Natural gas hydrate control system and method and natural gas well

Abstract

The invention relates to the technical field of gas well natural gas hydrate prevention and control, in particular to a natural gas hydrate prevention and control system and method and a natural gas well. The natural gas hydrate prevention and control system comprises two flow meters, a tubular catalytic heater, an electric control valve, an emergency cut-off valve, a power supply device and a control device; production natural gas of a wellhead pipeline is heated, a gas well wellhead valve and the pipeline are prevented from being blocked, the pressure of the pipeline is ensured to be within a required pressure range, and the pressure of the pipeline is protected from being abnormal. The self energy of the natural gas is used as input energy, open fire operation is avoided by adopting a catalytic combustion technology, the heat exchange amount of the tubular heat exchanger is improved, the natural gas pipeline is prevented from being frozen and blocked, and the anti-freezing effect reaches 100%. Compared with a traditional natural gas anti-freezing and anti-blocking method, the method has the advantages of being small in occupied area, free of open fire operation and low in production cost. The problems of high energy consumption, high cost and poor control effect in the natural gas hydrate control process in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas hydrate prevention and control in gas wells, specifically to a natural gas hydrate prevention and control system, method and natural gas well, especially to a natural gas hydrate prevention and control system, method and natural gas well under high-pressure throttling state of the gas well. Background Art

[0002] Winter is the season when the natural gas supply and demand relationship in the north and some southern regions is the most tense. The freezing and blocking of pipelines caused by the freezing of natural gas hydrates is the core factor affecting the stable production of natural gas in winter. Gas wells generally have the problem of rapid drop in natural gas temperature due to throttling of wellhead valves during well opening or factors such as winter environment and low temperature, which leads to the formation of natural gas hydrates. The formation of hydrates in the wellhead valves and pipelines of gas wells will cause local blockage, reduce the flow area of ​​the gas pipeline, cause throttling, increase the pressure difference of the pipeline, and accelerate the further formation of hydrates. When hydrates continue to gather and grow, they will cause blockage of pipelines, valves and equipment, damage to pipe fittings, and affect the normal production of natural gas. In particular, in the low temperature environment of winter, oil pipes, gas trees and gas gathering pipelines are more susceptible to hydrate blockage in water-producing gas wells, which may cause pipeline blockage, pipe burst and other accidents in severe cases. When hydrates decompose, the hydrate segment can be quickly accelerated to the speed of sound under a certain pressure difference, causing huge force. The moving hydrates can cause serious damage to downstream equipment, such as control valves and ball seats with sharp changes in direction. Therefore, freezing and blockage of gas wellheads, valves and natural gas pipelines are the main bottlenecks for maintaining the quantity and increasing the efficiency of natural gas production.

[0003] At present, in order to effectively prevent the formation of natural gas hydrates and solve the problem of hydrate freezing and blockage of on-site gas well pipelines, when hydrate blockage occurs, gas fields generally adopt two methods. One is to frequently unblock and vent, which causes a large waste of natural gas resources and poses safety and environmental risks; the other is to add methanol, which is expensive and cannot guarantee that the filling position can effectively act on hydrates. It still cannot effectively solve the problem of hydrate freezing and blockage of gas wellheads, valves and natural gas pipelines.

[0004] Therefore, there is an urgent need for a safe, energy-saving and effective method to solve the problem of hydrate freezing and blockage in natural gas pipelines, so as to promote the production of natural gas and increase its efficiency. Summary of the invention

[0005] In view of the problems of high energy consumption, high cost and poor prevention effect in the natural gas hydrate prevention and control process in the prior art, the present invention provides a natural gas hydrate prevention and control system, method and natural gas well.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a natural gas hydrate prevention and control system, comprising a shell-and-tube catalytic heater, an electric regulating valve, an emergency shut-off valve, a power supply device and a control device; the produced natural gas in the wellhead pipeline enters the gas supply pipeline in sequence through the shell-and-tube catalytic heater, the electric regulating valve and the emergency shut-off valve; the shell-and-tube catalytic heater, the electric regulating valve and the emergency shut-off valve are all electrically connected or communication-connected with the control device; the shell-and-tube catalytic heater, the electric regulating valve, the emergency shut-off valve and the control device are all electrically connected with the power supply device.

[0008] Preferably, a first flow meter is provided on the pipeline connecting the shell-and-tube catalytic heater to the wellhead, the first flow meter is electrically connected to the power supply device, and the first flow meter is electrically connected or communicatively connected to the control device.

[0009] Preferably, a second flow meter is provided on the pipeline between the shell-and-tube catalytic heater and the electric regulating valve, the second flow meter is electrically connected to the power supply device, and the second flow meter is electrically connected or communicatively connected to the control device.

[0010] Preferably, temperature probes are provided in both the first flow meter and the second flow meter.

[0011] Preferably, a starting gas source interface is provided on the shell-and-tube catalytic heater, and the starting gas source interface is connected to the gas well casing.

[0012] Preferably, the power supply device is a solar cell group.

[0013] The natural gas hydrate prevention and control method using the natural gas hydrate prevention and control system comprises the following steps:

[0014] Step 1: Pass the starting gas source into the tubular catalytic heater through the starting gas source interface;

[0015] Step 2: preheating the tubular catalytic heater to which the starting gas source is introduced, and when the preheating temperature reaches the starting temperature, starting the tubular catalytic heater and cutting off the preheating power supply;

[0016] Step 3: After the shell-and-tube catalytic heater is started, the shell-and-tube catalytic heater is made to produce flameless combustion, release heat energy to the outside, and continuously and stably heat the produced natural gas in the wellhead pipeline;

[0017] Step 4: The heated production natural gas is passed through the electric regulating valve and the emergency shut-off valve in sequence to throttle the produced natural gas.

[0018] Preferably, the preheating temperature for preheating the shell-and-tube catalytic heater is 160°C to 200°C.

[0019] Preferably, the heating temperature of the produced natural gas in the wellhead pipeline by the shell-and-tube catalytic heater is 300°C to 550°C.

[0020] A natural gas well comprises the natural gas hydrate prevention and control system.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention discloses a natural gas hydrate prevention and control system. The system realizes heating of the production natural gas of the wellhead pipeline by setting a shell-and-tube catalytic heater to prevent the formation of hydrates due to the decrease of the wellhead natural gas temperature, thereby avoiding the blockage of the gas wellhead valve and pipeline affecting the production of natural gas. The shell-and-tube catalytic heater cooperates with the setting of the electric regulating valve to ensure that the pipeline pressure is always within the set pressure range during the well opening process; the setting of the emergency shut-off valve plays the function of abnormal pipeline pressure protection to avoid the downstream pipeline and equipment from being damaged by high pressure; the setting of the power supply device and the control device realizes the power supply and integrated control and monitoring of the system, and improves the operability and safety and stability of the system. The system does not need to unblock and vent the pipeline, which not only avoids a large amount of natural gas waste but also ensures production safety, and does not need to add additional substances such as methanol. It can effectively prevent and control hydrates at the gas wellhead, valve and natural gas pipeline. The device is simple and the transformation cost is low, which provides guarantee for the production of natural gas to ensure quantity and increase efficiency.

[0023] The first flow meter and the second flow meter are provided to record the instantaneous flow and the accumulated flow of the natural gas at both ends of the shell-and-tube catalytic heater.

[0024] The first flow meter and the second flow meter are provided with temperature probes, which can monitor the temperature of the inlet and outlet of the shell-and-tube catalytic heater.

[0025] The shell-and-tube catalytic heater uses natural gas as the starting gas source and utilizes clean and efficient natural gas combustion technology. It generates carbon dioxide and water through an oxidation reaction between natural gas and air, thereby achieving flameless combustion while releasing heat energy. It will not have any impact on the human body and the environment, and is safer, energy-saving, and efficient.

[0026] The system uses a solar cell group as the power supply device of the system, further improving the safety, environmental protection and energy saving of the system.

[0027] The present invention also provides a method for preventing and controlling natural gas hydrates using the above-mentioned natural gas hydrate prevention and control system. The method first preheats the shell-and-tube catalytic heater, and then uses the shell-and-tube catalytic heater to stably heat the production natural gas of the wellhead pipeline to prevent the production of hydrates from blocking the pipeline and valves, and finally realizes the throttling production of natural gas through electric regulating valves and emergency shut-off valves. The method adopts the method of catalytic combustion technology to avoid open flame operation, improve the heat exchange capacity of the shell-and-tube heat exchanger, and prevent the freezing of the natural gas pipeline. Compared with the traditional natural gas anti-freezing method, it realizes local materials, small footprint, no-name fire operation, low production cost, and easy to realize unmanned operation, reducing operation and maintenance costs.

[0028] The present invention also provides a natural gas well, comprising the natural gas hydrate prevention and control system, which can ensure the quantity and improve the efficiency of natural gas production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of a natural gas hydrate prevention and control system of the present invention.

[0030] Figure 2 The present invention is a flow chart of a natural gas hydrate prevention and control system method.

[0031] Among them, 1-first flow meter, 2-tube catalytic heater, 3-second flow meter, 4-electric regulating valve, 5-emergency shut-off valve, 6-power supply device, 7-control device, 8-production natural gas, 9-starting gas source interface. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0035] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0036] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0037] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" 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 mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0038] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0039] The present invention discloses a natural gas hydrate prevention and control system, referring to Figure 1 , including a first flow meter 1, a second flow meter 3, a shell-and-tube catalytic heater 2, an electric regulating valve 4, an emergency shut-off valve 5, a power supply device 6 and a control device 7; the production natural gas 8 of the wellhead pipeline enters the gas supply pipeline in sequence through the first flow meter 1, the shell-and-tube catalytic heater 2, the second flow meter 3, the electric regulating valve 4 and the emergency shut-off valve 5; the first flow meter 1, the shell-and-tube catalytic heater 2, the second flow meter 3, the electric regulating valve 4 and the emergency shut-off valve 5 are all electrically connected or communication-connected with the control device 7; the shell-and-tube first flow meter 1, the catalytic heater 2, the second flow meter 3, the electric regulating valve 4, the emergency shut-off valve 5, and the control device 7 are all electrically connected with the power supply device 6; the first flow meter 1 and the second flow meter 3 are both provided with temperature probes; the starting gas source interface 9 of the shell-and-tube catalytic heater 2 is connected to the gas well casing, and natural gas is used as the starting gas source of the shell-and-tube catalytic heater 2.

[0040] Preferably, the power supply device 6 is a solar cell group; the shell-and-tube catalytic heater 2 mainly performs catalytic heating of natural gas on the pipeline, using natural gas for flameless combustion, and the catalytic heating temperature is between 200°C and 550°C. Different types of shell-and-tube catalytic heaters are matched according to the different production of natural gas wells. As the preferred shell-and-tube catalytic heater of the present invention, 300×300mm~900×900mm is selected, which is suitable for gas wells with a production of 0 to 100,000 cubic meters / day. Since the natural gas wellhead is far away from the operating area, the daily maintenance workload of the natural gas well is very large, and it is difficult to meet the requirements of rapid response, especially in winter, when the weather and road environment are bad, it is not easy to carry out on-site operations. In order to meet the needs of on-site production, the shell-and-tube catalytic heater 2 adopts 4G communication mode, MOUBUS communication protocol, and RS485 communication interface, which can remotely collect the supporting operation data of the heating technology, set the high and low temperature protection pressure of the heating technology supporting heating, and remotely control the action function of the solenoid valve 4 to achieve remote start and stop.

[0041] See also Figure 2 The method for preventing and controlling natural gas hydrates using the natural gas hydrate prevention and control system comprises the following steps:

[0042] Step 1: passing the starting gas source into the tubular catalytic heater 2 through the starting gas source interface 9, specifically: reducing the pressure of the natural gas in the gas well casing to 0.1-0.4 MPa; then, reducing the pressure of the natural gas for a second time to 2.5-4 kPa; finally, injecting the secondarily reduced pressure natural gas into the tubular catalytic heater 2 through the starting gas source interface 9;

[0043] Step 2: Preheat the shell-and-tube catalytic heater 2 to which the starting gas source is introduced. When the preheating temperature reaches the starting temperature, cut off the preheating power supply. Specifically, start the power supply of the shell-and-tube catalytic heater 2, electrically heat the tubular catalytic heater 2, and when it is detected that the preheating temperature of the catalytic blanket inside the radiation plate of the tubular catalytic heater 2 reaches the starting temperature of 160°C to 200°C, start the shell-and-tube catalytic heater 2 and cut off the preheating power supply.

[0044] Step 3: After starting the shell-and-tube catalytic heater 2, the shell-and-tube catalytic heater 2 is made to produce flameless combustion, release heat energy to the outside, and continuously and stably heat the production natural gas 8 of the wellhead pipeline, specifically:

[0045] The natural gas after the secondary pressure reduction is continuously introduced, and the natural gas after the secondary pressure reduction undergoes an oxidation reaction in the catalytic blanket inside the shell-and-tube catalytic heater 2, producing flameless combustion, releasing heat energy to the outside, and the temperature rises to 300°C to 550°C, and then reaches a stable state, which continuously heats the production natural gas 8 at the wellhead.

[0046] Step 4: The heated production natural gas 8 is passed through the electric regulating valve 4 and the emergency shut-off valve 5 in sequence to throttle the production of the produced natural gas 8. Specifically, the electric regulating valve 4 is used to control the pipeline pressure in the well opening process to always be within the set pressure range; the emergency shut-off valve 5 is used to protect the pipeline pressure from abnormal conditions to avoid damage to the downstream pipeline and equipment due to high pressure, thereby ensuring that the throttling production of the production natural gas 8 proceeds smoothly.

[0047] Taking a natural gas well as an example, in the above-mentioned natural gas hydrate prevention and control system, the first flow meter 1 and the second flow meter 3 both contain temperature probes with a measuring range of -50°C to 400°C and a measuring accuracy of ±0.01°C; the electric control valve 4 adopts a 62SH / ZKGT-250-00 electric control valve with an operating temperature of 29°C to 121°C and a maximum working pressure of 27.5MPa; the emergency shut-off valve 5 adopts a 50SH / YKQD-250-00 remote-controlled emergency shut-off valve with an operating temperature of -35°C to 1 21℃, maximum working pressure 27.5MPa; the shell-and-tube catalytic heater 2 uses 16Mn forging flange, 304 stainless steel pipe, aluminum plate heat sink, stainless steel plate heater shell, and the internal catalytic heating module uses 900×300mm catalytic blanket. The shell-and-tube catalytic heater 2 adopts 4G communication mode, MOUBUS communication protocol, RS485 communication interface, which can remotely collect heating technology supporting operation data, set heating technology supporting high and low temperature protection pressure, and remotely control the solenoid valve action function to achieve remote start and stop.

[0048] The natural gas in the gas well casing is depressurized to 0.4 MPa; then, the natural gas is depressurized for a second time to 3 kPa; finally, the depressurized natural gas is injected into the tubular catalytic heater 2 through the start-up gas source interface 9;

[0049] The power supply of the tubular catalytic heater 2 is started, and the tubular catalytic heater 2 is electrically heated. When the preheating temperature of the catalytic blanket inside the radiation plate of the tubular catalytic heater 2 is detected to reach the starting temperature of 180°C, the tubular catalytic heater 2 is started, and the preheating power supply is cut off; the natural gas after the secondary pressure reduction is continuously introduced, and the natural gas after the secondary pressure reduction undergoes an oxidation reaction in the catalytic blanket inside the tubular catalytic heater 2, producing flameless combustion, releasing heat energy to the outside, and the temperature rises to 400°C, and then reaches a stable state, which continuously heats the production natural gas 8 at the wellhead. The electric regulating valve 4 is used to control the pipeline pressure in the set pressure range during the well opening process; the emergency shut-off valve 5 is used to protect the pipeline pressure abnormality to prevent the downstream pipeline and equipment from being damaged due to high pressure, thereby ensuring the smooth throttling production of the production natural gas 8.

[0050] Under the condition of ambient temperature of -7℃, the electric regulating valve 4 adjusts the needle valve opening to 15° for throttling production. The casing pressure is 6.6MPa, the tubing pressure is 6.1MPa, the pipe pressure is 4.1MPa, and the outlet instantaneous flow rate is 455m 3 / h, the inlet natural gas temperature of the shell-and-tube catalytic heater 2 is -1.7℃, the outlet natural gas temperature is 26.7℃, the natural gas temperature is increased by 28.4℃, and the anti-freezing rate is 100%.

[0051] The present invention also provides a natural gas well, comprising the above-mentioned natural gas hydrate prevention and control system, which can achieve the goal of maintaining the quantity and improving the efficiency of natural gas production.

[0052] In summary, the present invention provides a natural gas hydrate prevention and control system, method and natural gas well, which heats the natural gas 8 produced at the wellhead by using catalytic combustion technology to prevent the generation of hydrates from blocking valves and pipelines, and uses natural gas to pass through a fiber catalytic blanket and air for oxidation reaction to generate carbon dioxide and water, thereby achieving flameless combustion and releasing heat energy at the same time. It can achieve no impact on the human body and the environment, and meet safety and environmental protection requirements. The natural gas hydrate prevention and control system can be used indoors to simulate the situation of natural gas hydrate prevention and control in a gas well under a dynamic environment, and use the relevant parameters optimized by indoor experiments to conduct dynamic experiments. By comparing the test results, the current status of production technology in the prevention and control of hydrate freezing in gas wells can be understood, and the influence of water production, ambient temperature, weather, needle valve opening, etc. on the hydrate prevention and control effect can be obtained. Compared with other natural gas pipeline heating technologies and traditional heating equipment based on natural gas combustion reactions, this technology has obvious advantages in terms of energy conversion efficiency, energy use quality, operability, heating stability and environmental protection, and can be widely used in multiple fields.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. A natural gas hydrate prevention and control system, characterized in that: The invention comprises a shell-and-tube catalytic heater (2), an electric regulating valve (4), an emergency shut-off valve (5), a power supply device (6) and a control device (7); the produced natural gas (8) in the wellhead pipeline enters the gas supply pipeline through the shell-and-tube catalytic heater (2), the electric regulating valve (4) and the emergency shut-off valve (5) in sequence; the shell-and-tube catalytic heater (2), the electric regulating valve (4) and the emergency shut-off valve (5) are all electrically connected or communication-connected with the control device (7); the shell-and-tube catalytic heater (2), the electric regulating valve (4), the emergency shut-off valve (5) and the control device (7) are all electrically connected with the power supply device (6).

2. The natural gas hydrate prevention and control system according to claim 1, characterized in that: A first flow meter (1) is provided on the pipeline connecting the shell-and-tube catalytic heater (2) to the wellhead, the first flow meter (1) is electrically connected to the power supply device (6), and the first flow meter (1) is electrically connected or communication-connected to the control device (7).

3. The natural gas hydrate prevention and control system according to claim 2, characterized in that: A second flow meter (3) is provided on the pipeline between the shell-and-tube catalytic heater (2) and the electric regulating valve (4); the second flow meter (3) is electrically connected to the power supply device (6); and the second flow meter (3) is electrically connected or communicatively connected to the control device (7).

4. The natural gas hydrate prevention and control system according to claim 3, characterized in that: The first flow meter (1) and the second flow meter (3) are both provided with temperature probes.

5. The natural gas hydrate prevention and control system according to claim 1, characterized in that: The tubular catalytic heater (2) is provided with a starting gas source interface (9), and the starting gas source interface (9) is connected to the gas well casing.

6. The natural gas hydrate prevention and control system according to claim 1, characterized in that: The power supply device (6) is a solar cell group.

7. A method for preventing and controlling natural gas hydrates using the natural gas hydrate prevention and control system according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: introducing the starting gas source into the tubular catalytic heater (2) through the starting gas source interface (9); Step 2: Power on the tubular catalytic heater (2) to which the starting gas source is introduced for preheating. When the preheating temperature reaches the starting temperature, the tubular catalytic heater (2) is started, and the preheating power source is cut off; Step 3: After starting the shell-and-tube catalytic heater (2), the shell-and-tube catalytic heater (2) generates flameless combustion, releases heat energy to the outside, and continuously and stably heats the produced natural gas (8) in the wellhead pipeline; Step 4: The heated production natural gas (8) is passed through the electric regulating valve (4) and the emergency shut-off valve (5) in sequence to throttle the production of the produced natural gas (8).

8. The natural gas hydrate prevention and control system method according to claim 7, characterized in that: The preheating temperature for preheating the tubular catalytic heater (2) is 160°C to 200°C.

9. The natural gas hydrate prevention and control system method according to claim 7, characterized in that: The tube-in-tube catalytic heater (2) heats the produced natural gas (8) in the wellhead pipeline to a temperature of 300° C. to 550° C.

10. A natural gas well, characterized in that: A natural gas hydrate prevention and control system comprising any one of claims 1-6.

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