Downhole gas-liquid-sand multi-stage separation device and method for oil and gas well

Abstract

The invention relates to the technical field of petroleum engineering, and discloses an underground gas-liquid-sand multi-stage separation device and method.The underground gas-liquid-sand multi-stage separation device comprises a first-stage inner pipe, a second-stage inner pipe and an outer pipe which are sequentially and annularly arranged from inside to outside, and the bottom end of the first-stage inner pipe and the bottom end of the second-stage inner pipe are both connected to a tail supporting plate; the top end of the second-stage inner pipe is connected to an annular head supporting plate, a cavity between the second-stage inner pipe and the outer pipe is sequentially divided into a first-stage sedimentation area, a second-stage sedimentation area and a third-stage sedimentation area from bottom to top through separation baffles, and a cavity between the second-stage inner pipe and the first-stage inner pipe is a cyclone separation area. An outer pipe inlet and an outer pipe exhaust port are formed in the side wall of the outer pipe, a second-stage inner pipe inlet is formed in the side wall of the second-stage inner pipe, and a first-stage inner pipe inlet is formed in the side wall of the first-stage inner pipe. Through the multi-stage separation process of the oil well produced liquid, the gas volume of an inlet of the oil well pump is reduced, the gas influence degree of the oil well pump is reduced, airlock is avoided, the pump efficiency is improved, and the production time rate of the oil well is increased.

Description

Technical Field

[0001] The present invention relates to the field of petroleum engineering technology, and more particularly to an underground gas-liquid-sand multi-stage separation device and method for oil and gas wells. Background Art

[0002] The anti-gas lift technology has shown a trend of large-scale application at the end of oil field development. First, with the continuous development of low-permeability / ultra-low permeability reservoirs, unconventional lift has become the research and development focus of new technologies. Low-permeability / ultra-low permeability oil wells cannot use water injection technology to displace oil reservoirs like conventional water drive, and can only rely on gas injection, CO 2 Unconventional development methods such as throughput have resulted in the generation of a large amount of gas and sand during the oil field lifting process, affecting the lifting efficiency. Especially in the application of tight oil, shale oil and other oil reservoirs, preventing gas lift has become a top priority; second, in the later stage of old oil field development, the reservoir pressure decreases, and the produced fluid is easily degassed inside the oil wellbore, causing the gas-liquid ratio of the oil well to increase and reduce pump efficiency; third, during the exploitation of gas wells, high water content is easy to cause well flooding, and a pump must be used to drain water and produce gas. The high gas content entering the pump will cause the pump to fail to work normally. The high gas content not only reduces the fullness of the pump and affects the pump efficiency, but also causes gas lock in severe cases, causing the oil well to be shut down and production to stop, making it impossible to guarantee production time. Therefore, it is necessary to use an efficient downhole gas-liquid separation device to reduce the gas volume at the inlet of the pump, ensure the normal operation of the pump, and maintain the continuous production of the oil well. Summary of the invention

[0003] In view of this, the present invention provides an underground gas-liquid-sand multi-stage separation device and method for oil and gas wells, which can reduce the gas volume at the inlet of the oil pump through a multi-stage separation process of the oil well production liquid, reduce the gas impact of the oil pump, avoid gas lock, improve pump efficiency and increase the production time rate of the oil well.

[0004] To achieve the above-mentioned purpose, the present invention provides an underground gas-liquid-sand multi-stage separation device for oil and gas wells, comprising a first-level inner tube, a second-level inner tube and an outer tube which are arranged in a circle from the inside to the outside, the bottom ends of the first-level inner tube and the second-level inner tube are connected to the tail support plate, the four sides of the tail support plate are connected to the inner wall of the outer tube, the top end of the second-level inner tube is connected to the annular head support plate, the inner ring of the head support plate is connected to the outer wall of the first-level inner tube, and the outer ring is connected to the inner wall of the outer tube, the top end of the second-level inner tube is connected between the inner ring and the outer ring of the head support plate, the chamber between the second-level inner tube and the outer tube is divided into a first-level sedimentation zone, a second-level sedimentation zone and a third-level sedimentation zone from bottom to top by a separation baffle, the chamber between the second-level inner tube and the first-level inner tube is a cyclone separation zone, the separation baffle is provided with a trapezoidal channel for connecting the first-level sedimentation zone, the second-level sedimentation zone and the third-level sedimentation zone, and the part of the tail support plate located in the first sedimentation zone is provided with a hole running through the upper and lower sides; An outer tube inlet connected to the first-stage sedimentation zone and an outer tube exhaust port connected to the third-stage sedimentation zone are provided on the side wall of the outer tube; a secondary inner tube inlet connected to the second-stage sedimentation zone and the cyclone separation zone is provided on the side wall of the secondary inner tube; a primary inner tube inlet connected to the cyclone separation zone and the inner cavity of the primary inner tube is provided on the side wall of the primary inner tube.

[0005] Preferably, two separation baffles are provided, namely a primary separation baffle and a secondary separation baffle, and the primary separation baffle is provided below the secondary separation baffle.

[0006] Preferably, there are a plurality of trapezoidal channels on the first-level separation baffle, and the plurality of trapezoidal channels are arranged radially along the first-level separation baffle, and the trapezoidal channels close to the second-level inner tube are of a wide-upper-narrow-lower structure, while the trapezoidal channels of the remaining first-level separation baffles are of a narrow-upper-wide-lower structure.

[0007] Preferably, a plurality of trapezoidal channels arranged radially on the primary separation baffle plate form a channel belt, and a plurality of channel belts are arranged in a circumferential array on the primary separation baffle plate.

[0008] Preferably, there are a plurality of trapezoidal channels on the secondary separation baffle, and the plurality of trapezoidal channels are arranged radially along the secondary separation baffle, and the trapezoidal channels close to the secondary inner tube are of a wide-upper-narrow-lower structure, while the trapezoidal channels of the remaining secondary separation baffles are of a narrow-upper-wide-lower structure.

[0009] Preferably, a plurality of trapezoidal channels arranged radially on the secondary separation baffle plate form a channel band, and the secondary separation baffle plate has a plurality of channel bands arranged in a circumferential array.

[0010] Preferably, the side wall of the first-level inner tube is inclined, and the acute angle between the side wall and the tail support plate is 60-75°.

[0011] Preferably, the side wall of the secondary inner tube is inclined, and the acute angle between the side wall and the tail support plate is 60-75°.

[0012] Preferably, the top end of the first-stage inner tube is connected to a pump, and the bottom end of the outer tube is connected to an oil pipe.

[0013] The present invention also provides a method for multi-stage separation of gas, liquid and sand in a downhole for an oil and gas well, which is applied to the above-mentioned multi-stage separation device for a downhole for an oil and gas well, and comprises the following steps: a. The gas-liquid-sand multiphase mixed medium enters the first-stage sedimentation area surrounded by the outer tube, the first-stage separation baffle, the second-stage inner tube, and the tail support plate through the outer tube inlet on the outer tube for the first sedimentation separation. The sand after the first sedimentation separation enters the oil pipe connected to the tail of the separation device through the holes on the tail support plate; b. After the first sedimentation separation, the mixed medium enters the second-stage sedimentation area surrounded by the first-stage separation baffle, the outer tube, the second-stage separation baffle, and the second-stage inner tube through the trapezoidal channel on the first-stage separation baffle for the second sedimentation separation; c. During the second sedimentation separation, a large portion of the gas and a small portion of the liquid enter the third sedimentation area surrounded by the outer tube, the second separation baffle, the second inner tube, and the head support plate through the trapezoidal channel on the second separation baffle for the third separation. The gas separated in the third separation is discharged from the separation device through the exhaust port of the outer tube, and the remaining liquid re-enters the second sedimentation area through the trapezoidal channel on the second separation baffle by gravity. The sand separated in the second sedimentation separation falls back to the first sedimentation area along the outer wall of the second inner tube, and continues to fall back along the outer wall of the second inner tube to the oil pipe connected to the tail of the separation device; d. During the second sedimentation separation, the remaining large portion of liquid and a small portion of gas enter the cyclone separation area surrounded by the first inner tube, the second inner tube, the tail support plate and the head support plate through the second inner tube inlet. The gas is separated from the liquid through cyclone separation and sedimentation. When the oil pump is in the downstroke, the gas enters the second sedimentation area from the cyclone separation area through the second inner tube inlet and is separated by sedimentation with the mixed medium entering from the first sedimentation area. The liquid separated in the cyclone separation area enters the first inner tube through the first inner tube inlet to be supplied to the oil pump for lifting.

[0014] It can be seen from the above technical solutions that, compared with the prior art, the downhole gas-liquid-sand multi-stage separation device for oil and gas wells provided by the present invention has a simple structure, no operating parts, and high reliability; the multi-stage separation method can remove the gas and sand in the mixed medium to the greatest extent through four separation processes of sedimentation and cyclone, which can not only improve the pumping efficiency of the oil pump, but also reduce the probability of sand entering the oil pump and causing the pump to get stuck, thereby extending the efficient operation cycle and pump inspection cycle of the oil well, and assisting the efficient exploitation of the oil field. At the same time, the present invention also has the following advantages: 1. The present invention adopts a multi-stage gas-liquid-sand separation mode that cooperates with three-stage sedimentation separation and one-stage cyclone separation. Most of the gas and sand in the produced liquid can be removed through the first three sedimentation separations. The gas entering the cyclone separation drive can be further removed by the final cyclone separation, thus achieving four separations as a whole. 2. Both the primary separation baffle and the secondary separation baffle use a trapezoidal structure as a channel for the flow of produced fluid, and the contraction direction of the trapezoidal channel on the primary separation baffle close to the secondary inner tube is opposite to the direction of gas movement. The trapezoidal channel can provide sand recovery and reduce the amount of liquid loss downward by using the gradually shrinking size downward. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0016] Figure 1 It is a vertical cross-sectional view of the underground gas-liquid-sand multi-stage separation device of the present invention; Figure 2 A top view of a primary separation baffle of the present invention; Figure 3 It is a bottom view of the primary separation baffle of the present invention.

[0017] Description of reference numerals: 1-outer tube, 2-outer tube inlet, 3-first-stage separation baffle, 4-second-stage separation baffle, 5-outer tube exhaust port, 6-head support plate, 7-first-stage inner tube, 8-second-stage inner tube, 9-second-stage inner tube inlet, 10-first-stage inner tube inlet, 11-rear support plate; A-first stage sedimentation zone, B-second stage sedimentation zone, C-third stage sedimentation zone, D-cyclone separation zone. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of an exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Please see attached Figure 1-3 The present invention discloses an underground gas-liquid-sand multi-stage separation device for oil and gas wells, which is applied to oil wells with high gas and sand content. On the one hand, the sand in the produced fluid is removed, and on the other hand, the gas in the produced fluid is removed through a multi-stage separation process, thereby reducing the gas content and sand content of the produced fluid at the inlet of the oil pump, so as to maintain the normal production of the oil pump and realize the continuous production of the oil well.

[0020] The present invention provides an underground gas-liquid-sand multi-stage separation device for oil and gas wells, comprising an outer tube 1, a primary separation baffle 3, a secondary separation baffle 4, a head support plate 6, a primary inner tube 7, a secondary inner tube 8, and a tail support plate 11. The top end of the primary inner tube 7 is connected to a pump, and the bottom end of the outer tube 1 is connected to an oil pipe.

[0021] The primary inner tube 7, the secondary inner tube 8 and the outer tube 1 are arranged in sequence from the inside to the outside. The primary inner tube 7 is located inside the secondary inner tube 8 and is fixed by the head support plate 6 and the tail support plate 11 to prevent displacement and shaking. The side wall of the primary inner tube 7 is inclined, and the acute angle between it and the tail support plate 11 is 60-75°. The side wall of the secondary inner tube 8 is inclined, and the acute angle between it and the tail support plate 11 is 60-75°. The vertical section of the primary inner tube 7 and the secondary inner tube 8 is trapezoidal, and the upper wide and lower narrow or upper narrow and lower wide structures are both possible.

[0022] The tail support plate 11 is located at the bottom of the primary inner tube 7 and the secondary inner tube 8. The tail support plate 11 is respectively interference fit with the primary inner tube 7 and the secondary inner tube 8, and is connected to the outer tube 1 by welding or threading. The four sides of the tail support plate 11 are connected to the inner wall of the outer tube 1.

[0023] The head support plate 6 is annular, and the lower part of the head support plate 6 contacts the top of the secondary inner tube 8, relying on interference fit to ensure sealing, and the top of the secondary inner tube 8 is located between the inner ring and the outer ring of the head support plate 6. The outer side of the head support plate 6 contacts the inner wall of the outer tube 1 and is connected by welding or threading; the inner side of the head support plate 6 contacts the outer wall of the primary inner tube 7 and is connected by welding or threading.

[0024] The chamber between the secondary inner tube 8 and the outer tube 1 is divided into a first-stage sedimentation zone A, a second-stage sedimentation zone B and a third-stage sedimentation zone C from bottom to top by a separation baffle. Two separation baffles are provided, namely a first-stage separation baffle 3 and a second-stage separation baffle 4. The first-stage separation baffle 3 is arranged below the second-stage separation baffle 4. The chamber between the secondary inner tube 8 and the first-stage inner tube 7 is a cyclone separation zone D. The separation baffle is provided with a plurality of trapezoidal channels for connecting the first-stage sedimentation zone A, the second-stage sedimentation zone B and the third-stage sedimentation zone C. The part of the tail support plate 11 located in the first sedimentation zone is provided with a hole penetrating the upper and lower surfaces.

[0025] An outer tube inlet 2 communicating with the first-stage sedimentation zone A and an outer tube exhaust port 5 communicating with the third-stage sedimentation zone C are provided on the side wall of the outer tube 1 .

[0026] The outer tube inlet 2 is located at the lower part of the outer tube 1, and is a channel for the underground gas-liquid-sand multiphase mixed medium to enter the multistage separation device. The underground gas-liquid-sand multiphase mixed medium enters the first-stage sedimentation zone A of the annular space formed by the first-stage separation baffle 3, the outer tube 1, the tail support plate 11, and the second-stage inner tube 8 through the channel.

[0027] The outer tube exhaust port 5 is located at the upper part of the outer tube 1 and is used to discharge the internal gas of the annular space of the third-stage sedimentation zone C. Preferably, the position of the outer tube exhaust port 5 is above the vertical distance of the secondary separation baffle 4 and the head support plate 6.

[0028] A secondary inner tube inlet 9 connecting the second-stage sedimentation zone B and the cyclone separation zone D is provided on the side wall of the secondary inner tube 8. Preferably, the position of the secondary inner tube inlet 9 is above the middle of the vertical distance between the primary separation baffle 3 and the secondary separation baffle 4. It is the channel for most of the fluid and a small amount of gas in the annular space of the third-stage sedimentation zone C to enter the cyclone separation zone D, and it is also the outlet of the gas after separation in the cyclone separation zone D is completed.

[0029] A first-level inner tube inlet 10 connecting the cyclone separation zone D and the inner cavity of the first-level inner tube 7 is provided on the side wall of the first-level inner tube 7. Preferably, the first-level inner tube inlet 10 is located at the lower part of the first-level inner tube 7 and is a channel for the fluid in the cyclone separation zone D to enter the first-level inner tube 7.

[0030] The outer sides of the primary separation baffle 3 and the secondary separation baffle 4 are in contact with the inner wall of the outer tube 1 and are connected by welding or threading; the inner sides of the primary separation baffle 3 and the secondary separation baffle 4 are connected to the outer wall of the secondary inner tube 8 and are connected by welding or threading.

[0031] The primary separation baffle 3 is symmetrically distributed at 90°, the single trapezoidal channel on the primary separation baffle 3 is vertically arranged, and a plurality of trapezoidal channels are arranged along the radial direction of the primary separation baffle 3, the trapezoidal channel structure close to the secondary inner tube 8 is wide at the top and narrow at the bottom, and the remaining trapezoidal channel structures are narrow at the top and wide at the bottom; the secondary separation baffle 4 is symmetrically distributed at 90°, the trapezoidal channel on the secondary separation baffle 4 is vertically close to the trapezoidal channel of the secondary inner tube, and has a wide top and narrow bottom structure, and the remaining trapezoidal channels have a narrow top and wide bottom structure, and a plurality of trapezoidal channels are arranged along the radial direction of the secondary separation baffle 4.

[0032] The plurality of trapezoidal channels radially arranged on the primary separation baffle 3 and the secondary separation baffle 4 form a plurality of radial channel bands, and the plurality of channel bands are arranged along the circumferential array of the primary separation baffle 3 and the secondary separation baffle 4, respectively.

[0033] On the other hand, the present invention provides a multi-stage gas-liquid-sand separation method for an oil and gas well, comprising the following steps: a. The gas-liquid-sand multiphase mixed medium enters the first-stage settling area A surrounded by the outer tube 1, the first-stage separation baffle 3, the second-stage inner tube 8, and the tail support plate 11 through the outer tube inlet 2 on the outer tube 1 for the first settling separation. The sand after the first settling separation enters the oil pipe connected to the tail of the separation device through the holes on the tail support plate 11; b. After the first sedimentation separation, the mixed medium enters the second sedimentation area B surrounded by the first separation baffle 3, the outer tube 1, the second separation baffle 4, and the second inner tube 8 through the trapezoidal channel on the first separation baffle 3 for the second sedimentation separation; c. During the second sedimentation separation, a large portion of the gas and a small portion of the liquid enter the third sedimentation area C surrounded by the outer tube 1, the secondary separation baffle 4, the secondary inner tube 8, and the head support plate 6 through the trapezoidal channel on the secondary separation baffle 4 for the third separation. The gas separated in the third separation is discharged from the separation device through the outer tube exhaust port 5, and the remaining liquid re-enters the second sedimentation area B through the trapezoidal channel on the secondary separation baffle 4 under the action of gravity. The sand separated in the second sedimentation separation falls back to the first sedimentation area A along the outer wall of the secondary inner tube 8, and continues to fall back along the outer wall of the secondary inner tube 8 to the oil pipe connected to the tail of the separation device; d. During the second sedimentation separation, the remaining large portion of liquid and a small portion of gas enter the cyclone separation area D surrounded by the primary inner tube 7, the secondary inner tube 8, the tail support plate 11, and the head support plate 6 through the secondary inner tube inlet 9. The gas is separated from the liquid through the cyclone separation and sedimentation effects. When the oil pump is in the downstroke, the gas enters the second-stage sedimentation area B from the cyclone separation area D through the secondary inner tube inlet 9, and is separated by sedimentation with the mixed medium entering from the first-stage sedimentation area A. The liquid separated in the cyclone separation area D enters the primary inner tube 7 through the primary inner tube inlet 10 to be supplied to the oil pump for lifting.

[0034] Test Example 1: Test Example 1 of a multi-stage gas-liquid-sand separation method for an oil and gas well, comprising: Step 1: Take the target well A1 as an example. The well is located in the gas drive test area of ​​an oil field. The ground lifting device is a pumping unit. Initially, a Ø38 general pumping pump is used for production. No gas anchor is installed. The stroke frequency is 4 times per minute, which is the minimum stroke frequency. The pump efficiency at production is 50%; Step 2: Six months after the gas-driven oil well was put into production, the gas-liquid ratio was detected to be gradually increasing at the wellhead, and the pump efficiency was reduced to 20%. Twelve months after the well was put into production, the gas-liquid ratio further increased by ≥400m³ / m³, and the pump efficiency of the oil well pump dropped to below 10%. The dynamometer test showed that the well was seriously affected by gas, and gas lock often occurred to stop the well, which seriously affected the oil well production capacity; Step 3: Since the well gas has a serious impact, a pump inspection is performed on it. After the original well Ø38 general pumping oil well pump is tested and found to have no problems, the downhole gas-liquid-sand multi-stage separation device of the present invention is installed under the pump and lowered into the original well along with the oil well pump. After the measures are implemented, the dynamometer diagram test shows that the gas impact is significantly reduced, the dynamometer diagram tends to be full, and the pump efficiency of the oil well pump is restored to 35%.

[0035] Test Example 2: Test Example 2 of a multi-stage gas-liquid-sand separation method for an oil and gas well, comprising: Step 1: Take the target well A2 as an example. The well is located in an old area of ​​an oil field and has been in production for 30 years. The formation pressure is significantly lower than when it was put into production. It has high water and sand content. The pump inspection cycle is 60 days. A 57-type oil well pump is used for production. The stroke frequency is 4 times per minute. Conventional spiral gas anchor is used for production. As the gas-liquid ratio increases and the liquid production decreases, the pump efficiency decreases from 50% to 10%, and gas lock often occurs; Step 2: During the pump inspection operation, the conventional spiral air anchor is replaced by the downhole gas-liquid-sand multi-stage separation device of the present invention, and the oil pump is the original well Ø57 general oil pumping pump, so as to observe the working performance of the downhole gas-liquid-sand multi-stage separation device of the present invention; Step 3: After applying the downhole gas-liquid-sand multi-stage separation device of the present invention, the well still adopts a working system of 5 flushes / minute for production, and the gas-liquid ratio, pump efficiency, and dynamometer diagram tests are carried out on the well every 3 days. After the implementation of the measures, relying on the downhole gas-liquid-sand multi-stage separation device of the present invention, there is no gas lock phenomenon in the well, and the influence of the dynamometer diagram test gas is significantly reduced. The pump efficiency is maintained above 30% for 30 consecutive days, and the pump inspection cycle exceeds 120 days. The sand content in the produced fluid is significantly reduced, and the working performance is stable.

[0036] In summary, the present invention further improves the downhole gas-liquid separation effect through the four-time separation effect of sedimentation and cyclone, and can also remove solid particle sand in the produced fluid, reduce the inlet gas volume and sand content of the oil pump, improve pump efficiency, extend the pump inspection cycle, and assist in efficient exploitation of the oil field.

[0037] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A downhole gas-liquid-sand multi-stage separation device for oil and gas wells, characterized in that: The invention comprises a first-level inner tube (7), a second-level inner tube (8) and an outer tube (1) which are arranged in a circle from the inside to the outside in sequence, wherein the bottom ends of the first-level inner tube (7) and the second-level inner tube (8) are connected to a tail support plate (11), the four sides of the tail support plate (11) are connected to the inner wall of the outer tube (1), the top end of the second-level inner tube (8) is connected to a ring-shaped head support plate (6), the inner ring of the head support plate (6) is connected to the outer wall of the first-level inner tube (7), the outer ring is connected to the inner wall of the outer tube (1), and the top end of the second-level inner tube (8) is connected to the ring-shaped head support plate (6). Connected between the inner ring and the outer ring of the head support plate (6), the chamber between the secondary inner tube (8) and the outer tube (1) is divided into a first-stage sedimentation zone, a second-stage sedimentation zone and a third-stage sedimentation zone from bottom to top by a separation baffle, the chamber between the secondary inner tube (8) and the primary inner tube (7) is a cyclone separation zone, the separation baffle is provided with a trapezoidal channel for connecting the first-stage sedimentation zone, the second-stage sedimentation zone and the third-stage sedimentation zone, and the portion of the tail support plate (11) located in the first sedimentation zone is provided with a hole penetrating the upper and lower surfaces; The outer tube (1) is provided with an outer tube inlet (2) communicating with the first-stage sedimentation zone and an outer tube exhaust port (5) communicating with the third-stage sedimentation zone on its side wall; the second-stage inner tube (8) is provided with a second-stage inner tube inlet (9) communicating with the second-stage sedimentation zone and the cyclone separation zone on its side wall; and the first-stage inner tube (7) is provided with a first-stage inner tube inlet (10) communicating with the cyclone separation zone and the inner cavity of the first-stage inner tube (7) on its side wall.

2. The downhole gas-liquid-sand multi-stage separation device for oil and gas wells according to claim 1, characterized in that: The separation baffles are provided with two, namely a primary separation baffle (3) and a secondary separation baffle (4); the primary separation baffle (3) is provided below the secondary separation baffle (4).

3. The downhole gas-liquid-sand multi-stage separation device for oil and gas wells according to claim 2, characterized in that: A plurality of trapezoidal channels are provided on the first-stage separation baffle (3), and the plurality of trapezoidal channels are arranged along the radial direction of the first-stage separation baffle (3), and the trapezoidal channels close to the second-stage inner tube (8) are of a structure that is wide at the top and narrow at the bottom, while the trapezoidal channels of the remaining first-stage separation baffles (3) are of a structure that is narrow at the top and wide at the bottom.

4. The downhole gas-liquid-sand multi-stage separation device for oil and gas wells according to claim 3, characterized in that: A plurality of trapezoidal channels arranged radially on the primary separation baffle (3) form a channel belt, and the primary separation baffle (3) has a plurality of channel belts arranged in an array along the circumferential direction.

5. The downhole gas-liquid-sand multi-stage separation device for oil and gas wells according to claim 2, characterized in that: A plurality of trapezoidal channels are provided on the secondary separation baffle (4), and the plurality of trapezoidal channels are arranged along the radial direction of the secondary separation baffle (4), and the trapezoidal channels close to the secondary inner tube (8) are of a structure that is wide at the top and narrow at the bottom, while the trapezoidal channels of the remaining secondary separation baffles (4) are of a structure that is narrow at the top and wide at the bottom.

6. The downhole gas-liquid-sand multi-stage separation device for oil and gas wells according to claim 5, characterized in that: A plurality of trapezoidal channels arranged radially on the secondary separation baffle (4) form a channel belt, and the secondary separation baffle (4) has a plurality of channel belts arranged in an array along the circumferential direction.

7. The downhole gas-liquid-sand multi-stage separation device for oil and gas wells according to claim 1, characterized in that: The side wall of the first-stage inner tube (7) is arranged to be inclined, and the acute angle between the side wall and the tail support plate (11) is 60-75°.

8. The downhole gas-liquid-sand multi-stage separation device for oil and gas wells according to claim 1, characterized in that: The side wall of the secondary inner tube (8) is arranged to be inclined, and the acute angle between the side wall and the tail support plate (11) is 60-75 degrees.

9. The downhole gas-liquid-sand multi-stage separation device for oil and gas wells according to claim 1, characterized in that: The top end of the first-stage inner tube (7) is connected to an oil pump, and the bottom end of the outer tube (1) is connected to an oil pipe.

10. A method for downhole gas-liquid-sand multi-stage separation for oil and gas wells, applied to the downhole gas-liquid-sand multi-stage separation device according to any one of claims 1 to 9, characterized in that: The multi-stage separation method comprises the following steps: a. The gas-liquid-sand multiphase mixed medium enters the first-stage sedimentation area surrounded by the outer tube (1), the first-stage separation baffle (3), the second-stage inner tube (8), and the tail support plate (11) through the outer tube inlet (2) on the outer tube (1) for the first sedimentation separation. The sand after the first sedimentation separation enters the oil pipe connected to the tail of the separation device through the holes on the tail support plate (11); b. After the first sedimentation separation, the mixed medium enters the second sedimentation area surrounded by the first separation baffle (3), the outer tube (1), the second separation baffle (4), and the second inner tube (8) through the trapezoidal channel on the first separation baffle (3) for second sedimentation separation; c. During the second sedimentation separation, a large portion of the gas and a small portion of the liquid enter the third sedimentation area surrounded by the outer tube (1), the second separation baffle (4), the second inner tube (8), and the head support plate (6) through the trapezoidal channel on the second separation baffle (4) for a third separation. The gas separated in the third separation is discharged from the separation device through the outer tube exhaust port (5), and the remaining liquid re-enters the second sedimentation area through the trapezoidal channel on the second separation baffle (4) under the action of gravity. The sand separated in the second sedimentation separation falls back to the first sedimentation area along the outer wall of the second inner tube (8), and continues to fall back along the outer wall of the second inner tube (8) to the oil pipe connected to the tail of the separation device; d. During the second sedimentation separation, the remaining large portion of liquid and a small portion of gas enter the cyclone separation zone surrounded by the first inner tube (7), the second inner tube (8), the tail support plate (11), and the head support plate (6) through the second inner tube inlet (9). The gas is separated from the liquid through the cyclone separation and sedimentation action. When the oil pump is in the downstroke, the gas enters the second sedimentation zone from the cyclone separation zone through the second inner tube inlet (9) and is subjected to sedimentation separation with the mixed medium entering from the first sedimentation zone. The liquid separated in the cyclone separation zone enters the first inner tube (7) through the first inner tube inlet (10) and is supplied to the oil pump for lifting.

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