Downhole oil sleeve annulus flow limiting device

Abstract

The invention discloses an annular flow limiting device for an underground oil sleeve. A flow limiting plate provided with staggered converging runners is fixed in a flow limiting plate mounting groove in the pipe wall of a central pipe, and a seat sealing hole and a seat sealing boosting hole are formed in the pipe wall without the flow limiting plate mounting groove; a sliding barrel, a leather cup and an upper pushing barrel are sequentially installed above an upper pushing barrel limiting step of a center pipe from top to bottom, sealing pieces are installed in sealing faces of the outer circle of the center pipe, the leather cup is installed in the sliding barrel, and the lower portion of the leather cup is located between the sliding barrel and the upper pushing barrel. And the upper pushing cylinder is matched with a locking ring mounted in a locking ring mounting groove of the central pipe through a horse tooth buckle. The working principle is simple and reliable, the sealing capacity of the leather cup is improved, meanwhile, an inverse well flushing process channel is provided, and the safety performance of the whole tool is enhanced. The service life of an injection-production well in a gas storage and a conventional oil-water well pipe column is prolonged, the working efficiency of a single well is improved, and the method can be used for the injection-production well in the gas storage and can also be used for a conventional oil production well.

Description

Technical Field

[0001] The invention relates to a downhole flow limiting tool in the development of oil fields in the petroleum industry, in particular to a downhole oil casing annulus flow limiting device. Background Art

[0002] With the rapid development of our society, the demand for energy is also increasing day by day. In recent years, my country has also vigorously developed the construction of gas storage facilities. In order to meet the seasonal peak load and ensure gas supply, gas storage facilities play a top priority role. However, with the long-term operation of gas storage facilities, the annular pressure problem of corresponding production wells has become increasingly prominent, seriously affecting the development and operation of oil and gas wells.

[0003] Due to its special operation mode, underground gas storage adopts a production method of periodic alternation of gas injection and gas production, and a strong injection and strong production mode. The temperature and pressure in the oil pipes of the injection and production wells change back and forth with the injection and production operations, causing the annulus protection fluid to expand and the annulus volume to change. The pipe string is affected by the additional pressure, making it very easy for the gas storage well to have annulus pressure problems caused by failure of the bottom packer of the injection and production pipe string.

[0004] At the same time, due to the irregular adjustment of gas production and injection volume in some intensive production and injection gas storage wells, the wellbore temperature and pressure fluctuate greatly in a short period of time, and the pressure change of the casing annulus can reach 20 to 30 MPa. The tubing vibration and huge load caused by the sudden annulus pressure may cause fatigue damage to the casing and oil pipe gas seal buckles, and the failure of the seal will cause the annulus to be pressurized.

[0005] Therefore, under the conditions of strong production and injection, it is easy for the gas storage to have annular pressure. Even if it does not occur in the initial operation, it will occur in the long-term operation. However, no matter what the cause of the annular pressure is, it needs to be paid great attention. Because once the annular pressure of the casing is abnormal, there is a risk of blowout that may occur at any time, which seriously threatens the safety of the on-site production process.

[0006] At present, the injection and production wells of gas storage reservoirs only have downhole safety control tools and downhole safety valves installed inside the oil pipes to prevent blowouts, but no downhole safety control tools for the oil casing annulus are set; conventional injection and production wells only follow the industry's years of experience and use downhole packers to isolate and protect the oil casing annulus. However, facts have proved that no matter what type of injection and production string with packers is used, whether domestic or foreign, the problem of annular pressure always exists, it just occurs at different times, and the risk of annular blowout always exists. The existence of the above situation can be seen from the following disclosed patent technologies and articles: The "Bottom-hole Throttling Device and Throttling Method for Gas Storage Reservoirs" disclosed in the authorized announcement number CN105401925B describes a bottom-hole throttling device and throttling method for gas storage reservoirs. The bottom-hole throttling device for gas storage reservoirs includes an electric control device arranged on the ground; a gas production pipe string arranged in the wellbore, and a packer arranged between the gas production pipe string and the wellbore; a screw pump connected to the bottom end of the gas production pipe string; a power-consuming device connected to the screw pump; a monitoring device for monitoring the fluid type and performance at the bottom of the wellbore, arranged at the bottom of the wellbore and below the power-consuming device; and a cable connecting the electric control device, the power-consuming device, and the monitoring device.

[0007] In the throttling method disclosed in the above patent technology, a bottom-hole throttling device for gas storage reservoirs is adopted, which only solves the problems of high investment in gas production equipment, low energy utilization rate, and inability to significantly increase production capacity in the later stage during the gas production process. There is no additional safety control device for the oil-casing annulus in case of a blowout in the injection-production pipe string, and the level of downhole safety control cannot be improved based on the existing technology.

[0008] The "Injection-Production Pipe String" disclosed in the authorized announcement number CN204703779U includes a flow nipple, a downhole safety valve, a flow nipple, a circulating sliding sleeve, a retrievable packer, a plug setting nipple, a test setting nipple, and a flared outlet connected in sequence from top to bottom through an oil pipe. The flared outlet is cylindrical, and an internal chamfer is provided at the lower end.

[0009] The above injection-production pipe string can improve the gas supply capacity of the gas storage reservoir, and has the advantages of strong corrosion resistance, long service life, and easy maintenance. It mainly uses a packer for anchoring and sealing, aiming to protect the upper casing and slow down the influence of corrosion on the casing, but it also completely does not consider the blowout prevention safety of the oil-casing annulus.

[0010] It can be seen from the published "Research and Application of Annulus Protection Packers for Injection Wells in Bohai Oilfield" that about 1 / 2 of the existing injection wells in Bohai Oilfield have annulus pressure problems to varying degrees, which seriously affect the normal development of the oilfield. The solution is to develop a new type of packer to solve the annulus pressure problem.

[0011] However, the above article only aims to solve the annulus pressure problem caused by packer failure, and the application field is also in the injection field. For the injection-production gas wells in gas storage reservoirs, due to the different states of injection-production substances and the annulus pressure problems that occur, its reference significance is not great. At the same time, this technology also has no downhole safety control device for the annulus in case of a blowout.

[0012] It can be seen from the published "Research and Application of Annulus Protection Technology for High-Pressure Gas Wells" that the operating conditions of high-pressure gas wells in Xinjiang Oilfield vary greatly, and higher requirements are imposed on the performance of the pipe string and the annulus sealing. The solution is to form a set of annulus protection technologies through technical means such as material optimization, gas sealing performance evaluation and testing, and pipe string structure optimization, including tubing made of SM-13Cr110 material, JFE-BEAR gas-tight connections, permanent packers, and new annulus protection fluids, and these technologies have been applied in some gas storage reservoirs and gas fields. Applications have proved that this technology can, to a certain extent, extend the service life of injection and production pipe strings and slow down the corrosion of pipe strings.

[0013] However, for the safety of the downhole tubing-casing annulus, the above technology is also a passive safety measure, that is, whether the tubing-casing annulus is under pressure still depends on the gas-tight state of the packer and the pipe string thread downhole, and there is no special safety control tool or technical means, and no additional safety protection can be provided for the tubing-casing annulus during a blowout.

[0014] To sum up, there is no mature and available tool or device for limiting and preventing blowouts in the downhole tubing-casing annulus of gas storage injection and production wells in China to improve the downhole safety control level of injection and production wells and meet the safety requirements of limiting flow and preventing blowouts in the downhole tubing-casing annulus during a blowout. Therefore, a new type of downhole tubing-casing annulus flow-limiting device is urgently needed to solve the above problems. Summary of the Invention

[0015] To solve the above problems, the present invention provides a downhole tubing-casing annulus flow-limiting device, which is mainly used to solve the problem that there is no device for limiting the degree of blowout and controlling blowout by limiting flow in the tubing-casing annulus when a blowout occurs in the downhole pipe string of gas storage injection and production wells, to gain time for controlling blowouts in gas storage injection and production wells, add an additional safety guarantee, avoid the adverse consequences brought by blowouts, and improve economic benefits.

[0016] To achieve the above object, the present invention adopts the following technical solution: A downhole tubing-casing annulus flow-limiting device is provided with a cup leather. Specifically, a flow-limiting plate with an intersecting converging flow channel is fixed in a flow-limiting plate installation groove in the inner wall of the central pipe, and a setting hole and a setting boosting hole are arranged in the pipe wall without a flow-limiting plate installation groove; above the upper thrust cylinder limiting step of the central pipe, a sliding cylinder, a cup leather, and an upper thrust cylinder are sequentially installed from top to bottom, and sealing members are installed in the sealing surfaces of the outer circle of the central pipe; the cup leather is installed in the sliding cylinder and the lower part is located between the sliding cylinder and the upper thrust cylinder, a limiting ring with a locking ring installed is installed in the sliding cylinder above the cup leather, and the locking ring is installed in a locking ring groove on the outer circle of the central pipe; the upper thrust cylinder is in mating connection with a locking ring installed in a locking ring groove of the central pipe through a buttress thread.

[0017] Preferably, the intersecting converging flow channel is composed of a main channel groove processed in the center of the flow-limiting plate and auxiliary channel grooves communicated with the main channel groove; one set or more of a limiting plate installation groove is arranged on the outer wall of the central pipe, and the flow-limiting plate is welded in the limiting plate installation groove.

[0018] Preferably, the main channel groove is a straight groove that runs through both ends of the current-limiting plate body; the auxiliary channel grooves are arranged on both sides of the main channel groove, and the flow channel shape is an arc-shaped downward slope. The auxiliary channel grooves arranged on both sides are staggered and connected end to end in the main channel groove.

[0019] Preferably, both the locking ring and the locking stop ring are broken rings with axial cuts. The cuts provided axially are oblique cuts or vertical cuts, and the oblique angle is set between 1 degree and 89 degrees; the inner diameter of the locking ring in the natural state is smaller than the outer diameter of the center pipe section where it is located; the outer circle of the locking stop ring is machined with a buttress thread and can cooperate with the buttress thread machined on the inner circle of the upper push cylinder.

[0020] Preferably, the lip seal is installed with the lip facing downwards between the upper push cylinder outside the center pipe and the sliding cylinder; the lip seal also has a bottom and a body. The bottom is the force-applying step for the upward push of the upper push cylinder, the body is a straight cylinder type, the lip is a flared shape and the outer diameter is a vertical outer circle, and there is a tapered transition surface between the two outer circle surfaces of the body and the lip. The lip seal is made of rubber material.

[0021] Preferably, the upper push cylinder is a non-uniform diameter cylinder body, provided with an upper cylinder body and anti-backoff threads arranged in the lower cylinder body. The inner diameter of the upper cylinder body is smaller than that of the lower cylinder body. At least one liquid-assisted sealing and passing groove is arranged on the outer wall of the upper cylinder body, and the liquid-assisted sealing and passing groove communicates with the top of the upper cylinder body; the inner circle of the lower cylinder body of the upper push cylinder is provided with anti-backoff threads, and the anti-backoff threads are buttress threads and can cooperate with the buttress threads on the outer circle of the locking stop ring.

[0022] Preferably, the outer circle of the center pipe below the limit step of the upper push cylinder is machined with a connecting thread, and through this connecting thread, it can be threadedly connected with the washing-assisting and blowout-preventing mechanism.

[0023] Preferably, the washing-assisting and blowout-preventing mechanism is provided with an upper outer cylinder, a lower outer cylinder, a lower push cylinder, a spring and a limit cylinder. The two ends of the upper outer cylinder are respectively threadedly connected with the connecting thread in the center pipe and the lower outer cylinder. The lower push cylinder and the spring are installed inside the lower outer cylinder, and the limit cylinder is installed below the spring and is threadedly connected with the lower outer cylinder; at least one washing-assisting and blowout-preventing liquid-passing groove is arranged in the limit cylinder.

[0024] Preferably, the inner circle of the lower outer cylinder is a non-uniform diameter inner circle, and the internal threads at both ends are respectively threadedly connected with the upper outer cylinder and the limit cylinder; an inner taper mating surface is arranged between the two non-uniform diameter inner circles of the lower outer cylinder, and the inner taper mating surface is a lower inclined surface.

[0025] Preferably, the lower pushing cylinder is a non-uniform-diameter cylindrical body. The outer wall of the upper part of the lower pushing cylinder is an outer conical mating surface, which is an upper inclined surface and can cooperate with the inner conical mating surface in the lower outer cylinder. At least one sealing ring groove is machined in the outer conical mating surface; the spring is installed in the inner cavity below the spring limiting step in the lower pushing cylinder.

[0026] Preferably, the upper outer circle of the limiting cylinder is provided with an external thread and can be threadedly connected to the lower outer cylinder; the washing aid and blowout prevention liquid passing groove provided in the outer wall of the limiting cylinder is a vertically through groove and at least one is provided; the upper outer cylinder is a non-uniform-diameter cylindrical body, and the internal and external threads in the cylinders at the upper and lower ends can be respectively threadedly connected to the continuous thread of the central pipe and the lower outer cylinder. The lower inner cavity of the upper outer cylinder after being connected to the central pipe is communicated with the limiting plate installation groove.

[0027] Compared with the prior art, the present invention has the following remarkable use effects: The device of the present invention can be used in both injection-production wells in gas storage reservoirs and conventional oil production wells. By squeezing the cup leather, the positive sealing ability of the device for the oil-casing annulus is ensured, specifically manifested in: (1) Through the structural optimization of the channel groove in the flow-limiting plate, the present invention realizes the functions of allowing the water and liquid coming from above the device to flow through smoothly and throttling and limiting the water and liquid coming from below the device, so that the device has both the function of well washing and the function of blowout prevention and flow limiting; (2) In order to further ensure the working reliability of the present invention, a washing aid and blowout prevention mechanism is connected and installed at the lower part of the upper outer cylinder, providing double protection for positive flow limiting, further improving the service life and safety factor of the present invention, and making it easier to kill the well by means of reverse circulation during a blowout, reducing the difficulty of killing the well during a blowout.

[0028] The working principle of the present invention is simple and reliable. While improving the sealing ability of the cup leather, it provides a reverse well washing process channel, enhances the safety performance of the whole tool, extends the service life of the injection-production wells in gas storage reservoirs and the pipe strings of conventional oil and water wells, improves the single-well working efficiency, has good economic and social benefits, and has a huge promotion space. Description of the Drawings

[0029] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention. In the drawings: Figure 1 It is a schematic structural diagram of an underground oil-casing annulus flow-limiting device of the present invention.

[0030] Figure 2 is Figure 1 a schematic structural diagram of the central pipe in

[0031] Figure 3 is Figure 1 a schematic structural diagram of the cup leather in

[0032] Figure 4 is Figure 1 a schematic structural diagram of the upper push cylinder in the middle.

[0033] Figure 5 is Figure 1 a schematic structural diagram of the current-limiting plate in the middle.

[0034] Figure 6 is Figure 1 a schematic structural diagram of the lower outer cylinder in the middle.

[0035] Figure 7 is Figure 1 a schematic structural diagram of the lower push cylinder in the middle.

[0036] Figure 8 is Figure 1 a schematic structural diagram of the middle limiting cylinder.

[0037] In the figure: upper joint 1; central tube 2, limiting plate installation groove 2-1, setting hole 2-2, lock ring groove 2-3, setting boost hole 2-4, lock ring installation groove 2-5, upper push cylinder limiting step 2-6, continuous thread 2-7; sliding cylinder 3, lock ring 4, limiting ring 5; leather cup 6, cup bottom 6-1, cup body 6-2, cup mouth 6-3; upper push cylinder 7, anti-back-off thread 7-1, upper cylinder body 7-2, assisting sealing liquid passing groove 7-3; knuckle lock ring 8, upper outer cylinder 9; current-limiting plate 10, main channel groove 10-1, auxiliary channel groove 10-2; lower outer cylinder 11, inner cone mating surface 11-1; lower push cylinder 12, outer cone mating surface 12-1; spring 13; limiting cylinder 14, assisting washing and anti-blowout liquid passing groove 14-1. Specific embodiments

[0038] The accompanying drawings are only for reference and illustration, and are not intended to limit the protection scope of the present invention. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, in the description of the present invention, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0041] See Figure 1 - Figure 8 , a downhole oil-casing annulus flow-limiting device, provided with a cup packer 6, wherein: a flow-limiting plate 10 with staggered converging flow channels is fixed in a flow-limiting plate installation groove 2-1 in the wall of the central tube 2, and a setting hole 2-2 and a setting boosting hole 2-4 are provided in the wall of the tube without the flow-limiting plate installation groove 2-1; above the upper push cylinder limiting step 2-6 of the central tube 2, a sliding cylinder 3, a cup packer 6 and an upper push cylinder 7 are installed in sequence from top to bottom, and seals are installed in the sealing surfaces of the outer circle of the central tube 2; the cup packer 6 is installed in the sliding cylinder 3 and the lower part is located between the sliding cylinder 3 and the upper push cylinder 7, a limiting ring 5 with a locking ring 4 installed is installed in the sliding cylinder 3 above the cup packer 6, and the locking ring 4 is installed in a locking ring groove 2-3 on the outer circle of the central tube 2; the upper push cylinder 7 is in mating connection with a locking ring 8 installed in a locking ring installation groove 2-5 of the central tube 2 through a buttress thread.

[0042] The present invention is connected to the tubing string through an upper sub 1 and lowered into the well. According to the process requirements, when the cup packer 6 is set, when the liquid flow enters the gap between the sliding cylinder 3 and the limiting ring 5 from the tubing through the setting hole 2-2, after the sliding cylinder 3 is pushed upward, the cup packer 6 is released from the sliding cylinder 3; as the liquid entering through the setting boosting hole 2-4 causes the upper push cylinder 7 to move upward and presses the cup packer 6 firmly in the oil-casing annulus, the sealing between the sliding cylinder 3 and the casing is realized. At this time, the backwashing operation can be carried out through the staggered converging flow channels in the flow-limiting plate 10.

[0043] When the bottom-hole pressure rises and a blowout occurs, the well fluid surges upward through the staggered converging flow channels in the flow-limiting plate 10 of the device of the present invention and is blocked, effectively slowing down the flow rate of the well fluid and weakening the intensity of the blowout, thus winning precious time for the blowout control work on the ground.

[0044] The flow-limiting plate 10 in the device of the present invention is provided with staggered converging flow channels and is fixed in a flow-limiting plate installation groove 2-1 in the wall of the central tube 2, and a setting hole 2-2 and a setting boosting hole 2-4 are provided in the wall of the central tube 2 without the flow-limiting plate installation groove 2-1.

[0045] The leather cup 6 is installed in the slide 3 and the lower part is located between the slide 3 and the upper push cylinder 7. The limit ring 5 with the locking ring 4 is installed in the slide 3 above the leather cup 6; the locking ring 4 installed in the locking ring groove 2-3 on the outer circle of the center tube 2 locks the limit ring 5 at the top end of the slide 3 outside the center tube 2; the locking ring 8 is installed in the locking ring installation groove 2-5 of the center tube 2 and cooperates with the upper push cylinder 7 through the horse tooth buckle. The locking ring 8 is fixed in the locking ring installation groove 2-5 and cannot move axially. The upper push cylinder 7 can move upward along the locking ring 8 to expand the leather cup 6 and seal the annulus between the slide 3 and the casing.

[0046] The present invention can backwash the well while sealing the annulus of the oil casing with the leather cup 6, and can throttle and limit the upwelling well fluid through the flow limiting plate 10, so it has both the function of backwashing the well and the function of limiting and throttling the blowout.

[0047] The invention can buy time for controlling the blowout of the gas storage injection and production well when a blowout occurs in the downhole pipe string of the gas storage injection and production well, add a safety guarantee, avoid the adverse consequences caused by the blowout, improve the economic benefits, and have a significant use effect. The invention can also be used in conventional oil production wells.

[0048] Based on the above embodiment 1, the present invention also has the following embodiments: A preferred embodiment: Figure 4 The staggered converging flow channel is composed of a main channel groove 10-1 processed in the center of the limiting plate 10 and an auxiliary channel groove 10-2 connected to the main channel groove 10-1; the limiting plate mounting groove 2-1 and the limiting plate 10 arranged on the outer wall of the central tube 2 are arranged in more than one set, and the limiting plate 10 is welded in the limiting plate mounting groove 2-1.

[0049] A preferred embodiment: the main channel groove 10-1 is a straight groove that passes through both ends of the plate body of the flow limiting plate 10; the auxiliary channel grooves 10-2 are arranged on both sides of the main channel groove 10-1 and the flow channel shape is arc-shaped and inclined downward, and the auxiliary channel grooves 10-2 arranged on both sides are staggered and connected end to end in the main channel groove 10-1. The staggered converging flow channels in the flow limiting plate 10 can also have other shapes and structures. In principle, the liquid flow from the upper side of the invention can flow downward smoothly and the liquid flow from the lower side of the invention is difficult to return upward.

[0050] A preferred embodiment: the locking ring 4 and the locking ring 8 are both broken rings with axial cuts, the cuts set in the axial direction are oblique cuts or vertical cuts and the oblique angle is set between 1 degree and 89 degrees; the inner diameter of the locking ring 4 in a natural state is smaller than the outer diameter of the central tube 2 section in which it is located, which is mainly due to installation issues. The inner diameter of the locking ring 4 is slightly smaller than the outer diameter of the upper part of the central tube 2, and after installation and restoration, it can still be clamped in the locking ring groove 2-3; the outer circle of the locking ring 8 is machined with a tooth buckle and can cooperate with the inner circle of the upper push tube 7.

[0051] A preferred embodiment: The mouth 6-3 of the leather cup 6 is installed downward between the upper push cylinder 7 outside the central pipe 2 and the sliding cylinder 3; the leather cup 6 is also provided with a bottom 6-1 and a body 6-2. The bottom 6-1 is the force application step for the upper push cylinder 7 to push upward. The body 6-2 is a straight cylinder. The mouth 6-3 is a flared shape and its outer diameter is the vertical outer circle. A tapered transition surface is provided between the two outer circular surfaces of the body 6-2 and the mouth 6-3. The leather cup 6 is made of rubber material.

[0052] A preferred embodiment: The upper push cylinder 7 is a non-uniform diameter cylinder body, provided with an upper cylinder body 7-2 and an anti-backoff thread 7-1 arranged in the lower cylinder body. The inner diameter of the upper cylinder body 7-2 is smaller than that of the lower cylinder body. At least one liquid-assisted sealing and passing groove 7-3 is arranged on the outer wall of the upper cylinder body 7-2, and the liquid-assisted sealing and passing groove 7-3 communicates with the top of the upper cylinder body 7-2; an anti-backoff thread 7-1 is arranged on the inner circle of the lower cylinder body of the upper push cylinder 7. The anti-backoff thread 7-1 is a horse-tooth buckle type thread and can cooperate with the horse-tooth buckle thread on the outer circle of the locking ring 8.

[0053] A preferred embodiment: A continuous thread 2-7 is machined on the outer circle of the central pipe 2 below the upper push cylinder limiting step 2-6. Through this continuous thread 2-7, it can be threadedly connected with the washing and anti-blowout prevention mechanism.

[0054] A preferred embodiment: Refer to Figure 1 As shown in the figure, the washing and anti-blowout prevention mechanism is provided with an upper outer cylinder 9, a lower outer cylinder 11, a lower push cylinder 12, a spring 13 and a limiting cylinder 14. The two ends of the upper outer cylinder 9 are respectively threadedly connected with the continuous thread 2-7 in the central pipe 2 and the lower outer cylinder 11. The lower push cylinder 12 and the spring 13 are installed in the lower outer cylinder 11. The limiting cylinder 14 is installed below the spring 13 and is threadedly connected with the lower outer cylinder 11; at least one washing and anti-blowout prevention liquid passing groove 14-1 is arranged in the limiting cylinder 14. The water and liquid coming from below the annulus flow-limiting device cannot enter the upper part of the annulus flow-limiting device through the lower push cylinder 12. The water and liquid coming from the upper part of the annulus flow-limiting device can push open the lower push cylinder 12 tightened by the spring 13 and enter the lower part of the annulus flow-limiting device.

[0055] A preferred embodiment: Refer to Figure 6 As shown in the figure, the inner circle of the lower outer cylinder 11 is a non-uniform diameter inner circle, and the inner threads at both ends are respectively threadedly connected with the upper outer cylinder 9 and the limiting cylinder 14; an inner taper mating surface 11-1 is arranged between the two non-uniform diameter inner circles of the lower outer cylinder 11. The inner taper mating surface 11-1 is a lower inclined surface.

[0056] A preferred embodiment: Refer to Figure 7, the lower pushing cylinder 12 is a non-uniform-diameter cylinder, the upper outer wall of the lower pushing cylinder 12 is an outer conical mating surface 12-1, which is an upper inclined surface and can cooperate with the inner conical mating surface 11-1 in the lower outer cylinder 11, and at least one sealing ring groove is machined in the outer conical mating surface 12-1; the spring 13 is installed in the inner cavity below the spring limit step 12-2 in the lower pushing cylinder 12.

[0057] A preferred embodiment: Refer to Figure 8 , the upper outer circle of the limit cylinder 14 is provided with an external thread and can be threadedly connected to the lower outer cylinder 11; the washing aid anti-spray overflow groove 14-1 provided in the outer wall of the limit cylinder 14 is a vertically penetrating groove and at least one is provided; the upper outer cylinder 9 is a non-uniform-diameter cylinder, and the internal and external threads in the cylinders at the upper and lower ends can be threadedly connected to the continuous thread 2-7 of the central pipe 2 and the lower outer cylinder 11 respectively. After being connected to the central pipe 2, the lower inner cavity of the upper outer cylinder 9 is communicated with the limit plate installation groove 2-1. In the annular flow-limiting device, sealing elements are provided in the sealing mating surfaces between components.

[0058] The washing aid anti-spray mechanism connected to the lower part of the central pipe 2 adds another guarantee for the backwashing well and limiting the spray and throttling during a blowout of the device. The backwashing well water from above the device can increase the pump pressure, push open the lower pushing cylinder 12, and spray and flush into the oil-casing annulus from the washing aid anti-spray overflow groove 14-1 for reverse circulation well washing.

[0059] When the downhole pressure increases and a blowout occurs, due to the sealing of the cup leather 6 and the inner and outer conical mating surfaces in the lower outer cylinder 11 and the lower pushing cylinder 12, the incoming water and liquid cannot return upward from the washing aid anti-spray overflow groove 14-1 of the limit cylinder 14; if the washing aid anti-spray mechanism fails due to some reason and the inner and outer conical mating surfaces in the lower outer cylinder 11 and the lower pushing cylinder 12 cannot be sealed and the one-way flow control function cannot be realized, the liquid flow can only pass through the staggered converging flow channels of the flow-limiting plate 10. When the liquid passes through the staggered converging flow channels, due to the impact of the liquid flow directions in the main channel groove 10-1 and the auxiliary channel groove 10-2 on each other, the upwelling flow rate and pressure are greatly reduced, buying more time for the ground staff to prevent blowout.

[0060] The embodiments described above are only typical embodiments, but the present invention is not limited to these embodiments, and those skilled in the art can make modifications without departing from the spirit and inspiration of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the creative spirit and creative concept of the present invention shall be included within the protection scope of the present invention. Therefore, the protection scope is not limited to the above description.

Claims

1. An underground oil-casing annulus flow-limiting device is provided with a cup leather (6). Its characteristics are: A flow-limiting plate (10) with staggered converging flow channels is fixed in a flow-limiting plate installation groove (2-1) in the pipe wall of the central pipe (2), and a setting hole (2-2) and a setting boosting hole (2-4) are arranged in the pipe wall without the flow-limiting plate installation groove (2-1); above the upper thrust cylinder limiting step (2-6) of the central pipe (2), a sliding cylinder (3), a cup leather (6) and an upper thrust cylinder (7) are installed in sequence from top to bottom. Sealing elements are installed in the sealing surfaces of the outer circle of the central pipe (2); the cup leather (6) is installed in the sliding cylinder (3) and the lower part is located between the sliding cylinder (3) and the upper thrust cylinder (7). A limiting ring (5) with a locking ring (4) installed is installed in the sliding cylinder (3) above the cup leather (6), and the locking ring (4) is installed in a locking ring groove (2-3) on the outer circle of the central pipe (2); the upper thrust cylinder (7) is in mating connection with a locking ring (8) installed in a locking ring installation groove (2-5) of the central pipe (2) through a buttress thread.

2. An underground oil-casing annulus flow-limiting device according to claim 1. Its characteristics are The staggered converging flow channels are composed of a main channel groove (10-1) processed in the center of the flow-limiting plate (10) and auxiliary channel grooves (10-2) communicated with the main channel groove (10-1); the limiting plate installation groove (2-1) arranged on the outer wall of the central pipe (2) and the flow-limiting plate (10) are provided with more than one set, and the flow-limiting plate (10) is welded in the limiting plate installation groove (2-1).

3. An underground oil-casing annulus flow-limiting device according to claim 2. Its characteristics are The main channel groove (10-1) is a straight groove directly leading to both ends of the plate body of the flow-limiting plate (10); the auxiliary channel grooves (10-2) are arranged on both sides of the main channel groove (10-1), and the flow channel shape is arc-shaped and inclined downward. The auxiliary channel grooves (10-2) arranged on both sides are staggeredly connected end to end in the main channel groove (10-1).

4. An underground oil-casing annulus flow-limiting device according to claim 1. Its characteristics are Both the locking ring (4) and the locking ring (8) are broken rings with axial cuts. The cuts arranged axially are oblique cuts or vertical cuts, and the oblique angle is set between 1 degree and 89 degrees; the inner diameter of the locking ring 4 in the natural state is smaller than the outer diameter of the pipe section of the central pipe (2) where it is located; the outer circle of the locking ring (8) is processed with a buttress thread and can be in mating connection with the buttress thread processed in the inner circle of the upper thrust cylinder (7).

5. An underground oil-casing annulus flow-limiting device according to claim 1. Its characteristics are The bowl mouth (6-3) of the cup leather (6) is installed downward between the upper thrust cylinder (7) and the sliding cylinder (3) located outside the central pipe (2); the cup leather (6) is also provided with a bowl bottom (6-1) and a bowl body (6-2). The bowl bottom (6-1) is a force-applying step for the upper thrust cylinder (7) to push upward. The bowl body (6-2) is a straight cylinder type. The bowl mouth (6-3) is a flared mouth and the outer diameter is a vertical outer circle. The two outer circle surfaces between the bowl body (6-2) and the bowl mouth (6-3) are conical transition surfaces. The cup leather (6) is made of rubber material.

6. A downhole oil-casing annulus flow-limiting device according to any one of claims 1-5, characterized in that, the upper pushing cylinder (7) is a non-uniform-diameter cylinder, provided with an upper cylinder body (7-2) and anti-backoff threads (7-1) arranged in the lower cylinder body. The inner diameter of the upper cylinder body (7-2) is smaller than that of the lower cylinder body. At least one liquid-assisted sealing and passing groove (7-3) is arranged on the outer wall of the upper cylinder body (7-2), and the liquid-assisted sealing and passing groove (7-3) communicates with the top of the upper cylinder body (7-2); the inner circle of the lower cylinder body of the upper pushing cylinder (7) is provided with anti-backoff threads (7-1), and the anti-backoff threads (7-1) are buttress threads and can be matched with the buttress threads on the outer circle of the locking ring (8).

7. A downhole oil-casing annulus flow-limiting device according to claim 6, characterized in that, a continuous thread (2-7) is machined on the outer circle of the central pipe (2) below the upper pushing cylinder limiting step (2-6), and the continuous thread (2-7) can be threadedly connected with the washing and blowout prevention mechanism.

8. A downhole oil-casing annulus flow-limiting device according to claim 7, characterized in that, the washing and blowout prevention mechanism is provided with an upper outer cylinder (9), a lower outer cylinder (11), a lower pushing cylinder (12), a spring (13) and a limiting cylinder (14). The two ends of the upper outer cylinder (9) are respectively threadedly connected with the continuous thread (2-7) in the central pipe (2) and the lower outer cylinder (11). The lower pushing cylinder (12) and the spring (13) are installed in the lower outer cylinder (11), and the limiting cylinder (14) is installed below the spring (13) and is threadedly connected with the lower outer cylinder (11); at least one liquid-assisted washing and blowout prevention passing groove (14-1) is arranged in the limiting cylinder (14).

9. A downhole oil-casing annulus flow-limiting device according to claim 8, characterized in that, the inner circle of the lower outer cylinder (11) is a non-uniform-diameter inner circle, and the inner threads at both ends are respectively threadedly connected with the upper outer cylinder (9) and the limiting cylinder (14); an inner conical mating surface (11-1) is arranged between the two non-uniform-diameter inner circles of the lower outer cylinder (11), and the inner conical mating surface (11-1) is a lower inclined surface.

10. A downhole oil-casing annulus flow-limiting device according to claim 9, characterized in that, the lower pushing cylinder (12) is a non-uniform-diameter cylinder. The outer wall of the upper part of the lower pushing cylinder (12) is an outer conical mating surface (12-1), and the outer conical mating surface (12-1) is an upper inclined surface and can be mutually matched with the inner conical mating surface (11-1) in the lower outer cylinder (11). At least one sealing ring groove is machined in the outer conical mating surface (12-1); the spring (13) is installed in the inner cavity below the spring limiting step (12-2) in the lower pushing cylinder (12).

11. A downhole oil-casing annulus flow-limiting device according to claim 10, characterized in that, The upper outer circumference of the limiting cylinder (14) is provided with an external thread and can be threadedly connected to the lower outer cylinder (11); the washing-assisting anti-spray overflow groove (14-1) provided in the outer wall of the limiting cylinder (14) is a vertically penetrating groove and at least one such groove is provided; the upper outer cylinder (9) is a non-uniform diameter cylindrical body, and the internal and external threads in the cylindrical bodies at the upper and lower ends can be threadedly connected to the continuous thread (2-7) of the central tube (2) and the lower outer cylinder (11) respectively. After being connected to the central tube (2), the lower inner cavity of the upper outer cylinder (9) communicates with the limiting plate installation groove (2-1).

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