increases the liquid pressure in the closed chamber and drives the liquid to pass through the micropores from the outside to the inside of the microporous diffuser, flushing out the blockage in the micropores.

[0019] S6: Gas and liquid in the sealed chamber leak into the primary generation channel through the gap between the inner and outer protective sleeves, causing the internal pressure of the microporous diffuser to drop back to the normal operating pressure. The thrust spring pushes the floating ratchet to reset, the lower ratchet tooth of the floating ratchet separates from the lower end face ratchet, and the upper ratchet tooth of the floating ratchet re-engages with the upper end face ratchet. During the engagement process, the floating ratchet rotates in the opposite direction, causing the inner protective sleeve to rotate in the opposite direction, so that the inner guide groove and the outer guide groove are realigned, and normal ventilation is restored.

[0020] Furthermore, the above-mentioned CO2 oil displacement method includes: increasing the gas supply pressure of the gas injection system so that the thrust generated by the pressure inside the microporous diffuser exceeds the elastic force of the thrust spring, triggering the above-mentioned S3-S6 flushing action, and reducing the gas supply pressure to restore normal ventilation after flushing is completed.

[0021] As can be seen from the above technical solution, the present invention has the following beneficial effects: ① In this invention, the gas injection port is located on the side wall of the check valve cover, and the pressure detection element is located at the top of the through groove. The gas does not directly impact the pressure detection element, thus extending the service life of the pressure detection element.

[0022] ②The present invention forms a double one-way seal between the first check valve and the second check valve to prevent liquid from backflowing into the gas injection system under high pressure, thus ensuring the stable operation of the device.

[0023] ③ This invention allows CO2 and liquid to be injected from opposite ends of the device, forming a counter-current turbulent flow in the primary generation channel, extending the mixing path and improving the mixing effect. After being swirled and sheared by the spiral guide groove of the protective sleeve, and then repeatedly cut and mixed by three static mixers of SK, SX and SV, the concentration and uniformity of CO2 micro-nano bubble liquid are improved, thereby improving the CO2 oil displacement efficiency.

[0024] ④ This invention automatically triggers backflushing when the microporous diffuser is blocked by the linkage between the ratchet assembly and the inner and outer protective sleeves. The residual high-pressure CO2 gas inside the microporous diffuser drives the liquid in the closed chamber to flow back through the micropores, flushing out the blockage and achieving self-cleaning. After flushing, the pressure is slowly released through the mating gap, so that the floating ratchet automatically resets without external intervention, thus extending the continuous operation cycle of the device.

[0025] ⑤ This invention provides two modes: passive flushing and active flushing. The passive mode is automatically triggered when blockage occurs naturally, while the active mode can perform preventative flushing by manually increasing the air supply pressure, adapting to different maintenance needs. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the micro / nano bubble liquid oil displacement device of the present invention; Figure 2 This is a schematic diagram of the valve body. Figure 3 This is an axial sectional view of the present invention; Figure 4 This is an exploded view of the flushing assembly; Figure 5 This is an exploded view of the ratchet assembly; Figure 6 This is a top view of the floating ratchet; Figure 7 for Figure 4Enlarged view of the middle ratchet assembly Figure 8 for Figure 3 The enlarged view shown below; Figure 9 This is a schematic diagram of the second check valve.

[0027] In the diagram: 1. Valve body; 11. Air inlet; 12. Liquid inlet; 13. First outlet; 14. Second outlet; 2. Check valve cover; 21. Through groove; 22. Air inlet groove; 221. First sealing groove; 23. Second check valve; 231. Second valve seat; 2311. Second sealing ring; 2312. Second sealing groove; 2313. Threaded part; 232. Second valve core; 233. Second elastic component; 234. Second plug; 3. Gas generator; 31. Sealing head; 32. First check valve; 321. First valve seat; 3211. First sealing ring. 322. First valve core; 323. First elastic component; 324. First plug; 33. Microporous diffuser; 331. Sealing seat; 34. Flushing component; 341. Ratchet assembly; 3411. Upper end face ratchet; 3412. Lower end face ratchet; 3413. Floating ratchet; 34131. Central boss; 34132. Annular pressure surface; 3414. Thrust spring; 342. Inner protective sleeve; 3421. Inner guide groove; 343. Outer protective sleeve; 3431. Outer guide groove; 35. Conical guide head; 4. Gas-liquid mixing device; 41. Gas-liquid mixer. Detailed Implementation Example

[0028] like Figure 1-3 The illustrated micro / nano bubble liquid-driven oil device includes a valve body 1 with a primary generation channel along its axis. The primary generation channel has an air inlet 11 and a liquid inlet 12 at its two ends. A check valve cover 2 is sealed to the air inlet 11, which is connected to the gas injection system. A gas generator 3 is connected within the primary generation channel and extends towards the liquid inlet 12.

[0029] In this embodiment, the gas generating device 3 includes a sealing assembly, a microporous diffuser 33 fixedly connected to the sealing assembly, and a flushing assembly 34 sleeved around the microporous diffuser 33. The flushing assembly 34 has a passive flushing mode and an active flushing mode. In the passive flushing mode, backflushing is triggered when the internal pressure of the microporous diffuser 33 increases due to blockage. In the active flushing mode, backflushing is triggered by increasing the gas supply pressure of the gas injection system. The side wall of the valve body 1 is provided with a first outlet 13 and a second outlet 14 communicating with the primary generation channel. A gas-liquid mixing device 4 is sealed and connected to the first outlet 13. A secondary mixing channel is provided along the axis inside the gas-liquid mixing device 4, and a gas-liquid mixer 41 is provided in the secondary mixing channel. The first outlet 13 is connected to the downhole gas injection string through the gas-liquid mixer 41 to inject CO2 micro-nano bubble liquid into the formation for oil displacement. In this embodiment, the microporous diffuser 33 is made of sintered metal and has densely distributed micropores inside. When CO2 gas flows through, it is cut into fine bubbles by the micropores.

[0030] like Figure 3 The micro / nano bubble liquid-driven oil device shown includes a sealing assembly comprising a sealing head 31 and a first check valve 32 disposed between the sealing head 31 and the microporous diffuser 33. One end of the sealing head 31 is threadedly sealed to the inner wall of the air inlet 11, and the end of the sealing head 31 away from the microporous diffuser 33 is sealed to the check valve cover 2. The sealing head 31 has a first air inlet channel along its axis, and the inner wall of the first air inlet channel has a spiral guide groove. When CO2 gas flows through the spiral guide groove, it forms a swirling flow, giving the CO2 before entering the microporous diffuser 33 initial kinetic energy, which is beneficial for the subsequent cutting and dispersion of bubbles.

[0031] like Figure 4 The micro / nano bubble liquid-driven oil device shown includes a flushing component 34 comprising an inner protective sleeve 342 and an outer protective sleeve 343, with the outer protective sleeve 343 fitted around the outer periphery of the inner protective sleeve 342. The inner protective sleeve 342 has an inner guide groove 3421 on its sidewall, and the outer protective sleeve 343 has an outer guide groove 3431 on its sidewall, with the inner and outer guide grooves corresponding to each other. An annular space is defined between the inner sidewall of the inner protective sleeve 342 and the outer sidewall of the microporous diffuser 33. When the inner and outer guide grooves 3421 are misaligned and closed, the annular space forms a closed chamber.

[0032] Ratchet assembly 341 is connected to the end of microporous diffuser 33 away from the sealing assembly. Ratchet assembly 341 includes a floating element whose outer peripheral surface slides against the inner wall of outer protective sleeve 343. Ratchet assembly 341 is driven to connect with inner protective sleeve 342. A clearance exists between the sliding surfaces of inner protective sleeve 342 and outer protective sleeve 343. This clearance provides a drainage channel connecting the sealed chamber to the primary generation channel when the inner guide channel 3421 and outer guide channel 3431 are misaligned and closed. The clearance is configured to allow backwash pressure to build up within the sealed chamber during flushing, and to allow the pressure within the sealed chamber to decrease to a level comparable to the pressure within the primary generation channel after a predetermined time following flushing.

[0033] like Figure 5-7 The micro / nano bubble liquid-driven oil device shown has a tapered guide head 35 connected to the end of the outer protective sleeve 343 away from the sealing assembly. The ratchet assembly 341 includes: an upper ratchet 3411, fixedly connected to the microporous diffuser 33; and a lower ratchet 3412, fixedly connected to the tapered guide head 35 and positioned opposite the upper ratchet 3411, with their ratchet teeth on the same vertical plane. A floating ratchet 3413, i.e., a floating element, is located between the upper ratchet 3411 and the lower ratchet 3412. The outer circumferential surface of the floating ratchet 3413 is splined with the inner protective sleeve 342. When the internal pressure of the microporous diffuser 33 increases and overcomes the elastic force of the thrust spring 3414, the floating ratchet 3413 is pressed and moves axially downwards. At this time, the splined engagement allows the floating ratchet 3413 to slide smoothly relative to the inner protective sleeve 342. The upper end of the floating ratchet 3413 is provided with a central boss 34131, an annular pressure-bearing surface 34132, and an upper ratchet tooth, arranged sequentially from the inside to the outside. The central boss 34131 is a conical boss. A sealing seat 331 is provided at one end of the microporous diffuser 33 connected to the upper end ratchet 3411. The sealing seat 331 has a conical hole that mates with the outer circumference of the central boss 34131. The lower end of the floating ratchet 3413 is provided with a lower ratchet tooth, and the vertical surfaces of the upper and lower ratchet teeth are circumferentially offset. A thrust spring 3414 is located between the lower end ratchet 3412 and the floating ratchet 3413. The thrust spring 3414 applies a thrust to the floating ratchet 3413 in the direction of the upper end ratchet 3411, so that the upper ratchet teeth engage with the upper end ratchet 3411. At the same time, the outer wall of the central boss 34131 and the inclined surface of the inner wall of the tapered hole provided in the sealing seat 331 are sealed together.

[0034] To further clarify the relative positions and assembly positioning relationships of the ratchet components 341: the upper end face ratchet 3411 has an internal thread, which engages with the corresponding external thread on the lower end face of the microporous diffuser 33, and its upper end face abuts against the lower edge of the sealing seat 331, thus fixing the upper end face ratchet 3411 axially and circumferentially on the microporous diffuser 33; the lower end face ratchet 3412 has an internal thread, which engages with the corresponding external thread on the upper end face of the conical guide head 35, thus fixing the lower end face ratchet 3412 axially and circumferentially on the conical guide head 35. The outer periphery of the conical guide head 35 has an outer circumference, and the inner wall of the outer protective sleeve 343 has an internal thread at a corresponding position, fixing the conical guide head 35 and the outer protective sleeve 343 by threaded engagement, thus determining the axial direction and axial reference of the lower end face ratchet 3412. The microporous diffuser 33, the outer protective sleeve 343, and the valve body 1 are circumferentially positioned by a locating pin. The relative positions of the upper ratchet 3411, the lower ratchet 3412, and the floating ratchet 3413 are determined. When the floating ratchet 3413 engages with the upper ratchet 3411, the vertical surface of the lower ratchet tooth of the floating ratchet 3413 is also circumferentially misaligned with the vertical surface of the ratchet tooth of the lower ratchet 3412 by half a tooth pitch. When the floating ratchet 3413 moves downward, its lower ratchet tooth can only slide along a single slope of the inclined surface of the ratchet tooth of the lower ratchet 3412, forcing the floating ratchet 3413 to rotate unidirectionally only in a single set direction, driving the inner protective sleeve 342 to rotate unidirectionally.

[0035] In this embodiment, the trigger pressure of the floating ratchet 3413 is lower than the air supply pressure of the air injection system. When the internal pressure of the microporous diffuser 33 rises to the trigger pressure, the first check valve 32 remains open, and the air injection system continues to supply air to maintain the internal pressure of the microporous diffuser 33, driving the floating ratchet 3413 to complete the movement to the rinsing position.

[0036] like Figure 8 The micro / nano bubble liquid-driven oil device shown has a through groove 21 and an air inlet groove 22 on the check valve cover 2. The through groove 21 is arranged along the axis of the check valve cover 2. The air inlet groove 22 is located on the side wall of the check valve cover 2 and communicates with the through groove 21. The end of the air inlet groove 22 away from the through groove 21 has an interface for connecting to the gas injection system, and the end of the through groove 21 away from the valve body 1 is used to connect to the pressure detection element. The end of the through groove 21 near the valve body 1 is sealed with the sealing head 31 by a sealing ring. A second check valve 23 is installed in the air inlet groove 22. The air inlet groove 22 is set perpendicular to the through groove 21, and the pressure detection element is set at the top of the through groove 21, so that high-pressure CO2 enters from the side, without directly impacting the pressure detection element, thus protecting the pressure detection element.

[0037] like Figure 8The micro / nano bubble liquid-driven oil device shown includes a first check valve 32 comprising a first valve seat 321, a first valve core 322, and a first elastic component 323. The first valve seat 321 has a receiving channel along its axis, within which the first elastic component 323 and the first valve core 322 are located. A first sealing ring 3211 is provided within the receiving channel, and a first plug 324 is provided at the end of the receiving channel away from the sealing head 31. The first plug 324 is threaded into the receiving channel. Both ends of the first elastic component 323 abut against the first valve core 322 and the first plug 324, respectively. The first elastic component 323 applies a thrust to the first valve core 322, moving it towards the first sealing ring 3211, causing the first valve core 322 to abut against the first sealing ring 3211 to form a seal. The first valve seat 321 is located inside the air inlet 11. Its lower end abuts against the top of the bubble generating assembly 33, and its upper end abuts against the sealing head 31. A sealing ring is provided between the outer circumferential surface of the first valve seat 321 and the inner wall of the air inlet 11. The first valve core 322 has a second air inlet channel extending from the side wall of the first valve core 322 near the first sealing ring 3211 to the other end of the first valve core 322. When CO2 gas flows in forward, the gas pressure overcomes the thrust of the first elastic component 323, pushing the first valve core 322 away from the first sealing ring 3211, and CO2 enters the downstream through the second air inlet channel. When the downstream pressure abnormally increases, the first valve core 322 resets under the action of the first elastic component 323, abutting against the first sealing ring 3211 to form a seal, cutting off the passage and preventing liquid backflow.

[0038] like Figure 9The micro / nano bubble liquid-driven oil device shown includes a second check valve 23 comprising a second valve seat 231, a second valve core 232, and a second elastic component 233. The second valve seat 231 has a receiving channel along its axis, within which the second elastic component 233 and the second valve core 232 are located. A second sealing ring 2311 is provided within the receiving channel, and a second plug 234 is provided at the end of the receiving channel away from the through groove 21. The second plug 234 is threaded into the receiving channel. Both ends of the second elastic component 233 abut against the second valve core 232 and the second plug 234, respectively. The second elastic component 233 applies a thrust to the second valve core 232, moving it towards the second sealing ring 2311, causing the second valve core 232 to abut against the second sealing ring 2311 to form a seal. The second valve seat 231 is located within the air inlet groove 22. The second valve seat 231 has a second sealing groove 2312 and a threaded portion 2313 on its outer periphery. A sealing ring is provided in the second sealing groove 2312. The second valve seat 231 is threadedly connected to the air inlet groove 22 through the threaded portion 2313, and is sealed to the air inlet groove 22 through the sealing ring in the second sealing groove 2312. The second valve core 232 has a third air inlet channel, which extends from the side wall of the second valve core 232 near the second sealing ring 2311 to the other end of the second valve core 232. When CO2 gas flows in forward, the gas pressure overcomes the thrust of the second elastic component 233, pushing the second valve core 232 away from the second sealing ring 2311, and CO2 enters the downstream through the second air inlet channel. When the downstream pressure rises abnormally, the second valve core 232 resets under the action of the second elastic component 233, abuts against the second sealing ring 2311 to form a seal, cuts off the passage, and prevents liquid backflow.

[0039] In this embodiment, at least two first sealing grooves 221 are provided at axial intervals along the inner sidewall of the through groove 21 near the valve body 1, and a sealing ring is provided in the first sealing groove 221. The sealing head 31 is sealed to the through groove 21 through the sealing ring in the first sealing groove 221, forming a floating plug-in assembly structure, which is adapted to the connection between the check valve cover 2 and the valve body 1, compensates for assembly tolerances, ensures the sealing reliability of the high-pressure CO2 gas passage, and improves the convenience of disassembly and maintenance.

[0040] In this embodiment, a connector for connecting the sampling mechanism is provided at the second outlet 14. The gas-liquid mixer 41 consists of an SK static mixer, an SX static mixer, and an SV static mixer, which are arranged sequentially away from the valve body 1. The three static mixers are connected in series in order of increasing shear strength: the SK static mixer first initially separates and rotates the gas and liquid phases, the SX static mixer then repeatedly separates and merges them, and the SV static mixer finally applies strong shear and turbulent mixing, forming a progressively stronger mixing path from coarse to fine. The SK, SX, and SV static mixers are conventional techniques in the art, and their specific structures will not be described in detail here.

[0041] The CO2 oil displacement method of this embodiment includes: Oil displacement stage: S1: The gas injection system injects CO2 gas into the microporous diffuser 33 through the air inlet 11 of the check valve cover 2. At the same time, pressurized liquid enters the primary generation channel from the liquid inlet 12 and flows at high speed. The CO2 gas is injected into the second check valve 23 through the air inlet groove 22. After pushing open the second valve core 232, it flows into the through groove 21 through the third air inlet channel. Then, through the spiral guide groove on the inner wall of the first air inlet channel of the sealing head 31, the CO2 forms a swirling flow and enters the first check valve 32. After pushing open the first valve core 322, it enters the microporous diffuser 33 through the second air inlet channel. It overflows from the micropores to form initial CO2 bubbles. The gas and liquid flow in opposite directions and mix. The gas-liquid mixture is pressed into the secondary mixing channel of the gas-liquid mixing device 4 from the first outlet 13. It flows through the three static mixers SK, SX, and SV in sequence. It is repeatedly split, rotated, and merged and is fully cut into CO2 micro-nano bubble liquid. Finally, it is injected downhole for CO2 oil displacement.

[0042] Self-cleaning phase (S2-S6): S2: When the microporous diffuser 33 becomes blocked, CO2 cannot escape through the micropores of the microporous diffuser 33, and the internal pressure of the microporous diffuser 33 gradually increases.

[0043] S3: The internal air pressure of the microporous diffuser 33 overcomes the elastic force of the thrust spring 3414, pushing the floating ratchet 3413 to move downward. The upper ratchet tooth of the floating ratchet 3413 separates from the upper end ratchet 3411 to form a gap. The central boss 34131 disengages from the sealing seat of the microporous diffuser 33. The side of the central boss 34131 and the annular pressure-bearing surface 34132 are exposed to the internal air pressure, which increases the effective pressure-bearing area of ​​the floating ratchet 3413 and significantly enhances the driving force.

[0044] S4: The floating ratchet 3413 continues to move towards the lower end ratchet 3412. The lower ratchet tooth of the floating ratchet 3413 slides along the inclined surface of the ratchet tooth of the lower end ratchet 3412. While moving axially, it generates circumferential rotation, driving the inner protective sleeve 342 to rotate. This causes the inner guide groove 3421 and the outer guide groove 3431 to be misaligned circumferentially, trapping the liquid in the annular space between the protective sleeve 342 and the microporous diffuser 33 in the closed cavity between the inner side wall of the inner protective sleeve 342 and the outer side wall of the microporous diffuser 33, until the lower ratchet tooth of the floating ratchet 3413 engages with the lower end ratchet 3412.

[0045] S5: The high-pressure gas inside the microporous diffuser 33 is introduced into the closed chamber through the gap between the floating ratchet 3413 and the upper end ratchet 3411, which increases the liquid pressure in the closed chamber and drives the liquid to pass through the micropores from the outside to the inside of the microporous diffuser 33, flushing out the blockage in the micropores.

[0046] S6: Gas and liquid in the sealed chamber continuously leak into the primary generation channel through the fitting gap between the inner protective sleeve 342 and the outer protective sleeve 343, causing the internal pressure of the microporous diffuser 33 to drop back to the normal operating pressure. When the pressure drops below the reset force of the thrust spring 3414, the thrust spring 3414 pushes the floating ratchet 3413 to reset towards the upper end ratchet 3411, and the lower ratchet tooth of the floating ratchet 3413 separates from the lower end ratchet 3412. During the upward movement of the floating ratchet 3413, the upper ratchet tooth of the floating ratchet 3413 contacts and slides with the inclined surface of the ratchet tooth of the upper end ratchet 3411, generating a reverse rotation, which drives the inner protective sleeve 342 to rotate in the opposite direction, causing the inner guide groove 3421 to realign with the outer guide groove 3431, and the upper ratchet tooth to re-engage with the upper end ratchet 3411, returning to the normal ventilation position. The inner guide channel 3421 overlaps with the outer guide channel 3431, and CO2 and liquid resume normal counter-current mixing, returning to S1 to continue oil displacement. If some incompletely flushed blockage remains in the micropores of the micropore diffuser at this time, after a brief restoration of ventilation, the micropores will gradually become clogged again with continuous gas injection, causing the internal pressure to rise again. When the pressure reaches the trigger threshold again, the flushing actions from S2 to S6 will be repeated, performing multiple intermittent backflushing operations on the micropore diffuser to gradually remove the blockage, thereby maintaining long-term basic flow and oil displacement capacity in complex downhole environments.

[0047] During the active cleaning phase, when active preventive cleaning is required, the air supply pressure of the air injection system is increased, so that the thrust generated by the pressure inside the microporous diffuser 33 exceeds the elastic force of the thrust spring 3414, triggering the above-mentioned S3-S6 flushing actions. After flushing is completed, the air supply pressure is reduced to restore normal ventilation and continue to drive the oil.

[0048] The above embodiments are exemplary and are intended to illustrate the technical concept and features of the present invention, so that those skilled in the art can understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A micro / nano bubble liquid oil displacement device, characterized in that: It includes a valve body (1) and a primary generation channel along the axis. The two ends of the primary generation channel are respectively provided with an air inlet (11) and a liquid inlet (12). Check valve cover (2) is sealed to the air inlet (11), and the air inlet (11) is connected to the air injection system through the check valve cover (2); A gas generating device (3) is connected to the primary generating channel and extends toward the liquid inlet (12); the gas generating device (3) includes a sealing component, a microporous diffuser (33) fixedly connected to the sealing component, and a flushing component (34) sleeved on the outer periphery of the microporous diffuser (33); the flushing component (34) has a passive flushing mode and an active flushing mode. In the passive flushing mode, the microporous diffuser (33) triggers backflushing when the internal pressure increases due to blockage. In the active flushing mode, backflushing is triggered by increasing the gas supply pressure of the gas injection system. The valve body (1) has a first outlet (13) and a second outlet (14) connected to the first-stage generation channel on its side wall; a gas-liquid mixing device (4) is sealed and connected to the first outlet (13); a secondary mixing channel is provided along the axis inside the gas-liquid mixing device (4); a gas-liquid mixer (41) is provided inside the secondary mixing channel; the first outlet (13) is connected to the downhole gas injection string through the gas-liquid mixer (41).

2. The micro / nano bubble liquid oil displacement device according to claim 1, characterized in that: The flushing assembly (34) includes: An inner protective sleeve (342) and an outer protective sleeve (343) are provided, wherein the outer protective sleeve (343) is fitted around the outer periphery of the inner protective sleeve (342); the inner protective sleeve (342) has an inner guide groove (3421) on its side wall, and the outer protective sleeve (343) has an outer guide groove (3431) on its side wall, wherein the inner guide groove (3421) and the outer guide groove (3431) are correspondingly arranged; an annular space is defined between the inner side wall of the inner protective sleeve (342) and the outer side wall of the microporous diffuser (33); when the inner guide groove (3421) and the outer guide groove (3431) are misaligned and closed, the annular space constitutes a closed chamber; A ratchet assembly (341) is connected to the end of the microporous diffuser (33) away from the sealing assembly. The ratchet assembly (341) includes a floating member. The outer peripheral surface of the floating member is slidably engaged with the inner sidewall of the outer protective sleeve (343). The ratchet assembly (341) is drivenly connected to the inner protective sleeve (342). There is a clearance between the sliding mating surfaces of the inner protective sleeve (342) and the outer protective sleeve (343). When the inner guide groove (3421) and the outer guide groove (3431) are misaligned and closed, the clearance provides a discharge channel for the closed chamber to communicate with the primary generation channel. The clearance is configured to allow backwash pressure to be established in the closed chamber during flushing, and to allow the pressure in the closed chamber to drop to a level equivalent to the pressure in the primary generation channel after a predetermined time after flushing.

3. The micro / nano bubble liquid oil displacement device according to claim 2, characterized in that: A tapered guide head (35) is connected to the end of the outer protective sleeve (343) away from the sealing assembly. The ratchet assembly (341) includes: The upper end ratchet (3411) is fixedly connected to the microporous diffuser (33); The lower end ratchet (3412) is fixedly connected to the conical guide head (35) and is arranged opposite to the upper end ratchet (3411), and the vertical surfaces of the ratchet teeth of the two are on the same plane; A floating ratchet (3413), i.e., the floating component, is disposed between the upper end ratchet (3411) and the lower end ratchet (3412). The upper end of the floating ratchet (3413) is provided with a central boss (34131), an annular pressure surface (34132), and an upper ratchet tooth from the inside to the outside. The central boss (34131) is a conical boss. The microporous diffuser (33) is connected to the upper end ratchet (3411) with a sealing seat (331). The sealing seat (331) is provided with a conical hole that mates with the outer periphery of the central boss (34131). The lower end of the floating ratchet (3413) is provided with a lower ratchet tooth. The vertical surfaces of the upper ratchet tooth and the lower ratchet tooth are circumferentially offset. A thrust spring (3414) is disposed between the lower end face ratchet (3412) and the floating ratchet (3413); the thrust spring (3414) applies a thrust to the floating ratchet (3413) in the direction of the upper end face ratchet (3411), so that the upper ratchet teeth engage with the upper end face ratchet (3411).

4. The micro / nano bubble liquid oil displacement device according to claim 3, characterized in that: The sealing assembly includes a sealing head (31) and a first check valve (32) disposed between the sealing head (31) and the microporous diffuser (33); one end of the sealing head (31) is threadedly sealed to the inner wall of the air inlet (11), and the end of the sealing head (31) away from the microporous diffuser (33) is sealed to the check valve cover (2); the sealing head (31) is provided with a first air inlet channel along the axis, and the inner wall of the first air inlet channel is provided with a spiral drainage groove.

5. The micro / nano bubble liquid oil displacement device according to claim 4, characterized in that: The trigger pressure of the floating ratchet (3413) is lower than the air supply pressure of the air injection system. When the internal pressure of the microporous diffuser (33) rises to the trigger pressure, the first check valve (32) remains open, and the air injection system continues to supply air to maintain the internal pressure of the microporous diffuser (33), driving the floating ratchet (3413) to complete the movement to the flushing position.

6. The micro / nano bubble liquid oil displacement device according to claim 4, characterized in that: The check valve cover (2) is provided with a through groove (21) and an air inlet groove (22). The through groove (21) is arranged along the axis of the check valve cover (2). The air inlet groove (22) is located on the side wall of the check valve cover (2) and communicates with the through groove (21). The end of the air inlet groove (22) away from the through groove (21) is provided with an interface for connecting the air injection system. The end of the through groove (21) away from the valve body (1) is used to connect the pressure detection element. The end of the through groove (21) close to the valve body (1) is sealed with the sealing head (31) by a sealing ring. A second check valve (23) is installed in the air inlet groove (22).

7. The micro / nano bubble liquid oil displacement device according to claim 6, characterized in that: The inner wall of the through groove (21) near the valve body (1) is provided with at least two first sealing grooves (221) spaced apart along the axial direction of the through groove (21), and a sealing ring is provided in the first sealing groove (221).

8. The micro / nano bubble liquid oil displacement device according to claim 1, characterized in that: The second outlet (14) is provided with a connector for connecting the sampling mechanism; the gas-liquid mixer (41) is composed of an SK static mixer, an SX static mixer and an SV static mixer, which are arranged in sequence along the direction away from the valve body (1).

9. A CO2 oil displacement method, applied to the micro / nano bubble liquid oil displacement device according to any one of claims 1 to 8, characterized in that: include: S1. The gas injection system injects gas into the microporous diffuser (33) through the air inlet (11) of the check valve cover (2). The gas overflows from the micropores of the microporous diffuser (33) to form initial bubbles. At the same time, the liquid enters the first-stage generation channel from the liquid inlet (12). The gas and liquid flow in opposite directions to form a counter-current mixing. After being sheared by the spiral flow channel formed by the inner guide groove (3421) and the outer guide groove (3431), the gas-liquid mixture enters the gas-liquid mixing device (4) from the first outlet (13). After being further refined by the gas-liquid mixer (41) to form micro-nano bubble liquid, it is injected downhole to displace crude oil. S2: The internal pressure of the microporous diffuser (33) increases due to blockage; S3: The floating ratchet (3413) is pressed and separated from the upper end ratchet (3411) to form a gap. The central boss (34131) is disengaged from the sealing seat of the microporous diffuser (33). The side of the central boss (34131) and the annular pressure surface (34132) are exposed to the internal air pressure, thereby increasing the effective pressure area. S4: The floating ratchet (3413) continues to move towards the lower end face ratchet (3412). The lower ratchet tooth of the floating ratchet (3413) slides along the ratchet tooth slope of the lower end face ratchet (3412). While moving axially, it generates circumferential rotation, driving the inner protective sleeve (342) to rotate. This causes the inner guide groove (3421) and the outer guide groove (3431) to be misaligned circumferentially, trapping the liquid in the annular space between the protective sleeve (342) and the microporous diffuser (33) in the closed chamber between the inner side wall of the inner protective sleeve (342) and the outer side wall of the microporous diffuser (33) until the lower ratchet tooth of the floating ratchet (3413) engages with the lower end face ratchet (3412). S5: The high-pressure gas inside the microporous diffuser (33) is introduced into the closed chamber through the gap between the floating ratchet (3413) and the upper end ratchet (3411), which increases the liquid pressure in the closed chamber and drives the liquid to pass through the micropores from the outside to the inside of the microporous diffuser (33) in the opposite direction, flushing out the blockage in the micropores. S6: The gas and liquid in the sealed chamber leak into the primary generation channel through the gap between the inner protective sleeve (342) and the outer protective sleeve (343), causing the internal pressure of the microporous diffuser (33) to drop back to the normal operating pressure. The thrust spring (3414) pushes the floating ratchet (3413) to reset. The lower ratchet of the floating ratchet (3413) separates from the lower end face ratchet (3412), and the upper ratchet of the floating ratchet (3413) re-engages with the upper end face ratchet (3411). During the engagement process, the floating ratchet (3413) rotates in the opposite direction, causing the inner protective sleeve (342) to rotate in the opposite direction, so that the inner guide groove (3421) and the outer guide groove (3431) are realigned, and normal ventilation is restored.

10. The CO2 oil displacement method according to claim 9, characterized in that: include: By increasing the gas supply pressure of the gas injection system, the thrust generated by the pressure inside the microporous diffuser (33) exceeds the elastic force of the thrust spring (3414), triggering the S3-S6 flushing action. After flushing is completed, the gas supply pressure is reduced to restore normal ventilation.

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