Gas recovery well shaft natural gas hydrate removing device and method

Abstract

The invention provides a gas recovery well shaft natural gas hydrate removing device and method.The device comprises a pressure relief device used for relieving casing pressure to set conditions before hydrate removing operation is conducted, heat source equipment used for providing stable heating fluid, and an injection mechanism used for injecting the heating fluid into an oil pipe-casing annulus; comprising an injection pipeline and a pressure regulating device, and a return pipeline is connected with a tubing head gate and used for providing a return path for heating fluid to form fluid circulation. By adopting the device, the problems of long construction period, high risk of under-pressure operation and limited applicability in the prior art can be solved, the risk of under-pressure operation and high-pressure gas leakage in an oil pipe is avoided by taking the oil pipe and a casing annulus as an injection channel, and meanwhile, the device is suitable for the situation that foreign matters are blocked and occupied in the oil pipe; and the oil pipe sleeve structure does not need to be greatly modified, the operation principle is efficient and simple, and the construction cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of reliability test and evaluation, and particularly to a device and method for removing natural gas hydrates in a gas production wellbore. Background Art

[0002] In oil and gas field development operations, when the temperature in the wellbore is lower than the formation temperature of natural gas hydrates, hydrates are likely to form, causing ice blockage in the wellbore. Moreover, as the hydrogen sulfide content in the gas increases and the pressure in the wellbore rises, the formation temperature of hydrates will increase to 23 - 28°C. Therefore, when opening a gas well, due to the low temperature in the upper part of the wellbore or the low temperature caused by throttling tools such as downhole safety valves, hydrates are extremely likely to form inside the tubing string, resulting in wellbore blockage. In engineering applications, generally, in order to prevent corrosive gases from entering the annulus, a packer is set at the lower part of the tubing string to seal the tubing-casing annulus. Therefore, it is impossible to remove hydrates by heating with a surface water jacket furnace or squeezing hot water into the wellbore.

[0003] The prior art generally uses coiled tubing to inject steam or hot water into the tubing for heating to solve hydrate blockage. When applied, there are problems such as high operation cost, long cycle, the risk of sudden upward movement of coiled tubing due to sudden pressure release during the pressure-bearing operation, and if there are wire or tool blockages in the tubing, it is impossible to lower the coiled tubing for injection operation.

[0004] The information disclosed in the background art part of the present invention is only intended to deepen the understanding of the general background technology of the present invention, and should not be regarded as an admission or any form of implication that this information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0005] To solve the above problems, the present invention provides a device and method for removing natural gas hydrates in a gas production wellbore. The device includes a pressure relief device for relieving the casing pressure to a set condition before performing hydrate removal operations, a heat source device for providing a stable heating fluid, an injection mechanism for injecting the heating fluid into the tubing-casing annulus, including an injection pipeline and a pressure regulating device. In addition, a return pipeline is connected to the tubing head gate for providing a return path for the heating fluid to form a fluid circulation. This device can overcome the problems of long construction period, high risk of pressure-bearing operation, and limited applicability in the prior art. Using the tubing-casing annulus as the injection channel, it avoids the risks of pressure-bearing operation and leakage of high-pressure gas in the tubing. At the same time, it is applicable to the situation of foreign object blockage in the tubing and does not require major modification of the tubing-casing structure. The operation principle is efficient and concise, and the construction cost is low. Preferably, in one embodiment, the device includes: a pressure relief device, a heat source device, an injection mechanism, and a return pipeline;

[0006] The pressure relief device is used to relieve the casing pressure to the set conditions before the hydrate dissociation operation;

[0007] The heat source device is configured to generate a heating fluid, which is used to directly provide a fluid for circulation heating after the casing pressure meets the set requirements. The heating fluid includes hot water and steam;

[0008] The injection mechanism includes an injection pipeline and a pressure regulating device. One end of the injection pipeline is connected to the heat source device, and the other end is connected to the tubing-casing annulus for injecting the heating fluid into the tubing-casing annulus;

[0009] One end of the return pipeline is connected to the tubing head gate, and the other end is connected to the input side of the heat source device, which is used to provide a return path for the heating fluid to form a heating fluid circulation.

[0010] Further, in one embodiment, the device further includes an auxiliary injection mechanism, which adopts a tubing injection mechanism and is configured to continuously inject a dissolution-promoting substance into the tubing when the degree of hydrate dissolution reaches the set requirements. The dissolution-promoting substance adopts ethylene glycol or methanol.

[0011] Optionally, in one embodiment, the auxiliary injection mechanism includes a pressure detection device, which determines the degree of hydrate dissolution in the tubing by monitoring the pressure change in the tubing.

[0012] In a preferred embodiment, the heat source device is equipped with a temperature control device to control the temperature of the heating fluid at a stable value or range, providing a heating fluid with stable temperature.

[0013] In an alternative embodiment, the injection pipeline adopts a pipe material with high temperature resistance, and the pipe weight and hardness meet the set conditions, so that the pipeline can stably transport high-temperature fluid and reach the target position underground in the set direction.

[0014] Specifically, in an alternative embodiment, the injection pipeline is connected to the output end of the ground heat source system through a rotary table structure to achieve ground fixation, ensuring that the pipeline is fixed during the lowering process and during the pumping of the heating fluid and does not fall into the well.

[0015] Further, in one embodiment, the injection pipeline is connected to the side gate of the tubing-casing annulus, and the outer diameter of the pipeline of the injection pipeline is matched with the size of the side gate of the tubing-casing annulus.

[0016] Optionally, in one embodiment, the end of the injection pipeline connected to the tubing-casing annulus is provided with an injection head with double chamfers and is connected to the side gate of the tubing-casing annulus in a lowering form.

[0017] Preferably, in one embodiment, the pressure-bearing capacity of the injection pipeline is greater than or equal to the pressure-bearing degree required to overcome the friction during liquid injection and the liquid return.

[0018] Based on the application aspects of the device in any one or more of the above embodiments, the present invention further provides a method for removing natural gas hydrates in a gas production wellbore. This method is applied to the device in any one or more of the above embodiments, and the method includes:

[0019] When it is determined that there is a need to remove hydrates, first use the pressure relief device to relieve the casing pressure to the set conditions;

[0020] After the casing pressure meets the set requirements, start the heat source device to generate a stable heating fluid, and the heating fluid includes hot water and steam;

[0021] After the ground inspection of the injection pipeline is passed, remove the flat valve on the outer side of the casing pressure of one wing, lower the injection pipe of the injection mechanism into the tubing-casing annulus, so that the pipeline injection port is located below the well depth of the hydrate formation section, and connect the pipeline injection port with the side gate of the tubing-casing annulus in a lowering form;

[0022] Connect the return pipeline to the tubing head gate;

[0023] Start the heat source device, output the heating fluid, and use the pressure regulating device of the injection mechanism to control the fluid to be injected into the tubing-casing annulus at a set pressure;

[0024] During the injection of the heating fluid, use the pressure detection device of the auxiliary injection mechanism to monitor the pressure change of the tubing to determine the dissolution degree of the hydrates in the tubing;

[0025] If there are effective channels due to partial dissolution of the hydrates in the tubing, start the auxiliary injection mechanism to inject a dissolution-promoting substance into the tubing at the same time;

[0026] After the hydrates are fully dissolved, open the well for blowout and unblocking. During this period, continuously pump the heating fluid into the annulus, and perform blowout to determine the unblocking situation in the tubing;

[0027] After it is determined that the tubing is fully unblocked, restore the wellhead, stop pumping the heating fluid, remove the injection pipeline, push in the flat valve on the outer side of the casing pressure, and restore the casing pressure gate.

[0028] Compared with the closest prior art, the present invention also has the following beneficial effects:

[0029] A device and method for removing natural gas hydrates from the wellbore of a gas production well provided by the present invention. The device includes a pressure relief device for reducing the casing pressure to a set condition before the hydrate removal operation, a heat source device for providing a stable heating fluid, an injection mechanism for injecting the heating fluid into the tubing-casing annulus, including an injection pipeline and a pressure regulating device. In addition, a return pipeline is connected to the tubing head gate for providing a return path for the heating fluid to form a fluid circulation. By using this device, hot water or steam is pumped into the tubing-casing annulus of the wellbore where hydrate blockage occurs through the pipeline, so that the hot water or steam flows out from the tubing head gate to form a circulation. Due to the sealing of the lower packer, there is no risk of pressure operation and leakage of high-pressure gas in the tubing. At the same time, it is applicable to the situation where foreign objects are stuck and occupy positions in the tubing, with a wide range of applications, and does not require major modification of the tubing and casing structure. The operating principle is simple. By using hot water or steam to form a heating fluid circulation, a large amount of heat can be quickly transferred, the operation efficiency is high, and at the same time, the risk of falling objects in the wellbore can be effectively controlled and reduced. In addition, the selection of conventional materials and the high-efficiency heat transfer make the overall operation cost controlled at a low level.

[0030] Other features and advantages of the present invention will be described in the following specification, and in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained by the structures specifically pointed out in the specification, claims, and drawings. Brief Description of the Drawings

[0031] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0032] Figure 1 is a schematic structural diagram of a device for removing natural gas hydrates from the wellbore of a gas production well provided by an embodiment of the present invention;

[0033] Figure 2 is a schematic flow diagram of a method for removing natural gas hydrates from the wellbore of a gas production well provided by another embodiment of the present invention. Detailed Description of the Embodiments

[0034] The following will describe the embodiments of the present invention in detail with reference to the drawings and embodiments. Through this, the implementers of the present invention can fully understand how to apply technical means to solve technical problems and achieve the process of technical effects, and specifically implement the present invention based on the above implementation process. It should be noted that as long as there is no conflict, the various embodiments in the present invention and the various features of each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.

[0035] Although the flowchart depicts the operations as sequential processes, many of the operations can be implemented in parallel, concurrently, or simultaneously. The order of the operations can be rearranged. The process can be terminated when its operations are completed, but it can also have additional steps not included in the figures. The process can correspond to a method, function, procedure, subroutine, subprogram, and so on.

[0036] Computer devices include user devices and network devices. Among them, user devices or clients include, but are not limited to, computers, smartphones, PDAs (Personal Digital Assistants), etc.; network devices include, but are not limited to, a single network server, a server group composed of multiple network servers, or a cloud composed of a large number of computers or network servers based on cloud computing. The computer device can operate alone to implement the present invention, or can be connected to a network and implement the present invention through interactive operations with other computer devices in the network. The network where the computer device is located includes, but is not limited to, the Internet, wide area network, metropolitan area network, local area network, VPN network, etc.

[0037] Here, terms such as "first", "second", etc. may be used to describe various units, but these units should not be limited by these terms. These terms are only used to distinguish one unit from another. The term "and / or" used here includes any and all combinations of one or more of the listed associated items. When a unit is referred to as "connected" or "coupled" to another unit, it can be directly connected or coupled to the other unit, or there may be an intermediate unit.

[0038] The terms used here are only for describing specific embodiments and are not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "a", "an" used here are also intended to include the plural. It should also be understood that the terms "include" and / or "comprise" used here specify the presence of the stated features, integers, steps, operations, units, and / or components, and do not exclude the presence or addition of one or more other features, integers, steps, operations, units, components, and / or their combinations.

[0039] In oil and gas field development operations, when the temperature in the wellbore is lower than the formation temperature of natural gas hydrates, hydrates are likely to form, causing ice plugs in the wellbore. Moreover, as the hydrogen sulfide content in the gas increases and the pressure in the wellbore rises, the formation temperature of hydrates will increase to 23 - 28 °C. Therefore, when opening a gas well, due to the low temperature in the upper wellbore or the low temperature caused by throttling tools such as downhole safety valves, hydrates are extremely likely to form inside the pipe string, resulting in wellbore blockage.

[0040] Generally, in order to prevent corrosive gases from entering the annulus, a packer is set at the lower part of the tubing string to seal the tubing-casing annulus. Therefore, it is impossible to use a surface water jacket furnace for heating or squeeze hot water into the wellbore to remove hydrates. Based on this, the existing technology generally uses coiled tubing to inject steam or hot water into the tubing for heating to solve the hydrate blockage. When applied, there are problems such as high operation cost, long cycle, and the risk of sudden upward movement of the coiled tubing due to sudden pressure release during the pressure-bearing operation. Moreover, if there are steel wires or tool blockages in the tubing, it is impossible to lower the coiled tubing for injection operation.

[0041] In view of the above problems existing in the prior art, the present invention proposes a method for removing natural gas hydrates in the wellbore of a gas production well, which can overcome the problems of high cost and long cycle of traditional operation methods. Specifically, an injection device is used to pump hot water or steam into the tubing-casing annulus of the wellbore where hydrate blockage occurs through a pipeline, so that the hot water or steam flows out from the tubing head gate to form a circulation. The circulating hot water or steam transfers heat to the inside of the tubing, dissolving the hydrates in the tubing and removing the tubing blockage. In the present invention, the tubing-casing annulus is used as the injection channel. Due to the sealing of the lower packer, the risk of pressure-bearing operation and leakage of high-pressure gas in the tubing is avoided, and the problem that it is impossible to lower the coiled tubing for injection operation if there are steel wires and tool blockages in the tubing can also be solved.

[0042] Next, the structural components, connection methods, and functional principles of the system according to the embodiments of the present invention will be described in detail based on the accompanying drawings. Although the logical sequence of each operation is shown in the process of describing the operating principle of the system structure, in some cases, the operations shown or described may be executed in a different order than here.

[0043] Embodiment 1

[0044] Figure 1 Fig. shows the structural schematic diagram of the device for removing natural gas hydrates in the wellbore of a gas production well provided by Embodiment 1 of the present invention. Referring to Figure 1 it can be seen that the device includes: a pressure relief device, a heat source device, an injection mechanism, and a return pipeline;

[0045] The pressure relief device is used to relieve the casing pressure to a set condition before performing the hydrate removal operation;

[0046] The heat source device is configured to generate a heating fluid, which is used to directly provide the fluid for circulating heating after the casing pressure meets the set requirements. The heating fluid includes hot water and steam;

[0047] The injection mechanism includes an injection pipeline and a pressure regulating device. One end of the injection pipeline is connected to the heat source device, and the other end is connected to the tubing-casing annulus, and is used to inject the heating fluid into the tubing-casing annulus;

[0048] One end of the return pipeline is connected to the tubing head gate, and the other end is connected to the input side of the heat source device, which is used to provide a return path for the heating fluid to form a heating fluid cycle.

[0049] The device for removing hydrate blockage in the production wellbore provided by the embodiment of the present invention pumps hot water or steam into the tubing-casing annulus of the wellbore where hydrate blockage occurs through a pipeline by an injection mechanism, and then flows out from the tubing head gate to form a cycle. The circulating hot water or steam transfers heat to the inside of the tubing, dissolving the hydrate in the tubing and removing the tubing blockage.

[0050] Preferably, in one embodiment, the heat source device is configured with a temperature control device to control the temperature of the heating fluid at a stable value or range, providing heating fluid with stable temperature.

[0051] In practical applications, hot water or steam is injected through the injection mechanism to ensure sufficient heat transfer and provide pressure to ensure that the fluid returns after entering the pipeline. The injection pipeline is temperature-resistant and can meet the injection of hot water or steam.

[0052] Therefore, in one embodiment, the injection pipeline is made of high-temperature-resistant material to enable the pipeline to stably transport high-temperature fluid.

[0053] In a preferred embodiment, the pipe material of the injection pipeline has a weight and hardness that meet the set conditions, that is, the pipeline has a certain weight and hardness and can be lowered between the tubing and casing in the well, facilitating the lowering to the target position in the well according to the set direction. In practical applications, the injection pipeline can be selected to use a metal hose in oil / gas well operations, etc.

[0054] In an optional embodiment, the pressure regulating equipment of the injection mechanism can use a pump truck, such as a conventional oil / gas engineering pump truck or a pressure test pump.

[0055] Based on this, in an optional embodiment of the present invention, a pump truck is used to pump hot water into the tubing-casing annulus of the wellbore where hydrate blockage occurs through a metal hose. The hot water then flows out from the tubing head gate to form a cycle. The circulating hot water transfers heat to the inside of the tubing, dissolving the hydrate and removing the blockage.

[0056] Considering that during the process of lowering the well and pumping the heating fluid, the injection pipeline is inevitably affected by large external forces and there is a risk of large-scale movement or falling into the well. Therefore, the injection process of the embodiment of the present invention is designed with a turntable structure to realize the storage, pipe laying and ground fixing of the injection pipeline, ensuring that the pipeline is fixed during the lowering period and during the pumping of hot water and does not fall into the well. That is, in one embodiment, the injection pipeline is connected to the output end of the ground heat source system through the turntable structure to achieve ground fixing and ensure that the pipeline is fixed and does not fall into the well during the lowering period and during the pumping of the heating fluid.

[0057] Furthermore, in an optional embodiment, the injection pipeline is connected to the wing gate of the tubing-casing annulus, and the outer diameter of the injection pipeline is matched with the size of the wing gate of the tubing-casing to ensure that the outer diameter of the pipeline can meet the requirements of the lowering of the wing gate.

[0058] Specifically, in a preferred embodiment, the end of the injection pipeline connected to the tubing-casing annulus is provided with an injection head with a two-way chamfer, and is connected to the side gate of the tubing-casing annulus in a lowering manner; the two-way chamfering is adopted to facilitate the lowering between the tubing and casing in the well.

[0059] In actual application, the pipeline can withstand pressure and meet the pressure-bearing capacity required to overcome frictional resistance and liquid return during liquid injection; therefore, in a preferred embodiment, the pressure-bearing capacity of the injection pipeline is greater than or equal to the pressure-bearing capacity required to overcome frictional resistance and liquid return during the liquid injection process.

[0060] In an optional embodiment, in order to improve the tensile strength and pressure bearing capacity of the injection pipeline, a metal hose with a plastic tube inside and steel wire wrapped outside can be used as the injection pipeline according to needs and engineering conditions.

[0061] One end of the return pipeline is connected to the oil pipe head gate, and the other end of the return pipeline is connected to the input side of the heat source equipment, which is used to provide a return path for the heating fluid to form a heating fluid circulation. The returned fluid or steam directly returns to the square well through the oil pipe head gate;

[0062] In a preferred embodiment, a pressure regulating device, such as a booster pump, is provided on the return pipeline, and the return fluid is pumped into a storage tank of a heat source device by the booster pump for recycling and reuse; because it is clean water, there is no need to consider environmental protection, and it can also provide materials for the circulation to provide heating fluid.

[0063] In an optional embodiment, the return pipeline is made of the same material as the injection pipeline, and the size of the return pipeline interface is matched with the size of the tubing head gate.

[0064] Preferably, in one embodiment, the device further comprises an auxiliary injection mechanism, which adopts an oil pipe injection mechanism and is configured to ensure that when the degree of hydrate dissolution reaches the set requirements, after there is an effective channel in the oil pipe, a dissolution-promoting substance is continuously injected into the oil pipe, and the dissolution-promoting substance adopts ethylene glycol or methanol.

[0065] In an optional embodiment, the auxiliary injection mechanism includes a pressure detection device, which determines the degree of hydrate dissolution in the oil pipe by monitoring the pressure change of the oil pipe.

[0066] During the implementation process, considering that after partial dissolution of hydrates in the oil pipe during cyclic hot water, it may cause solid substances in the well to impact upward under pressure and damage the wellhead; in order to avoid the upward impact of solid substances in the well under pressure after partial dissolution of hydrates in the oil pipe, the embodiment of the present invention is also provided with a backpressure valve, designed to connect the upper oil pressure to a pump truck to apply backpressure, and the pump truck is configured with a backpressure valve to connect to the oil pressure end to apply backpressure, so that the pressures above and below the blockage point are the same to avoid impact; after the backpressure meets the requirements, close the gate valve at the oil pipe end to maintain the pressure.

[0067] In addition, use the set pressure monitoring equipment to monitor the pressure change at the oil pipe end, such as a pressure gauge. When there is a pressure change and it is judged that there is a channel in the well, continuously inject ethylene glycol or methanol that can dissolve hydrates. While avoiding the upward impact of solid substances in the well under pressure, it accelerates the dissolution of hydrates in the oil pipe and improves the plug removal efficiency.

[0068] Using the natural gas hydrate removal device for the gas production wellbore provided by the present invention, common materials are used, and construction preparation is convenient; using hot water or steam circulation can transfer a large amount of heat, with high operation efficiency and fast time; using annulus injection reduces the risk of falling objects in the wellbore; and the selection of conventional materials and efficient heat transfer keep the overall operation cost at a relatively low level.

[0069] In actual application, taking hot water as the heating fluid as an example, the natural gas hydrate removal device for the gas production wellbore based on the embodiment of the present invention realizes the overall hydrate dissolution and oil pipe plug removal functions according to the following logic:

[0070] (1) Release the casing pressure. Use the pressure relief process device to release the casing pressure to 0 MPa; then monitor or observe to ensure that there is no gas leakage in the annulus.

[0071] (2) Remove the flat valve on the outside of the casing pressure on one wing. In order to facilitate the lowering of the pipeline, remove the flat valve on the outside of the casing pressure on one wing.

[0072] (3) Lower the pipeline into the annulus. After the annulus heating pipeline is verified to be unobstructed on the ground, lower the pipeline into the annulus to below the well depth where hydrates are formed. Lift and lower the pipeline every 5 - 8 m to prevent the pipeline from being stuck and twisted.

[0073] (4) Pump hot water into the annulus. After the pipeline is connected to the injection equipment, continuously pump hot water into the annulus; for the oil pipe, use an auxiliary injection equipment to pump ethylene glycol or methanol that can dissolve hydrates from the oil pressure into the well.

[0074] (5) Dissolve hydrates. Shut in the well, wait for the ethylene glycol or methanol that can dissolve hydrates injected into the oil pipe to heat up, and fully dissolve the hydrates.

[0075] (6) Open the well for blowout and plug removal. During the well opening period, keep continuously pumping hot water into the annulus, blow out, and determine that the plug in the oil pipe has been removed.

[0076] (7) Restore the wellhead. After successful plug removal, stop pumping hot water, immediately pull out the annulus heating pipeline or cut the stuck annulus heating pipeline, push it into the annulus of the casing pressure and then close the flat valve outside the casing pressure; immediately restore the casing pressure gate.

[0077] In the natural gas hydrate removal device for the gas production wellbore provided by the embodiment of the present invention, each module or unit structure can operate independently or in combination according to actual parameter acquisition requirements or real-time control requirements to achieve corresponding technical effects.

[0078] Embodiment 2:

[0079] In the above embodiments disclosed by the present invention, the system is described in detail. Based on other aspects of the system described in any one or more of the above embodiments, the present invention also provides a method for removing natural gas hydrates from a gas production wellbore, and this method is applied to the natural gas hydrate removal system described in any one or more of the above embodiments. Specific embodiments are given below for detailed description.

[0080] Specifically, Figure 2 The flow schematic diagram of the method for removing natural gas hydrates from a gas production wellbore provided by the embodiment of the present invention is shown. This method uses the natural gas hydrate removal device described in the above embodiment to implement each operation, such as Figure 2 As shown, this method includes:

[0081] When it is determined that there is a need to remove hydrates, first use the pressure relief device to relieve the casing pressure to the set conditions;

[0082] After the casing pressure meets the set requirements, start the heat source device to generate stable heating fluid, and the heating fluid includes hot water and steam;

[0083] After the ground of the injection pipeline is verified to be unblocked, remove the flat valve outside one wing of the casing pressure, lower the injection pipe of the injection mechanism into the tubing-casing annulus, make the pipeline injection port located below the well depth of the hydrate formation section, and connect the pipeline injection port with the wing gate of the tubing-casing annulus in a lowering form;

[0084] Connect the return pipeline to the tubing head gate;

[0085] Start the heat source device, output the heating fluid, and use the pressure regulating device of the injection mechanism to control the fluid to be injected into the tubing-casing annulus at a set pressure;

[0086] During the injection of the heating fluid, use the pressure detection device of the auxiliary injection mechanism to monitor the pressure change of the tubing to determine the dissolution degree of the hydrates in the tubing;

[0087] If there are effective channels due to partial dissolution of the hydrates in the tubing, simultaneously start the auxiliary injection mechanism to inject dissolution-promoting substances into the tubing;

[0088] After the hydrate is fully dissolved, open the well for blowout and unplugging. During this period, continuously pump the heating fluid into the annulus to keep the blowout and determine the unplugging situation in the tubing.

[0089] After determining that the tubing is fully unplugged, restore the wellhead, stop pumping the heating fluid, remove the injection pipeline, push in the flat valve outside the casing pressure, and restore the casing pressure gate.

[0090] The method of the embodiment of the present invention uses an injection device to pump hot water or steam through a pipeline into the tubing-casing annulus in the wellbore blocked by hydrates, and then flows out from the tubing head gate to form a cycle. The circulating hot water or steam transfers heat to the inside of the tubing, dissolving the hydrates in the tubing and removing the tubing blockage.

[0091] Among them, the natural gas hydrate removal device for the production wellbore includes: a pressure relief device, a heat source device, an injection mechanism, and a return pipeline;

[0092] The pressure relief device is used to relieve the casing pressure to the set condition before the hydrate removal operation;

[0093] The heat source device is configured to generate a heating fluid, which is used to directly provide the fluid for circulating heating after the casing pressure meets the set requirements. The heating fluid includes hot water and steam;

[0094] The injection mechanism includes an injection pipeline and a pressure regulating device. One end of the injection pipeline is connected to the heat source device, and the other end is connected to the tubing-casing annulus for injecting the heating fluid into the tubing-casing annulus;

[0095] One end of the return pipeline is connected to the tubing head gate, and the other end is connected to the input side of the heat source device, which is used to provide a return path for the heating fluid to form a heating fluid cycle.

[0096] Further, in a preferred embodiment, the device further includes an auxiliary injection mechanism, which adopts a tubing injection mechanism and is configured to continuously inject a dissolution-promoting substance into the tubing when the dissolution degree of the hydrate reaches the set requirement. The dissolution-promoting substance adopts ethylene glycol or methanol.

[0097] Optionally, the auxiliary injection mechanism includes a pressure detection device, which determines the dissolution degree of the hydrates in the tubing by monitoring the pressure change in the tubing.

[0098] Optionally, in one embodiment, the heat source device is equipped with a temperature control device to control the temperature of the heating fluid at a stable value or range and provide a heating fluid with stable temperature.

[0099] In actual application, in one embodiment, the injection pipeline uses a high temperature resistant pipe whose weight and hardness meet the set conditions, so that the pipeline can stably transmit high temperature fluid and go down to the target position underground in the set direction.

[0100] Specifically, in an optional embodiment, the injection pipeline is connected to the output end of the ground heat source system through a turntable structure to achieve ground fixation, thereby ensuring that the pipeline is fixed during the lowering and pumping of the heating fluid and does not fall into the well.

[0101] Furthermore, in one embodiment, the injection pipeline is connected to the wing gate of the tubing-casing annulus, and the outer diameter of the injection pipeline is matched with the size of the wing gate of the tubing-casing annulus.

[0102] In a preferred embodiment, the end of the injection pipeline connected to the tubing-casing annulus is provided with an injection head with a bidirectional chamfer, and is connected to the wing gate of the tubing-casing annulus in a lowered manner.

[0103] In addition, in one embodiment, the pressure bearing capacity of the injection pipeline is greater than or equal to the pressure bearing level required for overcoming friction during the liquid injection process and for liquid return.

[0104] Preferably, in actual application, the embodiment of the present invention uses a pump truck to pump hot water into the tubing-casing annulus in the wellbore where hydrate blockage occurs through a metal hose, and the hot water then flows out from the tubing head gate to form a circulation. The circulating hot water transfers heat to the tubing, dissolving the hydrate and removing the blockage.

[0105] The method for removing natural gas hydrate from the wellbore of a gas production well of the present invention is simple to operate and can be realized by using common on-site facilities and equipment. It can effectively transfer the heat required for removing ice blockage, thereby greatly shortening the time and operating cost for removing hydrate blockage, and will not cause the risk of falling objects inside the oil pipe string.

[0106] For the above-mentioned method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present invention.

[0107] It should be pointed out that in other embodiments of the present invention, the method can also obtain a new method for removing natural gas hydrates in the wellbore of a gas production well by combining one or several of the above embodiments, so as to achieve efficient and reliable removal of natural gas hydrates.

[0108] It should be noted that, based on the method in any one or more of the above embodiments of the present invention, the present invention further provides a storage medium, on which program codes capable of implementing the method described in any one or more of the above embodiments are stored. When the codes are executed by an operating system, the gas production wellbore natural gas hydrate removal method as described above can be implemented.

[0109] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are for the purpose of describing specific embodiments only and do not imply limitation.

[0110] The phrase "an embodiment" mentioned in the specification means that the specific feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Therefore, the phrase "an embodiment" that appears throughout the specification does not necessarily refer to the same embodiment.

[0111] Although the disclosed embodiments of the present invention are as above, the content described is only an embodiment adopted for the convenience of understanding the present invention and is not used to limit the present invention. Any person skilled in the technical field to which the present invention pertains can make any modifications and changes in the form of implementation and details without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A natural gas hydrate removal device for a gas production wellbore, characterized in that, the device comprises: a pressure relief device, a heat source device, an injection mechanism and a return pipeline; the pressure relief device is used to relieve the casing pressure to a set condition before the hydrate removal operation; the heat source device is configured to generate a heating fluid, which is used to directly provide a fluid for circulating heating after the casing pressure meets the set requirements, and the heating fluid includes hot water and steam; the injection mechanism includes an injection pipeline and a pressure regulating device. One end of the injection pipeline is connected to the heat source device, and the other end is connected to the tubing-casing annulus for injecting the heating fluid into the tubing-casing annulus; one end of the return pipeline is connected to the tubing head gate, and the other end is connected to the input side of the heat source device, which is used to provide a return path for the heating fluid to form a heating fluid circulation.

2. The device according to claim 1, characterized in that, the device further includes an auxiliary injection mechanism, which adopts a tubing injection mechanism and is configured to continuously inject a dissolution-promoting substance into the tubing when the dissolution degree of the hydrate reaches the set requirement, and the dissolution-promoting substance adopts ethylene glycol or methanol.

3. The device according to claim 2, characterized in that, the auxiliary injection mechanism includes a pressure detection device, which determines the dissolution degree of the hydrate in the tubing by monitoring the pressure change in the tubing.

4. The device according to claim 1, characterized in that, the heat source device is equipped with a temperature control device to control the temperature of the heating fluid at a stable value or range, and provide a heating fluid with stable temperature.

5. The device according to claim 1, characterized in that, the injection pipeline adopts a pipe material that is resistant to high temperature and whose pipe weight and hardness meet the set conditions, so that the pipeline can stably transport high-temperature fluid and reach the target position underground in the set direction.

6. The device according to claim 1, characterized in that, the injection pipeline is connected to the output end of the ground heat source system through a rotary table structure to achieve ground fixation, ensuring that the pipeline is fixed during the lowering process and during the pumping of the heating fluid, and does not fall into the well.

7. The device according to claim 1, characterized in that, the injection pipeline is connected to the side gate of the tubing-casing annulus, and the outer diameter of the pipeline of the injection pipeline is matched with the size of the side gate of the tubing-casing.

8. The device according to claim 1, characterized in that, the end of the injection pipeline connected to the tubing-casing annulus is provided with an injection head with a double chamfer, and is connected to the side gate of the tubing-casing annulus in a lowering form.

9. The device according to claim 1, characterized in that, the pressure bearing capacity of the injection pipeline is greater than or equal to the pressure bearing degree required to overcome the friction during the liquid injection process and the liquid return.

10. A method for removing natural gas hydrates from a gas production wellbore, characterized in that, the method is applied to the device according to any one of claims 1 to 9, and the method includes: when it is determined that there is a need to remove hydrates, first use the pressure relief device to relieve the casing pressure to the set condition; after the casing pressure meets the set requirements, start the heat source device to generate a stable heating fluid, and the heating fluid includes hot water and steam; After the surface inspection of the injection pipeline is passed, remove the flat valve on the outside of the casing pressure of one wing, lower the injection pipeline of the injection mechanism into the annulus between the tubing and the casing, so that the injection port of the pipeline is located below the well depth of the hydrate formation section, and connect the injection port of the pipeline with the wing gate of the annulus between the tubing and the casing in a lowered form; Connect the return pipeline to the gate valve of the tubing port; Start the heat source equipment to output the heating fluid, and use the pressure regulating device of the injection mechanism to control the fluid to be injected into the annulus between the tubing and the casing at the set pressure; During the injection of the heating fluid, use the pressure detection device of the auxiliary injection mechanism to monitor the pressure change of the tubing to determine the dissolution degree of the hydrate in the tubing; If there is an effective channel due to partial dissolution of the hydrate in the tubing, start the auxiliary injection mechanism to inject the dissolution-promoting substance into the tubing at the same time; After the hydrate is fully dissolved, open the well for blowout and unblocking. During this period, continuously pump and inject the heating fluid in the annulus, and blow out to determine the unblocking situation in the tubing; After determining that the tubing is fully unblocked, restore the wellhead, stop pumping and injecting the heating fluid, pull out the injection pipeline, push in the flat valve outside the casing pressure, and restore the casing pressure gate.

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