Downhole throttling device for gas well full life cycle gas production and control method

Abstract

The invention relates to the technical field of oil and gas field oil and gas production, and discloses an underground throttling device for gas well full-life-cycle gas production and a control method. The underground throttling device comprises a temperature difference power generation mechanism used for power generation, a cathode protection mechanism and a throttling mechanism used for throttling fluid entering the temperature difference power generation mechanism, and the throttling mechanism comprises at least one throttling unit and an anode mechanism arranged corresponding to the throttling unit. The negative electrode of the thermoelectric power generation mechanism is connected with the throttling unit through the anode mechanism, and the positive electrode of the thermoelectric power generation mechanism is connected with the cathode protection mechanism. The anode mechanism can be corroded and fused when the current I passing through the anode mechanism is smaller than the protection current I0 of the anode mechanism. The underground throttling device has the function of enabling the throttling mechanism to fall off and form a large channel, normal production of a gas well is not affected, and salvage and replacement of the underground throttling device can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field oil and gas production, and specifically, to a downhole throttling device and a control method for gas production throughout the life cycle of a gas well. Background Art

[0002] The downhole throttling gas production technology is one of the core technologies for low-cost development of gas fields. It can effectively prevent the generation of hydrates, avoid surface heating and high-pressure gathering and transportation of the gas production pipeline network. The throttler is the key tool for downhole throttling and pressure reduction gas production. Currently, there are many types: retrievable with slips, retrievable with preset, fixed short joint type, retrievable with electric setting, remotely adjustable electric nozzle type. Generally, when throttling gas production is not required in the later stage of gas well production or when the throttler fails, in order to avoid affecting normal gas production, fishing is required. At present, the overall success rate of wireline operation fishing is only 60-70%. If the fishing fails or cannot be carried out, the production string needs to be pulled out to handle the throttler, which is costly. In addition, the existing non-fishing throttlers cannot accurately control the unsealing duration, often resulting in the early loss of the throttling function and the need to re-inject a new throttler, which is difficult to meet the needs of gas production throughout the life cycle of the gas well. Moreover, the fishing of the throttler is complex, and the fishing is prone to failure, resulting in a long processing cycle, which will cause a production loss of hundreds of millions of cubic meters of natural gas, and easily cause the gas well to be flooded and reduce the life of the gas well.

[0003] Therefore, there is an urgent need to provide a downhole throttling device that can meet the gas production requirements throughout the life cycle of a gas well and avoid the problem of fishing and replacement of the throttler. Summary of the Invention

[0004] The object of the present invention is to provide a downhole throttling device and a control method for gas production throughout the life cycle of a gas well. The downhole throttling device has the function of enabling the throttling mechanism to fall off and form a large channel, without affecting the normal production of the gas well and being able to avoid the fishing and replacement of the downhole throttling device.

[0005] To achieve the above object, in a first aspect of the present invention, there is provided a downhole throttling device for gas production throughout the life cycle of a gas well. The downhole throttling device includes a thermoelectric power generation mechanism for generating electricity, a cathodic protection mechanism, and a throttling mechanism for throttling the fluid entering the thermoelectric power generation mechanism. The throttling mechanism includes at least one throttling unit and an anode mechanism corresponding to the throttling unit. The negative electrode of the thermoelectric power generation mechanism is connected to the throttling unit through the anode mechanism, and the positive electrode is connected to the cathodic protection mechanism; the anode mechanism can be corroded and melted when the current I passing through the anode mechanism is less than the protection current I0 of the anode mechanism.

[0006] Preferably, the throttling unit includes a convex throttling seat with a hollow interior. The convex throttling seat is connected to the thermoelectric power generation mechanism through the anode mechanism, and a gas nozzle is arranged in the inner cavity of the convex throttling seat.

[0007] Preferably, the outer diameter of the air nozzle is greater than the inner diameter of the outlet of the convex throttle seat.

[0008] Preferably, a hollow fastening stud is further provided in the inner cavity of the convex throttle seat, and the fluid is adapted to enter the air nozzle from the hollow fastening stud.

[0009] More preferably, the inner diameter of the hollow fastening stud is greater than the inner diameter of the air nozzle.

[0010] Preferably, the throttle unit further includes a sealing structure, and the sealing structure includes a sealing ring disposed between the convex throttle seat and the thermoelectric power generation mechanism and a gasket disposed between the air nozzle and the convex throttle seat.

[0011] Preferably, the throttle unit further includes a prestressing mechanism disposed on the shoulder of the convex throttle seat.

[0012] More preferably, the number of the throttle units is multiple, and the multiple throttle units are connected in series. Along the flow direction of the fluid, the inner diameter of the air nozzle at the front end is smaller than the inner diameter of the air nozzle at the rear end.

[0013] Even more preferably, when the materials of the anode mechanisms are the same, along the flow direction of the fluid, the volume of the anode mechanism at the front end is smaller than the volume of the anode mechanism at the rear end; or, when the volumes of the anode mechanisms are the same, along the flow direction of the fluid, the standard electrode potential of the anode mechanism at the front end is smaller than the standard electrode potential of the anode mechanism at the rear end; or, a control circuit is provided on the thermoelectric power generation mechanism, and the control circuit can adjust the magnitude of the current I passing through the anode mechanism.

[0014] Specifically, a rechargeable battery is further provided in the thermoelectric power generation mechanism.

[0015] Preferably, an anode material layer is provided outside the anode mechanism, and the standard electrode potential of the anode material layer is greater than the standard electrode potential of the anode mechanism.

[0016] Preferably, the thermoelectric power generation mechanism includes a heat conduction layer and a thermoelectric power generation layer disposed outside the heat conduction layer, and the thermoelectric power generation layer contains a semiconductor material.

[0017] More preferably, the thermoelectric power generation mechanism further includes a protective layer disposed outside the thermoelectric power generation layer.

[0018] Preferably, a sand prevention mechanism is provided in the fluid inflow direction of the throttle mechanism.

[0019] Preferably, the cathodic protection mechanism is a shaped part made of high silicon cast iron material.

[0020] Preferably, the downhole throttling device further includes a rubber barrel sealing mechanism, a slip anchoring mechanism, and a fishing head that are sequentially connected to the thermoelectric power generation mechanism, and the rubber barrel sealing mechanism, the slip anchoring mechanism, the fishing head, and the thermoelectric power generation mechanism are in communication.

[0021] Preferably, the slip anchoring mechanism includes slips, an upper slip seat, and a lower slip seat, and one end of the slips is connected to the upper slip seat and the other end is connected to the lower slip seat.

[0022] The second aspect of the present invention provides a control method for a downhole throttling device for gas production throughout the life cycle of a gas well. The control method for the downhole throttling device includes the following steps:

[0023] The fluid in the gas well enters the thermoelectric power generation mechanism through the throttling mechanism to cause the thermoelectric power generation mechanism to generate electricity. When the current I passing through the anode mechanism is greater than or equal to the protection current I0 of the anode mechanism, the anode mechanism is not corroded, and the fluid continues to enter the thermoelectric power generation mechanism through the throttling mechanism; when the current I passing through the anode mechanism is less than the protection current I0 of the anode mechanism, the anode mechanism corrodes and fuses, and finally the fluid directly enters the thermoelectric power generation mechanism.

[0024] Further preferably, the throttling mechanism includes a plurality of throttling units and the anode mechanism corresponding to each throttling unit, and the plurality of throttling units are connected in series; wherein,

[0025] When the materials of the anode mechanisms are the same, along the flow direction of the fluid, the volume of the anode mechanism at the front end is larger than the volume of the anode mechanism at the rear end;

[0026] Or, when the volumes of the anode mechanisms are the same, along the flow direction of the fluid, the standard electrode potential of the anode mechanism at the front end is less than the standard electrode potential of the anode mechanism at the rear end;

[0027] Or, a control circuit is provided on the thermoelectric power generation mechanism, and the control circuit can adjust the magnitude of the current I passing through the anode mechanism;

[0028] The fluid enters the thermoelectric power generation mechanism through a plurality of the throttling units to enable the thermoelectric power generation mechanism to generate electricity. When the current I passing through the first anode mechanism is greater than or equal to the protection current I0 of the anode mechanism, the anode mechanism is not corroded, and the fluid continues to enter the thermoelectric power generation mechanism through a plurality of the throttling units; when the current I of the first anode mechanism is less than the protection current I0 of the anode mechanism, the anode mechanism is corroded and fused, and the fluid enters the thermoelectric power generation mechanism through the remaining throttling units; when the current I passing through the second anode mechanism is less than the protection current I0 of the anode mechanism, the anode mechanism is corroded and fused until all the anode mechanisms are corroded and fused.

[0029] Optionally, when it is required that the downhole throttling device loses its throttling function in advance or the throttling mechanism is scaled and blocked and cannot work properly, after pumping a chemical agent into the downhole throttling device, the gas well is closed, and after the chemical agent reacts and dissolves with the anode mechanism or the scale, the gas well is opened for blowout and then production is carried out.

[0030] Through the above technical solutions, the beneficial effects of the present invention are as follows:

[0031] The downhole throttling device provided by the present invention includes a thermoelectric power generation mechanism, a cathodic protection mechanism and a throttling mechanism. The thermoelectric power generation mechanism generates electric energy through the temperature difference between the throttling mechanism and the gas well. Through the synergistic effect of the thermoelectric power generation mechanism and the cathodic protection mechanism, the negative potential of the anode mechanism is increased to protect the anode mechanism from corrosion; moreover, as the production capacity of the gas well decreases, the temperature difference between the throttling mechanism and the gas well decreases or disappears. When the electric energy provided by the thermoelectric power generation mechanism is not enough to protect the anode mechanism, the anode mechanism is corroded and fused, and then the throttling unit drops, thereby opening a larger production channel for the next production, avoiding the fishing and replacement of the downhole throttling device, and being able to realize automatic control without manual intervention, meeting the gas production in the whole life cycle of the gas well. The structure of the downhole throttling device is simple, the installation method is flexible, no manual intervention is required, and the cost is low.

[0032] In a preferred embodiment, the downhole throttling device provided by the present invention is provided with a plurality of throttling units connected in series, and along the flow direction of the fluid, the inner diameter of the nozzle that first contacts the fluid at the front end is smaller than the inner diameter of the nozzle at the rear end. As the production capacity of the gas well decreases, the nozzle with a smaller inner diameter falls off first, and the nozzle with a larger inner diameter falls off later, which can meet the needs of gas production in the whole life cycle of the gas well, not only avoiding the fishing and replacement of the throttling device, but also avoiding the well workover method of pulling out the pipe string, and realizing that one downhole throttling device can meet the lifelong application of the gas well without affecting the subsequent plunger gas lift drainage gas production of the gas well.

[0033] Other advantages of the present invention and the technical effects of the preferred embodiments will be further described in the following specific embodiments. Brief Description of the Drawings

[0034] The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0035] Figure 1 is a schematic structural diagram of a specific embodiment of the downhole throttling device in the present invention;

[0036] Figure 2 is in the present invention Figure 1 a sectional view of the downhole throttling device shown;

[0037] Figure 3 is a schematic structural diagram of a second specific embodiment of the downhole throttling device in the present invention;

[0038] Figure 4 is a schematic structural diagram of a third specific embodiment of the downhole throttling device in the present invention.

[0039] Figure 5 is a schematic structural diagram of a specific embodiment of the anode mechanism of the downhole throttling device in the present invention.

[0040] Description of the Reference Numerals

[0041] 1 - Thermoelectric power generation mechanism, 2 - Cathodic protection mechanism, 3 - Throttling unit, 31 - Convex throttling seat, 32 - Nozzle, 33 - Hollow fastening stud, 34 - Sealing ring, 35 - Sealing gasket, 36 - Prestress mechanism, 4 - Anode mechanism, 5 - Sand control mechanism, 6 - Rubber barrel sealing mechanism, 7 - Slip anchoring mechanism, 71 - Slip, 72 - Upper slip seat, 73 - Lower slip seat, 8 - Fishing head, 9 - Spacer ring, A - Production channel, B - Input channel. Detailed Description of the Specific Embodiments

[0042] The following is a detailed description of the specific embodiments of the present invention in conjunction with the drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0043] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "connected" and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, it can be an abutting connection, or the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] It should be understood that the orientation or positional relationship indicated by terms such as "upper", "lower", "front", "rear", "inner", "outer", etc. is based on the direction 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. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features.

[0045] In a basic embodiment of the present invention, referring to Figure 1 , a downhole throttling device for gas production throughout the life cycle of a gas well includes a thermoelectric power generation mechanism 1 for power generation, a cathodic protection mechanism 2, and a throttling mechanism for throttling the fluid entering the thermoelectric power generation mechanism 1. The throttling mechanism includes at least one throttling unit 3 and an anode mechanism 4 corresponding to the throttling unit 3. The negative electrode of the thermoelectric power generation mechanism 1 is connected to the throttling unit 3 through the anode mechanism 4, and the positive electrode is connected to the cathodic protection mechanism 2; the anode mechanism 4 can be corroded and melted when the current I passing through the anode mechanism 4 is less than the protection current I0 of the anode mechanism 4.

[0046] In the present invention, the downhole throttling device can be applied to the oil and gas production of various gas wells, such as vertical wells, directional wells, and horizontal wells; a throttling channel for the fluid to pass through is formed in the throttling mechanism. The inlet of the throttling mechanism is communicated with the input channel B, and the outlet is communicated with the production channel A. The inner diameter of the throttling channel is smaller than the inner diameter of the production channel A and also smaller than the inner diameter of the input channel B; the thermoelectric power generation mechanism 1 is of a hollow structure and the inner cavity forms a part of the production channel A; the throttling mechanism can include one throttling unit 3 or multiple throttling units 3, and each throttling unit 3 is respectively connected to the inner wall of the thermoelectric power generation mechanism 1 through the corresponding anode mechanism 4. The cathodic protection mechanism 2 is of a hollow structure, and the specific position of the cathodic protection mechanism 2 is not limited. The inner cavity of the cathodic protection mechanism 2 can be a part of the input channel B (i.e., the cathodic protection mechanism 2 is located below the throttling mechanism), or can be a part of the production channel A (i.e., the cathodic protection mechanism 2 is located above the throttling mechanism).

[0047] Through the downhole throttling device of the above basic embodiment of the present invention, the downhole throttling device is put into a predetermined depth of the wellbore of a gas well for production. The fluid in the downhole reservoir enters the throttling mechanism through the gas wellbore, where it is throttled and expands to absorb heat, creating a temperature difference between the throttling mechanism and the geothermal energy of the gas well. The thermoelectric power generation mechanism 1 utilizes this temperature difference to generate electric energy. The negative electrode of the thermoelectric power generation mechanism 1 is connected to the throttling unit 3 through the anode mechanism 4, and the positive electrode is connected to the cathodic protection mechanism 2 to form a circuit. Consequently, the thermoelectric power generation mechanism 1 generates a continuous current I, causing the potential of the anode mechanism 4 to be higher than the negative potential of the cathodic protection mechanism 2, ensuring that the anode mechanism 4 is not corroded. At this time, the current I flowing through the anode mechanism 4 is greater than or equal to the protection current I0 of the anode mechanism 4. As the productivity of the gas well decreases, the temperature difference between the throttling mechanism and the geothermal energy of the gas well decreases, and the current I generated by the thermoelectric power generation mechanism 1 decreases until it is less than the protection current I0 of the anode mechanism 4. Then, the potential of the cathodic protection mechanism 2 increases, and the potential of the anode mechanism 4 is the lowest and begins to corrode. Subsequently, the anode mechanism 4 melts and breaks, causing the throttling unit 3 to fall off, automatically opening the production channel A, avoiding the fishing and replacement of the downhole throttling device, and enabling automatic control without human intervention, meeting the gas production requirements throughout the life cycle of the gas well.

[0048] It should be noted that in the present invention, the protection current I0 of the anode mechanism 4 refers to the minimum current value required to protect the anode mechanism 4 from corrosion when the current flows through the anode mechanism 4. When the current I flowing through the anode mechanism 4 is greater than or equal to its protection current I0, the anode mechanism 4 is not corroded; when the current I flowing through the anode mechanism 4 is less than its protection current I0, the anode mechanism 4 corrodes and melts, and the throttling unit 3 will fall off.

[0049] In the present invention, the protection currents I0 of different anode mechanisms 4 are different, and the magnitude of the protection current I0 of the anode mechanism 4 is related to the material, structure, and size of the anode mechanism 4. The standard electrode potential of the anode mechanism 4 is less than the standard electrode potential of the material of the downhole throttling device body (the material of the downhole throttling device body contains steel and / or iron). Exemplarily, the material of the anode mechanism 4 can be lithium, magnesium, sodium, aluminum, zinc, manganese, indium, or chromium, or it can also be an alloy of at least two of the foregoing metals. There is no limitation on the shape and structure of the anode mechanism 4. As a specific embodiment of the anode mechanism 4, the anode mechanism 4 can be a shear pin.

[0050] In the present invention, as a preferred embodiment of the throttling unit 3, refer to Figure 2 , the throttling unit 3 includes a convex throttling seat 31 with a hollow interior. The convex throttling seat 31 is connected to the thermoelectric power generation mechanism 1 through the anode mechanism 4. A gas nozzle 32 is provided in the inner cavity of the convex throttling seat 31 to throttle the fluid entering the throttling unit 3 through the gas nozzle 32.

[0051] In the present invention, the convex throttle seat 31 is a rotating body with a "convex"-shaped cross-section, and the convex throttle seat 31 includes a large-diameter section of the throttle seat and a small-diameter section of the throttle seat. As a specific implementation manner of connecting the thermoelectric power generation mechanism 1 with the convex throttle seat 31, the inner cavity where the thermoelectric power generation mechanism 1 is connected to the convex throttle seat 31 is arranged as a convex inner cavity that fits with the convex throttle seat 31, so as to improve the stability and firmness of the throttle mechanism.

[0052] In the present invention, as another preferred implementation manner of the air nozzle 32, refer to Figure 2 , the outer diameter of the air nozzle 32 is larger than the inner diameter of the outlet of the convex throttle seat 31, which can prevent the air nozzle 32 from moving along the flow direction of the fluid under the action of the fluid, and further prevent the air nozzle 32 from entering the inner cavity of the thermoelectric power generation mechanism 1 after falling off from the convex throttle seat 31, avoid premature failure of the throttle mechanism and cause loss of output, and improve the firmness and service life of the air nozzle 32.

[0053] It should be noted that in the present invention, the inner diameter refers to the internal diameter, and the outer diameter refers to the external diameter.

[0054] In the present invention, in order to further improve the firmness of the air nozzle 32, preferably, refer to Figure 2 , a hollow fastening stud 33 is further arranged in the inner cavity of the convex throttle seat 31, and the fluid is adapted to enter the air nozzle 32 from the hollow fastening stud 33.

[0055] In the present invention, the inner diameter of the hollow fastening stud 33 can be the same as or different from the inner diameter of the air nozzle 32. Preferably, the inner diameter of the hollow fastening stud 33 is larger than the inner diameter of the air nozzle 32, so as to improve the throttling effect of the air nozzle 32.

[0056] In the present invention, in order to further improve the sealing performance and throttling effect of the throttle unit 3, preferably, refer to Figure 2 , the throttle unit 3 further includes a sealing structure, and the sealing structure includes a sealing ring 34 arranged between the convex throttle seat 31 and the thermoelectric power generation mechanism 1 and a gasket 35 arranged between the air nozzle 32 and the convex throttle seat 31. There is no special limitation on the specific position of the sealing ring 34. The sealing ring 34 can be arranged at the small-diameter section of the throttle seat or at the large-diameter section of the throttle seat, as long as the sealing performance between the convex throttle seat 31 and the thermoelectric power generation mechanism 1 can be improved; the gasket 35 can be arranged between the outlet of the air nozzle 32 and the outlet of the convex throttle seat 31.

[0057] In the present invention, as another preferred implementation manner of the throttle unit 3, refer to Figure 2, the throttling unit 3 further includes a prestress mechanism 36 disposed on the shoulder of the convex throttling seat 31. When the anode mechanism 4 fuses, the prestress mechanism 36 can push the convex throttling seat 31 downward to make it fall, avoiding the situation where the anode mechanism 4 has fused but the convex throttling seat 31 cannot fall under the action of fluid or scale. The prestress mechanism 36 can be a conventional choice in the art, for example, a spring.

[0058] It should be noted that, referring to Figure 2 , the shoulder of the convex throttling seat 31 refers to the position where the upper end of the large-diameter section of the throttling seat removes the small-diameter section of the throttling seat in the horizontal direction.

[0059] In the present invention, as a preferred embodiment of the throttling mechanism, the number of throttling units 3 is multiple, and the multiple throttling units 3 are connected in series. Along the flow direction of the fluid, the inner diameter of the nozzle 32 at the front end is smaller than the inner diameter of the nozzle 32 at the rear end. It should be noted that the nozzle 32 at the front end refers to the nozzle 32 that first contacts the fluid, and the nozzle 32 at the rear end refers to the nozzle 32 that later contacts the fluid. When the fluid enters the throttling mechanism, it sequentially enters the thermoelectric power generation mechanism 1 through the nozzle 32 with a small inner diameter at the front end and the nozzle 32 with a large inner diameter at the rear end. As the gas well productivity continuously decreases, the anode mechanism 4 corresponding to the nozzle 32 with a small inner diameter preferably fuses and then the connected convex throttling seat 31 drops downward; as the gas well productivity continues to decrease, the throttling unit 3 will repeat the dropping of the convex throttling seat 31 according to the change of the gas well productivity, and the inner diameter of the throttling channel in the throttling mechanism will continuously increase until all the throttling units 3 drop, so that the input channel B and the production channel A are directly connected, which can meet the gas production needs of the entire life cycle of the gas well, not only avoiding the fishing and replacement of the throttling device, but also avoiding the workover method of pulling out the tubing string, realizing that one throttling device can meet the lifelong application of the gas well and does not affect the later plunger gas lift drainage gas production of the gas well.

[0060] In the present invention, when multiple throttling units 3 are connected in series, they can be directly connected in series along the flow direction of the fluid, or the convex throttling seat 31 where the nozzle 32 with a small inner diameter is located can be nested on the convex throttling seat 31 where the nozzle 32 with a large inner diameter is located.

[0061] In the present invention, when the number of throttling units 3 is multiple, the fluid entering the multiple throttling units 3 throttles and expands to absorb heat, so that a temperature difference is formed between the throttling mechanism and the geothermal heat of the gas well. The thermoelectric power generation mechanism 1 uses this temperature difference to generate electric energy. The negative electrode of the thermoelectric power generation mechanism 1 is connected to the corresponding throttling unit 3 through multiple anode mechanisms 4, and the positive electrode is connected to the cathodic protection mechanism 2 to form a circuit. That is, in the formed circuit, the multiple anode mechanisms 4 are connected in parallel, and the protection currents I0 of different anode mechanisms 4 are different.

[0062] In order to achieve the effect of automatically replacing the gas nozzle 32 with a larger inner diameter according to the change in the gas well production capacity, preferably, when the materials of the anode mechanisms 4 are the same, along the fluid flow direction, the volume of the anode mechanism 4 at the front end is smaller than that of the anode mechanism 4 at the rear end; or, when the volumes of the anode mechanisms 4 are the same, along the fluid flow direction, the standard electrode potential of the anode mechanism 4 at the front end is smaller than that of the anode mechanism 4 at the rear end; or, a control circuit is provided on the thermoelectric power generation mechanism 1, and the control circuit can adjust the magnitude of the current I passing through the anode mechanism 4.

[0063] In the present invention, as a specific implementation manner of the throttling mechanism, the number of the throttling units 3 is 2, and the 2 throttling units 3 are connected in series. When the current I passing through the first anode mechanism 4 is greater than or equal to its protection current I0, and the current I passing through the second anode mechanism 4 is greater than or equal to its protection current I0, neither the first anode mechanism 4 nor the second anode mechanism 4 is corroded. After the fluid enters the throttling mechanism, it continues to pass through the throttling unit 3 corresponding to the first anode mechanism 4 and the throttling unit 3 corresponding to the second anode mechanism 4 in sequence and then enters the thermoelectric power generation mechanism 1; when the current I passing through the first anode mechanism 4 is less than the protection current I0 of the anode mechanism 4, and the current I passing through the second anode mechanism 4 is greater than or equal to its protection current I0, the first anode mechanism 4 is corroded and fused, and the convex throttling seat 31 where it is located drops downward, and the second anode mechanism 4 is not corroded, and the fluid enters the thermoelectric power generation mechanism 1 through the throttling unit 3 corresponding to the second anode mechanism 4; as the production capacity of the gas well continues to decrease, the current I passing through the second anode mechanism 4 decreases until it is less than the protection current I0 of the anode mechanism 4, and the second anode mechanism 4 is corroded and fused, and the convex throttling seat 31 where it is located drops downward, that is, the production channel A is opened, and the fluid directly enters the production channel A from the input channel B.

[0064] It should be noted that along the fluid flow direction, the first anode mechanism 4 in contact with the fluid is the first anode mechanism 4, and the gas nozzle 32 in the corresponding throttling unit 3 is the first gas nozzle 32; the second anode mechanism 4 in contact with the fluid is the second anode mechanism 4, and the gas nozzle 32 in the corresponding throttling unit 3 is the second gas nozzle 32, and so on.

[0065] In the present invention, as a preferred implementation manner of the thermoelectric power generation mechanism 1, the thermoelectric power generation mechanism 1 is further provided with a rechargeable battery. When a rechargeable battery is provided on the thermoelectric power generation mechanism 1, the current I passing through the anode mechanism 4 can be controlled through the control circuit. When the gas well needs to be shut down for maintenance, the electric energy of the rechargeable battery can be used to protect the anode mechanism 4 from corrosion, and when the gas well is in normal production, normal charging of the rechargeable battery can be achieved.

[0066] In the present invention, in order to avoid the premature fusing of the anode mechanism 4 in the early stage of gas well exploitation, as a preferred embodiment of the anode mechanism 4, an anode material layer is provided outside the anode mechanism 4. The standard electrode potential of the anode material layer is greater than that of the anode mechanism 4, effectively increasing the corrosion fusing duration of the anode mechanism. Exemplarily, the material of the anode material layer can be lithium, magnesium, sodium, aluminum, zinc, manganese, indium or chromium, or an alloy of at least two of the foregoing metals. There is no limitation on the method of providing the anode material layer on the anode mechanism 4. For example, the anode material layer can be provided on the outer layer of the anode mechanism 4 by electroplating the material of the anode material layer.

[0067] In the present invention, there is no limitation on the overall structure of the anode mechanism 4 and the anode material layer. As a preferred embodiment of the overall structure of the anode mechanism 4 and the anode material layer, refer to Figure 5 , the overall structure of the anode mechanism 4 and the anode material layer is a semi-circular ring of a semi-circular ring structure, and the sector angle of the semi-circular ring ≤ 180°.

[0068] In the present invention, the thermoelectric power generation mechanism 1 realizes semiconductor power generation through semiconductor materials. As a preferred embodiment of the thermoelectric power generation mechanism 1, the thermoelectric power generation mechanism 1 includes a heat conduction layer and a thermoelectric power generation layer provided outside the heat conduction layer. The thermoelectric power generation layer contains semiconductor materials. The semiconductor materials can be conventional semiconductors selected in the art, such as silicon, germanium, gallium, etc.; the heat conduction layer can be made of steel materials to meet the strength requirements of downhole throttling gas production and the heat conduction performance requirements of the thermoelectric power generation mechanism 1, and further improve the power generation efficiency of the thermoelectric power generation mechanism 1.

[0069] In the present invention, as a specific embodiment of the thermoelectric power generation mechanism 1, the thermoelectric power generation mechanism 1 further includes a protective layer provided outside the thermoelectric power generation layer. The protective layer can be made of a material with high strength and good heat conductivity, which can avoid damaging the thermoelectric power generation layer, ensure the heat conduction performance of the thermoelectric power generation mechanism 1, and further improve the power generation efficiency of the thermoelectric power generation mechanism 1.

[0070] In the present invention, as a preferred embodiment of the connection of the heat conduction layer, the thermoelectric power generation layer and the protective layer, the heat conduction layer, the thermoelectric power generation layer and the protective layer are connected by a nested fixing method to improve the sealing performance and power generation efficiency of the thermoelectric power generation mechanism 1. The nested fixing can adopt the conventional nested fixing methods selected in the art. For example, it can be adhesively fixed with a high-strength heat-resistant conductive glue, can be thread-fixed, or can be fixed by soldering fusion.

[0071] In the present invention, as another preferred embodiment of the thermoelectric power generation mechanism 1, the thermoelectric power generation mechanism 1 is connected to a rechargeable battery and a thermoelectric power generation controller. During the overhaul and shut-in period of the gas well, the rechargeable battery and the thermoelectric power generation controller can make a continuous current I pass through the anode mechanism 4 and the current I is greater than or equal to its protection current I0 to protect the anode mechanism 4 from corrosion.

[0072] In the present invention, during the exploitation process of the gas well, sand production may occur, which easily clogs the throttling mechanism, thereby affecting the throttling effect and service life of the downhole throttling device. To further improve the throttling effect and service life of the throttling device, preferably, referring to Figures 1 - 3 , a sand prevention mechanism 5 is arranged in the fluid inflow direction of the throttling mechanism.

[0073] In the present invention, as a preferred embodiment of the cathodic protection mechanism 2, the cathodic protection mechanism 2 is a formed part made of high-silicon cast iron material.

[0074] In the present invention, to improve the applicability of the downhole throttling device, preferably, referring to Figure 1 and Figure 2 , the downhole throttling device further includes a rubber barrel sealing mechanism 6, a slip anchoring mechanism 7 and a fishing head 8 which are sequentially connected to the thermoelectric power generation mechanism 1. The rubber barrel sealing mechanism 6, the slip anchoring mechanism 7, the fishing head 8 and the thermoelectric power generation mechanism 1 are communicated. The fishing head 8 drops the downhole throttling device to a predetermined depth in the wellbore of the gas well, and the slip anchoring mechanism 7 is used to fix the downhole throttling device. The rubber barrel sealing mechanism 6 can radially expand to form a seal with the wellbore, improving the throttling effect of the downhole throttling device.

[0075] In the present invention, there is no special limitation on the position of the rubber barrel sealing mechanism 6. Referring to Figures 1 - 4 , the rubber barrel sealing mechanism 6 can be located above the throttling mechanism; there is also no special limitation on the number of the rubber barrel sealing mechanisms 6, which can be 1 or multiple. As a specific embodiment of the rubber barrel sealing mechanism 6, referring to Figure 4 , the number of the rubber barrel sealing mechanisms 6 is 2, and a spacer ring 9 is arranged between the two rubber barrel sealing mechanisms 6 to further improve the sealing effect of the rubber barrel sealing mechanism 6.

[0076] In the present invention, the rubber barrel sealing mechanism 6, the slip anchoring mechanism 7 and the fishing head 8 are all of hollow structures, and the inner cavities of the rubber barrel sealing mechanism 6, the slip anchoring mechanism 7 and the fishing head 8 are communicated with each other. The inner cavities of the rubber barrel sealing mechanism 6, the slip anchoring mechanism 7 and the fishing head 8 can be a part of the production channel A.

[0077] In the present invention, the cathodic protection mechanism 2 can be located between the rubber cylinder sealing mechanism 6 and the thermoelectric power generation mechanism 1; alternatively, the cathodic protection mechanism 2 can be combined with the sand control mechanism 5 to avoid structural redundancy and reduce production costs. When adjusting the position of the cathodic protection mechanism 2, the inner cavity size of the cathodic protection mechanism 2 needs to be adjusted accordingly so that the inner cavity of the cathodic protection mechanism 2 serves as part of the production channel A or the input channel B.

[0078] In the present invention, as a preferred embodiment of the slip anchoring mechanism 7, refer to Figure 1 , the slip anchoring mechanism 7 includes slips 71, an upper slip seat 72, and a lower slip seat 73. One end of the slips 71 is connected to the upper slip seat 72 and the other end is connected to the lower slip seat 73. The slips 71 are fixed and protected by setting the upper slip seat 72 and the lower slip seat 73.

[0079] The second aspect of the present invention provides a method for using a downhole throttling device for gas production throughout the life cycle of a gas well. The control method of the downhole throttling device includes the following steps:

[0080] The fluid in the gas well enters the thermoelectric power generation mechanism 1 through the throttling mechanism to cause the thermoelectric power generation mechanism 1 to generate electricity. When the current I passing through the anode mechanism 4 is greater than or equal to the protection current I0 of the anode mechanism 4, the anode mechanism 4 is not corroded, and the fluid continues to enter the thermoelectric power generation mechanism 1 through the throttling mechanism; when the current I passing through the anode mechanism 4 is less than the protection current I0 of the anode mechanism 4, the anode mechanism 4 corrodes and fuses, and finally the fluid directly enters the thermoelectric power generation mechanism 1 so that the input channel B and the production channel A are directly connected, avoiding the fishing and replacement of the throttling device, and also avoiding the workover method of pulling out the tubing string. Moreover, it can achieve automatic control without manual intervention, meeting the gas production throughout the life cycle of the gas well.

[0081] In the present invention, as a preferred embodiment of the control method of the downhole throttling device, the throttling mechanism includes a plurality of throttling units 3 and an anode mechanism 4 corresponding to each throttling unit 3, and the plurality of throttling units 3 are connected in series; wherein,

[0082] When the materials of the anode mechanisms 4 are the same, along the flow direction of the fluid, the volume of the anode mechanism 4 at the front end is smaller than the volume of the anode mechanism 4 at the rear end; or, when the volumes of the anode mechanisms 4 are the same, along the flow direction of the fluid, the standard electrode potential of the anode mechanism 4 at the front end is less than the standard electrode potential of the anode mechanism 4 at the rear end; or, a control circuit is provided on the thermoelectric power generation mechanism 1, and the control circuit can adjust the magnitude of the current I passing through the anode mechanism 4;

[0083] The fluid enters the thermoelectric power generation mechanism 1 through multiple throttling units 3 to enable the thermoelectric power generation mechanism 1 to generate electricity. When the current I passing through the first anode mechanism 4 is greater than or equal to the protection current I0 of the anode mechanism 4, the anode mechanism 4 is not corroded, and the fluid continues to enter the thermoelectric power generation mechanism 1 through multiple throttling units 3; when the current I of the first anode mechanism 4 is less than the protection current I0 of the anode mechanism 4, the anode mechanism 4 is corroded and fused, and the fluid enters the thermoelectric power generation mechanism 1 through the remaining throttling units 3; when the current I passing through the second anode mechanism 4 is less than the protection current I0 of the anode mechanism 4, the anode mechanism 4 is corroded and fused, until all the anode mechanisms 4 are corroded and fused, so that the input channel B and the production channel A are directly connected. This downhole throttling device can meet the gas production needs of the entire life cycle of the gas well, not only avoiding the fishing and replacement of the downhole throttling device, but also avoiding the well workover method of pulling out the tubing string, realizing that one downhole throttling device can meet the lifelong application of the gas well without affecting the later plunger gas lift drainage gas production of the gas well.

[0084] In the present invention, as another preferred embodiment of the control method of the downhole throttling device, when it is necessary for the downhole throttling device to lose its throttling function in advance or the throttling mechanism is fouled and blocked and cannot work properly, after pumping the agent into the downhole throttling device, the gas well is closed, and after the agent reacts and dissolves with the anode mechanism 4 or the scale, the gas well is opened for blowout and then production is carried out to realize the change of the inner diameter of the throttling passage inside the downhole throttling device, or to make all the throttling units 3 fall off so as to be able to directly connect the production channel A and the input channel B.

[0085] In the present invention, the type of the agent is not limited. The agent can be a scale remover. Preferably, the agent is an acidic agent, which can not only remove scale but also accelerate the corrosion of the anode mechanism 4, so that the throttling unit 3 falls off smoothly to open a throttling channel with a larger inner diameter, or all the throttling units 3 fall off to be able to directly connect the production channel A and the input channel B.

[0086] In the present invention, if the energy of the gas well itself is insufficient, after pumping the agent, nitrogen or carbon dioxide can be pumped into the wellbore through a compressor by means of pump injection backpressure to supplement energy on the one hand and ensure sufficient contact between the agent and the downhole throttling device on the other hand, improve the scale removal effect, and further improve the throttling effect of the downhole throttling device.

[0087] The downhole throttling device provided by the above embodiment of the present invention has the functions of enabling the throttling mechanism to fall off so that the production channel A and the input channel B are directly connected, not affecting the normal production of the gas well, avoiding the fishing and replacement of the downhole throttling device, and being able to realize automatic control without manual intervention, meeting the gas production needs of the entire life cycle of the gas well. The structure of the downhole throttling device is simple, the installation method is flexible, no manual intervention is required, and the cost is low.

[0088] Example 1

[0089] The downhole throttling device for gas production in the whole life cycle of a gas well includes a thermoelectric power generation mechanism 1 for power generation, a cathodic protection mechanism 2, a throttling mechanism for throttling the fluid entering the thermoelectric power generation mechanism 1, a sand control mechanism 5, a rubber barrel sealing mechanism 6, a slip anchoring mechanism 7 and a fishing head 8. The throttling mechanism includes 2 throttling units 3 and an anode mechanism 4 corresponding to each throttling unit 3. The anode mechanism 4 can corrode and fuse when the current I passing through the anode mechanism 4 is less than the protection current I0 of the anode mechanism 4. The anode mechanism 4 is a shear pin. The negative pole of the thermoelectric power generation mechanism 1 is connected to the corresponding throttling unit 3 through 2 anode mechanisms 4 respectively, and the positive pole is connected to the cathodic protection mechanism 2. Each throttling unit 3 includes a convex throttling seat 31 with a hollow interior. The convex throttling seat 31 is connected to the thermoelectric power generation mechanism 1 through the anode mechanism 4. The inner cavity of the thermoelectric power generation mechanism 1 connected to the convex throttling seat 31 is set as a convex inner cavity that fits with the convex throttling seat 31. The inner cavity of the convex throttling seat 31 is provided with a gas nozzle 32. The outer diameter of the gas nozzle 32 is larger than the inner diameter of the outlet of the convex throttling seat 31. The inner cavity of the convex throttling seat 31 is also provided with a hollow fastening stud 33. The fluid is suitable to enter the gas nozzle 32 from the hollow fastening stud 33. The inner diameter of the hollow fastening stud 33 is larger than the inner diameter of the gas nozzle 32. The throttling unit 3 also includes a sealing structure and a prestress mechanism 36. The sealing structure includes a sealing ring 34 arranged between the convex throttling seat 31 and the thermoelectric power generation mechanism 1 and a gasket 35 arranged between the gas nozzle 32 and the convex throttling seat 31. The prestress mechanism 36 is arranged at the shoulder of the convex throttling seat 31. The 2 throttling units 3 are connected in series. Along the flow direction of the fluid, the inner diameter of the gas nozzle 32 at the front end (i.e., the first gas nozzle 32) is smaller than the inner diameter of the gas nozzle 32 at the rear end (i.e., the second gas nozzle 32). The anode mechanism 4 at the front end (i.e., the first anode mechanism 4) and the anode mechanism 4 at the rear end (i.e., the second anode mechanism 4) are made of the same material, and the volume of the first anode mechanism 4 is smaller than the volume of the second anode mechanism 4. The thermoelectric power generation mechanism 1 includes a heat conduction layer, a thermoelectric power generation layer arranged outside the heat conduction layer and a protective layer arranged outside the thermoelectric power generation layer. The thermoelectric power generation layer contains semiconductor materials. The heat conduction layer, the thermoelectric power generation layer and the protective layer are connected in a nested and fixed manner. A sand control mechanism 5 is arranged in the fluid inflow direction of the throttling mechanism. The cathodic protection mechanism 2 is a formed part made of high silicon cast iron. The rubber barrel sealing mechanism 6, the slip anchoring mechanism 7, the fishing head 8 and the thermoelectric power generation mechanism 1 are communicated. The slip anchoring mechanism 7 includes a slip 71, an upper slip seat 72 and a lower slip seat 73. One end of the slip 71 is connected to the upper slip seat 72 and the other end is connected to the lower slip seat 73. The inner diameters of the cathodic protection mechanism 2 and the sand control mechanism 5 are larger than the outer diameter of the throttling mechanism, and the cathodic protection mechanism 2 and the sand control mechanism 5 are combined and arranged.

[0090] The control method of the above downhole throttling device includes the following steps:

[0091] The fishing head 8 lowers the downhole throttling device to the predetermined depth in the wellbore of the gas well. The downhole throttling device is fixed by the slip anchoring mechanism 7. The rubber cylinder sealing mechanism 6 expands radially to form a seal with the wellbore, and the gas well starts production. The fluid in the downhole reservoir enters the throttling mechanism from the wellbore, and successively passes through the first nozzle 32 and the second nozzle 32 for throttling and then enters the thermoelectric power generation mechanism 1. The thermoelectric power generation mechanism 1 generates electric energy by using the temperature difference formed between the throttling mechanism and the geothermal energy of the gas well. The negative electrode of the thermoelectric power generation mechanism 1 is connected to the corresponding throttling unit 3 through 2 anode mechanisms 4, and the positive electrode is connected to the cathodic protection mechanism 2 to form an electric circuit. The current I flowing through the first anode mechanism 4 and the second anode mechanism 4 is greater than or equal to its protection current I0, which can ensure that both 2 anode mechanisms 4 are not corroded. The fluid enters the throttling mechanism and successively passes through the first nozzle 32 and the second nozzle 32 and enters the production channel A;

[0092] As the production capacity of the gas well decreases, the temperature difference between the throttling mechanism and the geothermal energy of the gas well decreases, and the electric energy obtained by the thermoelectric power generation mechanism 1 decreases. When the current I passing through the first anode mechanism 4 is less than its protection current I0, and the current I passing through the second anode mechanism 4 is greater than or equal to its protection current I0, the first anode mechanism 4 fuses. The prestress mechanism 36 located at the shoulder of the convex throttling seat 31 corresponding to the first anode mechanism 4 pushes the convex throttling seat 31 to fall off. The fluid enters the throttling mechanism and is throttled by the second nozzle 32 and then enters the thermoelectric power generation mechanism 1;

[0093] As the production capacity of the gas well continues to decrease, when the current I passing through the second anode mechanism 4 is less than its protection current I0, the second anode mechanism 4 fuses and corrodes. The prestress mechanism 36 located at the shoulder of the convex throttling seat 31 corresponding to the second anode mechanism 4 pushes the convex throttling seat 31 to fall off, so that the input channel B and the production channel A are directly connected and the next production is carried out.

[0094] Embodiment 2

[0095] The downhole throttling device for gas production throughout the life cycle of a gas well includes a thermoelectric power generation mechanism 1 for power generation, a cathodic protection mechanism 2, a throttling mechanism for throttling the fluid entering the thermoelectric power generation mechanism 1, a sand control mechanism 5, a rubber barrel sealing mechanism 6, a slip anchoring mechanism 7, and a fishing head 8. The throttling mechanism includes one throttling unit 3 and an anode mechanism 4 arranged corresponding to the throttling unit 3. The anode mechanism 4 can corrode and fuse when the current I passing through the anode mechanism 4 is less than the protection current I0 of the anode mechanism 4. The anode mechanism 4 is a shear pin. The negative electrode of the thermoelectric power generation mechanism 1 is connected to the corresponding throttling unit 3 through the anode mechanism 4, and the positive electrode is connected to the cathodic protection mechanism 2. The throttling unit 3 includes a convex throttling seat 31 with a hollow interior. The convex throttling seat 31 is connected to the thermoelectric power generation mechanism 1 through the anode mechanism 4. The inner cavity of the thermoelectric power generation mechanism 1 connected to the convex throttling seat 31 is set as a convex inner cavity that fits with the convex throttling seat 31. The inner cavity of the convex throttling seat 31 is provided with a gas nozzle 32. The outer diameter of the gas nozzle 32 is larger than the inner diameter of the outlet of the convex throttling seat 31. The inner cavity of the convex throttling seat 31 is also provided with a hollow fastening stud 33. The fluid is suitable for entering the gas nozzle 32 from the hollow fastening stud 33. The inner diameter of the hollow fastening stud 33 is larger than the inner diameter of the gas nozzle 32. The throttling unit 3 further includes a sealing structure and a prestress mechanism 36. The sealing structure includes a sealing ring 34 arranged between the convex throttling seat 31 and the thermoelectric power generation mechanism 1 and a gasket 35 arranged between the gas nozzle 32 and the convex throttling seat 31. The prestress mechanism 36 is arranged on the shoulder of the convex throttling seat 31. The thermoelectric power generation mechanism 1 includes a heat conduction layer, a thermoelectric power generation layer arranged outside the heat conduction layer, and a protective layer arranged outside the thermoelectric power generation layer. The thermoelectric power generation layer contains semiconductor materials. The heat conduction layer, the thermoelectric power generation layer, and the protective layer are connected in a nested and fixed manner. A sand control mechanism 5 is arranged in the fluid inflow direction of the throttling mechanism. The cathodic protection mechanism 2 is a formed part made of high silicon cast iron. The rubber barrel sealing mechanism 6, the slip anchoring mechanism 7, the fishing head 8, and the thermoelectric power generation mechanism 1 are communicated. The slip anchoring mechanism 7 includes slips 71, an upper slip seat 72, and a lower slip seat 73. One end of the slips 71 is connected to the upper slip seat 72, and the other end is connected to the lower slip seat 73. The inner diameters of the cathodic protection mechanism 2 and the sand control mechanism 5 are larger than the outer diameter of the throttling mechanism.

[0096] The control method of the above downhole throttling device includes the following steps:

[0097] The fishing head 8 lowers the downhole throttling device to a predetermined depth in the wellbore of the gas well. The downhole throttling device is fixed by the slip anchoring mechanism 7. The rubber barrel sealing mechanism 6 expands radially to form a seal with the wellbore. The gas well starts production. The fluid in the downhole reservoir enters the throttling mechanism through the wellbore, and after throttling by the choke nozzle 32, it enters the thermoelectric power generation mechanism 1. The thermoelectric power generation mechanism 1 generates electric energy by using the temperature difference formed between the throttling mechanism and the geothermal energy of the gas well. The negative electrode of the thermoelectric power generation mechanism 1 is connected to the corresponding throttling unit 3 through the anode mechanism 4, and the positive electrode is connected to the cathodic protection mechanism 2 to form an electric circuit. The current I flowing through the anode mechanism 4 is greater than or equal to its protection current I0, which can ensure that the anode mechanism 4 is not corroded. The fluid enters the throttling mechanism and then enters the production channel A through the choke nozzle 32;

[0098] As the production capacity of the gas well decreases, the temperature difference between the throttling mechanism and the geothermal energy of the gas well decreases, and the electric energy obtained by the thermoelectric power generation mechanism 1 decreases. When the current I flowing through the anode mechanism 4 is less than its protection current I0, the anode mechanism 4 fuses. The prestress mechanism 36 located at the shoulder of the convex throttling seat 31 pushes the convex throttling seat 31 to drop, so that the input channel B and the production channel A are directly connected and the next production step is carried out.

[0099] Embodiment 3

[0100] The downhole throttling device for gas production throughout the life cycle of a gas well is different from Embodiment 2 in that, see Figure 5 The overall structure of the anode mechanism 4 and the anode material layer is set as a semi-circular ring with a sector angle of 150°.

[0101] Embodiment 4

[0102] The downhole throttling device for gas production throughout the life cycle of a gas well includes a thermoelectric power generation mechanism 1 for power generation, a cathodic protection mechanism 2, and a throttling mechanism for throttling the fluid entering the thermoelectric power generation mechanism 1. The throttling mechanism includes a throttling unit 3 and an anode mechanism 4 arranged corresponding to the throttling unit 3. The anode mechanism 4 can be corroded and melted when the current I passing through the anode mechanism 4 is less than the protection current I0 of the anode mechanism 4. The anode mechanism 4 is a shear pin. The negative pole of the thermoelectric power generation mechanism 1 is connected to the corresponding throttling unit 3 through the anode mechanism 4, and the positive pole is connected to the cathodic protection mechanism 2. The throttling unit 3 includes a convex throttling seat 31 with a hollow interior. The convex throttling seat 31 is connected to the thermoelectric power generation mechanism 1 through the anode mechanism 4. The inner cavity of the thermoelectric power generation mechanism 1 connected to the convex throttling seat 31 is set as a convex inner cavity fitted with the convex throttling seat 31. A gas nozzle 32 is arranged in the inner cavity of the convex throttling seat 31. The outer diameter of the gas nozzle 32 is larger than the inner diameter of the outlet of the convex throttling seat 31. A hollow fastening stud 33 is also arranged in the inner cavity of the convex throttling seat 31. The fluid is suitable for entering the gas nozzle 32 from the hollow fastening stud 33. The inner diameter of the hollow fastening stud 33 is larger than the inner diameter of the gas nozzle 32. The throttling unit 3 further includes a sealing structure and a prestress mechanism 36. The sealing structure includes a sealing ring 34 arranged between the convex throttling seat 31 and the thermoelectric power generation mechanism 1 and a gasket 35 arranged between the gas nozzle 32 and the convex throttling seat 31. The prestress mechanism 36 is arranged on the shoulder of the convex throttling seat 31. The thermoelectric power generation mechanism 1 includes a heat conduction layer, a thermoelectric power generation layer arranged outside the heat conduction layer, and a protective layer arranged outside the thermoelectric power generation layer. The thermoelectric power generation layer contains semiconductor materials. The heat conduction layer, the thermoelectric power generation layer, and the protective layer are connected in a nested and fixed manner. The inner diameter of the cathodic protection mechanism 2 is larger than the outer diameter of the throttling mechanism.

[0103] The control method of the above downhole throttling device includes the following steps:

[0104] Directly connect the downhole throttling device to the production string. The fluid in the string enters the throttling mechanism, is throttled by the gas nozzle 32, and then enters the thermoelectric power generation mechanism 1. The thermoelectric power generation mechanism 1 generates electric energy by using the temperature difference formed between the throttling mechanism and the geothermal heat of the gas well. The negative pole of the thermoelectric power generation mechanism 1 is connected to the corresponding throttling unit 3 through the anode mechanism 4, and the positive pole is connected to the cathodic protection mechanism 2 to form a circuit. The current I flowing through the anode mechanism 4 is greater than or equal to its protection current I0, which can ensure that the anode mechanism 4 is not corroded. The fluid enters the production channel A through the gas nozzle 32 after entering the throttling mechanism.

[0105] As the production capacity of the gas well decreases, the temperature difference between the throttling mechanism and the geothermal heat of the gas well decreases, and the electric energy obtained by the thermoelectric power generation mechanism 1 decreases. When the current I flowing through the anode mechanism 4 is less than its protection current I0, the anode mechanism 4 melts. The prestress mechanism 36 located on the shoulder of the convex throttling seat 31 pushes the convex throttling seat 31 to fall off, so that the input channel B and the production channel A are directly connected and the next production is carried out.

[0106] Example 5

[0107] The downhole throttling device for gas production throughout the life cycle of a gas well includes a thermoelectric power generation mechanism 1 for power generation, a cathodic protection mechanism 2, a throttling mechanism for throttling the fluid entering the thermoelectric power generation mechanism 1, a sand control mechanism 5, a rubber barrel sealing mechanism 6, a slip anchoring mechanism 7, and a fishing head 8. The throttling mechanism includes 1 throttling unit 3 and an anode mechanism 4 correspondingly arranged with the throttling unit 3. The anode mechanism 4 can corrode and fuse when the current I passing through the anode mechanism 4 is less than the protection current I0 of the anode mechanism 4. The anode mechanism 4 is a shear pin. The negative pole of the thermoelectric power generation mechanism 1 is connected to the correspondingly arranged throttling unit 3 through the anode mechanism 4, and the positive pole is connected to the cathodic protection mechanism 2. The thermoelectric power generation mechanism 1 includes a heat conduction layer, a thermoelectric power generation layer arranged outside the heat conduction layer, and a protection layer arranged outside the thermoelectric power generation layer. The thermoelectric power generation layer contains semiconductor materials. The heat conduction layer, the thermoelectric power generation layer, and the protection layer are connected in a nested and fixed manner. A sand control mechanism 5 is arranged in the fluid inflow direction of the throttling mechanism. The cathodic protection mechanism 2 is a formed part made of high silicon cast iron material. The rubber barrel sealing mechanism 6, the slip anchoring mechanism 7, the fishing head 8, and the thermoelectric power generation mechanism 1 are communicated. The slip anchoring mechanism 7 includes slips 71, an upper slip seat 72, and a lower slip seat 73. One end of the slips 71 is connected to the upper slip seat 72, and the other end is connected to the lower slip seat 73. The inner diameters of the cathodic protection mechanism 2 and the sand control mechanism 5 are larger than the outer diameter of the throttling mechanism.

[0108] The control method of the above downhole throttling device includes the following steps:

[0109] The fishing head 8 drops the downhole throttling device to a predetermined depth in the wellbore of the gas well, and uses the slip anchoring mechanism 7 to fix the downhole throttling device. The rubber barrel sealing mechanism 6 radially expands to form a seal with the wellbore, and gas production of the gas well starts. The fluid in the gas well enters the throttling mechanism from the wellbore, is throttled, and then enters the thermoelectric power generation mechanism 1. The thermoelectric power generation mechanism 1 generates electric energy by using the temperature difference formed between the throttling mechanism and the geothermal heat of the gas well. The negative pole of the thermoelectric power generation mechanism 1 is connected to the correspondingly arranged throttling unit 3 through the anode mechanism 4, and the positive pole is connected to the cathodic protection mechanism 2 to form an electric circuit. The current I flowing through the anode mechanism 4 is greater than or equal to its protection current I0, which can ensure that the anode mechanism 4 does not corrode. The fluid enters the throttling mechanism and then enters the production channel A through the throttling unit 3;

[0110] As the production capacity of the gas well decreases, the temperature difference between the throttling mechanism and the geothermal heat of the gas well decreases, and the electric energy obtained by the thermoelectric power generation mechanism 1 decreases. When the current I flowing through the anode mechanism 4 is less than its protection current I0, the anode mechanism 4 fuses. After the throttling unit 3 drops off, the input channel B and the production channel A are directly communicated and further production is carried out.

[0111] Example 6

[0112] The downhole throttling device for gas production throughout the life cycle of a gas well includes a thermoelectric power generation mechanism 1 for power generation, a cathodic protection mechanism 2, and a throttling mechanism for throttling the fluid entering the thermoelectric power generation mechanism 1. The throttling mechanism includes a throttling unit 3 and an anode mechanism 4 arranged corresponding to the throttling unit 3. The negative electrode of the thermoelectric power generation mechanism 1 is connected to the corresponding throttling unit 3 through two anode mechanisms 4, and the positive electrode is connected to the cathodic protection mechanism 2. The thermoelectric power generation mechanism 1 includes a heat conduction layer, a thermoelectric power generation layer arranged outside the heat conduction layer, and a protective layer arranged outside the thermoelectric power generation layer. The thermoelectric power generation layer contains semiconductor materials. The heat conduction layer, the thermoelectric power generation layer, and the protective layer are connected in a nested and fixed manner. The inner diameter of the cathodic protection mechanism 2 is larger than the outer diameter of the throttling mechanism.

[0113] The control method of the above downhole throttling device includes the following steps:

[0114] Directly connect the downhole throttling device to the production string. The fluid in the string enters the throttling mechanism for throttling and then enters the thermoelectric power generation mechanism 1. The thermoelectric power generation mechanism 1 generates electric energy by using the temperature difference formed between the throttling mechanism and the geothermal energy of the gas well. The negative electrode of the thermoelectric power generation mechanism 1 is connected to the corresponding throttling unit 3 through the anode mechanism 4, and the positive electrode is connected to the cathodic protection mechanism 2 to form an electric circuit. The current I flowing through the anode mechanism 4 is greater than or equal to its protection current I0, which can ensure that the anode mechanism 4 is not corroded. The fluid enters the throttling mechanism and then enters the production channel A through the throttling unit 3;

[0115] As the production capacity of the gas well decreases, the temperature difference between the throttling mechanism and the geothermal energy of the gas well decreases, and the electric energy obtained by the thermoelectric power generation mechanism 1 decreases. When the current I flowing through the anode mechanism 4 is less than its protection current I0, the anode mechanism 4 fuses. Then, after the throttling unit 3 falls off, the input channel B and the production channel A are directly connected and the next production is carried out.

[0116] Example 7

[0117] The downhole throttling device for gas production throughout the life cycle of a gas well, compared with Example 2, is different in that the thermoelectric power generation mechanism 1 includes a heat conduction layer and a thermoelectric power generation layer arranged outside the heat conduction layer.

[0118] Example 8

[0119] The downhole throttling tool for gas production throughout the life cycle of a gas well, compared with Example 2, is different in that the cathodic protection mechanism 2 is a copper material formed part.

[0120] Example 9

[0121] The downhole throttling device for gas production throughout the life cycle of a gas well, compared with Example 2, is different in that the throttling unit 3 has no sealing structure.

[0122] Example 10

[0123] The downhole throttling device for gas production throughout the entire life cycle of a gas well. Compared with Embodiment 2, the difference is that the thermoelectric power generation mechanism 1 is further provided with a rechargeable battery and a control circuit.

[0124] The control method of the above-mentioned downhole throttling device. Compared with Embodiment 2, the difference is that when the gas well needs to be shut down for maintenance, the rechargeable battery can supply electric energy to the anode mechanism 4, and through the control circuit, the current I flowing through the anode mechanism 4 is made greater than or equal to its protection current I0, protecting the anode mechanism 4 from corrosion and effectively ensuring that the throttling mechanism does not lose its throttling function during the shut-down period of the gas well; when the gas well is in normal production, the rechargeable battery uses the electric energy provided by the thermoelectric power generation mechanism 1 to achieve normal charging.

[0125] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0126] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, they can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. An underground throttling device for gas production throughout the entire life cycle of a gas well, characterized in that, The downhole throttling device includes a thermoelectric power generation mechanism (1) for power generation, a cathodic protection mechanism (2), and a throttling mechanism for throttling the fluid entering the thermoelectric power generation mechanism (1). The throttling mechanism includes at least one throttling unit (3) and an anode mechanism (4) arranged corresponding to the throttling unit (3). The negative electrode of the thermoelectric power generation mechanism (1) is connected to the throttling unit (3) through the anode mechanism (4), and the positive electrode is connected to the cathodic protection mechanism (2); the anode mechanism (4) can be corroded and melted when the current I passing through the anode mechanism (4) is less than the protection current I0 of the anode mechanism (4).

2. The underground throttling device according to claim 1, characterized in that, The throttling unit (3) includes a convex throttling seat (31) with a hollow interior. The convex throttling seat (31) is connected to the thermoelectric power generation mechanism (1) through the anode mechanism (4), and a nozzle (32) is arranged in the inner cavity of the convex throttling seat (31).

3. The underground throttling device according to claim 2, characterized in that, The outer diameter of the nozzle (32) is greater than the inner diameter of the outlet of the convex throttling seat (31).

4. The underground throttling device according to claim 2, characterized in that, A hollow fastening stud (33) is further arranged in the inner cavity of the convex throttling seat (31), and the fluid is adapted to enter the nozzle (32) from the hollow fastening stud (33).

5. The underground throttling device according to claim 4, characterized in that, The inner diameter of the hollow fastening stud (33) is greater than the inner diameter of the nozzle (32).

6. The underground throttling device according to claim 2, characterized in that, The throttling unit (3) further includes a sealing structure, and the sealing structure includes a sealing ring (34) arranged between the convex throttling seat (31) and the thermoelectric power generation mechanism (1) and a gasket (35) arranged between the nozzle (32) and the convex throttling seat (31).

7. The underground throttling device according to claim 2, characterized in that, The throttling unit (3) further includes a prestress mechanism (36) arranged on the shoulder of the convex throttling seat (31).

8. The underground throttling device according to any one of claims 2 to 7, characterized in that, The number of the throttling units (3) is multiple, and the multiple throttling units (3) are connected in series. Along the flow direction of the fluid, the inner diameter of the nozzle (32) at the front end is smaller than the inner diameter of the nozzle (32) at the rear end.

9. The underground throttling device according to claim 8, characterized in that, When the materials of the anode mechanisms (4) are the same, along the flow direction of the fluid, the volume of the anode mechanism (4) at the front end is smaller than the volume of the anode mechanism (4) at the rear end; Or, when the volumes of the anode mechanisms (4) are the same, along the flow direction of the fluid, the standard electrode potential of the anode mechanism (4) at the front end is smaller than the standard electrode potential of the anode mechanism (4) at the rear end; Or, a control circuit is arranged on the thermoelectric power generation mechanism (1), and the control circuit can adjust the magnitude of the current I passing through the anode mechanism (4).

10. The underground throttling device according to claim 9, characterized in that, The thermoelectric power generation mechanism (1) is further provided with a rechargeable battery.

11. The underground throttling device according to any one of claims 1 to 7, characterized in that, An anode material layer is arranged outside the anode mechanism (4), and the standard electrode potential of the anode material layer is greater than the standard electrode potential of the anode mechanism (4).

12. The underground throttling device according to any one of claims 1 to 7, characterized in that, The thermoelectric power generation mechanism (1) includes a heat conduction layer and a thermoelectric power generation layer arranged outside the heat conduction layer, and the thermoelectric power generation layer contains semiconductor materials.

13. The underground throttling device according to claim 12, characterized in that, The thermoelectric power generation mechanism (1) further includes a protective layer arranged outside the thermoelectric power generation layer.

14. The underground throttling device according to any one of claims 1 to 7, characterized in that, A sand prevention mechanism (5) is arranged in the fluid inflow direction of the throttling mechanism.

15. The underground throttling device according to any one of claims 1 to 7, characterized in that, The cathodic protection mechanism (2) is a formed part made of high-silicon cast iron material.

16. The underground throttling device according to any one of claims 1 to 7, characterized in that, The downhole throttling device further includes a rubber barrel sealing mechanism (6), a slip anchoring mechanism (7) and a fishing head (8) which are sequentially connected to the thermoelectric power generation mechanism (1), and the rubber barrel sealing mechanism (6), the slip anchoring mechanism (7), the fishing head (8) and the thermoelectric power generation mechanism (1) are communicated with each other.

17. The underground throttling device according to claim 16, characterized in that, The slip anchoring mechanism (7) includes slips (71), an upper slip seat (72) and a lower slip seat (73), one end of the slips (71) is connected to the upper slip seat (72), and the other end is connected to the lower slip seat (73).

18. A control method for a downhole throttling device used in gas production throughout the entire life cycle of a gas well, characterized in that, The control method of the downhole throttling device includes the following steps: The fluid in the gas well enters the thermoelectric power generation mechanism (1) through the throttling mechanism to enable the thermoelectric power generation mechanism (1) to generate electricity. When the current I passing through the anode mechanism (4) is greater than or equal to the protection current I0 of the anode mechanism (4), the anode mechanism (4) is not corroded, and the fluid continues to enter the thermoelectric power generation mechanism (1) through the throttling mechanism; when the current I passing through the anode mechanism (4) is less than the protection current I0 of the anode mechanism (4), the anode mechanism (4) corrodes and fuses, and finally the fluid directly enters the thermoelectric power generation mechanism (1).

19. The control method according to claim 18, characterized in that, The throttling mechanism includes a plurality of throttling units (3) and the anode mechanism (4) correspondingly arranged for each throttling unit (3), and the plurality of throttling units (3) are connected in series; wherein, When the materials of the anode mechanisms (4) are the same, along the fluid flow direction, the volume of the anode mechanism (4) at the front end is smaller than the volume of the anode mechanism (4) at the rear end; Or, when the volumes of the anode mechanisms (4) are the same, along the fluid flow direction, the standard electrode potential of the anode mechanism (4) at the front end is smaller than the standard electrode potential of the anode mechanism (4) at the rear end; Or, a control circuit is arranged on the thermoelectric power generation mechanism (1), and the control circuit can adjust the magnitude of the current I passing through the anode mechanism (4); The fluid enters the thermoelectric power generation mechanism (1) through the plurality of throttling units (3) to enable the thermoelectric power generation mechanism (1) to generate electricity. When the current I passing through the first anode mechanism (4) is greater than or equal to the protection current I0 of this anode mechanism (4), this anode mechanism (4) is not corroded, and the fluid continues to enter the thermoelectric power generation mechanism (1) through the plurality of throttling units (3); when the current I of the first anode mechanism (4) is less than the protection current I0 of this anode mechanism (4), this anode mechanism (4) corrodes and fuses, and the fluid enters the thermoelectric power generation mechanism (1) through the remaining throttling units (3); when the current I passing through the second anode mechanism (4) is less than the protection current I0 of this anode mechanism (4), this anode mechanism (4) corrodes and fuses until all the anode mechanisms (4) are corroded and fused.

20. The control method according to claim 18 or 19, characterized in that, When it is necessary for the downhole throttling device to lose its throttling function in advance or the throttling mechanism becomes fouled and blocked, resulting in abnormal operation, after pumping chemicals into the downhole throttling device, close the gas well, and after the chemicals react and dissolve with the anode mechanism (4) or the scale, open the gas well for blowout and then carry out production.

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