Floating sand flushing tool for horizontal wells with long horizontal sections

Abstract

The present invention belongs to the technical field of sand flushing and well washing tools, specifically relating to a buoyant sand flushing tool for long horizontal wells. This tool aims to address the low efficiency and difficulty of existing sand flushing tools in reaching a predetermined position. The tool comprises an outer barrel and a buoyancy chamber assembly disposed within the barrel. The outer barrel has an oblique front end and rollers are evenly distributed circumferentially along its outer wall. As the tool advances and descends into the wellbore, high-pressure liquid within the wellbore enters the chamber of the buoyancy chamber assembly, ensuring that the buoyancy chamber assembly remains positioned in the lower half of the outer barrel under the action of gravity. When the tool reaches the sand flushing position, the impact of the reverse circulating liquid flow triggers a gas generator mechanism within the buoyancy chamber assembly to generate gas, which displaces the liquid and fills the chamber. Under the action of buoyancy, the buoyancy chamber assembly rotates and rises to the upper half of the outer barrel. This tool significantly improves sand flushing efficiency and generates a spiraling force that forces the sand flushing string down to the desired position.

Description

Technical Field

[0001] The invention belongs to the technical field of sand flushing and well washing tools, and in particular relates to a buoyancy sand flushing tool for a horizontal well with a long horizontal section. Background Art

[0002] In order to ensure stable and high production in various oil fields, the number of horizontal wells has increased rapidly. However, after a period of production, horizontal wells are prone to sand burial, which may affect production at the least and jam the pipe string or tools at the worst, causing the horizontal well to be scrapped. Therefore, horizontal well sand flushing is a common task in downhole operations, but horizontal well sand flushing, especially horizontal well sand flushing with long horizontal sections, is a high-risk operation project. This is mainly because: (1) The sand accumulated in the horizontal well forms a sand bed on the lower surface of the horizontal section and forms a sand bridge near the beveling section. Positive circulation sand flushing is to pump liquid into the tubing. The liquid stirs the sediment and flushes it, and then returns to the ground with the sand flushing liquid through the annulus of the tubing and casing. The working pressure required is high and the liquid volume is large. Once the pump is stopped, the sand settles quickly, resulting in sand burial in the pipe string. The current reverse circulation sand flushing is to pump liquid into the annulus of the tubing and casing. The liquid flows to the bottom of the sand flushing tool, reverses into the outer cylinder of the sand flushing tool, and returns to the ground through reverse circulation. Since the sand bed is on the lower surface, the flow resistance of the sand flushing fluid is large. Therefore, most of the sand flushing fluid flows away from the upper part of the reverse circulation sand flushing tool when it enters the oil pipe through the sand flushing tool, and fails to play the role of impacting the sand bed and carrying the settled sand, making it difficult to return the sand and inefficient. (2) For horizontal wells with long horizontal sections, since the body of the sand flushing pipe string will be close to the lower surface of the horizontal section under the action of gravity, the longer the horizontal section extends and the more pipe strings are lowered, the greater the friction. When the applied drilling pressure cannot overcome the friction of the pipe string, the entire sand flushing pipe string and the bottom sand flushing tool are difficult to be lowered into the predetermined position, resulting in the failure of the sand flushing operation. The use of existing hydraulic oscillators and metal resistance reducing agents is expensive and has limited effect, making horizontal well sand flushing with long horizontal sections time-consuming, labor-intensive and costly. Therefore, there is an urgent need for a horizontal well sand flushing tool with a simple and reliable structure and good and stable performance for long horizontal well sections to achieve efficient, safe, time-saving and labor-saving horizontal well sand flushing operations. Summary of the Invention

[0003] The invention provides a buoyancy type sand flushing tool for a horizontal well with a long horizontal section, so as to solve the problems that the existing sand flushing tools have low sand flushing efficiency and are difficult to be lowered into a predetermined position.

[0004] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0005] A buoyancy sand flushing tool for a horizontal well with a long horizontal section comprises an outer cylinder and a buoyancy chamber assembly arranged in the outer cylinder. The front end of the outer cylinder is an oblique opening and rollers are evenly distributed circumferentially on the outer wall of the outer cylinder. When the sand flushing tool is advanced and lowered into the wellbore, high-pressure liquid in the wellbore enters the cavity of the buoyancy chamber assembly so that the buoyancy chamber assembly is always located in the lower half of the outer cylinder under the action of gravity. When the sand flushing tool is lowered to the sand flushing position, under the impact of the reverse circulating liquid flow, a gas generator mechanism in the buoyancy chamber assembly generates gas, which discharges the liquid and fills the cavity of the buoyancy chamber assembly. Under the action of buoyancy, the buoyancy chamber assembly rotates and floats up and is located in the upper half of the outer cylinder.

[0006] Furthermore, the buoyancy chamber assembly is a hollow semi-cylindrical cylinder and is located at the front end of the outer cylinder cavity. The bottom wall of the buoyancy chamber assembly is flat and the outer diameter of the semicircle is smaller than the inner diameter of the outer cylinder. The buoyancy chamber assembly is sealed at one end close to the oblique mouth of the outer cylinder and extends upward from the bottom wall in the direction close to the oblique mouth to intersect with the arc-shaped top wall of the semi-cylindrical cylinder to form a guide end. A first valve hole and a two-way flow adaptive valve arranged in the first valve hole are provided on the sealing baffle at the other end. The two-way flow adaptive valve opens or closes under the action of pressure difference to control the liquid or gas entering and exiting the buoyancy chamber assembly.

[0007] Furthermore, a stepped structure is laterally arranged on the inner wall of the first valve hole, and the small-diameter end of the first valve hole faces the cavity of the buoyancy chamber assembly. The two-way flow adaptive valve includes a spherical valve core, a first valve plug, a valve core ball, a pressure spring and a long-tail pressure cover; the first valve plug is threadedly connected to the large-diameter end of the first valve hole, and the diameter of the valve core is between the large-diameter and small-diameter ends of the first valve hole; a stepped through hole is arranged on the central axis of the valve core, and the large-diameter end of the valve core faces the cavity of the buoyancy chamber assembly, and the diameter of the valve core ball is between the large-diameter and small-diameter ends of the valve core, the long-tail pressure cover is threadedly connected to the large-diameter end of the valve core, a stepped through hole is arranged inside the long-tail pressure cover, and the small-diameter end faces the cavity of the buoyancy chamber assembly, and the pressure spring is located between the valve core ball and the long-tail pressure cover.

[0008] Furthermore, an axially penetrating buoyancy tube is provided in the center of the bottom wall of the buoyancy chamber assembly along the central axis of the buoyancy chamber assembly; the gas generator mechanism includes a generator fixed on the bottom wall, a first motor connected to the generator, a first piston rod and a second piston rod connected to the output end of the first motor, a first medicine barrel connected to the first piston rod, a second medicine barrel connected to the second piston rod, a first spiral mixing nozzle connected to the outlet of the first medicine barrel and the second medicine barrel, and a power generation impeller located in the buoyancy tube; the medicines in the first medicine barrel and the second medicine barrel can generate gas after mixing; the shaft of the power generation impeller passes through the bottom wall and is connected to the generator, and when the power generation impeller rotates under the impetus of the liquid flow, it provides power for the generator to generate electricity.

[0009] Furthermore, the buoyancy chamber assembly also includes a ring, which is fixed in the middle of the arc-shaped top wall of the semi-cylindrical tube, and the outer tube is mounted outside the ring; the buoyancy chamber assembly is rotatably connected to the inner wall of the outer tube through a buoyancy rotation support mechanism; the buoyancy rotation support mechanism includes an upper semi-circular ball groove arranged on the inner wall of the outer tube, a lower semi-circular ball groove arranged on the outer wall of the ring, balls located between the ball grooves formed by the upper ball groove and the lower ball groove, a ball hole arranged on the wall of the outer tube and connected to the upper ball groove, and a screw plug threadedly connected to the ball hole.

[0010] Furthermore, two sealing rings and two sand-proof rings located outside the sealing rings are symmetrically arranged between the inner wall of the outer cylinder and the outer wall of the circular ring with the ball groove as the axis. The sand-proof rings are installed in the sand-proof groove on the inner wall of the outer cylinder and are used to prevent sand from entering the sealing structure formed by the sealing ring to affect the seal; a number of spiral grooves are arranged on the inner wall of the outer cylinder, and the spiral grooves extend from the oblique mouth in the direction away from the oblique mouth to the sand-proof groove, and the spiral grooves are equidistant.

[0011] Furthermore, the buoyancy chamber assembly also includes a sand-sinking gas back-blowing device mechanism and a sealed cavity located in the cavity of the buoyancy chamber assembly; the sealed cavity is a small sealed cavity located in the upper part of the cavity of the buoyancy chamber assembly, and the top wall of the sealed cavity and the side wall away from the oblique mouth are respectively the arc-shaped top wall of the buoyancy chamber assembly and a part of the sealing baffle, and the upper part of the first side wall of the sealed cavity parallel to the sealing baffle is fan-shaped and intersects with the arc-shaped top wall; the sand-sinking gas back-blowing device mechanism includes a gas back-blowing device arranged in the sealed cavity and fixed to the buoyancy chamber assembly The second motor is arranged on the arc-shaped inner wall, the third piston rod and the fourth piston rod are connected to the output end of the second motor, the third medicine barrel is connected to the third piston rod, the fourth medicine barrel is connected to the fourth piston rod, and the second spiral mixing nozzle is connected to the third medicine barrel and the fourth medicine barrel, and the battery is located outside the sealed cavity; the medicine in the third medicine barrel and the fourth medicine barrel can generate gas after mixing; when the buoyancy chamber assembly is reversed from the upper half of the outer cylinder to the lower half, the battery and the second motor are connected through the sliding ball power-on mechanism.

[0012] Furthermore, the sliding ball power supply mechanism includes an arc-shaped upper sliding groove arranged along the first side wall of the sealed cavity and facing the battery, a lower sliding groove arranged below the upper sliding groove and having the same size as the upper sliding groove, a bottom cover arranged at the bottom of the lower sliding groove, an intermediate baffle arranged between the upper sliding groove and the lower sliding groove, and a sliding ball sliding in the upper sliding groove and the lower sliding groove; the upper sliding groove and the lower sliding groove form a sliding track, and the sliding ball slides in the sliding track; the sliding ball is a metal ball, the intermediate baffle is made of fragile material, the power supply end of the second motor passes through the first side wall and the distance between the power supply end and the power supply end of the battery is equal to the diameter of the sliding ball; when the sand flushing tool advances and is lowered into the wellbore, the sliding ball is located above the intermediate baffle; when the sand flushing tool is lowered to the sand flushing position, the sliding ball slides to the bottom cover of the lower sliding groove under the action of gravity; when the buoyancy chamber assembly reverses back to the low position, the sliding ball slides from the bottom cover toward the baffle, breaks the intermediate baffle and slides to the arc-shaped top wall, and the power supply end of the second motor is connected to the power supply end of the battery through the sliding ball.

[0013] Furthermore, a second valve hole and a one-way check valve arranged in the second valve hole are also provided on the sealing baffle. A stepped structure is laterally provided on the inner wall of the second valve hole, and the small aperture end of the second valve hole faces the sealing cavity; the one-way check valve includes a one-way ball and a second valve plug, the diameter of the one-way ball is between the large aperture and the small aperture of the second valve hole, and the second valve plug is threadedly connected to the large aperture end of the second valve hole.

[0014] Furthermore, it also includes an auxiliary short section, one end of which is threadedly connected to the end of the outer cylinder, the length of the auxiliary short section is 1 / 2 of the outer cylinder, and rollers are evenly distributed on the outer wall of the auxiliary short section.

[0015] The beneficial effects of the buoyancy sand flushing tool for long horizontal wells in the present invention are analyzed as follows:

[0016] A buoyancy sand flushing tool for a horizontal well with a long horizontal section comprises an outer cylinder and a buoyancy chamber assembly arranged in the outer cylinder. The front end of the outer cylinder is an oblique opening and rollers are evenly distributed circumferentially on the outer wall of the outer cylinder. When the sand flushing tool is advanced and lowered into the wellbore, high-pressure liquid in the wellbore enters the cavity of the buoyancy chamber assembly so that the buoyancy chamber assembly is always located in the lower half of the outer cylinder under the action of gravity. When the sand flushing tool is lowered to the sand flushing position, under the impact of the reverse circulating liquid flow, a gas generator mechanism in the buoyancy chamber assembly generates gas, which discharges the liquid and fills the cavity of the buoyancy chamber assembly. Under the action of buoyancy, the buoyancy chamber assembly rotates and floats up and is located in the upper half of the outer cylinder.

[0017] During construction, the end of the outer tube is connected to the oil pipe, and the front end of the outer tube is beveled, with small forward resistance. When encountering resistance, the sand flushing string can be lowered and rotated at the same time, relying on the rolling friction between the roller on the outer wall of the outer tube and the inner wall of the casing to form a spiral forward force, forcing the sand flushing string to move forward, thereby achieving the purpose of lowering the sand flushing string to the predetermined position in a long horizontal section.

[0018] After the sand flushing tool is lowered to the designated position, a reverse circulation liquid flow is established. The gas generator mechanism in the buoyancy chamber assembly generates gas, which discharges the liquid out of the cavity and fills the cavity. The buoyancy of the buoyancy chamber assembly is greater than the gravity, and the buoyancy chamber assembly flips to the upper half of the outer cylinder, forcing the liquid to flow through the lower half of the outer cylinder, thereby flushing the settled sand at the bottom of the wellbore, greatly improving the efficiency and probability of sand particles entering the outer cylinder, and being carried by the liquid to be discharged from the inside of the oil pipe and the oil pipe reflux, thereby improving the utilization rate of hydraulic energy and the efficiency of sand flushing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in related technologies, the following briefly introduces the drawings required for use in the specific embodiments or related technical descriptions. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic diagram of a full cross-section structure of an outer cylinder and a buoyancy chamber assembly provided in an embodiment of the present invention;

[0021] Figure 2 A partial cross-sectional view of an outer cylinder and a buoyancy chamber assembly provided in an embodiment of the present invention;

[0022] Figure 3 A side view of an outer cylinder and buoyancy chamber assembly provided in accordance with an embodiment of the present invention;

[0023] Figure 4 A full cross-sectional view of an outer cylinder provided in an embodiment of the present invention;

[0024] Figure 5 A side view of an outer cylinder provided in accordance with an embodiment of the present invention;

[0025] Figure 6 Schematic diagram of the exterior of the buoyancy chamber assembly provided by an embodiment of the present invention (floating state);

[0026] Figure 7 A full cross-sectional view of a sealing baffle provided in an embodiment of the present invention;

[0027] Figure 8 A side view of a sealing baffle provided in accordance with an embodiment of the present invention;

[0028] Figure 9 A full cross-sectional view of a bidirectional flow adaptive valve provided in an embodiment of the present invention;

[0029] Figure 10 A schematic diagram of the installation of a bidirectional flow adaptive valve provided in an embodiment of the present invention;

[0030] Figure 11 Schematic diagram of the installation of a one-way check valve and a two-way flow adaptive valve provided in an embodiment of the present invention;

[0031] Figure 12 A schematic diagram of the full cross-section structure of the buoyancy chamber assembly provided in an embodiment of the present invention (floating state);

[0032] Figure 13 Provided for the embodiments of the present invention Figure 12 Partially enlarged views of points A and B, where B-1 is the exhaust state of the bidirectional flow adaptive valve, and B-2 is the water inlet state of the bidirectional flow adaptive valve;

[0033] Figure 14 A schematic diagram of a gas generator mechanism provided in an embodiment of the present invention;

[0034] Figure 15 A side view of a gas generator mechanism provided for an embodiment of the present invention;

[0035] Figure 16 A full cross-sectional view of the buoyancy chamber assembly provided in an embodiment of the present invention (reversed back to the low position);

[0036] Figure 17 Provided for the embodiments of the present invention Figure 16 A partial enlarged view of point C in the middle;

[0037] Figure 18 A partial cross-sectional view of a buoyancy chamber assembly provided in an embodiment of the present invention (in a floating state);

[0038] Figure 19 A partial cross-sectional view of a buoyancy chamber assembly provided in an embodiment of the present invention (reversed back to a low position);

[0039] Figure 20 Provided for the embodiments of the present invention Figure 19 A partial enlarged view of point D in the middle;

[0040] Figure 21 Three state views of the anti-sand deposition gas backblowing device mechanism provided in an embodiment of the present invention;

[0041] Figure 22 A side view of a balancing stabilizer provided in accordance with an embodiment of the present invention;

[0042] Figure 23 A side view of an auxiliary sub provided in accordance with an embodiment of the present invention;

[0043] Figure 24 A schematic diagram of the tubing string structure provided in an embodiment of the present invention.

[0044] Icons: 1-1-outer cylinder; 1-2-roller; 1-3-buoyancy rotation support mechanism; 1-3-1-ball hole; 1-3-2-upper ball groove; 1-3-3-ball; 1-3-4-lower ball groove; 1-3-5-screw plug; 1-4-spiral groove; 1-5-1-sealing ring; 1-6-1-sand control ring; 1-5-2-sealing groove; 1-6-2-sand control groove; 1-7-oblique mouth; 2-buoyancy chamber assembly; 2-1-1-arc top wall; 2-1-2-bottom wall; 2-2-gas generator mechanism; 2-2-1-power generation impeller; 2-2-2-generator; 2-2-3-power supply line; 2-2-4- First motor; 2-2-5-1-first piston rod; 2-2-5-2-second piston rod; 2-2-6-1-first medicine cartridge; 2-2-6-2-second medicine cartridge; 2-2-7-first spiral mixing nozzle; 2-2-7-1-first spiral mixing head; 2-3-sand-settling gas blowback mechanism; 2-3-1-battery; 2-3-2-sealed chamber; 2-3-2-1-bottom plate; 2-3-2-2-first side wall; 2-3-2-3-second side wall; 2-3-3-sliding ball electrification mechanism; 2-3-3-1-down slide body; 2-3-3-2-sliding track; 2-3-3-2-1-upper Slide; 2-3-3-2-2-slide slide; 2-3-3-3-slide ball; 2-3-3-4-middle baffle; 2-3-3-5-bottom cover; 2-3-4-second motor; 2-3-5-1-third piston rod; 2-3-5-2-fourth piston rod; 2-3-6-1-third medicine cartridge; 2-3-6-2-fourth medicine cartridge; 2-3-7-second spiral mixing nozzle; 2-3-7-1-second spiral mixing head; 2-4-sealing baffle; 2-4-1-baffle body; 2-4-1-1-second valve hole; 2-4-1-2-first valve hole; 2-4-2-one-way check valve; 2-4-2 -1-One-way ball; 2-4-1-1-1-Valve seat C; 2-4-2-2-Second valve plug; 2-4-3-Two-way flow adaptive valve; 2-4-3-1-Valve core; 2-4-3-1-1-Valve seat A; 2-4-3-2-Valve core ball; 2-4-3-2-1-Valve seat B; 2-4-3-3-First valve plug; 2-4-3-4-Pressure spring; 2-4-3-5-Long tail gland; 2-4-3-5-1-Flange; 2-5-Balance stabilizer; 2-5-1-Wing stabilizer; 2-5-2-Bracket; 2-6-Diversion end; 2-7-Buoyancy tube; 2-8-Ring; 3-Auxiliary short section. DETAILED DESCRIPTION

[0045] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0046] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. Physical quantities in formulas, unless separately marked, should be understood as basic quantities of the International System of Units, or derived quantities derived from basic quantities through mathematical operations such as multiplication, division, differentiation or integration.

[0047] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0048] Horizontal well sand flushing is a common task in downhole operations. However, horizontal well sand flushing, especially horizontal well sand flushing with long horizontal sections, has problems such as low sand flushing efficiency and difficulty in reaching the predetermined position.

[0049] In view of this, please refer to Figures 1 to 6 The present invention provides a buoyancy sand flushing tool for a horizontal well with a long horizontal section, comprising an outer cylinder 1-1 and a buoyancy chamber assembly 2 arranged in the outer cylinder 1-1, the front end of the outer cylinder 1-1 being an oblique opening 1-7 and rollers 1-2 being uniformly distributed circumferentially on the outer wall of the outer cylinder 1-1; when the sand flushing tool is advanced and lowered into the wellbore, the high-pressure liquid in the wellbore enters the cavity of the buoyancy chamber assembly 2 so that the buoyancy chamber assembly 2 is always located in the lower half of the outer cylinder 1-1 under the action of gravity; when the sand flushing tool is lowered to the sand flushing position, under the impact of the reverse circulating liquid flow, the gas generator mechanism 2-2 in the buoyancy chamber assembly 2 generates gas, the gas discharges the liquid and fills the cavity of the buoyancy chamber assembly 2, and under the action of buoyancy, the buoyancy chamber assembly 2 rotates and floats up and is located in the upper half of the outer cylinder 1-1.

[0050] In an optional solution of this embodiment, the front end connector of outer tube 1-1 is provided with external threads that can be threadedly connected to the internal threads of the oil pipe. It is located at the bottom end of the sand flushing string. The bevel 1-7 at the front end of outer tube 1-1 is angled relative to the axis of outer tube 1-1. Bevel 1-7 is used to guide the tool forward by rotating the string when encountering obstacles during horizontal movement.

[0051] In an optional solution of this embodiment, the surface of the roller 1-2 is a patterned surface, and it is obliquely hinged to the outer wall of the outer cylinder 1-1 and forms a certain angle with the axis of the outer cylinder 1-1. According to the outer diameter and length of the outer cylinder 1-1, several rows of rollers 1-2 can be axially evenly distributed on the upper half of the outer wall of the outer cylinder 1-1, and each row has several rollers 1-2 and is circumferentially evenly distributed on the outer wall of the outer cylinder 1-1. The rollers 1-2 in each row are staggered at a certain angle.

[0052] During construction, the end of the outer tube 1-1 is connected to the oil pipe, and the front end of the outer tube 1-1 is oblique 1-7, which has small forward resistance. When encountering resistance, the sand flushing string can be lowered and rotated at the same time, relying on the rolling friction between the roller 1-2 on the outer wall of the outer tube 1-1 and the inner wall of the casing to form a spiral forward force, forcing the sand flushing string to move forward, thereby achieving the purpose of lowering the string in a long horizontal section.

[0053] After the sand flushing tool is lowered to the designated position, a reverse circulation liquid flow is established, and the gas generator mechanism 2-2 in the buoyancy chamber assembly 2 generates gas, which discharges the liquid out of the cavity and fills the cavity. The buoyancy of the buoyancy chamber assembly 2 is greater than the gravity, and the buoyancy chamber assembly 2 flips to the upper half of the outer tube 1-1, forcing the liquid to flow through the lower half of the outer tube 1-1, thereby flushing the settled sand at the bottom of the wellbore, greatly improving the efficiency and probability of sand particles entering the inner part of the outer tube 1-1, and being carried by the liquid and discharged from the inside of the oil pipe and the oil pipe reflux.

[0054] In an optional solution of this embodiment, the buoyancy chamber assembly 2 is a hollow semi-cylindrical cylinder and is located at the front end of the cavity of the outer cylinder 1-1. The bottom wall 2-1-2 of the buoyancy chamber assembly 2 is flat and the outer diameter of the semi-circle is smaller than the inner diameter of the outer cylinder 1-1. The buoyancy chamber assembly 2 is blocked at one end close to the oblique opening 1-7 of the outer cylinder 1-1 and extends upward from the bottom wall 2-1-2 in the direction close to the oblique opening 1-7 to intersect with the arc-shaped top wall 2-1-1 of the semi-cylindrical cylinder to form a guide end 2-6. The guide end 2-6 can guide the sand flushing liquid and reduce the resistance of the sand flushing liquid to the lower half of the wall of the outer cylinder 1-1. The sealing baffle 2-4 at the other end includes a fan-shaped baffle body 2-4-1, on which the baffle body 2-4-1 is provided a first valve hole 2-4-1-2 and a two-way flow adaptive valve 2-4-3 arranged in the first valve hole 2-4-1-2. The two-way flow adaptive valve 2-4-3 opens or closes under the action of pressure difference to control the liquid or gas entering and exiting the buoyancy chamber assembly 2.

[0055] In an optional solution of this embodiment, the exterior of the buoyancy chamber assembly 2 is sprayed with a wear-resistant alloy material to reduce the wear on the internal material when the sand flushing fluid carries sand and flows through.

[0056] Please refer to the shape and structure of the two-way flow adaptive valve 2-4-3. Figures 6 to 11 , the details are as follows:

[0057] A stepped structure is laterally arranged on the inner wall of the first valve hole 2-4-1-2. The small-aperture end of the first valve hole 2-4-1-2 faces the cavity of the buoyancy chamber assembly 2. The two-way flow adaptive valve 2-4-3 includes a spherical valve core 2-4-3-1, a first valve plug 2-4-3-3, a valve core ball 2-4-3-2, a pressure spring 2-4-3-4 and a long-tail pressure cover 2-4-3-5. The first valve plug 2-4-3-3 is a hollow cylinder with an external thread, and is connected to the internal thread of the large-diameter end of the first valve hole 2-4-1-2; the diameter of the valve core 2-4-3-1 is between the large and small diameters of the first valve hole 2-4-1-2, and the connection point of the stepped structure of the first valve hole 2-4-1-2 is the valve seat A 2-4-3-1-1 of the valve core 2-4-3-1; a stepped through hole is provided on the central axis of the valve core 2-4-3-1, and the valve core 2-4-3- The large-aperture end of 1 faces the cavity of the buoyancy chamber assembly 2, the diameter of the valve core ball 2-4-3-2 is between the large-aperture and small-aperture of the valve core 2-4-3-1, and the connection point of the stepped structure of the valve core 2-4-3-1 is the valve seat B 2-4-3-2-1 of the valve core ball 2-4-3-2; the long-tail gland 2-4-3-5 is threadedly connected to the large-aperture end of the valve core 2-4-3-1, and a stepped through hole is provided inside the long-tail gland 2-4-3-5, and the small-aperture end faces the cavity of the buoyancy chamber assembly 2 The diameter of the large aperture of the long tail gland 2-4-3-5 is slightly larger than the diameter of the pressure spring 2-4-3-4. The pressure spring 2-4-3-4 is located between the valve core ball 2-4-3-2 and the long tail gland 2-4-3-5 and the pressure spring 2-4-3-4 is in a compressed state. The outer wall of the small aperture end of the long tail gland 2-4-3-5 is provided with a flange 2-4-3-5-1. When the valve core 2-4-3-1 drives the long tail gland 2-4-3-5 to move away from the cavity of the buoyancy chamber assembly 2, the pressure spring 2-4-3-4 is in a compressed state. When the two-way flow adaptive valve 2-4-3 moves in the horizontal direction, the flange 2-4-3-5-1 abuts against the inner wall of the sealing baffle 2-4 around the small-diameter end of the first valve hole 2-4-1-2 to prevent the valve core 2-4-3-1 from rotating and rolling after the long-tail pressure cover 2-4-3-5 completely enters the first valve hole 2-4-1-2. The function of the flange 2-4-3-5-1 of the long-tail pressure cover 2-4-3-5 is to make the two-way flow adaptive valve 2-4-3 move in a straight line only in the horizontal direction. Although there is a certain amount of clearance, it can prevent its flipping movement.

[0058] In the optional solutions of this embodiment, please refer to Figures 12 to 15The bottom wall 2-1-2 of the buoyancy chamber assembly 2 is provided with an axially extending buoyancy tube 2-7 along the central axis of the buoyancy chamber assembly 2; the gas generator mechanism 2-2 includes a generator 2-2-2 fixed on the bottom wall 2-1-2, a first motor 2-2-4 connected to the generator 2-2-2 through a power supply line 2-2-3, a first piston rod 2-2-5-1 and a second piston rod 2-2-5-2 connected to the output end of the first motor 2-2-4, A first medicine cartridge 2-2-6-1 connected to the first piston rod 2-2-5-1, a second medicine cartridge 2-2-6-2 connected to the second piston rod 2-2-5-2, a first spiral mixing nozzle 2-2-7 connected to the outlets of the first medicine cartridge 2-2-6-1 and the second medicine cartridge 2-2-6-2, and a power generation impeller 2-2-1 located in the buoyancy tube 2-7; a first spiral mixing head 2-2-7-1 is installed at the outlet of the first spiral mixing nozzle 2-2-7. The medicines in the first medicine cartridge 2-2-6-1 and the second medicine cartridge 2-2-6-2 can generate gas when mixed. For example, the first medicine cartridge 2-2-6-1 contains medicine A, which is a nitrite-based medicine, and the second medicine cartridge 2-2-6-2 contains medicine B, which is an ammonium chloride-based medicine. When the two are mixed, nitrogen gas can be generated. The shaft of the power generation impeller 2-2-1 passes through the circular shaft hole of the bottom wall 2-1-2 and is connected to the generator 2-2-2. An O-ring 1-5-1 is installed between the shaft and the circular shaft hole to prevent liquid from passing through. When the power generation impeller 2-2-1 rotates under the impetus of the liquid flow, it provides power for the generator 2-2-2 to generate electricity.

[0059] The specific working process of the gas generator mechanism 2-2 and the two-way flow adaptive valve 2-4-3 is described as follows:

[0060] After the reverse circulation liquid flow is established, the liquid flows in through the annulus of the oil pipe and the casing, and flows into the cavity of the outer cylinder 1-1 through the oblique mouth 1-7 of the outer cylinder 1-1. When the liquid passes through the buoyancy tube 2-7, it impacts the power generation impeller 2-2-1, and the power generation impeller 2-2-1 rotates rapidly in the liquid flow, so that the generator 2-2-2 generates electricity by using the kinetic energy of the liquid. The electric energy is transmitted to the first motor 2-2-4 through the power supply line 2-2-3, promoting the first piston rod 2-2-5-1 and the second piston rod 2-2-5-2 to perform synchronous axial propulsion movement in the first medicine barrel 2-2-6-1 and the second medicine barrel 2-2-6-2 respectively, thereby pushing the A medicine and the B medicine into the first spiral mixing nozzle 2-2-7, and the mixture reacts rapidly under the sufficient stirring of the first spiral mixing head 2-2-7-1 to continuously produce nitrogen.

[0061] This gas rapidly generates and expands, rapidly increasing the pressure within buoyancy chamber assembly 2. When the pressure within buoyancy chamber assembly 2 exceeds the pressure of the water in the wellbore, the pressure differential acts on valve core ball 2-4-3-2 of bidirectional flow adaptive valve 2-4-3, forcing valve core ball 2-4-3-2 into contact with valve seat B 2-4-3-2-1, closing the water inlet passage. Under the action of the gas pressure, valve core 2-4-3-1 opens, releasing valve seat A 2-4-3-1-1. The water within buoyancy chamber assembly 2 is then expelled by the gas flow until buoyancy chamber assembly 2 is completely filled with gas. At this point, because the buoyancy of buoyancy chamber assembly 2 is greater than the force of gravity, buoyancy chamber assembly 2 rotates upward along buoyancy rotation support mechanism 1-3, locating in the upper half of the cavity of outer cylinder 1-1.

[0062] For the optional solutions of this embodiment, please refer to Figure 1 and Figure 22 A balancing stabilizer 2-5 is provided outside the bottom wall 2-1-2 inside the buoyancy chamber assembly 2. The balancing stabilizer 2-5 consists of a wing-type stabilizer 2-5-1 and a bracket 2-5-2 with a triangular cross-section. Preferably, the wing-type stabilizer 2-5-1 is a metal shell, and the interior can be filled with lead. The bracket 2-5-2 is welded to the upper front end of the wing-type stabilizer 2-5-1, and then welded as a whole to the lower part of the buoyancy chamber assembly 2. Preferably, two or more balancing stabilizers 2-5 are provided on the bottom wall 2-1-2 of the buoyancy chamber assembly 2. The balancing stabilizer 2-5 can ensure the stability of the buoyancy chamber assembly 2 floating in the sand washing fluid.

[0063] In the optional solution of this embodiment, the main structural components of the buoyancy chamber assembly 2 are made of low-density aluminum-magnesium alloy with a density lower than 2000kg / m 3 According to Archimedes' law of buoyancy, it is ensured that the buoyancy chamber assembly 2 has a certain buoyancy after being inflated, so that the buoyancy chamber assembly 2 floats.

[0064] Horizontal wells in mature oilfields and established areas generally have lower formation pressures and longer perforation intervals. The longer sand flushing operations in these horizontal wells last, the more sand flushing fluid enters the reservoir under high pressure, leading to reservoir contamination and damage. This also causes repeated sand injection, creating significant safety risks for subsequent operations.

[0065] The sand blasting tool of the present invention can solve the above problems through the gas generator mechanism 2-2 and the two-way flow adaptive valve 2-4-3, please refer to Figure 1 and Figure 13 , the details are as follows:

[0066] During normal sand flushing, the generator impeller 2-2-1 is constantly impacted by the fluid flow, causing gas to continuously generate within the buoyancy chamber assembly 2. After the water inside is drained, when the gas pressure within the buoyancy chamber assembly 2 exceeds the water pressure within the wellbore, the gas pressure opens the valve core 2-4-3-1 of the two-way flow adaptive valve 2-4-3, ejecting a stream of air into the center of the outer tube 1-1 cavity. This causes the air pressure within the buoyancy chamber assembly 2 to drop. When the pressures inside and outside the buoyancy chamber assembly 2 are balanced, the two-way flow adaptive valve 2-4-3 closes. However, the continued generation of gas causes the air pressure within the buoyancy chamber assembly 2 to rise again, opening the valve core 2-4-3-1 of the two-way flow adaptive valve 2-4-3 again, ejecting a stream of air into the center of the outer tube 1-1 cavity. The air pressure within the buoyancy chamber assembly 2 then drops, and the two-way flow adaptive valve 2-4-3 closes. This process repeats continuously during normal sand flushing operations, creating a pulsed airflow effect. The pulsating airflow effect causes pressure fluctuations in the fluid flow within outer tube 1-1 during the flow process, preventing secondary sedimentation of sand. Since the gas migrates upward with the sand flushing fluid within the sand flushing string and gradually expands, it accelerates the upward migration of the fluid within the sand flushing string, enhancing sand carrying efficiency without the need for excessively high pump pressures and large pumping volumes. This effectively reduces formation losses caused by high pump pressures, and the reverse circulation method simultaneously carries settled sand into the sand flushing string, completely avoiding the problem of drill sticking associated with traditional positive circulation sand flushing methods.

[0067] For the shape and structure of the buoyancy rotation support mechanism 1-3, please refer to Figure 1 、 Figure 4 and Figure 6 , the specific instructions are as follows:

[0068] The buoyancy chamber assembly 2 also includes a ring 2-8, which is fixed in the middle of the arc-shaped top wall of the semi-cylindrical tube, and the outer tube 1-1 is sleeved on the outside of the ring 2-8; the buoyancy chamber assembly 2 is rotatably connected to the inner wall of the outer tube 1-1 through a buoyancy rotation support mechanism 1-3; the buoyancy rotation support mechanism 1-3 includes an upper ball groove 1-3-21-3-2 arranged on the upper semi-circular arc of the inner wall of the outer tube 1-1, a lower ball groove 1-3-4 arranged on the upper semi-circular arc of the outer wall of the ring 2-8, a ball 1-3-3 located between the ball 1-3-3 groove composed of the upper ball groove 1-3-21-3-2 and the lower ball groove 1-3-4, a ball hole 1-3-11-3-1 arranged on the wall of the outer tube 1-1 and connected to the upper ball groove 1-3-21-3-2, and a screw plug 1-3-5 threadedly connected to the ball hole 1-3-11-3-1. Upper ball groove 1-3-21-3-2 and lower ball groove 1-3-4 oppose each other, forming a circular track for accommodating balls 1-3-3. A number of balls 1-3-3 are placed one by one through ball hole 1-3-11-3-1. After grease is injected, screw plug 1-3-5 is tightened by threading. Grease allows balls 1-3-3 to roll within the circular track. When the buoyancy of buoyancy chamber assembly 2 and the force of gravity become unbalanced, buoyancy chamber assembly 2 drives ring 2-8 to rotate about the central axis of outer cylinder 1-1, but prevents horizontal displacement.

[0069] In an alternative embodiment of this embodiment, two sealing grooves 1-5-2 and two sand control grooves 1-6-2 are axially symmetrically arranged on the inner wall of the outer cylinder 1-1, along with the ball groove 1-3-21-3-2. The sealing grooves 1-5-2 are used to mount the sealing ring 1-5-1, and the sand control grooves 1-6-2 are used to mount the sand control ring 1-6-1. The sealing ring 1-5-1 is used to prevent liquid from entering. The sand control ring 1-6-1 is installed in the sand control grooves 1-6-2 on the inner wall of the outer cylinder 1-1 and is used to prevent sand from entering the seal formed by the sealing ring 1-5-1 and affecting the seal.

[0070] In an optional solution of this embodiment, a plurality of spiral grooves 1-4 are provided on the inner wall of the outer cylinder 1-1. The spiral grooves 1-4 extend from the oblique opening 1-7 in a direction away from the oblique opening 1-7 to the sand control groove 1-6-2, and the spiral grooves 1-4 are equidistant from each other. More preferably, six spiral grooves 1-4 are evenly distributed circumferentially on the inner wall, and the cross-sectional shape is rectangular. The swirl angle of the spiral grooves 1-4 is 60°, and the depth of the spiral grooves 1-4 is 1 / 2 of the wall thickness of the outer cylinder 1-1. After the reverse circulation sand flushing fluid enters the long horizontal section horizontal well buoyancy sand flushing tool, the sand-containing fluid passes through the internal swirl of the spiral grooves 1-4, guiding the fluid flow to generate a rotational motion inside the sand flushing string, thereby more easily stirring the settled sand and preventing the settled sand from settling in the string, thereby having a higher liquid flow sand carrying performance.

[0071] In the optional solutions of this embodiment, please refer to Figures 16 to 20 The buoyancy chamber assembly 2 also includes a sand-settling gas blowback mechanism 2-3 and a sealed chamber 2-3-2 located in the buoyancy chamber assembly 2; the sealed chamber is a small sealed chamber located at the upper part of the buoyancy chamber assembly 2, and the top wall of the sealed chamber 2-3-2 and the side wall away from the oblique opening 1-7 are respectively a part of the arc-shaped top wall 2-1-1 and the sealing baffle 2-4 of the buoyancy chamber assembly 2, and the upper part of the first side wall 2-3-2-2 of the sealed chamber 2-3-2 parallel to the sealing baffle 2-4 is fan-shaped and intersects at the arc-shaped top wall 2-1-1, and the sealed chamber 2-3-2 also includes a bottom plate 2-3-2-1 parallel to the bottom wall 2-1-2 and two mutually parallel square second side walls 2-3-2-3.

[0072] The anti-sand deposition gas blowback mechanism 2-3 includes a second motor 2-3-4 arranged in the sealed cavity 2-3-2 and fixed to the arc-shaped top wall 2-1-1 of the buoyancy chamber assembly 2, a third piston rod 2-3-5-1 and a fourth piston rod 2-3-5-2 connected to the output end of the second motor 2-3-4, a third medicine cartridge 2-3-6-1 connected to the third piston rod 2-3-5-1, a fourth medicine cartridge 2-3-6-2 connected to the fourth piston rod 2-3-5-2, and a second spiral mixing nozzle 2-3-7 connected to the third medicine cartridge 2-3-6-1 and the fourth medicine cartridge 2-3-6-2, and a battery 2-3-1 located outside the sealed cavity 2-3-2; A second spiral mixing head 2-3-7-1 is installed at the outlet of the spiral mixing nozzle 2-3-7; the agents in the third agent barrel 2-3-6-1 and the fourth agent barrel 2-3-6-2 can generate gas after mixing. For example, the third agent barrel 2-3-6-1 contains agent A, which is a nitrite system agent, and the fourth agent barrel 2-3-6-2 contains agent B, which is an ammonium chloride salt system agent. When the two are mixed, nitrogen can be generated; when the buoyancy chamber assembly 2 is reversed from the upper half of the outer barrel 1-1 to the lower half, the battery 2-3-1 and the second motor 2-3-4 are connected through the sliding ball 2-3-3-3 power supply mechanism 2-3-3.

[0073] Preferably, battery 2-3-1 is a cylindrical dry cell battery 2-3-1. The sealed cavity 2-3-2 has a flat upper surface facing away from battery 2-3-1. The lower edges of the two side surfaces of the sealed cavity 2-3-2 are aligned with and bonded to the inner wall of the buoyancy chamber assembly 2. The anti-sand settling gas blowback mechanism 2-3 and the gas generator mechanism 2-2 are located on the upper and lower surfaces of the cavity of the buoyancy chamber assembly 2, respectively.

[0074] Preferably, the sizes of the second motor 2-3-4, the third piston rod 2-3-5-1, the fourth piston rod 2-3-5-2, the third medicament cartridge 2-3-6-1, the fourth medicament cartridge 2-3-6-2, the second spiral mixing nozzle 2-3-7 and the second spiral mixing head 2-3-7-1 are 1 / 5 of the sizes of the first motor 2-2-4, the first piston rod 2-2-5-1, the second piston rod 2-2-5-2, the first medicament cartridge 2-2-6-1, the second medicament cartridge 2-2-6-2, the first spiral mixing nozzle 2-2-7 and the first spiral mixing head 2-2-7-1.

[0075] Please refer to the shape and structure of the sliding ball 2-3-3-3 power supply mechanism 2-3-3. Figures 16 to 21 , the specific instructions are as follows:

[0076] The sliding ball 2-3-3-3 power-on mechanism 2-3-3 includes an arc-shaped upper sliding groove 2-3-3-2-1 arranged along the first side wall 2-3-2-2 of the sealed cavity 2-3-2 and facing the battery 2-3-1, a lower sliding groove 2-3-3-2-2 arranged below the upper sliding groove 2-3-3-2-1 and having the same size as the upper sliding groove 2-3-3-2-1, a bottom cover 2-3-3-5 arranged at the bottom of the lower sliding groove 2-3-3-2-2, an intermediate baffle 2-3-3-4 arranged between the upper sliding groove 2-3-3-2-1 and the lower sliding groove 2-3-3-2-2, and a sliding ball 2-3-3-3 sliding in the upper sliding groove 2-3-3-2-1 and the lower sliding groove 2-3-3-2-2; the sliding ball 2-3-3-3 is a metal ball, the intermediate baffle 2-3-3-4 is made of fragile material, and the second power-on mechanism 2-3-3-3 includes an arc-shaped upper sliding groove 2-3-3-2-1 and a lower sliding groove 2-3-3-2-2. The power-on end of the motor 2-3-4 passes through the first side wall 2-3-2-2 and the distance between the power-on end and the power supply end of the battery 2-3-1 is equal to the diameter of the sliding ball 2-3-3-3; when the sand flushing tool advances and is lowered into the wellbore, the sliding ball 2-3-3-3 is located above the middle baffle 2-3-3-4; when the sand flushing tool is lowered to the sand flushing position, the sliding ball 2-3-3-3 slides to the bottom cover 2-3-3-5 of the lower slide chute 2-3-3-2-2 under the action of gravity; when the buoyancy chamber assembly 2 reverses and returns to the low position, the sliding ball 2-3-3-3 slides from the bottom cover 2-3-3-5 toward the baffle, breaks the middle baffle 2-3-3-4 and then slides to the arc-shaped top wall 2-1-1, and the power-on end of the second motor 2-3-4 is connected to the power supply end of the battery 2-3-1 through the sliding ball 2-3-3-3.

[0077] Preferably, the upper chute 2-3-3-2-1 is 2 / 3 or 3 / 4 of a full circle, with a diameter slightly larger than the diameter of the sliding ball 2-3-3-3. The lower chute 2-3-3-2-2 is set in the lower slide body 2-3-3-1. The lower slide body 2-3-3-1 is rectangular as a whole and is welded to the lower surface of the sealed cavity 2-3-2. The lower chute 2-3-3-2-2 is processed along the long side of the lower slide body 2-3-3-1 and a bottom cover 2-3-3-5 of a certain thickness is left. The lower chute 2-3-3-2-2 is aligned with the axis of the upper chute 2-3-3-2-1 and forms the sliding track 2-3-3-2 of the sliding ball 2-3-3-3. The intermediate baffle 2-3-3-4 is bonded at the connection between the lower slide body 2-3-3-1 and the sealed cavity 2-3-2.

[0078] In an optional scheme of this embodiment, the sealing baffle 2-4 is further provided with a second valve hole 2-4-1-1 and a one-way check valve 2-4-2 arranged in the second valve hole 2-4-1-1. A stepped structure is laterally provided on the inner wall of the second valve hole 2-4-1-1, and the small-aperture end of the second valve hole 2-4-1-1 faces the sealing cavity 2-3-2; the one-way check valve 2-4-2-1 includes a one-way ball 2-4-2-1 and a second valve plug 2-4-2-2, and the diameter of the one-way ball 2-4-2-1 is between the large aperture and small aperture of the second valve hole 2-4-1-1. The connection point of the stepped structure of the second valve hole 2-4-1-1 is the C valve seat 2-4-1-1-1 of the one-way ball 2-4-2-1; the second valve plug 2-4-2-2 is threadedly connected to the large-aperture end of the second valve hole 2-4-1-1.

[0079] Please refer to the specific working process of the anti-sand deposition gas back-blowing device mechanism 2-3 and the one-way check valve 2-4-2. Figures 7 to 13 , the specific instructions are as follows:

[0080] After the sand flushing tool has flushed the oil pipe to its forward depth, the pump can be stopped immediately, interrupting the reverse circulation flow. At this point, the generator impeller 2-2-1 stops rotating, the generator 2-2-2 stops generating electricity, and the gas generator mechanism 2-2 stops working, no longer producing gas. When the air pressure in the buoyancy chamber assembly 2 drops below the water pressure in the wellbore, the pressure differential causes the liquid to press the valve core 2-4-3-1 against the valve seat A 2-4-3-1-1. The valve core ball 2-4-3-2 compresses the pressure spring 2-4-3-4, causing the valve core ball 2-4-3-2 to move away from the valve seat B 2-4-3-2-1. Liquid then flows into the buoyancy chamber assembly 2 through the gap between the valve core ball 2-4-3-2 and the valve seat B 2-4-3-2-1, until the buoyancy chamber assembly 2 is completely filled with liquid. Since the gravity of the buoyancy chamber assembly 2 is greater than the buoyancy at this time, the buoyancy chamber assembly 2 quickly reverses to the lower half of the cavity of the outer cylinder 1-1.

[0081] During the rapid reversal of the buoyancy chamber assembly 2, the sliding ball 2-3-3-3 at the bottom cover 2-3-3-5 of the glide path accelerates downward along the sliding track 2-3-3-2 to impact the middle baffle 2-3-3-4. The sliding track 2-3-3-2 of the glide path body 2-3-3-1 provides an acceleration process for the sliding ball 2-3-3-3. After breaking the middle baffle 2-3-3-4, the sliding ball 2-3-3-3 continues to fall downward between the second motor 2-3-4 and the battery 2-3-1, thereby connecting the two. After the second motor 2-3-4 is activated, it propels the third and fourth piston rods 2-3-5-1 and 2-3-5-2 into synchronous axial motion within the third and fourth cartridges 2-3-6-1 and 2-3-6-2, respectively. This pushes Agent A and Agent B into the second spiral mixing nozzle 2-3-7. Under the thorough stirring of the second spiral mixing nozzle 2-3-7-1, the mixture rapidly reacts and continuously produces nitrogen. When the air pressure within the sealed chamber 2-3-2 exceeds the water pressure within the wellbore, the pressure differential forces the one-way ball 2-4-2-1 to disengage from the valve seat C 2-4-1-1-1, opening the one-way check valve 2-4-2. Since the outlet of the one-way check valve 2-4-2 is now located at the lower portion of the outer barrel 1-1 cavity, the generated gas is ejected toward the lower portion of the outer barrel 1-1 cavity, lifting and stirring the sand. This prevents sand from settling after the fluid stops during the pumping process to connect the sand flushing string.

[0082] For the optional solutions of this embodiment, please refer to Figure 23 The sand flushing tool also includes an auxiliary sub 3, one end of which is threadedly connected to the outer barrel 1-1 or the end of the oil pipe. The auxiliary sub 3 is half the length of the outer barrel 1-1, and its other dimensions are the same as those of the outer barrel 1-1. Rollers 1-2 are evenly distributed circumferentially on the outer wall of the auxiliary sub 3. The size and arrangement of the rollers 1-2 are the same as those of the outer barrel 1-1.

[0083] In the optional scheme of this embodiment, the auxiliary sub 3 can be installed according to the length of the horizontal section of the horizontal well. It can be not installed, assembled in a single stage, or assembled in multiple stages. When the auxiliary sub 3 is not installed, the front end of the outer cylinder 1-1 is directly connected to the tubing string. In the single-stage assembly, the tubing string is connected to the auxiliary sub 3, and the end of the auxiliary sub 3 is connected to the outer cylinder 1-1 of the buoyant sand flushing tool for the long horizontal section horizontal well. In the multi-stage assembly, the sand flushing string is, from top to bottom, the tubing string, the auxiliary sub 3, the tubing string, the auxiliary sub 3... the tubing string, the auxiliary sub 3 and the outer cylinder 1-1 of the buoyant sand flushing tool for the long horizontal section horizontal well, that is, the tubing string and the auxiliary sub 3 form a unit, and several units are connected to the outer cylinder 1-1 of the buoyant sand flushing tool for the long horizontal section horizontal well.

[0084] The auxiliary sub 3 has the same function as the rollers 1-2 on the barrel assembly. When the friction force of the pipe string is greater than the running pressure in the long horizontal section, the sand flushing pipe string is difficult to run in. The sand flushing pipe string can be lowered while rotating clockwise. Since the rollers 1-2 are evenly distributed on the auxiliary sub 3 and the barrel assembly, the rolling friction between multiple rollers 1-2 and the inner wall of the casing forms a clockwise spiral forward force, forcing the sand flushing pipe string to move forward. In a manner similar to tightening a screw, the sand flushing pipe string is helped to move forward in the horizontal section, thereby achieving the purpose of running the pipe string in the long horizontal well section.

[0085] For the working process of the buoyancy sand flushing tool for long horizontal wells, please refer to Figure 24 , the specific instructions are as follows:

[0086] During construction, the sand flushing string is connected in sequence: from bottom to top, the outer barrel 1-1 of the long horizontal section horizontal well buoyancy sand flushing tool, the auxiliary sub 3 (which can be assembled in multiple stages), the tubing string, and the wellhead rotary self-sealing device. If the horizontal well section is too long and the sand flushing string is difficult to lower, it can be lowered by rotating it clockwise. The spiral forward force generated by the combined action of the barrel assembly and the rollers 1-2 of the auxiliary sub 3 and the lowering pressure propels the sand flushing string forward.

[0087] When the sand flushing string is lowered into the horizontal wellbore, the initial pressure differential between atmospheric air in the buoyancy chamber assembly 2 and high-pressure liquid in the wellbore causes the valve core 2-4-3-1 of the two-way flow adaptive valve 2-4-3 to abut valve seat A 2-4-3-1-1. Driven by water pressure, the valve core ball 2-4-3-2 compresses the pressure spring 2-4-3-4, forcing the valve core ball 2-4-3-2 away from valve seat B 2-4-3-2-1, allowing water to flow into the buoyancy chamber assembly 2 until the internal and external pressures of the buoyancy chamber assembly 2 are balanced. Because the one-way check valve 2-4-2 is connected to the sealed chamber 2-3-2, high-pressure water is prevented from entering the sealed chamber 2-3-2. When the buoyancy chamber assembly 2 is filled with water, gravity outweighs the buoyancy, causing the buoyancy chamber assembly 2 to reside in the lower half of the barrel assembly during the lowering of the sand flushing string. At this time, under the action of gravity, the sliding ball 2-3-3-3 of the sliding ball 2-3-3-3 power supply mechanism 2-3-3 is located above the middle baffle 2-3-3-4 in the sliding track 2-3-3-2 and is supported by the middle baffle 2-3-3-4.

[0088] When the sand flushing tool is lowered to the sand flushing position, the sand flushing string is lifted a certain distance, and the cement pump truck of the pumping equipment is started on the ground. The liquid flows from the inlet tank through the four-way into the oil casing annulus, circulates to the bottom end of the sand flushing tool, and reverses to enter the outer cylinder 1-1 of the sand flushing tool, thereby establishing a reverse circulation liquid flow.

[0089] After the reverse circulation liquid flow is established, the fluid impacts the power generation impeller 2-2-1 of the gas generator mechanism 2-2, and the power generation impeller 2-2-1 rotates rapidly in the liquid flow, so that the generator 2-2-2 uses the kinetic energy of the liquid to generate electricity, and transmits the electric energy to the first motor 2-2-4 through the power supply line 2-2-3, promoting the first piston rod 2-2-5-1 and the second piston rod 2-2-5-2 to perform synchronous axial propulsion movement in the first medicine barrel 2-2-6-1 and the second medicine barrel 2-2-6-2 respectively, thereby pushing the A medicine and the B medicine into the first spiral mixing nozzle 2-2-7, and the mixture reacts rapidly under the sufficient stirring of the first spiral mixing head 2-2-7-1 to continuously produce nitrogen.

[0090] This gas rapidly generates and expands, rapidly increasing the pressure within buoyancy chamber assembly 2. When the pressure within buoyancy chamber assembly 2 exceeds the pressure of the water in the wellbore, the pressure differential acts on valve core ball 2-4-3-2 of bidirectional flow adaptive valve 2-4-3, forcing valve core ball 2-4-3-2 into contact with valve seat B 2-4-3-2-1, closing the water inlet passage. Under the action of the gas pressure, valve core 2-4-3-1 opens, releasing valve seat A 2-4-3-1-1. The water within buoyancy chamber assembly 2 is then expelled by the gas flow until buoyancy chamber assembly 2 is completely filled with gas. At this point, because the buoyancy of buoyancy chamber assembly 2 is greater than the force of gravity, buoyancy chamber assembly 2 rotates upward along buoyancy rotation support mechanism 1-3, locating in the upper half of the cavity of outer cylinder 1-1. At the same time, the sliding ball 2-3-3-3 of the sliding ball 2-3-3-3 power supply mechanism 2-3-3 slides downward along the sliding track 2-3-3-2 to the bottom cover 2-3-3-5 of the lower slide body 2-3-3-1 under the action of gravity.

[0091] As the sand flushing string gradually advances during the sand flushing process, the buoyancy chamber assembly 2 located in the upper half of the outer tube 1-1 will restrict the reverse circulation liquid flow from flowing through the upper half of the outer tube 1-1 cavity, forcing the liquid flow to flow through the lower half of the outer tube 1-1 cavity, thereby flushing the settled sand at the bottom of the wellbore, greatly improving the efficiency and probability of sand particles entering the outer tube 1-1 cavity, and being carried by the sand flushing fluid through the inside of the sand flushing string back to the outlet tank on the ground.

[0092] During normal sand flushing, the generator impeller 2-2-1 is constantly impacted by the fluid flow, causing gas to continuously generate within the buoyancy chamber assembly 2. After the water inside is drained, when the gas pressure within the buoyancy chamber assembly 2 exceeds the water pressure within the wellbore, the gas pressure opens the valve core 2-4-3-1 of the two-way flow adaptive valve 2-4-3, ejecting a stream of air into the center of the outer tube 1-1 cavity. This causes the air pressure within the buoyancy chamber assembly 2 to drop. When the pressures inside and outside the buoyancy chamber assembly 2 are balanced, the two-way flow adaptive valve 2-4-3 closes. However, the continued generation of gas causes the air pressure within the buoyancy chamber assembly 2 to rise again, opening the valve core 2-4-3-1 of the two-way flow adaptive valve 2-4-3 again, ejecting a stream of air into the center of the outer tube 1-1 cavity. The air pressure within the buoyancy chamber assembly 2 then drops, and the two-way flow adaptive valve 2-4-3 closes. This process repeats continuously during normal sand flushing operations, creating a pulsed airflow effect. The pulsating airflow effect causes pressure fluctuations in the fluid flow within outer tube 1-1 during the flow process, preventing secondary sedimentation of sand. Since the gas migrates upward with the sand flushing fluid within the sand flushing string and gradually expands, it accelerates the upward migration of the fluid within the sand flushing string, enhancing sand carrying efficiency without the need for excessively high pump pressures and large pumping volumes. This effectively reduces formation losses caused by high pump pressures, and the reverse circulation method simultaneously carries settled sand into the sand flushing string, completely avoiding the problem of drill sticking associated with traditional positive circulation sand flushing methods.

[0093] After flushing the depth of a tubing, the pump can be immediately stopped, interrupting the reverse circulation flow. At this point, the generator impeller 2-2-1 stops rotating, the generator 2-2-2 stops generating electricity, and the gas generator mechanism 2-2 ceases operation, no longer producing gas. When the air pressure within the buoyancy chamber assembly 2 drops below the water pressure within the wellbore, the pressure differential causes the liquid to press the valve core 2-4-3-1 against the valve seat A 2-4-3-1-1. The valve core ball 2-4-3-2 compresses the pressure spring 2-4-3-4, forcing the valve core ball 2-4-3-2 away from the valve seat B 2-4-3-2-1. Liquid then flows into the buoyancy chamber assembly 2 through the gap between the valve core ball 2-4-3-2 and the valve seat B 2-4-3-2-1, until the buoyancy chamber assembly 2 is completely filled with liquid. Because the gravity of the buoyancy chamber assembly 2 is now greater than its buoyancy, the buoyancy chamber assembly 2 rapidly reverses to the lower half of the outer cylinder 1-1 cavity.

[0094] During the rapid reversal of the buoyancy chamber assembly 2, the sliding ball 2-3-3-3 at the bottom cover 2-3-3-5 of the glide path accelerates downward along the sliding track 2-3-3-2 to impact the middle baffle 2-3-3-4. The sliding track 2-3-3-2 of the glide path body 2-3-3-1 provides an acceleration process for the sliding ball 2-3-3-3. After breaking the middle baffle 2-3-3-4, the sliding ball 2-3-3-3 continues to fall downward between the second motor 2-3-4 and the battery 2-3-1, thereby connecting the two. After the second motor 2-3-4 is activated, it propels the third and fourth piston rods 2-3-5-1 and 2-3-5-2 into synchronous axial motion within the third and fourth cartridges 2-3-6-1 and 2-3-6-2, respectively. This pushes Agent A and Agent B into the second spiral mixing nozzle 2-3-7. Under the thorough stirring of the second spiral mixing nozzle 2-3-7-1, the mixture rapidly reacts and continuously produces nitrogen. When the air pressure within the sealed chamber 2-3-2 exceeds the water pressure within the wellbore, the pressure differential forces the one-way ball 2-4-2-1 to disengage from the valve seat C 2-4-1-1-1, opening the one-way check valve 2-4-2. Since the outlet of the one-way check valve 2-4-2 is now located at the lower portion of the outer barrel 1-1 cavity, the generated gas is ejected toward the lower portion of the outer barrel 1-1 cavity, lifting and stirring the sand. This prevents sand from settling after the fluid stops during the pumping process to connect the sand flushing string.

[0095] After connecting the sand flushing string, restart the cement pump truck and, once reverse circulation flow is established, repeat the process of floating the buoyancy chamber assembly 2 and the subsequent steps to resume normal sand flushing operations. After the buoyancy chamber assembly 2 floats, the sliding ball 2-3-3-3 of the energizing mechanism 2-3-3 of the sliding ball 2-3-3-3 returns to the bottom cover 2-3-3-5 of the glide path body 2-3-3-1 under the action of gravity. This disconnects the second motor 2-3-4 from the battery 2-3-1, deactivates the anti-sand settling gas blowback mechanism 2-3, closes the one-way check valve 2-4-2, and leaves the sealed chamber 2-3-2 filled with gas. A new round of reverse circulation sand flushing operations begins.

[0096] The beneficial effects of the buoyancy sand flushing tool for long horizontal wells in the present invention are as follows:

[0097] 1. The buoyancy of the buoyancy chamber assembly 2 is used to float on the upper half of the outer cylinder 1-1 cavity during the sand flushing process, thereby forcing the sand flushing fluid to flow through the lower half and impact the sand at the bottom of the horizontal wellbore, thereby improving the utilization rate of hydraulic energy and the sand flushing efficiency;

[0098] 2. The interaction between buoyancy and gravity is used to make the buoyancy chamber assembly 2 float and reverse. The gas impact generated under these different working conditions suspends and carries the settled sand, preventing the sand from settling again, thereby improving the sand carrying efficiency. It can still achieve good sand carrying capacity under the condition of low pump pressure and displacement of the surface pumping system, effectively reducing the damage to the formation caused by high pump pressure and large displacement, while saving the fuel cost of the pumping equipment;

[0099] 3. Utilizing the liquid flow characteristics of reverse circulation sand flushing, the settled sand is brought into the interior of the sand flushing string, thus completely avoiding the problem of drill sticking in traditional positive circulation sand flushing;

[0100] 4. The use of different combinations of auxiliary pup joints 3 enhances the extension capability of the sand flushing string in long horizontal well sections, ensuring that the sand flushing string can be advanced to the predetermined position.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A buoyancy sand flushing tool for horizontal wells with long horizontal sections, characterized by: It comprises an outer cylinder (1-1) and a buoyancy chamber assembly (2) arranged in the outer cylinder (1-1), the front end of the outer cylinder (1-1) is an oblique opening (1-7), and rollers (1-2) are evenly distributed circumferentially on the outer wall of the outer cylinder (1-1); When the sand flushing tool is advanced and lowered into the wellbore, the high-pressure liquid in the wellbore enters the cavity of the buoyancy chamber assembly (2) so that the buoyancy chamber assembly (2) is always located in the lower half of the outer cylinder (1-1) under the action of gravity; When the sand flushing tool is lowered to the sand flushing position, under the impact of the reverse circulating liquid flow, the gas generator mechanism (2-2) in the buoyancy chamber assembly (2) generates gas, and the gas discharges the liquid and fills the cavity of the buoyancy chamber assembly (2). Under the action of buoyancy, the buoyancy chamber assembly (2) rotates and floats up and is located in the upper half of the outer cylinder (1-1); The buoyancy chamber assembly (2) is a hollow semi-cylindrical cylinder and is located at the front end of the cavity of the outer cylinder (1-1); the bottom wall (2-1-2) of the buoyancy chamber assembly (2) is a plane and the outer diameter of the semi-circle is smaller than the inner diameter of the outer cylinder (1-1); One end of the buoyancy chamber assembly (2) close to the oblique opening (1-7) of the outer cylinder (1-1) is blocked and extends upward from the bottom wall (2-1-2) in a direction close to the oblique opening (1-7) to intersect with the arc-shaped top wall (2-1-1) of the semi-cylindrical cylinder to form a guide end (2-6); a sealing baffle (2-4) at the other end is provided with a first valve hole (2-4-1-2) and a two-way flow adaptive valve (2-4-3) provided in the first valve hole (2-4-1-2); the two-way flow adaptive valve (2-4-3) is opened or closed under the action of a pressure difference to control the flow of liquid or gas into and out of the buoyancy chamber assembly (2); A buoyancy tube (2-7) is provided in the center of the bottom wall (2-1-2) of the buoyancy chamber assembly (2) along the central axis of the buoyancy chamber assembly (2); The gas generator mechanism (2-2) comprises a generator (2-2-2) fixed on the bottom wall (2-1-2), a first motor (2-2-4) connected to the generator (2-2-2), a first piston rod (2-2-5-1) and a second piston rod (2-2-5-2) connected to the output end of the first motor (2-2-4), a first medicine cartridge (2-2-6-1) connected to the first piston rod (2-2-5-1), a second medicine cartridge (2-2-6-2) connected to the second piston rod (2-2-5-2), a first spiral mixing nozzle (2-2-7) connected to the outlets of the first medicine cartridge (2-2-6-1) and the second medicine cartridge (2-2-6-2), and a power generation impeller (2-2-1) located in the buoyancy tube (2-7); The medicines in the first medicine cartridge (2-2-6-1) and the second medicine cartridge (2-2-6-2) are capable of generating gas after mixing; The shaft of the power generation impeller (2-2-1) passes through the bottom wall (2-1-2) and is connected to the generator (2-2-2). When the power generation impeller (2-2-1) rotates under the impetus of the liquid flow, it provides power for the generator (2-2-2) to generate electricity. The buoyancy chamber assembly (2) further includes a circular ring (2-8), the circular ring (2-8) being fixed in the middle of the arc-shaped top wall (2-1-1), and the outer cylinder (1-1) being sleeved outside the circular ring (2-8); The buoyancy chamber assembly (2) is rotatably connected to the inner wall of the outer cylinder (1-1) via a buoyancy rotation support mechanism (1-3); The buoyancy rotation support mechanism (1-3) comprises an upper semicircular ball groove (1-3-2) arranged on the inner wall of the outer cylinder (1-1), a lower semicircular ball groove (1-3-4) arranged on the outer wall of the ring (2-8), a ball (1-3-3) located between the ball grooves formed by the upper ball groove (1-3-2) and the lower ball groove (1-3-4), a ball hole (1-3-1) arranged on the wall surface of the outer cylinder (1-1) and connected to the upper ball groove (1-3-2), and a screw plug (1-3-5) threadedly connected to the ball hole (1-3-1).

2. The buoyancy sand flushing tool for horizontal wells with long horizontal sections according to claim 1, characterized in that: A stepped structure is laterally arranged on the inner wall of the first valve hole (2-4-1-2); the small-diameter end of the first valve hole (2-4-1-2) faces the cavity of the buoyancy chamber assembly (2); and the two-way flow adaptive valve (2-4-3) comprises a spherical valve core (2-4-3-1), a first valve plug (2-4-3-3), a valve core ball (2-4-3-2), a pressure spring (2-4-3-4) and a long-tail gland (2-4-3-5). The first valve plug (2-4-3-3) is threadedly connected to the large-diameter end of the first valve hole (2-4-1-2), and the diameter of the valve core (2-4-3-1) is between the large-diameter and small-diameter of the first valve hole (2-4-1-2); A stepped through hole is provided on the central axis of the valve core (2-4-3-1), the large-aperture end of the valve core (2-4-3-1) faces the cavity of the buoyancy chamber assembly (2), the diameter of the valve core ball (2-4-3-2) is between the large-aperture and small-aperture of the valve core (2-4-3-1), the long-tail pressure cover (2-4-3-5) is threadedly connected to the large-aperture end of the valve core (2-4-3-1), the long-tail pressure cover (2-4-3-5) is internally provided with a stepped through hole and the small-aperture end faces the cavity of the buoyancy chamber assembly (2), and the pressure spring (2-4-3-4) is located between the valve core ball (2-4-3-2) and the long-tail pressure cover (2-4-3-5).

3. The buoyancy sand flushing tool for horizontal wells with a long horizontal section according to claim 2, characterized in that: Two sealing rings (1-5-1) and two sand-proof rings (1-6-1) located outside the sealing rings (1-5-1) are symmetrically arranged between the inner wall of the outer cylinder (1-1) and the outer wall of the ring (2-8) with the ball groove as the axis. The sand-proof rings (1-6-1) are installed in the sand-proof groove (1-6-2) on the inner wall of the outer cylinder (1-1) to prevent sand from entering the sealing structure formed by the sealing rings (1-5-1) to affect the sealing. A plurality of spiral grooves (1-4) are provided on the inner wall of the outer cylinder (1-1), the spiral grooves (1-4) extending from the oblique opening (1-7) in a direction away from the oblique opening (1-7) to the sand control groove (1-6-2), and the spiral grooves (1-4) are equidistant from each other.

4. The buoyancy sand flushing tool for horizontal wells with a long horizontal section according to claim 3, characterized in that: The buoyancy chamber assembly (2) further comprises a sand-settling-proof gas blowback mechanism (2-3) and a sealed cavity (2-3-2) located within the buoyancy chamber assembly (2); The sealed cavity (2-3-2) is a small sealed cavity located at the upper part of the cavity of the buoyancy chamber assembly (2); the top wall of the sealed cavity (2-3-2) and the side wall away from the oblique opening (1-7) are respectively a part of the arc-shaped top wall (2-1-1) of the buoyancy chamber assembly (2) and the sealing baffle (2-4); and the upper part of the first side wall (2-3-2-2) of the sealed cavity (2-3-2) parallel to the sealing baffle (2-4) is fan-shaped and intersects with the arc-shaped top wall (2-1-1); The anti-sand settling gas blowback mechanism (2-3) comprises a second motor (2-3-4) arranged in the sealed cavity (2-3-2) and fixed on the arc-shaped top wall (2-1-1) of the buoyancy chamber assembly (2), a third piston rod (2-3-5-1) and a fourth piston rod (2-3-5-2) connected to the output end of the second motor (2-3-4), a third medicine cartridge (2-3-6-1) connected to the third piston rod (2-3-5-1), a fourth medicine cartridge (2-3-6-2) connected to the fourth piston rod (2-3-5-2), a second spiral mixing nozzle (2-3-7) connected to the third medicine cartridge (2-3-6-1) and the fourth medicine cartridge (2-3-6-2), and a battery (2-3-1) located outside the sealed cavity (2-3-2); The medicines in the third medicine cartridge (2-3-6-1) and the fourth medicine cartridge (2-3-6-2) can generate gas after mixing; When the buoyancy chamber assembly (2) is reversed from the upper half of the outer cylinder (1-1) to the lower half, the battery (2-3-1) and the second motor (2-3-4) are connected via a sliding ball power supply mechanism (2-3-3).

5. The buoyancy sand flushing tool for horizontal wells with long horizontal sections according to claim 4, characterized in that: The sliding ball power supply mechanism (2-3-3) comprises an arc-shaped upper sliding groove (2-3-3-2-1) arranged along the first side wall (2-3-2-2) of the sealed cavity (2-3-2) and facing the battery (2-3-1), a lower sliding groove (2-3-3-2-2) arranged below the upper sliding groove (2-3-3-2-1) and having the same size as the upper sliding groove (2-3-3-2-1), a bottom cover (2-3-3-5) arranged at the bottom of the lower sliding groove (2-3-3-2-2), an intermediate baffle (2-3-3-4) and a sliding ball (2-3-3-3) arranged between the upper sliding groove (2-3-3-2-1) and the lower sliding groove (2-3-3-2-2); The upper sliding groove (2-3-3-2-1) and the lower sliding groove (2-3-3-2-2) form a sliding track (2-3-3-2), and the sliding ball (2-3-3-3) slides in the sliding track (2-3-3-2); The sliding ball (2-3-3-3) is a metal ball, the intermediate baffle (2-3-3-4) is made of a fragile material, the power supply end of the second motor (2-3-4) passes through the first side wall (2-3-2-2), and the distance between the power supply end and the power supply end of the battery (2-3-1) is equal to the diameter of the sliding ball (2-3-3-3); When the sand flushing tool is advanced and lowered into the wellbore, the sliding ball (2-3-3-3) is located above the middle baffle (2-3-3-4); When the sand flushing tool moves down to the sand flushing position, the sliding ball (2-3-3-3) slides to the bottom cover (2-3-3-5) of the sliding trough (2-3-3-2-2) under the action of gravity; When the buoyancy chamber assembly (2) is reversed and returned to the low position, the sliding ball (2-3-3-3) slides downward from the bottom cover (2-3-3-5), breaks the middle baffle (2-3-3-4), and then slides to the arc-shaped top wall (2-1-1), and the power supply end of the second motor (2-3-4) is connected to the power supply end of the battery (2-3-1) through the sliding ball (2-3-3-3).

6. The buoyancy sand flushing tool for horizontal wells with a long horizontal section according to claim 5, characterized in that: The sealing baffle (2-4) is further provided with a second valve hole (2-4-1-1) and a one-way check valve (2-4-2) arranged in the second valve hole (2-4-1-1); a stepped structure is laterally provided on the inner wall of the second valve hole (2-4-1-1); and the small-diameter end of the second valve hole (2-4-1-1) faces the sealing cavity (2-3-2); The one-way check valve (2-4-2) comprises a one-way ball (2-4-2-1) and a second valve plug (2-4-2-2), wherein the diameter of the one-way ball (2-4-2-1) is between the large aperture and the small aperture of the second valve hole (2-4-1-1), and the second valve plug (2-4-2-2) is threadedly connected to the large aperture end of the second valve hole (2-4-1-1).

7. The buoyancy sand flushing tool for horizontal wells with long horizontal sections according to claim 1, characterized in that: It also includes an auxiliary short section (3), one end of which is threadedly connected to the end of the outer cylinder (1-1), the length of the auxiliary short section (3) is 1 / 2 of the outer cylinder (1-1), and the rollers (1-2) are evenly distributed circumferentially on the outer wall of the auxiliary short section (3).

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