A hydrate control system and method for a tight gas field gathering and transportation pipeline network

Abstract

The present invention discloses a hydrate control system and method for a tight gas field gathering and transportation pipeline network. The system includes a trunk transmission system, a temperature relay system, and an adjustable air cooling system. By implementing this system, the present invention implements green control of natural gas hydrates in a tight gas field gathering and transportation system that combines pressurized gas from multiple gathering stations and a series of trunk lines, achieving high efficiency and energy conservation.

Description

Technical Field

[0001] The present invention belongs to the technical field of tight gas gathering and transportation, and in particular relates to a hydrate control system and method for a tight gas field gathering and transportation pipeline network. Background Art

[0002] Tight sandstone gas, a major type of unconventional natural gas, is becoming increasingly significant in the natural gas resource landscape. Tight gas wells experience high wellhead pressures initially, but this pressure rapidly decreases within a short period, remaining at low pressure for the majority of the time. Due to the low production rates of individual wells, tight gas blocks are often developed using a large-radius gathering and centralized processing model. Therefore, gathering stations are preferably located between individual wells and processing plants to collect the product from individual wells within each area and transport it to the processing plant via a centralized gathering and transmission pipeline.

[0003] Because the gathering and transportation radius of tight gas blocks is often large, long-distance pipeline installations in winter can cause significant temperature drops, posing a challenge to natural gas hydrate prevention and control. Although hydrate inhibition technology for natural gas gathering and transportation systems has made significant progress, methods such as heating and insulation, and the injection of hydrate inhibitors can be used to increase pipeline transport medium temperature, reduce pipeline heat loss, or lower the hydrate formation temperature of the transport medium. However, these solutions have varying degrees of disadvantages (such as the addition of inhibitor recovery systems and increased pipeline operating investment). Especially for tight gas with low single-well production capacity, efficiently, environmentally friendly, and economically preventing natural gas hydrate formation is a crucial technical challenge. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the existing technology and provide a hydrate control system and method for a tight gas field gathering and transportation pipeline network. Based on the layout and operation characteristics of the tight gas gathering and transportation system, and targeting the process characteristics such as the long-term low initial pressure of the tight gas production medium, the large gathering and transportation radius, and the use of centralized pressurization at the gas gathering station, the present invention takes into account the full-season cycle operation effect, comprehensively optimizes the downstream natural gas processing energy consumption, and improves the hydrate inhibition effect of the gathering and transportation system. With temperature control as the main technical concept, it fully utilizes the waste heat of gas source pressurization, local insulation and natural environmental conditions to achieve green and efficient control of natural gas hydrates.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A hydrate control system for a tight gas field gathering and transportation pipeline network, the system comprising:

[0007] A trunk transmission system, comprising a transmission pipeline and an inlet block valve, a trunk block valve, and an outlet block valve provided on the transmission pipeline, a first trunk branch and a first temperature monitoring component provided between the trunk block valve and the inlet block valve, and a second trunk branch and a second temperature monitoring component provided between the trunk block valve and the outlet block valve;

[0008] A temperature relay system, comprising a fluid mixing pipe connected to the trunk transmission system via the first trunk branch and the second trunk branch, with a first trunk bypass shut-off valve and a second trunk bypass shut-off valve provided at both ends of the fluid mixing pipe, a hole being opened in the middle of the fluid mixing pipe and being inserted into a gas gathering station injection pipeline, and an injection pipeline temperature monitoring component and an injection pipeline pressure monitoring component being provided on the gas gathering station injection pipeline;

[0009] An adjustable air cooling system includes a gas-liquid separator, a booster compressor and an air cooler connected in series in sequence. The air cooler is connected to the fluid mixing pipe through the gas gathering station injection pipeline. An air cooler outlet temperature monitoring component is also provided between the air cooler and the gas gathering station injection pipeline. The air cooler controls the opening and closing of the inlet and outlet through the inlet shut-off valve and the outlet shut-off valve. The adjustable air cooling system also includes an air cooler bypass connected in parallel on both sides of the air cooler. The air cooler bypass includes an air cooler bypass shut-off valve and an air cooler bypass regulating valve.

[0010] Furthermore, the temperature monitoring component includes a temperature transmitter, and the pressure monitoring component includes a pressure transmitter.

[0011] Furthermore, the system also includes a segmented insulation system, which includes an external insulation layer of a preset length arranged at the front downstream section of the conveying pipeline, and the downstream section of the conveying pipeline is the pipeline after the outlet shut-off valve.

[0012] Furthermore, the preset length of the front downstream section of the delivery pipeline includes the front 1 / 3 to 1 / 2 of the downstream section of the delivery pipeline.

[0013] Furthermore, the gas-liquid separator is a horizontal structure separator.

[0014] Furthermore, the booster compressor is a reciprocating compressor.

[0015] Furthermore, the fluid mixing pipe is a carbon steel straight pipe with a diameter expansion reaching a preset index.

[0016] On the other hand, the present invention further provides a method for controlling hydrates in a tight gas field gathering and transportation pipeline network, the method being implemented based on any of the aforementioned control systems, the method comprising:

[0017] Analyze whether hydrates are forming in the gathering and transportation pipelines. If hydrates are formed in the gathering and transportation pipelines, compare the maximum tolerable medium temperature of the gathering and transportation trunk line with the temperature after pressurization without mixing of the medium at the gas gathering station and the incoming medium from the trunk line. Select a lower temperature and recalculate the hydrate formation temperature. If hydrate formation conditions still exist at the end of the pipeline, install an insulation layer at the front section of each gathering and transportation trunk line that meets the hydrate formation conditions, delay the occurrence of the largest temperature drop, and increase the inlet temperature at the end point.

[0018] When the pipeline operates above the preset temperature, the trunk tight gas enters the gas gathering station from the trunk transmission system, and the tight gas from each single well is collected and enters the gas-liquid separator. After gas-liquid separation, the gas phase enters the compressor, and the liquid phase enters the liquid pipeline system for external transmission. The pressurized gas phase is temperature-regulated by the air cooler and then injected into the fluid mixing pipe to mix with the upstream trunk medium before being introduced into the downstream of the trunk transmission system.

[0019] When the pipeline operates below the preset temperature, the trunk tight gas enters the gas gathering station from the trunk transmission system, and the tight gas from each single well is collected and enters the gas-liquid separator. After gas-liquid separation, the gas phase enters the compressor and the liquid phase enters the liquid pipeline system for external transmission. After pressurization, all the gas enters the air cooler for cooling. At the same time, the first shut-off valve of the trunk bypass is closed and the trunk shut-off valve is opened. The gas injected from the gas gathering station is directly mixed with the trunk tight gas on the trunk.

[0020] Furthermore, the analysis of whether hydrates are formed in the gathering and transportation pipeline specifically includes:

[0021] Based on the characteristics of multi-well station layout and multi-gathering station boosted gathering and transportation of tight gas, and taking advantage of the high temperature condition at the outlet of the booster compressor, the terminal temperatures of summer and winter operating conditions, as well as the corresponding hydrate formation in the pipeline, are analyzed based on the pressure, temperature and direction of the gathering and transportation trunk pipeline after boosting.

[0022] Furthermore, when the pipeline operates above a preset temperature, the parameters of the temperature monitoring component are monitored by coordinating with the temperature detection value of the entire gathering trunk system, and the bypass flow of the air cooler is dynamically adjusted so that the mixed medium does not generate hydrates in the gathering trunk, and the temperature of the mixed medium does not exceed the maximum allowable operating temperature of the anti-corrosion layer of the gathering trunk.

[0023] The beneficial effects of the present invention are:

[0024] (1) The present invention is aimed at the development of tight gas fields and the layout of the gathering and transportation system, and fully utilizes the technical characteristics of the boosting system installed at each gas gathering station. An adjustable air cooling system is installed at the gas gathering station. Under extreme environmental conditions in winter, the waste heat of the gas after boosting is fully utilized. After mixing with the trunk gas, the temperature of the trunk gas is adjusted, and the system heat energy is used to prevent and control hydrate formation to the greatest extent.

[0025] (2) The present invention optimizes the insulation layer setting mode based on the thermodynamic change law of the buried pipeline, and controls the temperature change of the large temperature drop pipe section in the form of local insulation in the front section. It not only provides an efficient prevention and control measure for hydrate prevention under extreme winter conditions, but also provides a guarantee for the natural cooling of the pipeline medium under non-winter conditions, thereby avoiding the excessively high temperature of the medium entering the downstream treatment plant under non-winter conditions, which causes a sharp increase in the energy consumption of the treatment plant.

[0026] (3) The present invention effectively controls the hydrate formation problem of the gathering and transportation trunk line by rationally setting up the insulation system and the air-cooling control system, making full use of the waste heat of the medium in the pressurization process. On the one hand, it replaces the traditional full-line insulation mode and realizes technical optimization and investment control in the setting of the pipeline insulation layer; on the other hand, it replaces the traditional hydrate inhibitor filling and treatment, greatly reducing the investment in the injection facilities of the gas gathering station and the recovery and treatment facilities of the treatment plant, and also saving operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a hydrate control system for a tight gas field gathering and transportation pipeline network provided by an embodiment of the present invention.

[0028] Reference numerals: 1-upstream pipeline, 2-station inlet shut-off valve, 3-trunk shut-off valve, 4-station outlet shut-off valve, 5-downstream pipeline, 6-trunk first temperature transmitter, 7-trunk second temperature transmitter, 11-gas gathering station inlet pipeline, 12-gas-liquid separator, 13-gas phase outlet pipeline, 14-liquid phase outlet pipeline, 15-boosting compressor, 16-air cooler inlet shut-off valve, 17-air cooler, 18-air cooler outlet Inlet shut-off valve, 19-air cooler outlet temperature transmitter, 20-air cooler bypass shut-off valve, 21-air cooler bypass regulating valve, 22-air cooler pipeline, 23-air cooler bypass, 31-gas gathering station injection pipeline, 32-injection pipeline temperature transmitter, 33-injection pipeline pressure transmitter, 34-trunk bypass, 35-trunk bypass first shut-off valve, 36-fluid mixing pipe fittings, 37-trunk bypass second shut-off valve. DETAILED DESCRIPTION

[0029] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0030] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0031] Because the gathering and transportation radius of tight gas blocks is often large, long-distance pipeline installations in winter can cause significant temperature drops, posing a challenge to natural gas hydrate prevention and control. Although hydrate inhibition technology for natural gas gathering and transportation systems has made significant progress, methods such as heating and insulation, and the injection of hydrate inhibitors can be used to increase pipeline transport medium temperature, reduce pipeline heat loss, or lower the hydrate formation temperature of the transport medium. However, these solutions have varying degrees of disadvantages (such as the addition of inhibitor recovery systems and increased pipeline operating investment). Especially for tight gas with low single-well production capacity, efficiently, environmentally friendly, and economically preventing natural gas hydrate formation is a crucial technical challenge.

[0032] In order to solve the above technical problems, the following embodiments of a hydrate control system and method for a tight gas field gathering and transportation pipeline network are proposed in the present invention.

[0033] Example 1

[0034] This embodiment provides a hydrate control system for a tight gas field gathering and transportation pipeline network, and its working principle is as follows:

[0035] (1) Due to the characteristics of large-scale production of tight gas, such as a large number of wells and a large gathering and transportation radius, the length of the gathering and transportation pipeline is long in terms of surface engineering. This has a great impact on the temperature of the pipeline medium and poses a challenge to hydrate prevention and control. At the same time, since the wellhead pressure of tight gas is generally low, when connecting to the gathering and transportation pipeline network, it is basically necessary to install a compressor at each gas gathering station to increase the medium pressure before connecting to the gas gathering trunk pipeline network. Therefore, the rational use of the heat energy of the medium after pressurization at each gas gathering station is a potential idea for exploring the green prevention and control of hydrates in the tight gas gathering and transportation system. At the same time, in addition to considering the prevention and control of hydrates in winter, it should also be considered that the medium under summer working conditions should be kept at a relatively low temperature before entering the downstream processing plant to reduce the operating load of the processing plant. In general, this system needs to develop technologies in the green prevention and control of hydrates in winter and the temperature control of the plant in summer.

[0036] (2) An adjustable air cooling system is installed at each gas gathering station. In winter, some (or even all) of the pressurized medium can be directly passed through the air cooler. This fully utilizes the heat energy naturally obtained during pressurization and mixes it with the relatively low-temperature dense gas connected to the upstream trunk line, thus playing a temperature relay role. This will increase the starting temperature of each section of the gas gathering trunk line and strive to increase the temperature at the end of each section of the gas gathering trunk line to minimize the risk of hydrate formation. In contrast, under summer operating conditions, the conventional method of allowing the pressurized medium to enter the air cooler is adopted to minimize the medium temperature, thereby reducing the inlet temperature when transported to the terminal processing plant and optimizing the gas processing energy consumption of the processing plant.

[0037] (3) A mixing device is installed at each gas gathering station to achieve full mixing of the high-temperature medium with the upstream input medium, avoiding uneven distribution of the medium, which causes unmixed medium to enter the existing downstream pipeline and affect the high temperature of the anti-corrosion layer of the adjacent buried pipeline.

[0038] (4) In extreme cases, if the problem of terminal hydrate formation cannot be overcome by temperature relay, this system proposes to set up segmented insulation layers in the pipe section where such problems occur, and conduct temperature drop analysis and control on the front section of the pipeline where the temperature drop is larger, so as to avoid taking full-line insulation. This can not only meet the formation in winter, but also avoid the temperature at the end of the pipeline system (downstream treatment plant entrance) being too high during transportation in summer, which will increase the additional cooling load and operating costs for the treatment plant.

[0039] Reference Figure 1 ,like Figure 1 Figure 1 is a schematic diagram of a hydrate control system for a tight gas field gathering and transportation pipeline network provided in this embodiment. The system includes an upstream pipeline 1, an inlet block valve 2, a trunk line block valve 3, an outlet block valve 4, a downstream pipeline 5, a first trunk line temperature transmitter 6, a second trunk line temperature transmitter 7, a gathering station inlet pipeline 11, a gas-liquid separator 12, a gas phase outlet pipeline 13, a liquid phase outlet pipeline 14, a booster compressor 15, an air cooler inlet block valve 16, an air cooler 17, an air cooler outlet block valve 18, an air cooler outlet temperature transmitter 19, an air cooler bypass block valve 20, an air cooler bypass regulating valve 21, an air cooler pipeline 22, an air cooler bypass 23, a gathering station injection pipeline 31, an injection pipeline temperature transmitter 32, an injection pipeline pressure transmitter 33, a trunk line bypass 34, a first trunk line bypass block valve 35, a fluid mixing pipe 36, and a second trunk line bypass block valve 37.

[0040] Among them, the upstream pipeline 1, the station inlet shut-off valve 2, the trunk line shut-off valve 3, the station outlet shut-off valve 4, the downstream pipeline 5, the trunk line first temperature transmitter 6, the trunk line second temperature transmitter 7, etc. constitute the trunk line transportation system, which is used to provide the function of collecting and centrally transmitting the medium after the dense gas is pressurized; at the same time, by opening or closing the trunk line shut-off valve 3, the process switching of the gas gathering station under pigging / non-pigging conditions is controlled, and the branch line is directly injected into the trunk line under pigging conditions in non-winter, and the branch line is injected into the trunk line bypass under non-pigging conditions in winter, so as to avoid the high-temperature branch line medium from damaging the local trunk pipeline anti-corrosion layer downstream of the injection point.

[0041] Specifically, the upstream pipeline 1 in the trunk transmission system is the upstream dense gas input pipeline; the inlet shut-off valve 2 is a full-bore electric ball valve, which is normally open and closed in case of an emergency at the gas gathering station; the trunk shut-off valve 3 is a full-bore electric ball valve, which is opened under trunk pipe cleaning, non-winter and other working conditions, and closed under non-air cooling adjustment and high-temperature medium mixing conditions in winter; the outlet shut-off valve 4 is a full-bore electric ball valve, which is normally open and closed in case of an emergency at the gas gathering station; the downstream pipeline 5 is the output pipeline for the mixed dense gas; the first trunk temperature transmitter 6 is arranged on the branch pipeline between the inlet shut-off valve 2, the trunk shut-off valve 3 and the outlet shut-off valve 4, and is used to measure the temperature of the medium in the pipe before mixing; the second trunk temperature transmitter 7 is arranged on the branch pipeline between the trunk shut-off valve 3 and the outlet shut-off valve 4, and is used to measure the temperature of the medium in the pipe after mixing.

[0042] Among them, the gas gathering station inlet pipeline 11, gas-liquid separator 12, gas phase outlet pipeline 13, liquid phase outlet pipeline 14, booster compressor 15, air cooler inlet shut-off valve 16, air cooler 17, air cooler outlet shut-off valve 18, air cooler outlet temperature transmitter 19, air cooler bypass shut-off valve 20, air cooler bypass regulating valve 21, air cooler pipeline 22, air cooler bypass 23, etc. constitute an adjustable air cooling system, which is used to control the temperature of the pressurized dense gas before it is injected into the trunk line according to the environmental conditions of different seasons; the adjustable air cooling system includes the air cooler body temperature adjustment function and the air cooler bypass jumper function, which can control the temperature of the compressor outlet and the air cooler outlet to the greatest extent, and is used to perform a wide range of temperature adjustment on the trunk medium after downstream injection.

[0043] Specifically, the gas gathering station inlet pipeline 11 in the adjustable air cooling system is connected to the upstream gas production pipeline, which is used to input the raw dense gas collected from each wellhead into the gas gathering station; the gas-liquid separator 12 is arranged downstream of the gas gathering station inlet pipeline 11, preferably a horizontal structure, with gas-liquid separation and sand removal functions, and provides pre-treatment support for the dense gas to be pressurized; the gas phase outlet pipeline 13 connects the gas phase outlet of the gas-liquid separator 12 with the downstream booster compressor 15; the liquid phase outlet pipeline 14 connects the gas phase outlet of the gas-liquid separator 12 with the downstream liquid boosting system, which is used The separated liquid phase is further processed and transported out; the booster compressor 15 is preferably a reciprocating compressor, which is used to provide energy for the separated dense gas to be fed into the gas gathering trunk line; an air cooler pipeline 22 and an air cooler bypass 23 are respectively provided downstream of the booster compressor 15, the air cooler pipeline 22 is a pipeline provided with an air cooler and a valve group, which is used to provide a channel for the medium that needs air cooling and cooling, and the air cooler bypass 23 is a pipeline provided with a regulating valve and a shut-off valve, which is used to provide a channel for the medium that does not need air cooling and cooling; the air cooler inlet shut-off valve 16 , air cooler 17, air cooler outlet shut-off valve 18, air cooler outlet temperature transmitter 19, etc. are sequentially arranged on the air cooler pipeline 22; the air cooler inlet shut-off valve 16 is a carbon steel ball valve, preferably electrically controlled; the air cooler outlet shut-off valve 18 is a carbon steel ball valve, preferably electrically controlled; the air cooler 17 is a complete set of air cooler products, preferably a forced ventilation type with an outlet temperature adjustment function; the air cooler outlet temperature transmitter 19 is used to detect the temperature of the medium after air cooling adjustment; the air cooler bypass shut-off valve 20, the air cooler bypass adjustment Valve 21 is arranged on the air cooler bypass 23. The air cooler bypass shut-off valve 20 is preferably an electrically controlled ball valve. The air cooler bypass regulating valve 21 is an electrically controlled regulating valve, which is used to coordinate with the air cooler 17 to adjust the medium flow through the air cooler pipeline 22 and the air cooler bypass 23, and ultimately control the temperature of the medium to be mixed into the gas gathering trunk line, compensate for the cooling temperature (natural temperature drop) of the air cooler itself, and provide further utilization efficiency of the heat energy of the compressor outlet medium; the temperature of the mixed medium is detected by the injection pipeline temperature transmitter 32.

[0044] Among them, the gas gathering station injection pipeline 31, injection pipeline temperature transmitter 32, injection pipeline pressure transmitter 33, trunk bypass 34, trunk bypass first shut-off valve 35, fluid mixing pipe 36, trunk bypass second shut-off valve 37, etc. constitute a temperature relay system, which is used to control the injection and mixing of the medium to be heated and injected according to environmental conditions, so as to achieve the purpose of safe and efficient injection into the trunk line.

[0045] Specifically, the gas gathering station injection pipeline 31 in the temperature relay system is made of carbon steel, connecting the adjustable air cooling system outlet of the gas gathering station and the fluid mixing pipe 36 to provide a medium flow channel; the injection pipeline temperature transmitter 32 and the injection pipeline pressure transmitter 33 are set at the front end of the gas gathering station injection pipeline 31, for real-time detection of the temperature and pressure of the medium to be injected, and providing the original data of the operation instructions to the upstream compressor, air cooler, etc.; the trunk bypass 34 is set on the gas gathering trunk line in the gas gathering station, and the pipe diameter and material are consistent with the gas gathering trunk line, and is used to provide a channel for medium mixing to avoid affecting the trunk line cleaning; the trunk bypass first shut-off valve 35 is set At the front end of the trunk bypass 34, it is preferably electrically controlled and made of carbon steel, and is used to switch the flow channel of the gas gathering trunk fluid; the second trunk bypass shut-off valve 37 is set at the end of the trunk bypass 34, and is preferably electrically controlled and made of carbon steel, and is used to switch the flow channel of the gas gathering trunk fluid; the fluid mixing pipe 36 is preferably a carbon steel straight pipe with an expanded diameter of more than 3 inches, and the two ends are respectively connected to the trunk bypass 34. At the same time, a hole is opened in the middle and inserted into the gas gathering station injection pipeline 31, which is used to provide space for the gas gathering station pressurized medium and the upstream medium of the gas gathering trunk to be fully mixed, and further increase the residence time by expanding the diameter to promote mixing, so as to achieve the effect of coordinating components and temperature.

[0046] As an implementation method, this embodiment installs a segmented insulation system in the front section of downstream pipeline 5, if necessary. This segmented insulation system comprises an external insulation layer on the pipeline, which is used to insulate the first 1 / 3 to 1 / 2 of the long-distance pipeline, mitigating heat loss from the pipeline medium. Based on the maximum allowable operating temperature of the buried pipeline and the temperature of the medium that can be injected into the branch line, the required insulated pipeline length under winter operating conditions was evaluated through system process analysis.

[0047] This embodiment, targeting the development of tight gas fields and the layout of gathering and transportation systems, fully leverages the technical characteristics of the boosting system installed at each gathering station. An adjustable air-cooling system is installed at each gathering station. Under extreme winter conditions, the residual heat of the boosted gas is fully utilized. After mixing with the mainline gas, the temperature of the mainline gas is adjusted, maximizing the use of system thermal energy to prevent hydrate formation. This embodiment optimizes the insulation layer configuration based on the thermodynamic characteristics of buried pipelines, controlling temperature changes in the high-temperature drop pipe section through localized insulation in the front section. This not only provides a highly effective preventive measure for hydrate prevention under extreme winter conditions, but also ensures the natural cooling of pipeline media in non-winter operating conditions, preventing excessively high media temperatures entering downstream processing plants during non-winter conditions, which could result in a significant increase in energy consumption at the processing plant. This embodiment effectively controls the hydrate formation problem in the gathering and transportation trunk line by rationally setting up the insulation system and air-cooling control system and making full use of the waste heat of the medium during the pressurization process. On the one hand, it replaces the traditional full-line insulation mode and achieves technical optimization and investment control in the setting of the pipeline insulation layer; on the other hand, it replaces the traditional hydrate inhibitor injection and treatment, significantly reducing the investment in the injection facilities of the gas gathering station and the recovery and treatment facilities of the treatment plant, and also saving operating costs.

[0048] Example 2

[0049] This embodiment uses the hydrate control system for the tight gas field gathering and transportation network provided in the previous embodiment to implement hydrate control for the tight gas field gathering and transportation network. The specific method is as follows:

[0050] Step 1: Based on the characteristics of multi-well station layout and multi-gathering station pressurized gathering and transportation of tight gas, and taking advantage of its inherent heat source (high temperature condition at the outlet of the booster compressor), analyze the terminal temperature of summer and winter working conditions and the corresponding hydrate formation in the pipeline according to the pressure, temperature (according to conventional design, the temperature after the air cooler is fully operated) and direction of the gathering and transportation trunk pipeline after pressurization. Under winter working conditions, if hydrates are formed in the pipeline, consider (1) the maximum medium temperature that the gathering and transportation trunk line can withstand, (2) the mixed temperature of the medium (injected by the gathering station) without air cooling after pressurization and the main line incoming medium, and select a lower temperature to calculate the hydrate formation temperature again. If hydrate formation conditions still exist at the end of the pipeline, then set an insulation layer at the front section of each gathering and transportation trunk line where hydrates may be formed. Taking advantage of the characteristics of the larger temperature difference and larger temperature drop between the front section of the pipeline and the environment, control the temperature drop at the front section, delay the location of the large temperature drop, increase the inlet temperature of the end point, and realize the control of hydrates in the gathering and transportation trunk line. Therefore, on the one hand, the residual heat of the pressurized medium is fully utilized to mix the hot medium (the medium injected after pressurization) with the cold medium (the medium input from the upstream trunk line), raising the temperature entering the next section of the gathering and transportation trunk line. On the other hand, in the pipeline section where the risk of hydrate formation still exists, an insulation layer is installed to control the temperature drop in the upstream section. This forms the basic method for ensuring hydrate control in gathering and transportation pipelines under winter conditions.

[0051] Step 2: When the pipeline is operating in winter, the trunk tight gas is input into the gas gathering station from the upstream pipeline 1, and the tight gas from each single well is collected into the gas gathering station inlet pipeline 11. After gas-liquid separation, the gas phase enters the compressor 15, and the liquid phase enters the liquid pipeline system for external transmission; the pressurized gas phase has a higher temperature. According to the injection temperature requirements, the gas flow through the air cooler 17 and the gas flow bypassing the air cooler are distributed through the flow regulation function of the air cooler 17 and the regulation function of the air cooler bypass regulating valve 21. A part of the gas passes through the air cooler through the air cooler bypass 23, and the other part is temperature-regulated by the air cooler 17 to ensure that the temperature of the mixed gas flowing out of the air cooling system meets the process requirements of the injection point; at the same time, the trunk shut-off valve 3 is closed, and the trunk medium flows through the trunk bypass 34. The mixed gas is mixed with the medium flowing into the upstream trunk in the mixing pipeline 36 and introduced into the downstream trunk 5. During operation, by coordinating with the temperature detection values ​​of the entire gathering trunk system, the parameters of the injection pipeline temperature transmitter 32 and the air cooler outlet temperature transmitter 19 are monitored, and the air cooler bypass flow is dynamically adjusted to ensure that the mixed medium does not form hydrates in the gathering trunk line and that the temperature of the mixed medium does not exceed the maximum allowable operating temperature of the anti-corrosion layer of the gathering trunk line.

[0052] Step 3: When the pipeline is operating in summer, the trunk tight gas is input into the gas gathering station from the upstream pipeline 1, and the tight gas from each single well is collected and enters the gas gathering station inlet pipeline 11. After gas-liquid separation, the gas phase enters the compressor 15, and the liquid phase enters the liquid pipeline system for external transmission; the pressurized gas phase has a higher temperature. In order to reduce the operating temperature in the downstream pipeline, the air cooler bypass 23 is closed, and all the pressurized gas enters the air cooler 17 and is cooled according to the design requirements; at the same time, the first shut-off valve 35 of the trunk bypass is closed, and the trunk shut-off valve 3 is opened. The gas injected into the gas gathering station is directly mixed with the upstream gas of the trunk line in the gas gathering station trunk line. This is mainly for the consideration of pigging operability in non-winter conditions, that is, the pig sent from the upstream directly passes through the upstream pipeline 1, the trunk shut-off valve 3, and the downstream pipeline 5 through this gas gathering station.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A hydrate control system for a tight gas field gathering and transportation pipeline network, characterized in that: The system comprises: A trunk transmission system, comprising a transmission pipeline and an inlet block valve, a trunk block valve, and an outlet block valve provided on the transmission pipeline, a first trunk branch and a first temperature monitoring component provided between the trunk block valve and the inlet block valve, and a second trunk branch and a second temperature monitoring component provided between the trunk block valve and the outlet block valve; A temperature relay system, comprising a fluid mixing pipe connected to the trunk transmission system via the first trunk branch and the second trunk branch, with a first trunk bypass shut-off valve and a second trunk bypass shut-off valve provided at both ends of the fluid mixing pipe, a hole being opened in the middle of the fluid mixing pipe and being inserted into a gas gathering station injection pipeline, and an injection pipeline temperature monitoring component and an injection pipeline pressure monitoring component being provided on the gas gathering station injection pipeline; An adjustable air cooling system includes a gas-liquid separator, a booster compressor and an air cooler connected in series in sequence. The air cooler is connected to the fluid mixing pipe through the gas gathering station injection pipeline. An air cooler outlet temperature monitoring component is also provided between the air cooler and the gas gathering station injection pipeline. The air cooler controls the opening and closing of the inlet and outlet through the inlet shut-off valve and the outlet shut-off valve. The adjustable air cooling system also includes an air cooler bypass connected in parallel on both sides of the air cooler. The air cooler bypass includes an air cooler bypass shut-off valve and an air cooler bypass regulating valve.

2. The hydrate control system for a tight gas field gathering and transportation pipeline network according to claim 1, characterized in that: The first temperature monitoring assembly, the second temperature monitoring assembly, the air cooler outlet temperature monitoring assembly and the injection pipeline temperature monitoring assembly all include temperature transmitters, and the injection pipeline pressure monitoring assembly includes a pressure transmitter.

3. The hydrate control system for a tight gas field gathering and transportation pipeline network according to claim 1, characterized in that: The system also includes a segmented insulation system, which includes an external insulation layer of a preset length arranged at the front downstream section of the delivery pipeline, and the downstream section of the delivery pipeline is the pipeline after the outlet shut-off valve.

4. The hydrate control system for a tight gas field gathering and transportation pipeline network according to claim 3, characterized in that: The preset length of the front downstream section of the delivery pipeline includes the front 1 / 3 to 1 / 2 of the downstream section of the delivery pipeline.

5. The hydrate control system for a tight gas field gathering and transportation pipeline network according to claim 1, characterized in that: The gas-liquid separator is a horizontal structure separator.

6. The hydrate control system for a tight gas field gathering and transportation pipeline network according to claim 1, characterized in that: The booster compressor is a reciprocating compressor.

7. The hydrate control system for a tight gas field gathering and transportation pipeline network according to claim 1, characterized in that: The fluid mixing pipe is a carbon steel straight pipe with a diameter expansion reaching a preset index.

8. A method for controlling hydrates in a tight gas field gathering and transportation pipeline network, characterized in that: The method is implemented based on the control system according to any one of claims 1 to 7, and the method includes: Analyze whether hydrates are forming in the gathering and transportation pipelines. If hydrates are formed in the gathering and transportation pipelines, compare the maximum tolerable medium temperature of the gathering and transportation trunk line with the temperature after pressurization without mixing of the medium at the gas gathering station and the incoming medium from the trunk line. Select a lower temperature and recalculate the hydrate formation temperature. If hydrate formation conditions still exist at the end of the pipeline, install an insulation layer at the front section of each gathering and transportation trunk line that meets the hydrate formation conditions, delay the occurrence of the largest temperature drop, and increase the inlet temperature at the end point. When the gathering and transportation pipeline operates above the preset temperature, the trunk tight gas enters the gas gathering station from the trunk transmission system, and the tight gas from each single well is collected and enters the gas-liquid separator. After gas-liquid separation, the gas phase enters the compressor, and the liquid phase enters the liquid pipeline system for external transmission. The pressurized gas phase is temperature-regulated by the air cooler and then injected into the fluid mixing pipe to mix with the upstream trunk medium before being introduced into the downstream of the trunk transmission system. When the gathering and transportation pipeline operates below the preset temperature, the trunk tight gas enters the gas gathering station from the trunk transmission system, and the tight gas from each single well is collected and enters the gas-liquid separator. After gas-liquid separation, the gas phase enters the compressor and the liquid phase enters the liquid pipeline system for external transmission. After pressurization, all the gas enters the air cooler for cooling. At the same time, the first shut-off valve of the trunk bypass is closed and the trunk shut-off valve is opened. The gas injected from the gas gathering station is directly mixed with the trunk tight gas on the trunk.

9. The method for controlling hydrates in a tight gas field gathering and transportation pipeline network according to claim 8, wherein: The analyzing whether hydrates are formed in the gathering and transportation pipeline specifically includes: Based on the characteristics of multi-well station layout and multi-gathering station boosted gathering and transportation of tight gas, and taking advantage of the high temperature condition at the outlet of the booster compressor, the terminal temperatures of summer and winter operating conditions, as well as the corresponding hydrate formation in the pipeline, are analyzed based on the pressure, temperature and direction of the gathering and transportation trunk pipeline after boosting.

10. The method for controlling hydrates in a tight gas field gathering and transportation pipeline network according to claim 8, wherein: When the gathering and transportation pipeline operates above the preset temperature, the parameters of the temperature monitoring component are monitored by coordinating with the temperature detection values ​​of the entire gathering and transportation trunk system, and the bypass flow of the air cooler is dynamically adjusted to prevent the mixed medium from generating hydrates in the gathering and transportation trunk line, and the temperature of the mixed medium does not exceed the maximum allowable operating temperature of the anti-corrosion layer of the gathering and transportation trunk line.

Images