Reliable and efficient thermal-washing circulation pipe string structure for oil well, and method for using same

Abstract

A reliable and efficient hot-washing circulation pipe string structure for an oil well, and a method for using same. The structure comprises: a well-washing circulation valve (100) connected to the bottom end of a wax deposition section of tubing, wherein the well-washing circulation valve comprises an outer cylinder (11) and an inner cylinder (5), a lifting structure capable of driving the inner cylinder (5) to move upwards and an axial limiting structure capable of axially limiting the inner cylinder (5) are provided between the inner cylinder (5) and the outer cylinder (11), an inner valve hole (8) is radially provided in the side wall of the inner cylinder (5) in a penetrating manner, and an outer valve hole (9) is radially provided in the side wall of the outer cylinder (11) in a penetrating manner; and a sucker rod switch (200) which is used to drive the inner cylinder (5) to move downwards such that the well-washing circulation valve (100) is switched from an open state to a closed state. In the method, a high-temperature well-washing fluid circulates only in a well section with severe wax deposition requiring thermal washing, instead of circulating from the wellhead to the bottom hole and then back to the wellhead, thereby greatly shortening the well-washing path of the high-temperature well-washing fluid, reducing the heat loss of the high-temperature well-washing fluid in a wellbore, shortening the well-washing operation time, improving the efficiency, and reducing costs.

Description

Reliable and efficient hot washing circulation tubing structure and its application method for oil wells

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. 202411710460.3, filed on November 26, 2024, and incorporates the entire contents of the disclosure of the aforementioned patent application as part of this application. Technical Field

[0003] This application relates to the field of oilfield production technology, and in particular to a reliable and efficient hot washing circulation tubing structure for oil wells and its usage method. Background Technology

[0004] In oilfield development, the problem of wax buildup in oil wells has long existed, causing difficulties for daily production. Currently, hot washing is one of the main methods for wax removal, but its effect is not ideal, mainly due to its low efficiency. Conventional hot washing involves injection through the casing, into the annulus at the bottom of the well, then pumped into the tubing and finally returned from the wellhead. Throughout the process, the hot fluid experiences significant heat loss as it flows from the wellhead downhole, and the temperature drops drastically upon returning to the wellhead, resulting in poor wax removal and a long washing time. Furthermore, existing technologies suffer from poor stability and reliability.

[0005] The existing technologies mainly include:

[0006] (1) Patent application number 202111672417.9 (New type of oil well anti-pollution high-efficiency hot washing and wax removal method) This invention patent mainly achieves the purpose of preventing the well washing fluid from leaking into the formation by adding a packer at the lower end of the perforated pipe and a check valve, also known as a one-way valve, at the bottom of the tubing string. The hot washing path still needs to reach the bottom of the well, resulting in large heat loss.

[0007] (2) Articles such as "Research and Application of Temperature-Controlled Short-Circuit Hot Washing, Wax Removal and Leakage Prevention Tubing String" provide a temperature-controlled short-circuit hot washing, wax removal, and leakage prevention tubing string. This string uses the thermal expansion of a temperature-controlled element to open the valve orifice of a temperature-controlled valve for short-circuit hot washing. When the well temperature drops to a certain value, the temperature-controlled element contracts and closes the valve orifice. This valve, which uses a temperature-controlled element for opening and closing, is not only slow to react but also has limited reliability and adaptability. The temperature-controlled element, when placed downhole for extended periods, cannot guarantee its aging and sensitivity. Furthermore, downhole heating and cooling require waiting time; if the well depth is deep, the temperature drops slowly, resulting in long and uncontrollable waiting times when closure is required. Moreover, this valve can only be used for hot washing; it cannot be used when high-temperature fluids are unavailable in conventional operations.

[0008] (3) Patent Application No. 201811485066.9 (A Packer for Repeated Hot Washing and Waxing) This invention provides a packer for repeated hot washing and waxing. It is mainly a packer that can automatically set and unseal, and needs to be used in conjunction with the upper well washing valve to complete the well washing operation. However, the structure of the well washing valve is not mentioned. Moreover, the packer is an expansion packer structure. The expansion and contraction of the rubber sleeve is achieved by the cooperation of the unseal piston, locking ring, conical surface, spring, etc. It mainly solves the problem of setting and unsealing the packer rubber sleeve during well washing. This structure is commonly used in packers. In practical applications, the sealing performance and reliability of repeated setting are difficult to guarantee.

[0009] Existing technologies primarily protect the formation by preventing well-washing fluid from leaking into it through the annulus during well washing. Another approach involves installing channel switches on the packer, using pressure and expansion to drive a piston and control the opening and closing of the channel. However, these patents and methods suffer from reliability issues; they cannot guarantee the channel switches will remain closed, a critical factor affecting usability. Failure to close or incomplete closure can lead to tubing leakage, affecting pump efficiency and, in severe cases, causing no pump output. Therefore, effectively ensuring the channel switches remain closed is the core focus.

[0010] Therefore, based on years of experience and practice in related industries, the inventor proposes a reliable and efficient hot washing circulation tubing structure for oil wells and its usage method to overcome the shortcomings of existing technologies. Summary of the Invention

[0011] The purpose of this application is to provide a reliable and efficient hot washing circulation tubing structure for oil wells and its usage method, overcoming the problem of poor dewaxing effect caused by large heat loss of hot liquid in the prior art. In this application embodiment, the high-temperature washing fluid is only circulated in the well section where wax is severely deposited and hot washing is required, without having to circulate from the wellhead to the bottom of the well and then back to the wellhead. This significantly shortens the washing path of the high-temperature washing fluid, reduces the heat loss of the high-temperature washing fluid in the wellbore, shortens the washing operation time, improves efficiency, and reduces costs.

[0012] The purpose of this application embodiment is achieved by providing a reliable and efficient hot washing circulation tubing string structure for oil wells, including a well washing circulation valve and a rod switch. The well washing circulation valve is connected to the bottom end of the waxed section of the tubing. The well washing circulation valve includes an outer cylinder and an inner cylinder coaxially sleeved together. A lifting structure capable of driving the inner cylinder upward and an axial limiting structure capable of axially limiting the inner cylinder are provided between the inner cylinder and the outer cylinder. An inner valve hole is radially provided through the side wall of the inner cylinder, and an outer valve hole is radially provided through the side wall of the outer cylinder. When the bottom end of the inner cylinder is axially limited below the axial limiting structure, the inner valve hole and the outer valve hole are sealed to keep the well washing circulation valve in a closed state. When pressure is applied to the tubing, the lifting structure pushes the inner cylinder upward under hydraulic action, connecting the inner valve hole and the outer valve hole. At this point, the well washing circulation valve is in an open state, and the tubing communicates with the external casing annulus through the inner cylinder, the inner valve hole, and the outer valve hole to form a well washing fluid circulation channel.

[0013] The oil rod switch is used to drive the inner cylinder to move downward, so that the well washing circulation valve switches from the open state to the closed state; it includes an oil rod whose top end is connected to the pumping unit and is movably inserted into the inner cylinder, and the oil rod is connected to a switch that can radially press against the inner cylinder to push the inner cylinder downward.

[0014] In an optional embodiment of this application, the lifting structure includes a hydraulic chamber and a lower piston. A first step is provided on the outer wall of the inner cylinder, and a second step is provided at the bottom end of the outer cylinder. The hydraulic chamber is formed between the outer wall of the inner cylinder, the first step, the inner wall of the outer cylinder, and the second step. The lower piston is fixedly connected to the inner cylinder and located below the first step. A sealing ring is abutted between the lower piston and the first step. When the well-washing circulation valve is in the closed state, the sealing ring is located between the inner valve hole and the outer valve hole to seal and close the well-washing fluid circulation channel. When the well-washing circulation valve is in the open state, the lower piston moves upward above the outer valve hole, and the inner cylinder communicates with the external casing annulus through the inner valve hole, the hydraulic chamber, and the outer valve hole.

[0015] In an optional embodiment of this application, the axial limiting structure includes a reducing ring structure disposed on the inner wall of the outer cylinder and located at the lower part of the hydraulic cavity. The bottom end of the inner cylinder is provided with a radially expandable and contractile claw. When the claw expands radially, its outer diameter is larger than the inner diameter of the reducing ring structure. When the well-washing circulation valve is in the closed state, the claw is located below the reducing ring structure, the claw is radially open, and its bottom end overlaps the second step. When the well-washing circulation valve is in the open state, the claw contracts and moves upward through the reducing ring structure.

[0016] In an optional embodiment of this application, the reduced diameter ring structure includes a lower reduced diameter section and an upper reduced diameter section. The inner diameter of both the lower reduced diameter section and the upper reduced diameter section is smaller than the inner diameter of the outer cylinder and larger than the outer diameter of the inner cylinder. The inner diameter of the lower reduced diameter section is smaller than the inner diameter of the upper reduced diameter section.

[0017] In an optional embodiment of this application, an adjustment hole is provided on the outer wall of the outer cylinder above the outer valve hole; a third step is provided on the outer wall of the inner cylinder above the inner valve hole; an adjuster is sleeved on the top of the outer wall of the inner cylinder; a spring is provided between the adjuster and the third step; the spring is used to drive the inner cylinder to move down and reset.

[0018] In one optional embodiment of this application, the bottom end of the outer cylinder is connected to a lower connector, and the top surface of the lower connector forms the second stepped portion.

[0019] In one optional embodiment of this application, the top end of the outer cylinder is connected to a hollow upper connector, the lower interior of the upper connector forms a receiving cavity, and the inner cylinder can move upward and extend into the receiving cavity.

[0020] In an optional embodiment of this application, an upper limit switch, a straightening stop, a lower limit switch, and the switch are provided axially at intervals on the sucker rod; the straightening stop is slidably sleeved on the sucker rod, and the upper limit switch and the lower limit switch axially limit the straightening stop.

[0021] In one optional embodiment of this application, the outer diameter of the straightening blocker is smaller than the inner diameter of the inner cylinder; the outer wall of the straightening blocker is provided with multiple oblique grooves.

[0022] In an optional embodiment of this application, the switch is arranged in a series structure; the switch includes a top unit, a middle unit and a bottom unit arranged sequentially from top to bottom, the diameter of the top unit gradually decreases from bottom to top, the diameter of the middle unit gradually decreases from the middle to both ends, and the diameter of the bottom unit gradually decreases from top to bottom.

[0023] In an optional embodiment of this application, the maximum outer diameter of the switch is smaller than the minimum inner diameter of the reduced-diameter ring structure.

[0024] In an alternative embodiment of this application, the switch is made of rubber, plastic or metal.

[0025] The objective of this application embodiment can also be achieved by providing a method for using the aforementioned reliable and efficient hot washing circulation tubing structure for oil wells, including the following steps:

[0026] Step a: Select the well for treatment, determine the wax deposits in the wellbore, and connect the well-washing circulation valve and tubing before running the entire production tubing string.

[0027] Step b: Calculate the position of the oil rod switch based on the position of the well-washing circulation valve;

[0028] Step c: Connect the oil rod switch to the sucker rod and lower all the sucker rods. The switch is located below the bottom of the inner cylinder. At this time, the well washing circulation valve is in the closed state.

[0029] Step d: When well washing is required, the wellhead is pressurized by injecting fluid into the tubing to the opening pressure of the well washing circulation valve; the fluid enters the lifting structure through the inner cylinder and the inner valve hole, and the lifting structure pushes the inner cylinder upward until the inner valve hole connects with the outer valve hole, the high-pressure fluid leaks from the inner cylinder into the annulus, and the inner cylinder no longer moves upward; the well washing circulation valve is in the open state.

[0030] Step e: Inject hot washing fluid into the wellhead and wash the well through the washing fluid circulation channel until the hot washing is completed;

[0031] Step f: When normal oil production needs to be restored after well washing is completed, the pumping unit is turned on. The switch moves up with the sucker rod and then pushes the inner cylinder down until the inner valve hole and the outer valve hole are sealed. The well washing circulation valve is closed, and the tubing returns to normal oil production.

[0032] As described above, the oil well reliable and efficient hot washing circulation tubing structure and its usage method of the embodiments of this application have the following beneficial effects:

[0033] This application differs from conventional hot washing methods. The well-washing circulation valve is connected to the bottom of the wax-contaminated section of the tubing. When hot washing is required, the wellhead is pressurized directly to open the well-washing circulation valve. The high-temperature washing fluid circulates only in the section of the well that is severely wax-contaminated and requires hot washing, without having to circulate from the wellhead to the bottom of the well and then back to the wellhead. This significantly shortens the well-washing path of the high-temperature washing fluid, reduces heat loss of the high-temperature washing fluid in the wellbore, shortens the well-washing operation time, improves efficiency, and reduces costs.

[0034] The opening method of this application is wellhead pressurization, and the closing method is to start the pumping unit to drive the corresponding oil rod switch to close and reset the well washing circulation valve, ensuring that the well washing circulation valve is in the closed state, and preventing tubing leakage caused by the circulation channel not being effectively closed.

[0035] The well-washing fluid circulation channel in this embodiment will not close automatically after being opened. It can only be closed after the pumping unit is turned on to resume production. Therefore, it can realize forward and reverse circulation well-washing operations. At the same time, the switch response is rapid, unlike some temperature control valves that require specific temperatures to open and close, and require a certain waiting time before and after operation, which cannot resume production in time. It is also not affected by environmental factors such as temperature and pressure. It can also be used for well washing with room temperature water, well washing with gasified water, and other operations.

[0036] The oil rod switch in this embodiment is equivalent to a conventional anti-wear sucker rod short section, which can play an anti-wear and straightening role without affecting the normal connection and use of the oil rod. Attached Figure Description

[0037] The following figures are intended only to illustrate and explain this application and do not limit the scope of this application. Wherein:

[0038] Figure 1 is a schematic diagram of the reliable and efficient hot washing circulation tubing structure of an oil well according to an embodiment of this application.

[0039] Figure 2 is a schematic diagram of the well-washing circulation valve according to an embodiment of this application.

[0040] Figure 3 is a schematic diagram of the hydraulic rod switch according to an embodiment of this application.

[0041] Figure 4 is a schematic diagram of the hot washing state of the oil well reliable and efficient hot washing circulation tubing structure according to an embodiment of this application.

[0042] In the diagram: 100, well-washing circulation valve; 200, rod switch; 1, upper connector; 2, receiving cavity; 3, regulator; 4, spring; 5, inner cylinder; 6, sealing ring; 7, lower piston; 8, inner valve hole; 9, outer valve hole; 10, hydraulic chamber; 11, outer cylinder; 12, reducing ring structure; 13, contraction claw; 14, lower connector; 15, sucker rod; 16, upper limit switch; 17, centralizing stop; 18, lower limit switch; 19, switch; 20, adjusting hole. Detailed Implementation

[0043] To provide a clearer understanding of the technical features, objectives, and effects of this application, specific embodiments of this application will now be described with reference to the accompanying drawings.

[0044] The specific embodiments of this application described herein are for illustrative purposes only and should not be construed as limiting the scope of this application in any way. Under the teachings of this application, those skilled in the art can conceive of any possible modifications based on this application, all of which should be considered within the scope of this application. It should be noted that when an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there may be an intervening element. The terms "mounted," "connected," and "linked" should be interpreted broadly; for example, they can refer to mechanical or electrical connections, or internal communication between two elements, and can be direct or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible embodiments.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0046] As shown in Figures 1 to 3, this application provides a reliable and efficient hot washing circulation tubing string structure for oil wells, which includes a well washing circulation valve 100 and a rod switch 200. The well washing circulation valve 100 is connected to the bottom end of the waxed section of the tubing. Below the well washing circulation valve 100, the tubing, pump, perforated tubing, plug, etc., continue to the bottom of the well (existing production tubing and equipment are sufficient).

[0047] The well-washing circulation valve 100 includes an outer cylinder 11 and an inner cylinder 5 coaxially sleeved together. That is, the inner cylinder 5 is located inside the outer cylinder 11 and is coaxially arranged with the outer cylinder 11. A lifting structure that can drive the inner cylinder 5 to move upward and an axial limiting structure that can axially limit (i.e., axially limit) the inner cylinder 5 are provided between the inner cylinder 5 and the outer cylinder 11. An inner valve hole 8 is radially provided through the side wall of the inner cylinder 5, and an outer valve hole 9 is radially provided through the side wall of the outer cylinder 11.

[0048] When the bottom end of the inner cylinder 5 is axially restricted below the axial limiting structure, the inner valve hole 8 and the outer valve hole 9 are sealed to keep the well washing circulation valve 100 in a closed state; when pressure is applied to the tubing and the lifting structure pushes the inner cylinder 5 upward under hydraulic action to connect the inner valve hole 8 and the outer valve hole 9, the well washing circulation valve 100 is in an open state, and the tubing is connected to the external casing annulus through the inner cylinder 5, the inner valve hole 8 and the outer valve hole 9 to form a well washing fluid circulation channel.

[0049] The rod switch 200 is used to drive the inner cylinder 5 downward to switch the well washing circulation valve 100 from the open state to the closed state. The rod switch 200 includes a sucker rod 15 whose top end is connected to the pumping unit and is movably inserted into the inner cylinder 5. A switch 19 is connected to the sucker rod 15 to radially press against the inner cylinder 5 to push the inner cylinder 5 downward.

[0050] This application differs from conventional hot washing methods. The well-washing circulation valve 100 is connected to the bottom of the wax-contaminated section of the tubing. When hot washing is required, the wellhead is pressurized directly to open the well-washing circulation valve. The high-temperature washing fluid circulates only in the section of the well that is severely wax-contaminated and requires hot washing, without having to circulate from the wellhead to the bottom of the well and then back to the wellhead. This significantly shortens the well-washing path of the high-temperature washing fluid, reduces heat loss of the high-temperature washing fluid in the wellbore, shortens the well-washing operation time, improves efficiency, and reduces costs.

[0051] The opening method of this application embodiment is wellhead pressurization, and the closing method is to start the pumping unit to drive the corresponding oil rod switch to close and reset the well washing circulation valve, ensuring that the well washing circulation valve is in the closed state, and preventing tubing leakage caused by the circulation channel not being effectively closed.

[0052] The well-washing fluid circulation channel in this embodiment will not close automatically after being opened. It can only be closed after the pumping unit is turned on to resume production. Therefore, it can realize forward and reverse circulation well-washing operations. At the same time, the switch response is rapid, unlike some temperature control valves that require specific temperatures to open and close, and require a certain waiting time before and after operation, which cannot resume production in time. It is also not affected by environmental factors such as temperature and pressure. It can also be used for well washing with room temperature water, well washing with gasified water, and other operations.

[0053] The oil rod switch in this embodiment is equivalent to a conventional anti-wear sucker rod short section, which can play an anti-wear and straightening role without affecting the normal connection and use of the oil rod.

[0054] Furthermore, as shown in Figures 1 and 2, the lifting structure includes a hydraulic chamber 10 and a lower piston 7. A first step is provided on the outer wall of the inner cylinder 5, and a second step is provided at the bottom of the outer cylinder 11. The outer wall of the inner cylinder 5, the first step, the inner wall of the outer cylinder 11, and the second step together constitute the aforementioned hydraulic chamber 10. The lower piston 7 is fixedly connected to the inner cylinder 5 and located below the first step. A sealing ring 6 is abutted between the lower piston 7 and the first step.

[0055] When the well-washing circulation valve 100 is in the closed state, the sealing ring 6 is located between the inner valve hole 8 and the outer valve hole 9 to seal and close the well-washing fluid circulation channel; when the well-washing circulation valve 100 is in the open state, the lower piston 7 moves upward above the outer valve hole 9, and the inner cylinder 5 is connected to the external casing annulus through the inner valve hole 8, the hydraulic chamber 10, and the outer valve hole 9.

[0056] Furthermore, as shown in Figure 2, the axial limiting structure includes a reducing ring structure 12 disposed on the inner wall of the outer cylinder 11 and located at the lower part of the hydraulic cavity 10. The bottom end of the inner cylinder 5 is provided with a radially expandable contraction claw 13. When the contraction claw 13 expands radially, its outer diameter is larger than the inner diameter of the reducing ring structure 12.

[0057] When the well-washing circulation valve 100 is in the closed state, the contraction claw 13 is located below the reducing ring structure 12, the contraction claw 13 is radially open and its bottom end overlaps the second step; when the well-washing circulation valve 100 is in the open state, the contraction claw 13 contracts and moves upward through the reducing ring structure.

[0058] Furthermore, the reduced diameter ring structure 12 includes a lower reduced diameter section and an upper reduced diameter section. The inner diameter of both the lower and upper reduced diameter sections is smaller than the inner diameter of the outer cylinder 11 and larger than the outer diameter of the inner cylinder 5, and the inner diameter of the lower reduced diameter section is smaller than the inner diameter of the upper reduced diameter section. In a specific embodiment, the reduced diameter of the upper reduced diameter section is not less than 3mm (i.e., the smaller value of the inner diameter of the upper reduced diameter section compared to the inner diameter of the outer cylinder 11 is greater than or equal to 3mm, that is, the difference between the inner diameter of the outer cylinder 11 and the inner diameter of the upper reduced diameter section is greater than or equal to 3mm), and the reduced diameter of the lower reduced diameter section is not less than 4mm (i.e., the smaller value of the inner diameter of the lower reduced diameter section compared to the inner diameter of the outer cylinder 11 is greater than or equal to 4mm, that is, the difference between the inner diameter of the outer cylinder 11 and the inner diameter of the lower reduced diameter section is greater than or equal to 4mm).

[0059] Furthermore, as shown in Figure 2, an adjustment hole 20 is provided on the outer wall of the outer cylinder 11 above the outer valve hole 9; a third step is provided on the outer wall of the inner cylinder 5 above the inner valve hole 8; an adjuster 3 is sleeved on the top of the outer wall of the inner cylinder 5; a spring 4 is provided between the adjuster 3 and the third step; the spring 4 is used to drive the inner cylinder 5 to move down and reset.

[0060] Furthermore, as shown in Figure 2, the bottom end of the outer cylinder 11 is connected to the lower connector 14, and the top surface of the lower connector 14 forms the aforementioned second stepped portion. In a specific embodiment, the outer wall of the lower connector is provided with a tapered thread for connecting to the lower oil pipe.

[0061] Furthermore, as shown in Figure 2, the top of the outer cylinder 11 is connected to the hollow upper connector 1, and the lower part of the upper connector 1 forms a receiving cavity 2, and the inner cylinder 5 can move upward and extend into the receiving cavity 2.

[0062] Furthermore, as shown in Figure 3, an upper limit switch 16, a straightening stop 17, a lower limit switch 18, and a switch 19 are provided axially at intervals on the sucker rod 15. The straightening stop 17 is slidably sleeved on the sucker rod 15, that is, the inner diameter of the straightening stop 17 is larger than the outer diameter of the sucker rod 15, and there is a certain gap between the two, so that the straightening stop 17 can slide on the sucker rod 15. The upper limit switch 16 and the lower limit switch 18 axially limit the straightening stop 17.

[0063] Furthermore, the outer diameter (maximum outer diameter) of the straightening blocker 17 is smaller than the inner diameter of the inner cylinder 5; the outer wall of the straightening blocker 17 is provided with multiple oblique grooves to facilitate the flow of liquid in the inner cylinder 5.

[0064] Furthermore, as shown in Figure 3, the switch 19 is arranged in a series structure, which can also be described as a candied hawthorn-like structure; the switch 19 includes a top unit, a middle unit and a bottom unit arranged sequentially from top to bottom. The diameter of the top unit gradually decreases from bottom to top (gradually becoming thicker from top to bottom), the diameter of the middle unit gradually decreases from the middle to both ends, and the diameter of the bottom unit gradually decreases from top to bottom (gradually becoming thinner from top to bottom).

[0065] Furthermore, the maximum outer diameter of the switch 19 is smaller than the minimum inner diameter of the reduced diameter ring structure 12.

[0066] In one specific embodiment, the intermediate unit is a spherical, near-spherical, or rhomboid structure with small ends and a large middle, and the number is no less than 3, preferably 5-8. Its maximum diameter is slightly smaller than the minimum bore diameter (minimum inner diameter) of the reduced-diameter ring structure 12.

[0067] Furthermore, the switch 19 is made of rubber, plastic, or metal. It is preferably made of nitrile rubber, which has a certain degree of elasticity and rigidity.

[0068] Furthermore, to prevent the well-washing fluid from flowing back into the formation, an anti-backflow packer or a rubber cup can be connected to the lower end of the well-washing circulation valve 100 for use.

[0069] The working principle of the well-washing circulation valve 100 in this embodiment is as follows:

[0070] During conventional oil production, the well-washing circulation valve 100 is in the closed state, and the sealing ring 6 is located between the inner valve hole 8 and the outer valve hole 9 to seal and close the well-washing fluid circulation channel; the inner cylinder 5 is located at the lowest point of the stroke, and the contraction claw 13 is located below the diameter reduction ring structure 12. The contraction claw 13 is in a radially open state and its bottom end overlaps on the second step, which can be used as the initial position.

[0071] When hot washing is required, pressure is applied from the wellhead into the tubing. Liquid flows through the inner cylinder 5 and inner valve port 8 into the hydraulic chamber 10. The high-pressure liquid acts on the bottom face of the lower piston 7, providing an upward thrust, causing the inner cylinder 5 to move upwards as a whole. After moving upwards, the upper part of the inner cylinder 5 enters the receiving chamber 2. When the contraction claw 13 reaches the reducing ring structure 12, the contraction claw 13 contracts under the action of the reducing ring structure 12 and continues to move upwards until the inner valve port 8, hydraulic chamber 10, and outer valve port 9 are connected. Then, the high-pressure liquid leaks from the inner cylinder 5 into the annulus, and the inner cylinder 5 stops moving upwards. Simultaneously, the contraction claw 13 contracts and locks onto the upper end of the reducing ring structure 12, maintaining constant communication between the inner valve port 8, hydraulic chamber 10, and outer valve port 9. At this point, the well washing circulation valve 100 is opened, the well washing fluid circulation channel is established, and forward or reverse circulation well washing operations can be performed.

[0072] When well washing is completed and normal oil production needs to be resumed, the pumping unit is directly turned on (existing technology). The switch 19 connected to the sucker rod 15 moves upward with the sucker rod 15 to the upper end of the contraction claw 13. Then, the pumping unit moves downward, driving the switch 19 downward to the contraction claw 13 and encountering greater resistance. The switch 19 moves downward with the contraction claw 13 to release the restriction of the diameter reduction ring structure 12. Under the action of the spring 4, the inner cylinder 5 continues to return to the initial position downward. The hydraulic chamber 10 separates from the outer valve hole 9, and the tubing and casing annular passage is closed under the isolation of the sealing ring 6. The well washing circulation valve 100 is closed, allowing the tubing to return to normal oil production.

[0073] This application also provides a method for using a reliable and efficient hot washing circulation tubing structure for oil wells, including the following steps:

[0074] Step a: Select the well for treatment, determine the location of wax buildup in the wellbore, connect the well washing circulation valve 100 and the tubing (production tubing), and then run in the entire production tubing string;

[0075] Step b: Calculate the position of the oil rod switch 200 based on the position of the well cleaning circulation valve 100;

[0076] Step c: Connect the rod switch 200 to the sucker rod and lower all the sucker rods. The switch 19 is located below the bottom of the inner cylinder 5. At this time, the well washing circulation valve 100 is in the closed state.

[0077] Step d: When well washing is required, the wellhead is pressurized by injecting fluid into the tubing to the opening pressure of the well washing circulation valve 100; the fluid enters the lifting structure through the inner cylinder 5 and the inner valve hole 8, and the lifting structure pushes the inner cylinder 5 upward until the inner valve hole 8 is connected to the outer valve hole 9. The high-pressure fluid is discharged from the inner cylinder 5 into the annulus of the casing, and the inner cylinder 5 no longer moves upward; the contraction claw 13 is engaged on the step of the diameter reduction ring structure 12 (the step between the lower diameter reduction section and the upper diameter reduction section caused by the diameter difference) and cannot retract, so the well washing circulation valve 100 is in the open state;

[0078] Step e: Inject hot washing fluid into the wellhead and wash the well through the hot washing circulation channel until the hot washing is completed; the hot washing state is shown in Figure 4; at this time, the requirements for both forward circulation and reverse circulation well washing can be met;

[0079] Step f: When normal oil production needs to be restored after well washing is completed, turn on the pumping unit. Switch 19 moves up with the sucker rod and then pushes the inner cylinder 5 down until it is sealed between the inner valve hole 8 and the outer valve hole 9. The well washing circulation valve 100 is closed, and the tubing returns to normal oil production.

[0080] Example 1

[0081] The steps for hot washing using the oil well reliable and efficient hot washing circulation tubing structure according to the embodiments of this application include:

[0082] 1. Select the well for treatment and determine the wax deposit location in the wellbore based on previous data. When working the well, connect the well-washing circulation valve 100 to the tubing (production tubing) through the upper connector 1 and the lower connector 14 and then run the entire production tubing string. The well-washing circulation valve is designed to be located more than 30m below the lower edge of the wax deposit location (the bottom of the wax-deposited section).

[0083] 2. Calculate the position of the oil rod switch 200 based on the position of the well washing circulation valve 100. The position is when the pumping unit is at the bottom dead center, the switch 19 is located at a position greater than or equal to 1m below the position of the contraction claw 13.

[0084] 3. Connect the oil rod switch to the sucker rod according to the preset position, and lower all the sucker rods to resume normal production. At this time, the well washing circulation valve 100 is in the closed state.

[0085] 4. When well washing is required, close the wellhead oil delivery valve (existing technology), stop the pumping unit (existing technology) at the bottom dead center, connect the hot wash truck (existing technology) to the tubing valve (existing technology), and slowly pressurize the wellhead to the opening pressure of the well washing circulation valve 100; the liquid enters the hydraulic chamber 10 through the inner cylinder 5 and the inner valve hole 8. The high-pressure liquid acts on the bottom end face of the lower piston 7 and provides an upward thrust, causing the inner cylinder 5 to move upward as a whole. After the inner cylinder 5 moves upward, its upper part enters the receiving chamber 2; when the contraction claw 13 reaches the reducing ring structure 12, the contraction claw 13 is contracted by the reducing ring structure 12 and continues to move upward until the inner valve hole 8, the hydraulic chamber 10 and the outer valve hole 9 are connected. Then the high-pressure liquid is discharged from the inner cylinder 5 into the annulus cavity, the pressure drops to zero instantly, and the inner cylinder 5 no longer moves upward; at the same time, the contraction claw 13 contracts and gets stuck at the upper end of the reducing ring structure 12, keeping the inner valve hole 8, the hydraulic chamber 10 and the outer valve hole 9 always connected.

[0086] 5. Connect the casing to the return tanker (existing technology), start the hot wash truck (existing technology) for hot washing. The hot wash liquid enters the oil sleeve annulus through the inner valve hole 8 to the outer valve hole 9, establishing a hot wash circulation channel until the hot wash is completed.

[0087] Example 2

[0088] Select a well for treatment, determine the location of wax buildup in the wellbore and the dynamic fluid level based on previous data, and calculate the required pressure rating for the well-washing circulation valve. If the dynamic fluid level is higher than the preset vertical depth of the insertion position, use the following formula to calculate; if it is lower than the preset vertical depth of the insertion position, then h... 环 Take 0.

[0089] Well cleaning circulation valve opening pressure = (ρ 水 ×f w +ρ 油 ×(1-f w ))gh 油 -(ρ 水 ×f w +ρ 油 ×(1-f w ))gh 环 +P 井口

[0090] ρ 水 —The density of water;

[0091] ρ 油 —The density of oil;

[0092] f w —Water content in oil wells;

[0093] g — acceleration due to gravity;

[0094] h 油 —Preset insertion position and vertical depth;

[0095] h 环 —The difference between the preset vertical depth of the insertion position and the vertical depth of the position of the moving liquid surface in the annulus;

[0096] P 井口 —Rated pressure of the wellhead Christmas tree;

[0097] For example, according to the well history data of well #1, the wax deposit is located at 700m, the dynamic fluid level is 1200m, and the water cut is 80%. Therefore, the preset vertical depth of the well washing circulation valve is set at 800m. The liquid column pressure on the well washing circulation valve is 7.6MPa. Considering that the wellhead pressure level is less than 6MPa, it is more appropriate to set the opening pressure of the well washing circulation valve to within 13MPa.

[0098] As described above, the oil well reliable and efficient hot washing circulation tubing structure and its usage method of the embodiments of this application have the following beneficial effects:

[0099] This application differs from conventional hot washing methods. The well-washing circulation valve is connected to the bottom of the wax-contaminated section of the tubing. When hot washing is required, the wellhead is pressurized directly to open the well-washing circulation valve. The high-temperature washing fluid circulates only in the section of the well that is severely wax-contaminated and requires hot washing, without having to circulate from the wellhead to the bottom of the well and then back to the wellhead. This significantly shortens the well-washing path of the high-temperature washing fluid, reduces heat loss of the high-temperature washing fluid in the wellbore, shortens the well-washing operation time, improves efficiency, and reduces costs.

[0100] The opening method of this application embodiment is wellhead pressurization, and the closing method is to start the pumping unit to drive the corresponding oil rod switch to close and reset the well washing circulation valve, ensuring that the well washing circulation valve is in the closed state, and preventing tubing leakage caused by the circulation channel not being effectively closed.

[0101] The well-washing fluid circulation channel in this embodiment will not close automatically after being opened. It can only be closed after the pumping unit is turned on to resume production. Therefore, it can realize forward and reverse circulation well-washing operations. At the same time, the switch response is rapid, unlike some temperature control valves that require specific temperatures to open and close, and require a certain waiting time before and after operation, which cannot resume production in time. It is also not affected by environmental factors such as temperature and pressure. It can also be used for well washing with room temperature water, well washing with gasified water, and other operations.

[0102] The oil rod switch in this embodiment is equivalent to a conventional anti-wear sucker rod short section, which can play an anti-wear and straightening role without affecting the normal connection and use of the oil rod.

[0103] The above description is merely an illustrative embodiment of this application and is not intended to limit the scope of this application. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of this application shall fall within the scope of protection of this application.

Claims

1. A reliable and efficient hot washing circulation tubing string structure for oil wells, wherein, include: A well-washing circulation valve is connected to the bottom end of the wax-contaminated section of the tubing. The well-washing circulation valve includes an outer cylinder and an inner cylinder coaxially sleeved together. A lifting structure capable of driving the inner cylinder upward and an axial limiting structure capable of axially limiting the inner cylinder are provided between the inner cylinder and the outer cylinder. An inner valve hole is radially provided through the side wall of the inner cylinder, and an outer valve hole is radially provided through the side wall of the outer cylinder. When the bottom end of the inner cylinder is axially limited below the axial limiting structure, the inner valve hole and the outer valve hole are sealed to keep the well-washing circulation valve in a closed state. When pressure is applied to the tubing, the lifting structure pushes the inner cylinder upward under hydraulic action to connect the inner valve hole and the outer valve hole, and the well-washing circulation valve is in an open state. The tubing is connected to the external casing annulus through the inner cylinder, the inner valve hole, and the outer valve hole to form a well-washing fluid circulation channel. A sucker rod switch is used to drive the inner cylinder to move downward so that the well washing circulation valve switches from an open state to a closed state; it includes a sucker rod whose top end is connected to the pumping unit and is movably inserted into the inner cylinder, and a switch is connected to the sucker rod to radially press against the inner cylinder to push the inner cylinder downward.

2. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 1, wherein, The lifting structure includes a hydraulic chamber and a lower piston. A first step is provided on the outer wall of the inner cylinder, and a second step is provided at the bottom of the outer cylinder. The hydraulic chamber is formed between the outer wall of the inner cylinder, the first step, the inner wall of the outer cylinder, and the second step. The lower piston is fixedly connected to the inner cylinder and located below the first step. A sealing ring is abutted between the lower piston and the first step. When the well-washing circulation valve is closed, the sealing ring is located between the inner valve hole and the outer valve hole to seal and close the well-washing fluid circulation channel. When the well-washing circulation valve is open, the lower piston moves upward above the outer valve hole, and the inner cylinder communicates with the external casing annulus through the inner valve hole, the hydraulic chamber, and the outer valve hole.

3. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 2, wherein, The axial limiting structure includes a reducing ring structure disposed on the inner wall of the outer cylinder and located at the lower part of the hydraulic chamber. The bottom end of the inner cylinder is provided with a radially expandable and contractile claw. When the claw expands radially, its outer diameter is larger than the inner diameter of the reducing ring structure. When the well-washing circulation valve is in the closed state, the claw is located below the reducing ring structure, the claw is radially open, and its bottom end overlaps the second step. When the well-washing circulation valve is in the open state, the claw contracts and moves upward through the reducing ring structure.

4. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 3, wherein, The reduced diameter ring structure includes a lower reduced diameter section and an upper reduced diameter section. The inner diameter of both the lower and upper reduced diameter sections is smaller than the inner diameter of the outer cylinder and larger than the outer diameter of the inner cylinder. The inner diameter of the lower reduced diameter section is smaller than the inner diameter of the upper reduced diameter section.

5. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 2, wherein, An adjustment hole is provided on the outer wall of the outer cylinder above the outer valve hole; a third step is provided on the outer wall of the inner cylinder above the inner valve hole; an adjuster is fitted on the top of the outer wall of the inner cylinder; a spring is provided between the adjuster and the third step; the spring is used to drive the inner cylinder to move down and reset.

6. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 2, wherein, The bottom end of the outer cylinder is connected to the lower connector, and the top surface of the lower connector forms the second stepped portion.

7. The reliable and efficient hot washing circulation tubing structure for oil wells as described in any one of claims 1 to 6, wherein, The top of the outer cylinder is connected to a hollow upper connector, and the lower part of the upper connector forms a receiving cavity, into which the inner cylinder can move upward and extend.

8. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 3, wherein, An upper limit switch, a centralizing stop, a lower limit switch, and the switch are provided axially at intervals on the sucker rod; the centralizing stop is slidably sleeved on the sucker rod, and the upper limit switch and the lower limit switch axially limit the centralizing stop.

9. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 8, wherein, The outer diameter of the straightening stop is smaller than the inner diameter of the inner cylinder; the outer wall of the straightening stop is provided with multiple oblique grooves.

10. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 3, wherein, The switch is arranged in a series structure; the switch includes a top unit, a middle unit and a bottom unit arranged sequentially from top to bottom. The diameter of the top unit gradually decreases from bottom to top, the diameter of the middle unit gradually decreases from the middle to both ends, and the diameter of the bottom unit gradually decreases from top to bottom.

11. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 10, wherein, The maximum outer diameter of the switch is smaller than the minimum inner diameter of the reduced-diameter ring structure.

12. The reliable and efficient hot washing circulation tubing structure for oil wells as described in claim 10, wherein, The switch is made of rubber, plastic or metal.

13. A method of using the reliable and efficient hot washing circulation tubing structure for oil wells as described in any one of claims 1 to 12, wherein, Includes the following steps: Step a: Select the well for treatment, determine the wax deposits in the wellbore, and connect the well-washing circulation valve and tubing before running the entire production tubing string. Step b: Calculate the position of the oil rod switch based on the position of the well-washing circulation valve; Step c: Connect the oil rod switch to the sucker rod and lower all of the sucker rods. The switch is located below the bottom of the inner cylinder. At this time, the well washing circulation valve is in the closed state. Step d: When well washing is required, the wellhead is pressurized by injecting fluid into the tubing to the opening pressure of the well washing circulation valve; the fluid enters the lifting structure through the inner cylinder and the inner valve hole, and the lifting structure pushes the inner cylinder upward until the inner valve hole is connected to the outer valve hole, the high-pressure fluid is discharged from the inner cylinder into the annulus, and the inner cylinder no longer moves upward; The well-washing circulation valve is in the open state; Step e: Inject hot washing fluid into the wellhead and wash the well through the washing fluid circulation channel until the hot washing is completed; Step f: When normal oil production needs to be restored after well washing is completed, the pumping unit is turned on. The switch moves up with the sucker rod and then pushes the inner cylinder down until the inner valve hole and the outer valve hole are sealed. The well washing circulation valve is closed, and the tubing returns to normal oil production.

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