CN113864653A - System and method for eliminating severe slug flow by combining gas-liquid separator and throttle valve - Google Patents

System and method for eliminating severe slug flow by combining gas-liquid separator and throttle valve Download PDF

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Publication number
CN113864653A
CN113864653A CN202111153241.6A CN202111153241A CN113864653A CN 113864653 A CN113864653 A CN 113864653A CN 202111153241 A CN202111153241 A CN 202111153241A CN 113864653 A CN113864653 A CN 113864653A
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pressure
gas
valve
liquid separator
pressure sensor
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郭烈锦
赵向远
徐强
常英杰
付吉强
曹业奇
于海洋
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Xian Jiaotong University
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Xian Jiaotong University
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
    • F17D1/00—Pipe-line systems
    • F17D1/20—Arrangements or systems of devices for influencing or altering dynamic characteristics of the systems, e.g. for damping pulsations caused by opening or closing of valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K31/00—Actuating devices; Operating means; Releasing devices
    • F16K31/02—Actuating devices; Operating means; Releasing devices electric; magnetic
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L55/00—Devices or appurtenances for use in, or in connection with, pipes or pipe systems
    • F16L55/07—Arrangement or mounting of devices, e.g. valves, for venting or aerating or draining
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
    • F17D1/00—Pipe-line systems
    • F17D1/005—Pipe-line systems for a two-phase gas-liquid flow
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17D—PIPE-LINE SYSTEMS; PIPE-LINES
    • F17D3/00—Arrangements for supervising or controlling working operations
    • F17D3/01—Arrangements for supervising or controlling working operations for controlling, signalling, or supervising the conveyance of a product

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Flow Control (AREA)
  • Control Of Fluid Pressure (AREA)

Abstract

The invention discloses a system and a method for eliminating severe slug flow by combining a gas-liquid separator and a throttle valve, belonging to the technical field of petroleum engineering multiphase flow control. The differential pressure sensor and the first pressure sensor are arranged at the top of the vertical pipe, the throttle valve is arranged at the outlet end of the vertical pipe, the second pressure sensor is arranged at the inlet of the high-pressure gas-liquid separator, the exhaust port control valve is arranged at the exhaust port at the top of the high-pressure gas-liquid separator, and the liquid discharge port control valve is arranged at the liquid discharge port at the bottom of the high-pressure gas-liquid separator; the differential pressure sensor, the first pressure sensor, the throttle valve, the second pressure sensor, the exhaust port control valve and the liquid outlet control valve are respectively connected with the industrial personal computer. The invention can complete the control elimination of the serious slug flow by adjusting the opening of the throttle valve and the pressure of the high-pressure gas-liquid separator, and can effectively reduce the system pressure, improve the oil gas yield and enhance the real-time performance of the control while eliminating the serious slug flow of the gathering and transportation-riser system.

Description

System and method for eliminating severe slug flow by combining gas-liquid separator and throttle valve
Technical Field
The invention belongs to the technical field of petroleum engineering multiphase flow control, and particularly relates to a system and a method for eliminating severe slug flow by combining a gas-liquid separator and a throttle valve.
Background
The deep sea oil and gas resources are extremely rich, and the development of the deep sea oil and gas resources faces unprecedented problems and great challenges. The deep sea oil gas development is mainly characterized by long distance of gathering and transportation pipelines, complex pipeline structure and violent temperature change of oil gas gathering and transportation environment. Due to the special composition structure of the gathering-transporting-vertical pipe system, when the gas-liquid flow is relatively low, an unstable flow phenomenon that the pressure difference changes periodically and greatly and gas-liquid alternately flows out of the vertical pipe is often generated in a pipeline, and the phenomenon is called serious slug flow. When severe slugging occurs, long liquid plugs often exist in the pipeline several times the height of the riser, thereby creating separator flow break and overflow, severe fluctuations in pressure differential causing pipeline vibration, oil field production loss, and other adverse effects. Therefore, the research on the flow characteristics of the severe slug flow and the online monitoring technology thereof under the conditions of long distance and complex pipeline structure is an important means for ensuring the safe and stable production of the deep sea oil and gas development system, and provides a powerful technical guarantee for the development process of the deep sea oil and gas resources in China.
Riser top throttling is a common method of eliminating severe slugging. The method controls the flow process by installing a throttle valve at the top of the vertical pipe and properly reducing the opening of the throttle valve according to the actual flow condition, thereby achieving the purpose of eliminating the phenomenon of serious slug flow. The method is simple and convenient to operate and low in cost, so that the method is a control method which is widely used at present. However, the throttling method causes the back pressure to rise, thereby bringing adverse effects such as production reduction of the oil field and the like.
The automatic control method is characterized in that a PID regulator which is most widely applied in an industrial field is adopted, appropriate input parameters and control parameters are given, and when the deviation between the actual parameters and the set parameters is measured, specific correction parameters are output to a corresponding control system to realize the process of controlling the severe slug flow. The method has the advantages of strong applicability, simple and convenient operation, stable control effect and technical difficulty that the setting process of the controller parameters is sometimes complex. The Chinese patent No. 200510042681.9, the name of the invention is: a dynamic throttling control method for eliminating severe slug flow of a valve (publication date: 11/23/2005) discloses a dynamic throttling control method for eliminating severe slug flow, which stabilizes the bottom pressure of a vertical pipe within a desired range by adjusting the opening of a throttle valve at the top of the vertical pipe. The Chinese patent No. 201110216748.1, the name of the invention is: a real-time throttling device and a method for eliminating the serious slug flow of a gathering-riser system (publication date: 2012, 4, 1) disclose the real-time throttling device and the method for eliminating the serious slug flow of the gathering-riser system, and the method takes the landing pressure of a wellhead platform and the landing pressure of an FPSO as the adjusting basis of a throttle valve and inhibits and eliminates the serious slug flow by a PID method.
At present, the control elimination process of the serious slug flow mostly adopts a single method: and throttling at the top of the vertical pipe or stabilizing the pressure of the gas-liquid separator. The combined control of two or even more devices to eliminate severe slugging has been less studied, ignoring possible synergy between the controlling devices. In the existing automatic control process, pressure signals need to be observed by naked eyes at first, and control can be performed only after severe slug flow is determined, the severe slug flow generally has a long period, the time for starting control obviously lags behind the time for generating the severe slug flow, so that control is not timely, the production efficiency is finally influenced, and even the pipeline safety is influenced.
Disclosure of Invention
In order to solve the problems, the invention provides a system and a method for eliminating the severe slug flow by combining a gas-liquid separator and a throttle valve, which can control and eliminate the severe slug flow by adjusting the opening degree of the throttle valve and the pressure of a high-pressure gas-liquid separator, effectively reduce the system pressure, improve the oil gas yield and enhance the real-time performance of control while eliminating the severe slug flow of a gathering and transportation-vertical pipe system.
The invention is realized by the following technical scheme:
the invention discloses an on-line identification method for a two-phase flow pattern of a gathering and transportation vertical pipe, which comprises a differential pressure sensor, an industrial personal computer, a first pressure sensor, a throttle valve, a second pressure sensor, an exhaust port control valve and a liquid discharge port control valve;
the differential pressure sensor and the first pressure sensor are arranged at the top of the vertical pipe, the throttle valve is arranged at the outlet end of the vertical pipe, the second pressure sensor is arranged at the inlet of the high-pressure gas-liquid separator, the exhaust port control valve is arranged at the exhaust port at the top of the high-pressure gas-liquid separator, and the liquid discharge port control valve is arranged at the liquid discharge port at the bottom of the high-pressure gas-liquid separator; the differential pressure sensor, the first pressure sensor, the throttle valve, the second pressure sensor, the exhaust port control valve and the liquid outlet control valve are respectively connected with the industrial personal computer.
Preferably, the throttle valve and the high-pressure gas-liquid separator are connected in series in the pipeline through connecting flanges, and the inner diameter of the throttle valve is equal to that of the pipeline.
Preferably, the single action amplitude of the throttle valve is between 2% and 10%.
Preferably, the opening range of the throttle valve is ± 15% of the opening set value.
Preferably, the industrial personal computer is internally provided with a PID controller, and the PID controller is connected with the throttle valve.
Preferably, the differential pressure sensor, the first pressure sensor, the throttle valve, the second pressure sensor, the exhaust port control valve and the liquid outlet control valve are in communication connection with the industrial personal computer through shielded cables.
The invention discloses a method for eliminating severe slug flow by adopting the system for eliminating severe slug flow by combining the gas-liquid separator and the throttle valve, which comprises the following steps:
the method comprises the following steps that a differential pressure sensor collects a local differential pressure signal at the top of a vertical pipe, a first pressure sensor collects a pressure signal at the top of the vertical pipe, a second pressure sensor collects a pressure signal at the inlet of a high-pressure gas-liquid separator, the signals are transmitted to an industrial personal computer, signal parameter values corresponding to different flow patterns are preset in the industrial personal computer, the flow pattern in a gathering and transporting-vertical pipe system is identified according to the collected signal parameters, and when the flow pattern is a serious slug flow, the pressure at the top of the vertical pipe is adjusted by controlling the opening of a throttle valve; meanwhile, the pressure of the high-pressure gas-liquid separator is adjusted by controlling the opening degrees of the exhaust port control valve and the liquid outlet control valve, so that the serious slug flow is eliminated.
Preferably, in particular:
the industrial personal computer comprises a signal acquisition module, a flow pattern recognition module and a slug control module, and the acquired signals are preprocessed by the signal acquisition module and then subjected to flow pattern recognition by the flow pattern recognition module; when the identification result is serious slug flow, calling a slug control model, calculating a vertical pipe top pressure set value required for eliminating the serious slug flow, reversely pushing out the throttle valve opening degree variation range by using the vertical pipe top pressure set value, and giving out a high-pressure gas-liquid separator pressure set value within an allowable pressure range; the PID controller is used for controlling the pressure of the high-pressure gas-liquid separator, the liquid outlet control valve is used for controlling the liquid level stability of the high-pressure gas-liquid separator, and the exhaust port control valve is used for controlling the pressure stability of the high-pressure gas-liquid separator; comparing the set value of the top pressure of the vertical pipe with the actually measured value of the top pressure of the vertical pipe, and performing PID (proportion integration differentiation) logical operation on the obtained difference value through a PID controller to obtain the corresponding valve opening of the throttle valve; the flow state can be influenced after the opening degree of the valve is changed, when the difference value approaches to 0, the flow reaches a stable state, and the phenomenon of serious slug flow is eliminated.
Further preferably, the valve opening of the throttle valve is calculated by the following valve pressure drop formula:
Figure BDA0003287749370000041
wherein DP is the pressure drop across the throttle valve; c is a throttle coefficient, which is related to the valve characteristic;
UMIXis a gas-liquid mixed flowSpeed, calculated by the following equation:
Figure BDA0003287749370000042
wherein a isGIs the gas fraction, rho, at the throttle valveGAnd ρLRespectively being gas and liquid density, UGAnd ULThe flow rates of the gas phase and the liquid phase are respectively;
the PID control process is calculated according to the following formula:
Figure BDA0003287749370000043
wherein z (t) is a valve opening adjustment value; e (t) is the deviation value of the output signal, and e (t) is the measured value of the top pressure of the vertical pipe-the set value of the top pressure of the vertical pipe; kPIs the proportional gain coefficient of the controller; t isIIntegrating the time constant for the controller; t isDIs the PID controller differential time constant.
Further preferably, the first controller proportional gain factor K is set when the deviation value of the output signal is greater than 20% of the measured value of the riser top pressureP1And a first controller integration time constant TI1(ii) a When the deviation value of the output signal is less than 20% of the measured value of the top pressure of the vertical pipe, setting a proportional gain coefficient K of the second controllerP2And a second controller integration time constant TI2(ii) a Wherein, KP1＝10KP2，TI1＝0.2TI2。
Compared with the prior art, the invention has the following beneficial technical effects:
the invention discloses a system for eliminating severe slug flow by combining a gas-liquid separator and a throttle valve.A pressure difference sensor is used for acquiring a local pressure difference signal at the top of a vertical pipe, a first pressure sensor is used for acquiring a pressure signal at the top of the vertical pipe, a second pressure sensor is used for acquiring a pressure signal at the inlet of the high-pressure gas-liquid separator, and the pressure at the top of the vertical pipe is regulated by controlling the opening of the throttle valve after being processed by an industrial personal computer; meanwhile, the pressure of the high-pressure gas-liquid separator is adjusted by controlling the opening degrees of the exhaust port control valve and the liquid outlet control valve, and the serious slug flow in the system is eliminated in time. Where the separator is responsible for stabilizing the system pressure and the throttle is responsible for controlling severe slugging. Compared with a control method of independently adopting throttling or separator pressure, the method can effectively reduce the system pressure, improve the oil gas yield and enhance the real-time performance of control while eliminating the serious slug flow of the gathering-riser system.
Furthermore, the throttle valve is connected in series in the pipeline through the connecting flange, and the inner diameter of the throttle valve is equal to that of the pipeline, so that the flowing state of the multiphase fluid is not influenced when the valve is fully opened.
Furthermore, the single action amplitude of the throttle valve is 2% -10%, the opening range is +/-15% of the opening set value, and the problems that the valve action frequency is too frequent and the action amplitude is too large are avoided.
Furthermore, the industrial personal computer is internally provided with a PID controller, and the PID controller is connected with the throttle valve, so that the automation degree is high.
The invention discloses a method for eliminating severe slug flow by adopting a system for eliminating severe slug flow by combining a gas-liquid separator and a throttle valve, which adopts a method of organically combining automatic control and flow pattern recognition technology, can realize the flow pattern rapid recognition and control process at the initial stage of the severe slug flow generation, solves the problem of control lag caused by the adoption of complete periodic signal recognition, and greatly improves the control real-time property. The automatically-established slug control model is adopted, the parameter set value is not required to be given manually, the automation degree of control can be effectively improved, the system pressure is reduced, and the oil gas yield is improved.
Drawings
FIG. 1 is a schematic diagram of the overall structure of the system of the present invention;
FIG. 2 is a schematic diagram of the control principle of the system of the present invention;
FIG. 3 is a graph illustrating the effect of the present invention on the control of severe slugging;
FIG. 4 is a schematic view showing the throttle opening increase according to the present invention;
FIG. 5 is a schematic diagram of the riser bottom pressure reduction amplitude of the present invention;
FIG. 6 is a schematic diagram of the magnitude of the reduction in riser steady state pressure differential of the present invention.
In the figure, 1 is a differential pressure sensor, 2 is an industrial personal computer, 3 is a first pressure sensor, 4 is a throttle valve, 5 is a second pressure sensor, 6 is a high-pressure gas-liquid separator, 7 is an exhaust port control valve, and 8 is a liquid discharge port control valve.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings, which are included to illustrate and not to limit the invention:
referring to fig. 1, the system for eliminating severe slug flow by combining a gas-liquid separator and a throttle valve of the invention comprises a differential pressure sensor 1, an industrial personal computer 2, a first pressure sensor 3, a throttle valve 4, a second pressure sensor 5, an exhaust port control valve 7 and a liquid outlet control valve 8.
The differential pressure sensor 1 and the first pressure sensor 3 are arranged at the top of the vertical pipe, the throttle valve 4 is arranged at the outlet end of the vertical pipe, the second pressure sensor 5 is arranged at the inlet of the high-pressure gas-liquid separator 6, the exhaust port control valve 7 is arranged at the exhaust port at the top of the high-pressure gas-liquid separator 6, and the liquid discharge port control valve 8 is arranged at the liquid discharge port at the bottom of the high-pressure gas-liquid separator 6; the differential pressure sensor 1, the first pressure sensor 3, the throttle valve 4, the second pressure sensor 5, the exhaust port control valve 7 and the liquid outlet control valve 8 are respectively connected with the industrial personal computer 2.
In a preferred embodiment of the invention, the throttle 4 is connected in series in the pipeline by a connecting flange, and the inner diameter of the throttle 4 is equal to that of the pipeline.
In a preferred embodiment of the invention, the single action amplitude of the throttle 4 is 2% to 10%. While the opening range of the throttle valve 4 is ± 15% of the opening set value.
In a preferred embodiment of the present invention, a PID controller is built in the industrial personal computer 2, and the PID controller is connected to the throttle valve 4.
In a preferred embodiment of the present invention, the differential pressure sensor 1, the first pressure sensor 3, the throttle valve 4, the second pressure sensor 5, the exhaust port control valve 7, and the drain port control valve 8 are communicatively connected to the industrial personal computer 2 via shielded cables.
The method for eliminating the severe slug flow by adopting the system for eliminating the severe slug flow by combining the gas-liquid separator and the throttle valve comprises the following steps:
the method comprises the following steps that a differential pressure sensor 1 collects a local differential pressure signal at the top of a vertical pipe, a first pressure sensor 3 collects a pressure signal at the top of the vertical pipe, a second pressure sensor 5 collects a pressure signal at the inlet of a high-pressure gas-liquid separator 6, the signals are transmitted to an industrial personal computer 2, signal parameter values corresponding to different flow patterns are preset in the industrial personal computer 2, the flow pattern in a gathering and transporting-vertical pipe system is identified according to the collected signal parameters, and when the flow pattern is a serious slug flow, the pressure at the top of the vertical pipe is adjusted by controlling the opening degree of a throttle valve 4; meanwhile, the pressure of the high-pressure gas-liquid separator 6 is adjusted by controlling the opening degrees of the exhaust port control valve 7 and the liquid outlet control valve 8, so that the serious slug flow is eliminated.
Specifically, the method comprises the following steps: the industrial personal computer 2 comprises a signal acquisition module, a flow pattern recognition module and a slug control module, and the acquired signals are preprocessed by the signal acquisition module and then subjected to flow pattern recognition by the flow pattern recognition module; when the identification result is serious slug flow, calling a slug control model, calculating a vertical pipe top pressure set value required for eliminating the serious slug flow, reversely pushing out the opening change range of the throttle valve 4 by using the vertical pipe top pressure set value, and giving a high-pressure gas-liquid separator pressure set value in an allowable pressure range; the pressure of the high-pressure gas-liquid separator is controlled by a PID controller, a liquid outlet control valve 8 is used for controlling the liquid level to be stable, and an exhaust port control valve 7 is used for controlling the pressure of the high-pressure gas-liquid separator to be stable; comparing the set value of the top pressure of the vertical pipe with the actually measured value of the top pressure of the vertical pipe, and performing PID logical operation on the obtained difference value through a PID controller to obtain the corresponding valve opening of the throttle valve 4; the flow state can be influenced after the opening degree of the valve is changed, when the difference value approaches to 0, the flow reaches a stable state, and the phenomenon of serious slug flow is eliminated.
The valve opening of the throttle valve 4 is calculated by the following valve pressure drop formula:
Figure BDA0003287749370000071
wherein DP is the pressure drop across the throttle valve; c is a throttle coefficient, which is related to the valve characteristic;
UMIXthe gas-liquid mixed flow rate is calculated by the following formula:
Figure BDA0003287749370000072
wherein a isGThe gas fraction at the valve of the throttle valve 4, rhoGAnd ρLRespectively being gas and liquid density, UGAnd ULThe flow rates of the gas phase and the liquid phase are respectively;
the PID control process is calculated according to the following formula:
Figure BDA0003287749370000081
wherein z (t) is a valve opening adjustment value; e (t) is the deviation value of the output signal, and e (t) is the measured value of the top pressure of the vertical pipe-the set value of the top pressure of the vertical pipe; kPIs the proportional gain coefficient of the controller; t isIIntegrating the time constant for the controller; t isDIs the PID controller differential time constant.
When the actual value of the top pressure of the vertical pipe is more than 20 percent of the actual value of the top pressure of the vertical pipe, setting a proportional gain coefficient K of the first controllerP1And a first controller integration time constant TI1(ii) a When the actual value of the top pressure of the vertical pipe is less than 20 percent of the actual value of the top pressure of the vertical pipe, setting a proportional gain coefficient K of a second controllerP1And a second controller integration time constant TI1(ii) a Wherein, KP1＝10KP2，TI1＝0.2TI2。
The invention is further illustrated below in a specific embodiment:
in the system of the embodiment, the hardware part mainly comprises a differential pressure sensor 1 at the top of a vertical pipe, an industrial personal computer 2, a first pressure sensor 3, a throttle valve 4, a second pressure sensor 5 and a high-pressure gas-liquid separator 6; wherein differential pressure sensor 1 is located the riser top, and industrial computer 2 is located the control cabinet of experimental system, realizes the signal transmission process through shielded cable and above-mentioned device, and pressure sensor is including the first pressure sensor 3 that is located the riser top and the second pressure sensor 5 of high pressure gas-liquid separator entrance, and choke valve 4 and high pressure gas-liquid separator 6 are all in the defeated-riser system of collection through the flange series connection access. The throttle valve 4 is generally arranged at the outlet end of the vertical pipe of the gathering and transferring-vertical pipe system, the inner diameter of the throttle valve is the same as that of the gathering and transferring-vertical pipe system, and the flowing state of the multiphase fluid is not influenced when the throttle valve is fully opened. The high-pressure gas-liquid separator 6 is generally positioned at the tail end of a gathering-transporting-vertical pipe system and comprises a gas-liquid inlet end and two outlet ends, wherein the exhaust port control valve 7 is positioned at the top of the high-pressure gas-liquid separator 6 and used for controlling the outflow process of a gas phase and stabilizing the pressure of the system, and the liquid discharge port control valve 8 is positioned at the bottom of the high-pressure gas-liquid separator 6 and used for controlling the discharge process of a liquid phase and adjusting the height of the liquid level.
The industrial personal computer 2 is preset with a signal acquisition module, a flow pattern recognition module and a slug control module. The signal acquisition module is compiled by adopting a LabVIEW program and is used for receiving a real-time signal sent by a sensor in the gathering and transportation-vertical pipe system and carrying out preprocessing processes such as digital-to-analog conversion, noise reduction and filtering and the like; the flow pattern recognition module adopts a binary tree algorithm to construct a recognition model, and extracts characteristic quantities to finish a flow pattern quick recognition process through 6 layers of wavelet multi-scale decomposition; and the slug control module is established according to the experimental database and used for calculating control parameters, sending a control instruction to the throttle valve and keeping the throttle valve at a preset opening degree.
Referring to the schematic control principle shown in fig. 2, the local pressure difference at the top of the riser is obtained by a pressure difference sensor 1 installed at the top of the riser, and the pressure at the top of the riser and the inlet pressure of the high-pressure gas-liquid separator are obtained by a first pressure sensor 3 and a second pressure sensor 5. Firstly, a flow pattern rapid identification technology is adopted to perform a rapid identification process of severe slug flow according to signals such as local pressure difference at the top of the vertical pipe, and other pressure signals can also be used to complete the flow pattern identification process. When the recognition result is severe slug flow, the slug control model is called, and the place for eliminating severe slug flow is calculated according to the recognition result and other pressure parametersDesired riser top pressure setpoint SPTOPUsing the set value SPTOPReversely deducing the opening variation range of the outlet valve and giving a pressure set value SP of the gas-liquid separator in an allowable pressure rangeS. And the pressure of the gas-liquid separator is controlled by utilizing a PID controller, wherein a bottom liquid discharge valve is used for controlling the liquid level stability of the separator, and a top exhaust valve is responsible for controlling the pressure stability of the separator. Setting the riser top pressure SPTOPAnd the actual measured riser top pressure value PTOPComparing to obtain a difference value delta PTOPAnd carrying out PID logical operation through a PID controller to calculate the corresponding opening of the throttle valve 4. The flow conditions are influenced by a change in the valve opening, when Δ PTOPWhen the flow approaches 0, the flow reaches a steady state and the phenomenon of severe slug flow disappears.
In the embodiment, the flow pattern recognition model is constructed by adopting a binary tree algorithm, and characteristic quantities are extracted through 6 layers of wavelet multi-scale decomposition to finish the flow pattern rapid recognition process; the establishment of the slug control model is based on the data accumulation of a large number of multiphase flow experiment databases, and corresponding statistical analysis is completed by using the obtained experiment data, so that the mathematical relationship of pressure-flow pattern one-to-one correspondence is established. The pressure at the top of the vertical pipe required by control can be automatically calculated according to the flow pattern recognition result, the pressure is set as a set value of a PID control process, and a valve opening set value and a valve opening change range are given according to a valve pressure drop formula.
The PID controller for controlling the vertical pipe top throttle valve 4 adopts two sets of control parameters, and the parameters are determined according to the conventional PID parameter setting rule. When the deviation between the actual value of the pressure at the top of the vertical pipe and the set value is larger, i.e. e (t)>0.2SPTOPUsing a larger proportional gain factor KP1And a smaller integration time constant TI1So that the control variable can quickly approach the target value; when the deviation between the actual value of the pressure at the top of the vertical pipe and the set value is smaller, i.e. e (t)<0.2SPTOPUsing a smaller proportional gain factor KP2And a large integration time constant TI2. In this example KP1＝10KP2，TI1＝0.2TI2Preventing the control parameter from appearing in large amplitude around the target valueFluctuating, maintaining system stability. The cycle sampling period is set to 0.5s, and the average value of data in the period is taken as an input value, so that the signal noise is reduced.
According to the system and the method, an experiment for eliminating the serious slug flow of the gathering-riser system is developed. The inlet reduced gas phase velocity U is given as shown in FIG. 3SG0＝0.4m·s-1Conversion of liquid phase velocity USL＝0.25m·s-1Graph of the riser differential pressure fluctuation. When no control process is applied, there is a severe slug flow in the pipeline of the first kind, the amplitude of the fluctuation of the riser differential pressure is about 155KPa, and the slug cycle is about 150 s. When the system and the method of the invention are adopted to start control, the fluctuation range of the pressure difference of the riser is reduced to about 40KPa after about 240s (1.6 severe slug flow cycles) is observed, and the severe slug flow phenomenon in the system disappears at the moment, and the flow is converted into a stable flow pattern.
Fig. 4 shows a method for controlling severe slug flow by combining platform separation and throttling, compared with the case of increasing the opening of the throttle valve when severe slug flow is controlled by adopting a throttling method alone. The whole experimental range is as follows: inlet converted gas phase velocity USG0＝0.25～16m·s-1Inlet converted liquid phase velocity USL＝0.065～0.7m·s-1. It can be seen from fig. 4 that the valve opening is improved to some extent in most regions, especially in all operating conditions where severe slugging occurs. In the case of a high reduced gas phase velocity and a low liquid phase velocity, i.e. a reduced gas phase velocity of about USG0＝1.5～3m·s-1The valve opening degree is reduced to a certain degree in the area (2), the former is generally close to a stable flow condition, and the latter belongs to an irregular flow area, is almost rarely met in engineering practice and does not need to be controlled. The improvement of the opening of the throttle valve means smaller pressure drop of the throttle valve and larger fluid circulation area, the flow resistance can be effectively reduced, the service life of the throttle valve is prolonged, and the oil gas yield is improved to a certain extent.
FIGS. 5 and 6 show riser bottom pressure when controlled using the system and method, as compared to when controlled manually using a throttle valveThe force and riser steady state pressure differential decrease magnitudes. The experimental ranges are as follows: inlet converted gas phase velocity USG0＝0.25～7m·s-1Inlet converted liquid phase velocity USL＝0.065～0.7m·s-1. As can be seen from fig. 5 and 6, the riser bottom pressure can be effectively reduced by adopting the method for controlling compared with the method adopting manual throttling, and the average pressure reduction amplitude in the severe slug flow occurrence area is about 20 percent and is up to approximately 60 percent. Meanwhile, the stable pressure difference of the vertical pipe is obviously reduced, and the average reduction amplitude is about 10-20%. Similar effects are also obtained for unstable oscillatory flow patterns and irregular flow patterns. Therefore, the system and the method can achieve better effect when the system and the method are used for controlling the severe slug flow.
The above description is only a part of the embodiments of the present invention, and although some terms are used in the present invention, the possibility of using other terms is not excluded. These terms are used merely for convenience in describing and explaining the nature of the invention and are to be construed as any additional limitation which is not in accordance with the spirit of the invention. The foregoing is merely an illustration of the present invention for the purpose of providing an easy understanding and is not intended to limit the present invention to the particular embodiments disclosed herein, and any technical extensions or innovations made herein are protected by the present invention.

Claims (10)

1. A system for eliminating severe slug flow by combining a gas-liquid separator and a throttle valve is characterized by comprising a differential pressure sensor (1), an industrial personal computer (2), a first pressure sensor (3), the throttle valve (4), a second pressure sensor (5), an exhaust port control valve (7) and a liquid discharge port control valve (8);
the differential pressure sensor (1) and the first pressure sensor (3) are arranged at the top of the vertical pipe, the throttle valve (4) is arranged at the outlet end of the vertical pipe, the second pressure sensor (5) is arranged at the inlet of the high-pressure gas-liquid separator (6), the exhaust port control valve (7) is arranged at the exhaust port at the top of the high-pressure gas-liquid separator (6), and the liquid discharge port control valve (8) is arranged at the liquid discharge port at the bottom of the high-pressure gas-liquid separator (6); the differential pressure sensor (1), the first pressure sensor (3), the throttle valve (4), the second pressure sensor (5), the exhaust port control valve (7) and the liquid outlet control valve (8) are respectively connected with the industrial personal computer (2).
2. The system for eliminating severe slugging by combining a gas-liquid separator and a throttling valve as recited in claim 1, wherein the throttling valve (4) and the high-pressure gas-liquid separator (6) are connected in series in a pipeline through connecting flanges, and the inner diameter of the throttling valve (4) is equal to that of the pipeline.
3. The gas-liquid separator and throttling valve combined severe slug flow elimination system according to claim 1, characterized in that the single action amplitude of the throttling valve (4) is 2% -10%.
4. The gas-liquid separator and throttling valve combined severe slugging system according to claim 1, characterized in that the opening of the throttling valve (4) is in the range of ± 15% of the opening set value.
5. The system for eliminating severe slug flow by combining the gas-liquid separator and the throttling valve as claimed in claim 1, wherein a PID controller is arranged in the industrial personal computer (2), and the PID controller is connected with the throttling valve (4).
6. The system for eliminating severe slug flow by combining a gas-liquid separator and a throttling valve according to claim 1, characterized in that the differential pressure sensor (1), the first pressure sensor (3), the throttling valve (4), the second pressure sensor (5), the exhaust port control valve (7) and the drain port control valve (8) are in communication connection with the industrial personal computer (2) through shielded cables.
7. The method for eliminating severe slugging by adopting the system for eliminating severe slugging by combining the gas-liquid separator and the throttling valve according to any one of claims 1 to 6, is characterized by comprising the following steps:
the method comprises the following steps that a differential pressure sensor (1) collects a local differential pressure signal at the top of a vertical pipe, a first pressure sensor (3) collects a pressure signal at the top of the vertical pipe, a second pressure sensor (5) collects a pressure signal at the inlet of a high-pressure gas-liquid separator (6), the signals are transmitted to an industrial personal computer (2), signal parameter values corresponding to different flow patterns are preset in the industrial personal computer (2), the flow pattern in a gathering and transporting-vertical pipe system is identified according to the collected signal parameters, and when the flow pattern is a serious slug flow, the pressure at the top of the vertical pipe is adjusted by controlling the opening degree of a throttle valve (4); meanwhile, the pressure of the high-pressure gas-liquid separator (6) is adjusted by controlling the opening degrees of the exhaust port control valve (7) and the liquid outlet control valve (8), so that the serious slug flow is eliminated.
8. Method for severe slugging elimination with a system for severe slugging elimination using a gas-liquid separator in combination with a throttling valve according to claim 7, characterized in that in particular:
the industrial personal computer (2) comprises a signal acquisition module, a flow pattern recognition module and a slug control module, and the acquired signals are preprocessed by the signal acquisition module and then subjected to flow pattern recognition by the flow pattern recognition module; when the identification result is serious slug flow, calling a slug control model, calculating a vertical pipe top pressure set value required for eliminating the serious slug flow, reversely pushing out the opening change range of the throttle valve (4) by using the vertical pipe top pressure set value, and giving a high-pressure gas-liquid separator pressure set value in an allowable pressure range; the pressure of the high-pressure gas-liquid separator is controlled by a PID controller, a liquid outlet control valve (8) is used for controlling the liquid level stability of the high-pressure gas-liquid separator, and an exhaust port control valve (7) is used for controlling the pressure stability of the high-pressure gas-liquid separator; comparing the set value of the top pressure of the vertical pipe with the actually measured value of the top pressure of the vertical pipe, and carrying out PID logical operation on the obtained difference value through a PID controller to obtain the corresponding valve opening of the throttle valve (4); the flow state can be influenced after the opening degree of the valve is changed, when the difference value approaches to 0, the flow reaches a stable state, and the phenomenon of serious slug flow is eliminated.
9. The method of severe slugging elimination using a gas-liquid separator in combination with a throttling valve system according to claim 8,
the valve opening of the throttle valve (4) is calculated by the following valve pressure drop formula:
Figure FDA0003287749360000021
wherein DP is the pressure drop across the throttle valve; c is a throttle coefficient, which is related to the valve characteristic;
UMIXthe gas-liquid mixed flow rate is calculated by the following formula:
Figure FDA0003287749360000031
wherein a isGIs the gas fraction, rho, at the valve of the throttle valve (4)GAnd ρLRespectively being gas and liquid density, UGAnd ULThe flow rates of the gas phase and the liquid phase are respectively;
the PID control process is calculated according to the following formula:
Figure FDA0003287749360000032
wherein z (t) is a valve opening adjustment value; e (t) is the deviation value of the output signal, and e (t) is the measured value of the top pressure of the vertical pipe-the set value of the top pressure of the vertical pipe; kPIs the proportional gain coefficient of the controller; t isIIntegrating the time constant for the controller; t isDIs the PID controller differential time constant.
10. The method of severe slugging elimination using a gas-liquid separator in combination with a throttling valve system according to claim 9,
when the deviation value of the output signal is larger than 20% of the measured value of the top pressure of the vertical pipe, setting a proportional gain coefficient K of the first controllerP1And a first controller integration time constant TI1(ii) a When the deviation value of the output signal is less than 20% of the measured value of the top pressure of the vertical pipe, setting a proportional gain coefficient K of the second controllerP2And a second controller integration time constant TI2(ii) a Wherein, KP1＝10KP2，TI1＝0.2TI2。
CN202111153241.6A 2021-09-29 2021-09-29 System and method for eliminating severe slug flow by combining gas-liquid separator and throttle valve Pending CN113864653A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117608201A (en) * 2024-01-24 2024-02-27 中海油能源发展股份有限公司采油服务分公司 Intelligent optimization controller, system and control method for FPSO primary separator

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117608201A (en) * 2024-01-24 2024-02-27 中海油能源发展股份有限公司采油服务分公司 Intelligent optimization controller, system and control method for FPSO primary separator
CN117608201B (en) * 2024-01-24 2024-03-29 中海油能源发展股份有限公司采油服务分公司 Intelligent optimization controller, system and control method for FPSO primary separator

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