A pipe string device and method for annulus production in oil and gas wells

Abstract

The application discloses a pipe string device and method for annular exploitation of an oil and gas well, which comprises a casing and a tubing, the tubing is located in the casing, and an annular drainage space is arranged between the casing and the tubing; the tubing comprises a plurality of anti-slippage structures which are arranged at intervals and connected through connecting pipes; the anti-slippage structure comprises an anti-slippage structure main body, and a convex part and a flow guide channel are arranged on the surface of the anti-slippage structure main body at intervals in the circumferential direction. The application has the advantages of reducing liquid slippage, and solves the problem that, in the process of exploitation of the existing oil and gas well, liquid slippage is prone to occurring with the decrease of formation energy, liquid cannot be effectively carried out by gas flow, and thus continuously accumulates at the well bottom to form wellbore fluid accumulation, with the increase of the well bottom fluid accumulation, the flow pressure in the well increases, and the formation output decreases, thus forming a vicious cycle.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, specifically to a tubing string device and method for annular extraction of oil and gas wells. Background Technology

[0002] Oil and gas wells are channels used for the exploration, development, and extraction of underground oil and gas resources. They are typically formed by drilling holes in the formation through drilling engineering, running casing, and cementing, and are the core hub connecting underground oil and gas reservoirs with the surface production system. The annulus, on the other hand, is the ring-shaped space between any two tubing strings within the wellbore, or between the tubing string and the well wall. The annulus can serve as a conduit for injecting gas into the well to enhance recovery rates.

[0003] Methods for extracting fluids from deep formations within a production well to the surface include self-flowing production and non-self-flowing production. Self-flowing production includes continuous self-flowing production and intermittent self-flowing production. Self-flowing production is the main production method in the early stages of oil and gas well development when formation energy is sufficient. It relies on gas to lift the fluid in the well to the surface. This method is the most economical and efficient. However, when formation energy decreases or becomes insufficient, that is, when the gas energy in the well is insufficient to maintain self-flowing or intermittent production, it is necessary to rely on external gas sources to supplement self-flowing and intermittent production. This production method is called gas lift production, which is between self-flowing and non-self-flowing methods.

[0004] During continuous flowing production in oil and gas wells, fluid slippage is a common problem as formation energy declines. Fluid slippage occurs because the viscosity of liquids is much greater than that of gases. When the fluid flows upwards in the wellbore, the frictional resistance between the liquid and the pipe wall, as well as the viscous resistance within the liquid, are significantly greater than those of gases. This enormous resistance consumes the kinetic energy of the gas, and the depletion of formation energy further reduces the gas flow velocity, severely restricting the upward velocity of the liquid and further widening the velocity difference between the gas and liquid phases. Existing methods, such as reducing the pipe diameter (i.e., velocity tubing), aim to alleviate fluid slippage by increasing flow velocity. While measures like bubble drainage or adding downhole equipment can also mitigate slippage, they often lead to increased flow resistance, higher costs, and hinder the implementation of subsequent operations such as logging tools and fracturing. Directly utilizing the annulus for oil well production results in low fluid carrying efficiency due to the excessively large cross-sectional area. Therefore, there is an urgent need for a tubing string device and method for reducing fluid slippage in oil and gas well annulus production. Summary of the Invention

[0005] The purpose of this invention is to provide a tubing string device and method for annular extraction in oil and gas wells. It employs a structure with protruding sections and multiple flow channels, which increases local flow velocity while compensating for the reduced channel size and increased resistance caused by velocity tubing. This reduces fluid slippage and solves the problem that existing oil and gas wells, during extraction, are prone to fluid slippage as formation energy decreases. The fluid cannot be effectively carried out by the gas flow, thus accumulating at the bottom of the well, forming wellbore fluid accumulation. As the amount of fluid at the bottom of the well increases, the wellbore pressure increases, and formation production decreases, creating a vicious cycle.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a tubing string device for annular extraction of oil and gas wells, comprising a casing and a tubing, wherein the tubing is located inside the casing and an annular extraction space is provided between the casing and the tubing;

[0007] The oil pipe includes several anti-slip structures, which are spaced apart and connected by connecting pipes;

[0008] The anti-slip structure includes an anti-slip structure body, and the surface of the anti-slip structure body is provided with protrusions and guide channels at intervals along the circumferential direction. The protrusions and guide channels are located in the annular drainage space to guide the fluid.

[0009] As a preferred embodiment of the tubing device for annular well exploitation according to the present invention, the tubing further includes a gas guide joint, which is spaced apart from the anti-slip structure. A connecting pipe connects the gas guide joint and the anti-slip structure. The number of gas guide joints is one or more, and the gas guide joint is connected to the annular drainage space.

[0010] As a preferred embodiment of the tubing device for annular extraction of oil and gas wells according to the present invention, the flow channel is either groove-shaped or perforated, the anti-slip structure body is either tubular or annular, and the inner cavity of the anti-slip structure body has a first channel.

[0011] As a preferred embodiment of the tubing device for annular extraction of oil and gas wells according to the present invention, when the anti-slip structure body is tubular, the surface of the anti-slip structure body is provided with a first threaded portion, the inner wall of the first channel is provided with a second threaded portion, and the first threaded portion and the second threaded portion of the anti-slip structure body are connected to the connecting pipe.

[0012] As a preferred embodiment of the tubing device for annular extraction of oil and gas wells according to the present invention, the protrusion forms an annular expanding nozzle with the inner wall of the casing, and the cross-section of the protrusion is triangular.

[0013] As a preferred embodiment of the tubing device for annular extraction of oil and gas wells according to the present invention, the protrusion is inclined relative to the centerline of the anti-slip structure body. When the protrusion is inclined, the flow guiding channels are distributed on the protrusion and at intervals. The angle α between the flow guiding channels and the centerline of the anti-slip structure body is 0-45 degrees, so as to guide the fluid in a vortex.

[0014] As a preferred embodiment of the tubing device for annular extraction of oil and gas wells according to the present invention, the protrusion is arranged perpendicularly to the centerline of the anti-slip structure body, and when the protrusion is arranged perpendicularly, the flow guiding channels are distributed at intervals of the protrusion.

[0015] As a preferred embodiment of the tubing device for annular well exploitation according to the present invention, the gas guide joint includes a gas guide joint body, a third threaded portion on the surface of the gas guide joint body, a second channel inside the gas guide joint body, a fourth threaded portion on the inner wall of the second channel, the gas guide joint body being connected to a connecting pipe through the third threaded portion and the fourth threaded portion, a gas guide hole on the gas guide joint body, the gas guide hole communicating with the second channel and the annular drainage space cavity, and the angle α between the gas guide hole and the center line of the gas guide joint body being 0-30 degrees.

[0016] As a preferred embodiment of the tubing string device for annular extraction of oil and gas wells according to the present invention, the top of the tubing is connected to a tubing valve, the air inlet end of the tubing valve is connected to an injection pipe, the air outlet end of the tubing valve is connected to the inner cavity of the tubing, the top of the casing is connected to a casing valve, the oil inlet end of the casing valve is connected to the inner cavity of the casing, and the oil outlet end of the casing valve is connected to an oil outlet pipe.

[0017] A method for annular extraction in oil and gas wells includes the following steps:

[0018] S1. The tubing is lowered into the casing to form an annular drainage space for mining between the tubing and the casing. The tubing is connected to several anti-slip structures set at intervals through connecting pipes, or the anti-slip structures and gas guide joints are connected at the same time.

[0019] S2. When conducting self-flowing extraction, close the tubing valve and open the casing valve. The fluid at the bottom of the well rises through the annular drainage space inside the casing. Guided by several anti-slip structures, the fluid is finally extracted through the casing valve and the oil outlet pipe.

[0020] S3. When performing gas lift extraction, open the tubing valve and inject gas into the tubing valve through the gas injection pipe. The gas enters the tubing cavity. Without the gas guide joint installed, the gas returns from the bottom anti-slip structure, driving the fluid to rise through the annular drainage space. When the gas guide joint is installed, the gas guide hole on the gas guide joint will also introduce the gas into the annular drainage space.

[0021] S4. When the fluid flows through the annular drainage space, the protrusions on the surface of the anti-slip structure form an annular expanding and contracting nozzle with the inner wall of the casing. This nozzle, in conjunction with the flow guiding channel, guides the fluid through a vortex or throttles and reduces pressure, thereby preventing fluid slippage and improving the fluid flow state.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. The anti-slip structure of the present invention has an outwardly protruding triangular cross-section protrusion on its main surface, which significantly increases the effective outer diameter of the structure, thereby reducing the annular gap between it and the inner wall of the sleeve. When the fluid passes through this narrowed area, the flow area is reduced and the flow velocity is correspondingly increased, reducing the tendency of the liquid to slide downward due to gravity.

[0024] 2. The protrusion of the present invention and the inner wall of the sleeve together form an annular expansion and contraction nozzle. The fluid undergoes a process of first contraction and then expansion, and a supersonic flow can be formed at the outlet end. The high-speed airflow generates a strong shearing effect on the liquid phase, breaking it into fine droplets and forming a highly atomized mixed flow state, which greatly weakens the stability of the liquid film and avoids liquid accumulation and fallback.

[0025] 3. The protruding part of the present invention has multiple flow guiding channels distributed in it, which divide the original continuous annular large cross-section channel into several independent small cross-section channels. This not only ensures the overall fluid throughput capacity, but also maintains high flow velocity due to the reduction of local cross-section, thus achieving a flow state with large flow rate, high flow velocity and little slippage. Attached Figure Description

[0026] Figure 1 This is a structural schematic diagram of Embodiment 1 of the present invention. Figure 1 ;

[0027] Figure 2 This is a structural schematic diagram of Embodiment 1 of the present invention. Figure 2 ;

[0028] Figure 3 This is a schematic diagram of the structure of Embodiment 2 of the present invention. Figure 1 ;

[0029] Figure 4 This is a schematic diagram of the structure of Embodiment 2 of the present invention. Figure 2 ;

[0030] Figure 5 This is a schematic diagram of the first embodiment of the anti-slip structure of the present invention;

[0031] Figure 6 This is a cross-sectional view of the first embodiment of the anti-slip structure of the present invention;

[0032] Figure 7 This is a schematic diagram of the air guide connector of the present invention;

[0033] Figure 8This is a cross-sectional view of the air guide connector of the present invention;

[0034] Figure 9 This is a schematic diagram of the second anti-slip structure of the present invention;

[0035] Figure 10 This is a cross-sectional view of the second embodiment of the anti-slip structure of the present invention;

[0036] Figure 11 This is a flowchart of the method of the present invention.

[0037] In the diagram: 1. Casing; 2. Tubing; 3. Annular drainage space; 4. Anti-slip structure; 5. Connecting pipe; 6. Gas guide joint; 7. Tubing valve; 8. Gas injection pipe; 9. Casing valve; 10. Oil outlet pipe; 401. Main body of anti-slip structure; 402. Protrusion; 403. Guide channel; 404. First threaded part; 405. Second threaded part; 406. First channel; 601. Main body of gas guide joint; 602. Third threaded part; 603. Fourth threaded part; 604. Gas guide hole; 605. Second channel. Detailed Implementation

[0038] Example 1

[0039] Please see Figure 1-2 and Figures 5-8 A tubing string device for annular extraction of oil and gas wells includes a casing 1 and a tubing 2, with the tubing 2 located inside the casing 1 and an annular extraction space 3 provided between the casing 1 and the tubing 2.

[0040] Furthermore, the oil pipe 2 includes several anti-slip structures 4, which are spaced apart and connected by connecting pipes 5.

[0041] Furthermore, the anti-slip structure 4 includes an anti-slip structure body 401. The surface of the anti-slip structure body 401 is provided with protrusions 402 and flow guiding channels 403 at intervals along the circumferential direction. The protrusions 402 and flow guiding channels 403 are located in the annular drainage space 3 to guide the fluid.

[0042] Furthermore, the oil pipe 2 also includes a gas guide joint 6, which is spaced apart from the anti-slip structure 4. The connecting pipe 5 connects the gas guide joint 6 and the anti-slip structure 4. There is one or more gas guide joints 6, and the gas guide joint 6 is connected to the annular drainage space 3.

[0043] Furthermore, the flow channel 403 is either groove-shaped or hole-shaped, the anti-slip structure body 401 is tubular, and the inner cavity of the anti-slip structure body 401 has a first channel 406.

[0044] Furthermore, when the anti-slip structure body 401 is tubular, the surface of the anti-slip structure body 401 is provided with a first threaded portion 404, and the inner wall of the first channel 406 is provided with a second threaded portion 405. The first threaded portion 404 and the second threaded portion 405 of the anti-slip structure body 401 are connected to the connecting pipe 5.

[0045] Furthermore, the protrusion 4 and the inner wall of the sleeve 1 form an annular expanding nozzle, and the cross-section of the protrusion 402 is triangular.

[0046] Furthermore, the protrusion 402 is inclined relative to the center line of the anti-slip structure body 401. When the protrusion 402 is inclined, the flow guiding channel 403 is distributed on the protrusion 402 and at intervals. The angle α between the flow guiding channel 403 and the center line of the anti-slip structure body 401 is 0-45 degrees, so as to guide the fluid in a vortex.

[0047] Furthermore, the flow channel 403 with a deflection angle of 0-45 degrees a causes the fluid to form a vortex when passing through the anti-slip structure body 401, which intensifies fluid atomization and upward liquid carrying.

[0048] Furthermore, the air guide connector 6 includes an air guide connector body 601. The surface of the air guide connector body 601 is provided with a third threaded portion 602. The interior of the air guide connector body 601 is provided with a second channel 605. The inner wall of the second channel 605 is provided with a fourth threaded portion 603. The air guide connector body 601 is connected to the connecting pipe 5 through the third threaded portion 602 and the fourth threaded portion 603. An air guide hole 604 is provided on the air guide connector body 601. The air guide hole 604 communicates with the second channel 605 and the inner cavity of the annular discharge space 3. The angle α between the air guide hole 604 and the center line of the air guide connector body 601 is 0-30 degrees. The angle α of 0-30 degrees allows the air guide hole 604 to exhaust downwards.

[0049] Furthermore, the top of the oil pipe 2 is connected to an oil pipe valve 7, the air inlet of the oil pipe valve 7 is connected to an air injection pipe 8, the air outlet of the oil pipe valve 7 is connected to the inner cavity of the oil pipe 2, the top of the casing 1 is connected to a casing valve 9, the oil inlet of the casing valve 9 is connected to the inner cavity of the casing 1, and the oil outlet of the casing valve 9 is connected to an oil outlet pipe 10.

[0050] Furthermore, the protrusion 402 protrudes outward from the center line of the anti-slip structure body 401, increasing the effective outer diameter of the anti-slip structure body 401. The anti-slip structure 4 reduces the gap between the anti-slip structure body 401 and the inner wall of the sleeve 1, increasing the velocity of the fluid when passing through the gap, thereby reducing the slippage of the liquid.

[0051] Furthermore, an annular expanding nozzle is formed between the protrusion 402 and the inner wall of the sleeve 1. When the fluid passes through the annular expanding nozzle, a supersonic flow is formed, which atomizes the fluid and thus avoids liquid accumulation and slippage.

[0052] Furthermore, the main body 401 of the anti-slip structure is also provided with several flow channels 403. The flow channels 403 increase the fluid throughput at the protrusion 402, thus solving the contradiction between the fluid throughput and the narrow channel.

[0053] Furthermore, the flow channel 403 is either a direct flow channel or a scaling flow channel. When it is a scaling flow channel, the fluid forms a supersonic flow at the outlet end, which increases the fluid atomization effect.

[0054] Furthermore, multiple guide channels 403 divide the large annular cross-section channel at the protrusion 402 into multiple small cross-section channels. These multiple small cross-section channels not only ensure a high flow rate and fluid throughput, but also reduce fluid resistance and fully atomize the fluid to prevent liquid slippage, thus achieving the effect of high flow rate, high flow velocity, and less slippage.

[0055] In the annular extraction operation of oil and gas wells, the tubing 2 is placed in the center of the inner cavity of the casing 1 to form an annular drainage space 3. The tubing 2 comes in two forms: one is to connect several anti-slip structures 4 at intervals through connecting pipe 5, and the other is to connect several anti-slip structures 4 and gas guide joints 6 at intervals through connecting pipe 5.

[0056] When conducting self-flowing extraction, the tubing valve 7 is closed and the casing valve 9 is opened. The fluid at the bottom of the well flows upward through the annular drainage space 3 inside the casing 1. The fluid is guided by several anti-slip structures 4 and finally extracted through the casing valve 9 and the oil outlet pipe 10.

[0057] When gas lift extraction is performed, the tubing valve 7 is opened and gas is injected into the tubing valve 7 through the gas injection pipe 8. The gas enters the inner cavity of the tubing 2. When the gas guide joint 6 is not installed, the gas returns from the bottom anti-slip structure 4 into the annular drainage space 3, driving the fluid to rise through the annular drainage space 3. When the gas guide joint 6 is installed, the gas guide hole 604 on the gas guide joint 6 also introduces gas into the annular drainage space 3 for auxiliary lifting.

[0058] When the compressed air from the gas lift extraction flows inside the oil pipe 2, it flows through the first channel 406, the inside of the connecting pipe 5, and the second channel 605.

[0059] When compressed air drives the fluid to rise inside the annular drainage space 3, the protrusion 402 and the inner wall of the casing 1 form an annular expanding and contracting nozzle, which promotes fluid atomization and prevents liquid accumulation and slippage. During this process, the guide channels 403 distributed on the protrusion 402 and at intervals divide the annular large cross-section channel into multiple small cross-section channels, which not only ensures the fluid throughput, but also achieves high flow rate, high flow velocity and full atomization. In particular, when the guide channel 403 forms an angle α of 0-45 degrees with the centerline, it can guide the fluid in a vortex, further amplifying the fluid atomization and liquid carrying upward. Finally, the oil and gas mixture carrying the fluid is discharged to the ground through the casing valve 9 and the oil outlet pipe 10, thus completing the efficient and anti-slip annular mining process.

[0060] Example 2

[0061] Please see Figures 3-4 and Figures 7-10 A tubing string device for annular extraction of oil and gas wells includes a casing 1 and a tubing 2, with the tubing 2 located inside the casing 1 and an annular extraction space 3 provided between the casing 1 and the tubing 2.

[0062] Furthermore, the oil pipe 2 includes several anti-slip structures 4, which are spaced apart and connected by connecting pipes 5.

[0063] Furthermore, the anti-slip structure 4 includes an anti-slip structure body 401. The surface of the anti-slip structure body 401 is provided with protrusions 402 and flow guiding channels 403 at intervals along the circumferential direction. The protrusions 402 and flow guiding channels 403 are located in the annular drainage space 3 to guide the fluid.

[0064] Furthermore, the oil pipe 2 also includes a gas guide joint 6, which is spaced apart from the anti-slip structure 4. The connecting pipe 5 connects the gas guide joint 6 and the anti-slip structure 4. There is one or more gas guide joints 6, and the gas guide joint 6 is connected to the annular drainage space 3.

[0065] Furthermore, the flow channel 403 is either groove-shaped or hole-shaped, the anti-slip structure body 401 is annular, and the inner cavity of the anti-slip structure body 401 is provided with a first channel 406, through which the anti-slip structure body 401 is connected to the connecting pipe 5.

[0066] Furthermore, the protrusion 4 and the inner wall of the sleeve 1 form an annular expanding nozzle, and the cross-section of the protrusion 402 is triangular.

[0067] Furthermore, the protrusion 402 is arranged perpendicularly to the center line of the anti-slip structure body 401. When the protrusion 402 is arranged perpendicularly, the guide channel 403 is distributed at the intervals of the protrusion 402.

[0068] Furthermore, the air guide connector 6 includes an air guide connector body 601. The surface of the air guide connector body 601 is provided with a third threaded portion 602. The interior of the air guide connector body 601 is provided with a second channel 605. The inner wall of the second channel 605 is provided with a fourth threaded portion 603. The air guide connector body 601 is connected to the connecting pipe 5 through the third threaded portion 602 and the fourth threaded portion 603. An air guide hole 604 is provided on the air guide connector body 601. The air guide hole 604 communicates with the second channel 605 and the inner cavity of the annular discharge space 3. The angle α between the air guide hole 604 and the center line of the air guide connector body 601 is 0-30 degrees. The angle α of 0-30 degrees allows the air guide hole 604 to exhaust downwards.

[0069] Furthermore, the top of the oil pipe 2 is connected to an oil pipe valve 7, the air inlet of the oil pipe valve 7 is connected to an air injection pipe 8, the air outlet of the oil pipe valve 7 is connected to the inner cavity of the oil pipe 2, the top of the casing 1 is connected to a casing valve 9, the oil inlet of the casing valve 9 is connected to the inner cavity of the casing 1, and the oil outlet of the casing valve 9 is connected to an oil outlet pipe 10.

[0070] Furthermore, the protrusion 402 protrudes outward from the center line of the anti-slip structure body 401, increasing the effective outer diameter of the anti-slip structure body 401. The anti-slip structure 4 reduces the gap between the anti-slip structure body 401 and the inner wall of the sleeve 1, increasing the velocity of the fluid when passing through the gap, thereby reducing the slippage of the liquid.

[0071] Furthermore, an annular expanding nozzle is formed between the protrusion 402 and the inner wall of the sleeve 1. When the fluid passes through the annular expanding nozzle, a supersonic flow is formed, which atomizes the fluid and thus avoids liquid accumulation and slippage.

[0072] Furthermore, the main body 401 of the anti-slip structure is also provided with several flow channels 403. The flow channels 403 increase the fluid throughput at the protrusion 402, thus solving the contradiction between the fluid throughput and the narrow channel.

[0073] Furthermore, the flow channel 403 is either a direct flow channel or a scaling flow channel. When it is a scaling flow channel, the fluid forms a supersonic flow at the outlet end, which increases the fluid atomization effect.

[0074] Furthermore, multiple guide channels 403 divide the large annular cross-section channel at the protrusion 402 into multiple small cross-section channels. These multiple small cross-section channels not only ensure a high flow rate and fluid throughput, but also reduce fluid resistance and fully atomize the fluid to prevent liquid slippage, thus achieving the effect of high flow rate, high flow velocity, and less slippage.

[0075] In the annular extraction operation of oil and gas wells, the tubing 2 is placed in the center of the inner cavity of the casing 1 to form an annular drainage space 3. The tubing 2 comes in two forms: one is to connect several anti-slip structures 4 at intervals through connecting pipe 5, and the other is to connect several anti-slip structures 4 and gas guide joints 6 at intervals through connecting pipe 5.

[0076] When conducting self-flowing extraction, the tubing valve 7 is closed and the casing valve 9 is opened. The fluid at the bottom of the well flows upward through the annular drainage space 3 inside the casing 1. The fluid is guided by several anti-slip structures 4 and finally extracted through the casing valve 9 and the oil outlet pipe 10.

[0077] When gas lift extraction is performed, the tubing valve 7 is opened and gas is injected into the tubing valve 7 through the gas injection pipe 8. The gas enters the inner cavity of the tubing 2. When the gas guide joint 6 is not installed, the gas returns from the bottom anti-slip structure 4 into the annular drainage space 3, driving the fluid to rise through the annular drainage space 3. When the gas guide joint 6 is installed, the gas guide hole 604 on the gas guide joint 6 also introduces gas into the annular drainage space 3 for auxiliary lifting.

[0078] When the compressed air from the gas lift extraction flows inside the oil pipe 2, it flows through the first channel 406, the inside of the connecting pipe 5, and the second channel 605.

[0079] When compressed air drives the fluid to rise inside the annular drainage space 3, the protrusion 402 and the inner wall of the casing 1 form an annular expanding and contracting nozzle, which promotes fluid atomization and prevents liquid accumulation and slippage. During this process, the guide channels 403 distributed at the intervals of the protrusion 402 divide the annular large cross-section channel into multiple small cross-section channels, which not only ensures the fluid throughput, but also achieves high flow rate, high flow velocity and full atomization. Finally, the oil and gas mixture carrying the fluid is discharged to the ground through the casing valve 9 and the oil outlet pipe 10, thus completing the efficient and anti-slip annular mining process.

[0080] Example 3

[0081] Please see Figures 1-11 A method for annular extraction in oil and gas wells, comprising the following steps:

[0082] S1. The tubing 2 is lowered into the casing 1, so that the tubing 2 and the casing 1 form an annular drainage space 3 for mining. The tubing 2 is connected to several anti-slip structures 4 at intervals through the connecting pipe 5, or the anti-slip structure 4 and the gas guide joint 6 are connected at the same time.

[0083] S2. When conducting self-flowing extraction, close the tubing valve 7 and open the casing valve 9. The fluid at the bottom of the well rises through the annular drainage space 3 inside the casing 1. The fluid is guided by several anti-slip structures 4 and finally extracted through the casing valve 9 and the oil outlet pipe 10.

[0084] S3. When gas lift extraction is carried out, the oil pipe valve 7 is opened and gas is injected into the oil pipe valve 7 through the gas injection pipe 8. The gas enters the inner cavity of the oil pipe 2. When the gas guide joint 6 is not installed, the gas returns from the bottom anti-slip structure 4, driving the fluid to rise through the annular drainage space 3. When the gas guide joint 6 is installed, the gas guide hole 604 on the gas guide joint 6 will also introduce the gas into the annular drainage space 3.

[0085] S4. When the fluid flows through the annular drainage space 3, the protrusion 402 on the surface of the anti-slip structure 4 forms an annular expansion nozzle with the inner wall of the casing 1. Together with the flow guiding channel 403, the fluid is vortex-guided or throttled and depressurized, thereby preventing fluid slippage and improving the fluid flow state.

[0086] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A tubing string assembly for annular extraction in oil and gas wells, comprising casing (1) and tubing (2), characterized in that: The tubing (2) is located inside the casing (1), and an annular drainage space (3) is provided between the casing (1) and the tubing (2). The oil pipe (2) includes several anti-slip structures (4), which are spaced apart and connected by a connecting pipe (5); The anti-slip structure (4) includes an anti-slip structure body (401). The surface of the anti-slip structure body (401) is provided with protrusions (402) and flow guiding channels (403) at intervals along the circumferential direction. The protrusions (402) and flow guiding channels (403) are located in the annular drainage space (3) to guide the fluid.

2. The tubing string device for annular extraction of oil and gas wells according to claim 1, characterized in that: The oil pipe (2) also includes a gas guide joint (6), which is spaced apart from the anti-slip structure (4). A connecting pipe (5) connects the gas guide joint (6) and the anti-slip structure (4). The number of gas guide joints (6) is one or more, and the gas guide joint (6) is connected to the annular drainage space (3).

3. A tubing string device for annular extraction of oil and gas wells according to claim 1, characterized in that: The flow channel (403) is either groove-shaped or hole-shaped, the anti-slip structure body (401) is either tubular or annular, and the inner cavity of the anti-slip structure body (401) is provided with a first channel (406).

4. A tubing string device for annular extraction of oil and gas wells according to claim 3, characterized in that: When the anti-slip structure body (401) is tubular, the surface of the anti-slip structure body (401) is provided with a first threaded part (404), and the inner wall of the first channel (406) is provided with a second threaded part (405). The first threaded part (404) and the second threaded part (405) of the anti-slip structure body (401) are connected to the connecting pipe (5).

5. A tubing string device for annular extraction of oil and gas wells according to claim 1, characterized in that: The protrusion (4) forms an annular zoom nozzle with the inner wall of the sleeve (1), and the cross-section of the protrusion (402) is triangular or trapezoidal.

6. A tubing string device for annular extraction of oil and gas wells according to claim 1, characterized in that: The protrusion (402) is inclined relative to the center line of the anti-slip structure body (401). When the protrusion (402) is inclined, the flow guiding channel (403) is distributed on the protrusion (402) and at intervals. The angle α between the flow guiding channel (403) and the center line of the anti-slip structure body (401) is 0-45 degrees, so as to guide the fluid in a vortex.

7. A tubing string device for annular extraction of oil and gas wells according to claim 1, characterized in that: The protrusion (402) is arranged perpendicularly to the center line of the anti-slip structure body (401). When the protrusion (402) is arranged perpendicularly, the flow channel (403) is distributed at the interval of the protrusion (402).

8. A tubing string device for annular extraction of oil and gas wells according to claim 2, characterized in that: The air guide connector (6) includes an air guide connector body (601), a third threaded part (602) on the surface of the air guide connector body (601), a second channel (605) inside the air guide connector body (601), a fourth threaded part (603) on the inner wall of the second channel (605), the air guide connector body (601) is connected to the connecting pipe (5) through the third threaded part (602) and the fourth threaded part (603), an air guide hole (604) is opened on the air guide connector body (601), the air guide hole (604) is connected to the second channel (605) and the inner cavity of the annular drainage space (3), and the angle α between the air guide hole (604) and the center line of the air guide connector body (601) is 0-30 degrees.

9. A tubing string device for annular extraction of oil and gas wells according to claim 1, characterized in that: The top of the oil pipe (2) is connected to an oil pipe valve (7), the air inlet of the oil pipe valve (7) is connected to an air injection pipe (8), the air outlet of the oil pipe valve (7) is connected to the inner cavity of the oil pipe (2), the top of the casing (1) is connected to a casing valve (9), the oil inlet of the casing valve (9) is connected to the inner cavity of the casing (1), and the oil outlet of the casing valve (9) is connected to an oil outlet pipe (10).

10. A method for annular extraction in oil and gas wells, characterized in that, Includes the following steps: S1. The tubing (2) is lowered into the casing (1) to form an annular drainage space (3) for mining between the tubing (2) and the casing (1). The tubing (2) is connected to several anti-slip structures (4) set at intervals through the connecting pipe (5), or the anti-slip structure (4) and the gas guide joint (6) are connected at the same time. S2. When conducting self-flowing extraction, close the tubing valve (7) and open the casing valve (9). The fluid at the bottom of the well rises through the annular drainage space (3) inside the casing (1). The fluid is guided by several anti-slip structures (4) and finally extracted through the casing valve (9) and the oil outlet pipe (10). S3. When gas lift extraction is carried out, the tubing valve (7) is opened and gas is injected into the tubing valve (7) through the gas injection pipe (8). The gas enters the inner cavity of the tubing (2). When the gas guide joint (6) is not installed, the gas returns from the bottom anti-slip structure (4) and drives the fluid to rise through the annular drainage space (3). When the gas guide joint (6) is installed, the gas guide hole (604) on the gas guide joint (6) will also introduce the gas into the annular drainage space (3). S4. When the fluid flows through the annular drainage space (3), the protrusion (402) on the surface of the anti-slip structure (4) forms an annular expansion nozzle with the inner wall of the casing (1), which, together with the flow guiding channel (403), guides the fluid in a vortex or throttles and reduces pressure, thereby preventing the fluid from slipping and improving the fluid flow state.

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