Subsea Christmas tree chemical reagent self-adaptive injection metering system and operation control method thereof

Abstract

The invention discloses an underwater Christmas tree chemical reagent self-adaptive injection metering system. The system comprises a self-adaptive analysis module located in an overwater master control station, a metering and adjusting module and a control module, wherein the metering and adjusting module and the control module are arranged in an underwater shell module; the shell module comprises a shell, and a Christmas tree connecting interface and an underwater robot interface which are arranged on the shell; the metering and adjusting module comprises a fluid inflow pipeline, a flow adjusting valve, a first buffer cavity, an ultrasonic flowmeter, a second buffer cavity and a fluid outflow pipeline which are arranged in the shell module and connected in sequence, the fluid inflow pipeline is connected with the reagent inlet pipe, and the fluid outflow pipeline is connected with the reagent outlet pipe; a valve needle driving mechanism matched with the flow adjusting valve is arranged in the shell. The invention further discloses an operation control method of the metering system.

Description

Technical Field

[0001] The invention belongs to the technical field of deepwater oil production, and relates to an underwater Christmas tree device, in particular to an underwater Christmas tree chemical reagent self-adaptive injection metering system. Background Art

[0002] At present, in the process of oil and natural gas extraction using offshore equipment, there is a problem of natural gas hydrates forming and blocking flow pipelines (Christmas tree production channels), valves and equipment. To this end, hydrate chemical reagents are injected into the Christmas tree production channel to resolve the risk of pipeline blockage.

[0003] Hydrate chemicals (also called reagents) currently in use include aqueous solutions of inorganic salt electrolytes such as sodium chloride and calcium chloride, and thermodynamically organic natural gas hydrate chemicals such as methanol and glycols (ethylene glycol, diethylene glycol). The process of injecting these hydrate chemicals / reagents into the production channel of the oil production tree is called "chemical reagent injection", but there are strict requirements on the amount of chemical reagents added. A submarine chemical injection metering valve disclosed in document CN107035335A includes a chemical injection flow path, an electric valve, a non-invasive flowmeter and a controller for adjusting the amount of fluid entering the wellhead; a vertically installed underwater chemical injection metering valve disclosed in document CN114893575A, the metering valve includes a packaging module, an electronic control module, a regulating valve and a flowmeter to achieve flow metering and flow regulation. The metering valve does not rely on a single flowmeter metering output, and outputs a high-precision flow measurement value through the flow data fusion of the flowmeter and the regulating valve, thereby avoiding the situation where the flowmeter fails and the metering is unable to be measured or the metering is inaccurate;

[0004] There are several problems in the existing chemical reagent injection technology that need to be optimized: 1) The injection volume of chemical reagents is affected by many factors such as free water content, wellhead pressure, wellhead temperature, etc., and the injection volume is difficult to control; 2) The injection volume of chemical reagents needs to be adjusted frequently, and manual operation causes the system injection flow rate to be unstable; 3) The injection of chemical reagents is affected by changes in the injection point pressure, and the discharge rate is unstable. At the same time, it is often affected by the chemical viscosity or ambient temperature of the chemical agent and deviates from the set rate. In order to ensure safety, the total amount of chemical reagents injected is often increased, resulting in excessively high costs for the use of chemical reagents. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an underwater chemical reagent self-adaptive injection metering system which can self-adaptively adjust the injection amount of the chemical reagent and can accurately meter it.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: an underwater Christmas tree chemical reagent adaptive injection metering system, including an adaptive analysis module located in an above-water main control station, and a housing module arranged underwater, the housing module including a housing and a Christmas tree connection interface and an underwater robot interface arranged on the housing; a metering and regulating module and a control module are arranged in the housing;

[0007] It also includes a wellhead free water content detector, a wellhead pressure sensor, and a wellhead temperature sensor electrically connected to the control module; the adaptive analysis module provides the control module with an adaptive injection amount of the chemical reagent of the oil tree based on the detection data of the wellhead free water content detector, the wellhead pressure sensor, and the wellhead temperature sensor; the control module is used to control the metering and regulating module to complete the adaptive injection of the chemical reagent;

[0008] The metering and regulating module comprises a fluid inflow pipeline, a flow regulating valve, a buffer chamber 1, an ultrasonic flowmeter, a buffer chamber 2, and a fluid outflow pipeline which are sequentially connected and arranged in a housing module. The fluid inflow pipeline is connected to a reagent inlet pipe, and the fluid outflow pipeline is connected to a reagent outlet pipe. A valve needle driving mechanism cooperating with the regulating flow valve is arranged in the housing; the ultrasonic flowmeter is electrically connected to the control module;

[0009] The flow regulating valve comprises a valve housing, a liquid inlet hole is provided on the valve housing, a liquid inlet joint and a locking nut for locking the liquid inlet joint are provided on the liquid inlet hole on the valve housing, a valve seat is provided at one end of the valve housing, a valve body is provided at the other end of the valve housing, a valve hole is provided in the valve body, a liquid outlet joint is provided at one end of the valve body away from the valve housing, an annular liquid inlet groove is provided on the outer periphery of one side of the valve seat close to the valve body, a plurality of liquid holes which are connected with the inner cavity of the valve housing are provided on the groove wall of the liquid inlet groove on the valve seat, a valve stem is passed through the valve seat, a boss portion which matches with the wall of the liquid inlet groove is provided on the valve stem, the end of the valve stem which passes through the valve hole is conical, and an end sealing device is provided on the valve seat at the end of the valve stem which passes through;

[0010] The valve stem driving mechanism includes a base connecting flange arranged on the valve housing, a connecting seat is provided on the base connecting flange, a guide rail is provided on the connecting seat, a sliding block moving parallel to the valve stem is provided on the guide rail, a driving rack is provided on the sliding block, a valve needle connecting block is provided at the end of the driving rack, the valve needle connecting block is connected to the end of the valve stem passing through the valve seat, a motor fixing seat is provided on the mounting seat, a driving motor is provided on the motor fixing seat, a driving gear meshing with the driving rack is provided on the output shaft of the driving motor, and the driving motor is electrically connected to the control module.

[0011] As a preferred solution, it also includes a self-cleaning module; the self-cleaning module includes a flushing liquid supply device and two switching modules respectively arranged on the reagent inlet pipe and the reagent outlet pipe, the two switching modules are connected by a flushing pipe, the outlet of the flushing liquid supply device is connected to the switching module on the reagent outlet pipe through the flushing pipe, and the switching module on the reagent inlet pipe is connected to the flushing liquid discharge pipe; the switching module includes a module body and a backwashing motor, and the module body is provided with a connecting hole connected to the pipe mouth of the fluid inlet pipe or the fluid outflow pipe, and a drug passing hole connected to the reagent inlet pipe or the reagent outlet pipe. , and a pair of flushing holes opened directly opposite; the module body is provided with an inner cavity with a central hole, and a T-shaped adapter is movably provided in the inner cavity, the middle part of the T-shaped adapter is connected with the output shaft of the backwashing motor extending into the module body, and the backwashing motor drives the T-shaped adapter to switch between the medication position and the flushing position; end face sealing rings are respectively provided on the pipe openings at both ends of the T-shaped tube; the middle pipe opening of the T-shaped adapter is connected with the connecting hole; when in the medication position, one end of the T-shaped adapter is connected to the medicine hole, and the other end of the T-shaped adapter forms a seal with the inner cavity wall of the module body; when in the flushing position, the two end pipe openings of the T-shaped adapter are respectively connected to a pair of flushing holes.

[0012] As a preferred solution, the ultrasonic flowmeter includes a π-shaped pipe, the two curved ends of the π-shaped pipe are respectively used to connect the buffer chamber one and the buffer chamber two, and ultrasonic transducers are respectively provided at the two ends of the straight pipe section of the π-shaped pipe, and the ultrasonic transducers are electrically connected to the control module.

[0013] As a preferred solution, it also includes a remotely-installed monitoring module located in the main control station on the water, and the control module communicates with the monitoring module to realize remote monitoring and reliability simulation of connection with external equipment.

[0014] As a preferred solution, two buffer plates are provided inside the buffer cavity 1, and through holes with different axes are opened on the two buffer plates; two buffer plates are provided inside the buffer cavity 2, and through holes with different axes are opened on the two buffer plates.

[0015] As a preferred solution, it also includes an internal pressure balancing mechanism arranged in the shell; the internal pressure balancing mechanism includes at least one bladder arranged on the shell and the inner cavity of which is connected to the outside.

[0016] Another technical problem to be solved by the present invention is to provide an operation control method for the above-mentioned underwater chemical reagent adaptive injection metering system.

[0017] In order to solve the above technical problems, the technical solution adopted by the present invention is: an operation control method of the underwater chemical reagent adaptive injection metering system as described above, comprising the following steps:

[0018] Step 1: System self-check

[0019] Before using the system, use the monitoring module to check whether the fluid pipeline interface and electrical connection interface are in good condition;

[0020] Step 2: Calculation of chemical reagent adaptive injection volume

[0021] Adopting the adaptive analysis module to calculate the injection amount of chemical reagents, and obtaining the value of the methanol injection amount Mcd or the ethylene glycol injection amount Ecd;

[0022] Step 3: Chemical reagent injection operation

[0023] The value of the methanol injection amount Mcd or the ethylene glycol injection amount Ecd is provided to the metering and regulation module and the control module, and the following judgment is made:

[0024] When one of the change in oil and gas free water content ΔW, wellhead pressure change ΔP, and wellhead temperature change ΔT exceeds the set threshold, the coarse control mode is executed: the methanol injection amount Mcd and ethylene glycol injection amount Ecd calculated by the adaptive analysis module are selected as the chemical reagent injection amount, and provided to the metering and regulation module and the control module, and the system executes the chemical reagent injection amount adjustment;

[0025] When the change in oil and gas free water content ΔW, wellhead pressure change ΔP, and wellhead temperature change ΔT do not exceed the set threshold, the precision control mode is executed: the adaptive analysis module is used to calculate the injection volume, and the results are provided to the metering and regulation module and the control module. A closed-loop control strategy is adopted to jointly control the accuracy of the chemical injection volume through the metering and regulation module and the control module; the details are as follows:

[0026] Step 310: The control module monitors the flow of the flow control valve in real time through the ultrasonic flow meter, records the flow value, and thus determines the flow error value and the flow error change rate;

[0027] Step 320: Input the flow error value and the flow error change rate into the fuzzy PID controller of the control module and output the flow control amount; including:

[0028] S321: Determine the fuzzy controller structure and use the differential algorithm to improve the fuzzy PID controller;

[0029] Definition: r(t) represents the flow setting value of the flow control valve, y(t) represents the measured flow value of the flow control valve, e(t) represents the error between the flow setting value and the measured flow value, that is, the flow error value e, de(t) / dt represents the flow error change rate ec, u(t) represents the output of the fuzzy PID controller, that is, the valve control amount, Kp, Ki, Kd represent the proportional coefficient setting value, integral coefficient setting value and differential coefficient setting value respectively;

[0030] The fuzzy PID controller structure satisfies:

[0031] E(t)=r(t)-y(t); (1)

[0032]

[0033] The differential optimization algorithm is used to optimize the parameters of the fuzzy PID so that Kp, Ki, and Kd converge to the minimum value;

[0034] S322: define the fuzzy distribution of input and output quantities, define the range of input quantities e, ec and output quantities ΔKp, ΔKi, ΔKd as the domain [-6, 6], select the seven-level fuzzy subset {NB, NM, NS, ZO, PS, PM, PB}, where N represents negative, P represents positive, B represents large, M represents medium, S represents small, and ZO represents 0;

[0035] S323: Establish fuzzy rules and find corresponding fuzzy rules according to fuzzy subsets;

[0036] S324: Convert the outputted fuzzy value into a clear value through defuzzification processing:

[0037] The fuzzy controller defuzzifies the fuzzy quantity of the PID coefficient and outputs the PID coefficient adjustment value; when making fuzzy subset decisions, the centroid method is used to map the actual domain to map the adjustment value of the PID coefficient to the actual domain; the PID coefficient setting value is obtained according to the following formula:

[0038]

[0039] Among them, K p0 , K i0 , K d0 They represent the preset value of proportional coefficient, the preset value of integral coefficient and the preset value of differential coefficient respectively, ΔKp, ΔKi and ΔKd represent the adjustment value of proportional coefficient, the adjustment value of integral coefficient and the adjustment value of differential coefficient respectively, Kp, Ki and Kd represent the setting value of proportional coefficient, the setting value of integral coefficient and the setting value of differential coefficient respectively;

[0040] Step 330: The control module adjusts the opening of the needle valve through the driving motor according to the flow control amount, thereby controlling the flow;

[0041] Step 340: The system automatically implements the cycle of steps 310 to 330 until the dosage meets the requirement. When the control module controls the system to stop running, the flow regulation automatically stops.

[0042] As a preferred solution, in step S323, according to preset fuzzy subsets, a triangle membership function is used to divide the values ​​on the standard domain into the fuzzy subsets.

[0043] As a preferred solution, it also includes cleaning and maintenance control; during cleaning and maintenance, the backwash motors on the two switching modules drive the T-shaped tube to rotate to the flushing position, and then the cleaning liquid of the flushing liquid supply device enters the switching module on the reagent outlet pipe in one way, directly flows through the switching module on the reagent inlet pipe, and is discharged from the flushing liquid discharge pipe; the other way enters the switching module on the reagent outlet pipe, passes through the flowmeter and the regulating valve, and then is discharged from the flushing liquid discharge pipe after the switching module on the reagent inlet pipe.

[0044] As a preferred solution, in step three, the threshold values ​​of the change in oil and gas free water content ΔW, the change in wellhead pressure ΔP, and the change in wellhead temperature ΔT are set to values ​​between 1% and 3%.

[0045] As a preferred solution, in step three, when the system has a flow metering error exceeding the range of ±5%, the monitoring module is used to monitor and determine whether a pipeline blockage occurs. If a pipeline blockage occurs, the chemical reagent injection operation is suspended and the cleaning and maintenance control operation is started. After cleaning, the chemical reagent injection operation is continued. If the system still has a flow metering error exceeding the range of ±5%, an alarm is prompted.

[0046] The beneficial effects of the present invention are:

[0047] The present invention provides an underwater Christmas tree chemical reagent adaptive injection metering system, which can automatically calculate the required injection flow rate by designing an adaptive analysis module, has the characteristics of adaptive scene / operating condition, and has higher accuracy compared with the calculation results of empirical formulas;

[0048] This system has developed a "series-parallel" integrated functional module to achieve the integration of flow metering and flow regulation functions; developed a two-level flow regulation method, based on the injection volume calculation of the adaptive analysis module, through the online closed-loop automatic regulation control of the flow of the regulating valve, to improve the real-time performance and accuracy of flow regulation;

[0049] Since the valve seat is provided with an annular liquid inlet groove on the outer periphery of one side close to the valve body, and the valve seat is provided with a number of liquid holes on the wall of the liquid inlet groove that are connected to the inner cavity of the valve shell, the fluid can evenly fill the interior of the valve seat, reducing the vibration effect of the fluid rushing into the valve seat on the valve needle. In addition, the regulating valve adopts a mobile support piston to ensure that the valve needle moves smoothly in high-pressure and high-speed fluids, reducing the influence of valve needle vibration on the flow regulation accuracy.

[0050] This system is equipped with a self-cleaning module for debris self-cleaning: the debris at the inlet and outlet of the underwater chemical injection metering valve pipeline is flushed and removed, which can effectively improve the use efficiency and service life of CIMV and marine equipment, reduce the cleaning frequency of the underwater chemical injection metering valve, and increase the use cycle of a single deployed underwater chemical injection metering valve; it can easily realize regular cleaning of the pipeline and its joints, avoiding the tedious work of separate recovery of the equipment for inspection or maintenance and re-lowering for installation and use.

[0051] Since the ultrasonic flowmeter includes a π-shaped pipe, the two curved ends of the π-shaped pipe are respectively used to connect the buffer chamber one and the buffer chamber two, and ultrasonic transducers are respectively provided at the two ends of the straight pipe section of the π-shaped pipe, and the ultrasonic transducers are electrically connected to the control module; the ultrasonic transducers are placed on both sides of the pipe, and the transmission speed direction of the ultrasonic wave is parallel to the flow direction of the fluid, which can reduce the interference of the fluid flow on the ultrasonic signal.

[0052] This system is equipped with an internal pressure balancing mechanism and a pressure self-balancing regulating valve used in a high-pressure environment to ensure the stability and reliability of flow regulation;

[0053] In this system, since two buffer plates are arranged inside buffer chamber 1 and through holes with different axes are opened on the two buffer plates, and two buffer plates are arranged inside buffer chamber 2 and through holes with different axes are opened on the two buffer plates, the influence of flow velocity change on flow rate is effectively reduced, and the flow velocity in the ultrasonic flowmeter pipeline is ensured to be uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 : The system composition of the present invention;

[0055] Figure 2 : The structural composition diagram of the metering and regulating module and other parts of the present invention;

[0056] Figure 3 : Structural composition diagram of the metering and regulating module and other parts of the present invention (from another perspective);

[0057] Figure 4 :The functional modules of the device of the present invention are as follows Figure 1 ;

[0058] Figure 5 :The functional modules of the device of the present invention are as follows Figure 2 ;

[0059] Figure 6 : A cross-sectional view of the flow control valve of the device of the present invention;

[0060] Figure 7 :Valve needle drive mechanism structure of the device of the present invention Figure 1 ;

[0061] Figure 8 : Composition diagram of the control module of the present invention;

[0062] Fig. 9 : A schematic diagram of the connection of the relevant parts of the self-cleaning module of the present invention;

[0063] Fig.10 : System control flow chart of the present invention;

[0064] Fig.11 : Flow chart of the system control method of the present invention;

[0065] In the figure: 1-adaptive analysis module, 2-metering and regulation module, 3-control module, 4-self-cleaning module, 5-monitoring module, 6-housing module; 61-xmas tree connection interface, 62-underwater robot interface;

[0066] 21-fluid inflow pipeline, 22-flow regulating valve, 23-valve needle driving mechanism, 24-buffer chamber 1, 25-ultrasonic flowmeter, 251-ultrasonic transducer, 26-buffer chamber 2, 27-fluid outflow pipeline, 28-electronic compartment, 29-internal pressure balancing mechanism, 290-skin bag, 291-locking screw;

[0067] 220-valve housing, 221-valve seat, 222-valve needle, 223-valve seat sealing ring, 224-valve seat sleeve, 225-end clamping flange, 226-valve needle sealing ring, 227-valve needle sleeve, 228-clamping block, 229-valve body, 2210-liquid outlet joint, 2211-liquid inlet joint, 2212-locking nut 1, 2213-locking nut 2, 2214-top sleeve; 230-fixed seat, 231-rack fixed seat sealing ring, 232-base connecting flange, 233-connecting seat, 234-guide rail, 235-sliding block, 236-driving gear, 237-driving rack, 238-gear support seat, 239-motor fixed seat, 2310-driving motor, 2311-coupling, 2312-bearing, 2313-valve needle connecting block;

[0068] 31-power supply unit, 32-main control chip, 33-storage unit, 34-RS485 conversion chip, 35-flow measurement chip, 36-wellhead free water content detector, 37-wellhead pressure sensor, 38-wellhead temperature sensor. DETAILED DESCRIPTION

[0069] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0070] like Figure 1-8As shown, the underwater Christmas tree chemical reagent adaptive injection metering system includes an adaptive analysis module 1 located in the above-water main control station, a metering and regulating module 2 and a control module 3 arranged in an underwater housing module 6; the housing module 6 includes a housing and a Christmas tree connection interface 61 and an underwater robot interface 62 arranged on the housing;

[0071] It also includes a wellhead free water content detector 36, a wellhead pressure sensor 37, and a wellhead temperature sensor 38 electrically connected to the control module 3; the adaptive analysis module 1 provides an adaptive injection amount of the chemical reagent of the oil tree based on the detection data of the wellhead free water content detector 36, the wellhead pressure sensor 37, and the wellhead temperature sensor 38, has the characteristics of adaptive scene / operating condition, and is connected to the control module 3 through a data line and a signal line; the control module 3 is connected to the metering and regulating module 2 and the self-cleaning module 4 through a data line and a signal line respectively; it also includes the self-cleaning module 4 and a remotely set monitoring module 5 located in the water main control station; the monitoring module 5 includes a monitor simulation device and a network for communicating with the control module 3;

[0072] The adaptive analysis module 1 is provided with an analyzer, a database and a chemical agent injection amount analysis software. The database is provided with a chemical agent injection amount analysis model and injection amount analysis results, which are provided to the metering and regulation module 2 for injection and flow regulation to meet the requirements of the Christmas tree process pipeline for inhibiting hydrate formation. At the same time, the database is also provided with the control module 3 data information and the metering and regulation data information of the metering and regulation module 2; the injection amount analysis software can select one of HYSYS software, PVT sim software, or Multiflash software according to different actual oil production scenarios, software characteristics and applicable range; the chemical agent injection amount obtained by the adaptive analysis module 1 is more accurate than the result calculated by the empirical formula;

[0073] The factors that affect the injection volume of chemical reagents include the free water content W at the wellhead, the wellhead pressure P and the wellhead temperature T. For a wellhead in a certain sea area, that is, the free water content W, the pressure P and the temperature T at the wellhead are fixed values ​​(different wellheads in different sea areas or in the same sea area have different fixed values), a set of corresponding methanol or ethylene glycol injection volumes can be obtained through the analysis model in the database, and the maximum value that meets the injection volume requirements is taken (first operation):

[0074] Methanol injection amount: Mcd = max{Mci, Mcj, Mck}; Mci, Mcj, Mck are the methanol injection amounts required under the conditions of free water content W, pressure P and temperature T as constant values;

[0075] Ethylene glycol injection amount: Ecd = max{Eci, Ecj, Eck}; Eci, Ecj, Eck are the ethylene glycol injection amounts required under the conditions of free water content W, pressure P and temperature T being constant values;

[0076] During the continuous operation of the same wellhead, due to the change of environmental conditions, the free water content of oil and gas, the wellhead pressure and the wellhead temperature have different effects on the injection amount of chemical reagents. When the changes of these three factors are significant, in order to improve the calculation accuracy of the injection amount of chemical reagents such as methanol and ethylene glycol, the correlation between the influence of the change of free water content, wellhead pressure and wellhead temperature factors on the injection amount is established as shown in the table below. The analyzer in the adaptive analysis module 1 calculates the incremental change of the required chemical reagents when the free water content, wellhead pressure and wellhead temperature change;

[0077]

[0078] Considering the influence of the above factors, the analyzer in the adaptive analysis module 1 is used to correct the injection amount of the chemical reagent, and the correction principle is as follows:

[0079] The free water content, wellhead pressure, and wellhead temperature changes (value-added) ΔWi, ΔPj, and ΔTk are set respectively. Each factor takes n nodes according to actual needs. The number of nodes for each factor can be the same or different. Based on this, the changes in the injection amount of methanol and ethylene glycol are calculated through the analysis model, and the following model is established:

[0080] Methanol injection amount:

[0081] ΔMcimax=max{ΔMci}; (i=1,…,n1)

[0082] Δmcjmax=max{ΔMcj}; (j=1,...,n2)

[0083] Δmckmax=max{ΔMck}; (k=1,...,n3)

[0084] ΔMcd=max{ΔMcimax, ΔMcjmax, ΔMckmax};

[0085] Ethylene glycol injection amount:

[0086] ΔEcimax=max{ΔEci}; (i=1,…,n1)

[0087] ΔEcjmax=max{ΔEcj}; (j=1,...,n2)

[0088] ΔEckmax=max{ΔEck}; (k=1,...,n3)

[0089] ΔEcd=max{ΔEcimax, ΔEcjmax, ΔEckmax};

[0090] The above-mentioned revised calculation results are stored in the database of the adaptive analysis module 1; the final actual injection volume considering the different oil and gas components and the changes in environmental conditions is:

[0091] Methanol injection amount: Mc=Mcd+ΔMcd;

[0092] Ethylene glycol injection amount: Ec = Ecd + ΔEcd;

[0093] It should be noted that the adaptive analysis module 1 is used to calculate the injection amount of chemical reagents. Considering the influence of multiple factors, the result has a certain deviation from the actual required injection amount, which belongs to the rough control mode; when the changes in the free water content, wellhead pressure and wellhead temperature, which are factors affecting the injection amount, are small (threshold control), the system does not correct the injection amount of chemical reagents. At this time, the flow regulation system (including the flow changes caused by other influencing factors) is automatically adjusted and controlled with high precision through the metering and regulation module 2, which belongs to the fine control mode; on the other hand, the above adaptive regulation of the changes in the three factors of free water content W, pressure P and temperature T can also be extended to the regulation of the injection amount of chemical reagents when more than three factors change, or the regulation of the injection amount of chemical reagents when two of the factors change;

[0094] The metering and regulating module 2 includes a fluid inlet pipeline 21, a flow regulating valve 22, a buffer chamber 1 24, an ultrasonic flowmeter 25, a buffer chamber 26, and a fluid outflow pipeline 27, which are sequentially connected in the housing module. The fluid inflow pipeline 21 is connected to the reagent inlet pipe, and the fluid outflow pipeline 27 is connected to the reagent outlet pipe. The housing is provided with a valve needle drive mechanism 23 that cooperates with the regulating flow valve; the buffer chamber 1 24 is provided with two buffer plates, and the two buffer plates are provided with through holes of different axes. The buffer chamber 26 is provided with two buffer plates, and the two buffer plates are provided with through holes of different axes. The pipeline flow channel is a variable diameter flow channel, and a buffer chamber is used between the variable diameter flow channels to effectively reduce the influence of flow velocity changes on the flow rate, and ensure uniform flow velocity at the ultrasonic flowmeter pipeline.

[0095] The ultrasonic flowmeter 25 includes a π-shaped pipe, and the two curved ends of the π-shaped pipe are respectively used to connect the buffer chamber 1 24 and the buffer chamber 2 26. Ultrasonic transducers 251 are respectively provided at the two ends of the straight pipe section of the π-shaped pipe, and the ultrasonic transducer 251 is electrically connected to the control module 3.

[0096] The π-shaped pipe can use the stability of the flow field as the evaluation standard, conduct a quantitative analysis on the influence of various structural parameters of the pipe, determine the size of each parameter with reference to the analysis results, and thus determine the final size of the pipe. The influence of each structural parameter on the flow field stability can be obtained through range analysis, and further optimization can be carried out based on the above results, so as to obtain the best pipe within the limited range, which can meet the requirements of wide range (range ratio can reach more than 30) injection and high-precision metering of flow under small diameter (diameter less than 20mm) working conditions.

[0097] The housing is provided with an electronic compartment 28 for accommodating the control module 3; it also includes an internal pressure balancing mechanism 29 arranged in the housing; the internal pressure balancing mechanism 29 includes at least one bladder 291 arranged on the housing and the inner cavity of which is connected to the outside, and a compression nut 292 for fixing the bladder 291. In order to balance the internal and external pressures, when working, allowing seawater to rush into the bladder 291 can effectively reduce the pressure difference between the inside and the outside, thereby optimizing the structure and reducing the stress strength of the overall structure.

[0098] The flow regulating valve 22 includes a valve housing 220, on which a liquid inlet hole is provided, on which a liquid inlet joint and a locking nut 1 for locking the liquid inlet joint are provided, a valve seat 221 is provided at one end of the valve housing 220, and an end clamping flange 225 is provided at the end of the valve seat 221 at the end of the valve housing 220; a valve seat sealing ring 223 and a valve seat shaft sleeve 224 are provided between the valve housing 220 and the valve seat 221, a step surface matching the valve seat sealing ring 223 is provided on the inner side of the valve housing 220, and a step surface matching the valve seat shaft sleeve 224 is provided on the valve seat 221;

[0099] The other end of the valve housing 220 is provided with a valve body 229, and a valve hole is provided in the valve body 229. A liquid outlet joint 2210 is provided on the end of the valve body 229 away from the valve housing 220. A top sleeve 2214 and a locking nut 2213 connected to the sealed liquid outlet joint 2210 are provided on the valve body 229. An annular liquid inlet groove is provided on the outer periphery of the side of the valve seat 221 close to the valve body 229. The valve seat 221 is provided with a plurality of grooves on the groove wall of the liquid inlet groove that are connected with the inner cavity of the valve housing 220. The valve seat 221 is provided with a valve stem 222, and the valve stem 222 is provided with a boss portion that matches the wall of the liquid inlet groove. The end of the valve stem 222 that penetrates the valve hole is conical, and the end of the valve seat 221 where the valve stem 222 penetrates is provided with an end sealing device; the end sealing device includes a valve needle sealing ring 226, a valve needle shaft sleeve 227, and a pressing block 228 that presses the valve needle shaft sleeve 227, which are arranged in sequence from the inside to the outside at the outlet of the valve stem on the outer side of the valve body 229;

[0100] The valve stem driving mechanism includes a fixed seat 230 arranged on the valve housing 220, the fixed seat 230 is provided with a base connecting flange 232, the fixed seat 230 is provided with a rack fixed seat sealing ring 231 on the periphery of the base connecting flange 232, the base connecting flange 232 is provided with a connecting seat 233, the connecting seat 233 is provided with a guide rail 234, the guide rail 234 is provided with a sliding block 235 which moves parallel to the valve stem, the sliding block 235 is provided with a driving rack 237, the end of the driving rack 237 is provided with a valve needle connecting block 2313, the valve needle connecting block 2313 is connected to the end of the valve stem passing through the valve seat 221, the mounting seat is provided with a motor fixed seat 239, the motor fixed seat 239 is provided with a driving motor 2310, and the output shaft of the driving motor 2310 is provided with a driving gear 236 which meshes with the driving rack 237;

[0101] The motor output shaft passes through the motor fixing seat 239, and the motor fixing seat 239 is provided with a coupling 2311 connected to one end of the gear 236 shaft of the driving gear 236. The connecting seat 233 is provided with a gear support seat 238, and the other end of the gear 236 shaft of the driving gear 236 is rotatably set in the gear support seat 238 through a bearing 2312.

[0102] The control module 3 is arranged in the electronic compartment 28, and includes a power supply unit 31, a main control chip 32, a storage unit 33, an RS485 conversion chip 34, a flow measurement chip 35, and a network and control software for communicating with the monitoring module 5, and is used for data information collection and transmission, command issuance, execution control, and local control of the underwater oil tree chemical reagent adaptive injection metering system;

[0103] The power supply unit 31 is used to supply power to the main control chip 32, the flow measurement chip 35, etc. The flow measurement chip 35 receives the signal from the ultrasonic transducer 251 and sends it to the main control chip 32 after processing. After processing, the data is stored through the storage unit 33 and sent to the data display device at the same time.

[0104] The self-cleaning module 4 includes a flushing liquid supply device and two switching modules respectively arranged on the reagent inlet pipe and the reagent outlet pipe, the two switching modules are connected through a flushing pipe, the outlet of the flushing liquid supply device is connected to the switching module on the reagent outlet pipe through the flushing pipe, and the switching module on the reagent inlet pipe is connected to the flushing liquid discharge pipe; the switching module includes a module body and a backwashing motor, the module body is provided with a connecting hole connected to the pipe mouth of the fluid inlet pipe or the fluid outflow pipe, a medicine hole connected to the reagent inlet pipe or the reagent outlet pipe, and a A pair of flushing holes; the module body is provided with an inner cavity with a central hole, in which a T-shaped adapter is movably provided, the middle part of the T-shaped adapter is connected to the output shaft of the backwashing motor extending into the module body, and the backwashing motor drives the T-shaped adapter to switch between the medication position and the flushing position; end face sealing rings are respectively provided on the two end openings of the T-shaped tube; the middle opening of the T-shaped adapter is connected to the connecting hole; in the medication position, one end opening of the T-shaped adapter is connected to the medicine hole, and the other end opening of the T-shaped adapter forms a seal with the inner cavity wall of the module body; in the flushing position, the two end openings of the T-shaped adapter are respectively connected to a pair of flushing holes.

[0105] like Fig. 9 As shown, the metering and regulating module 2 and the self-cleaning module 4 can be connected through pipelines and their control valves to form a debris and dirt self-cleaning path / channel, and the process pipeline and its joints are cleaned regularly. The process pipeline self-cleaning channel is divided into two, and the cleaning path one is the input and output interface debris cleaning path, that is, Fig.11 In the figure, the second cleaning path is the overall process pipeline cleaning path, that is, Fig.11 "F1-F2-D4-D1-C2-C1-B2-B1-A2-A3" in

[0106] The flow regulating valve 22 and the ultrasonic flow meter 25 are connected in series to form a chemical reagent injection metering and precision adjustment loop. The flow metering and adjustment loop is in parallel mode with the cleaning path one of the self-cleaning module 4, and in parallel mode with the cleaning path two of the self-cleaning module 4. This "series-parallel" integrated functional pipeline can easily realize the integration of functions such as flow metering, flow regulation, and fault handling, and the integration of common and standby functions, thereby avoiding the risk of the flow meter being disabled due to failure.

[0107] When the metering system is working normally, the chemical agent injection metering and regulation are realized through the fluid entering the metering and regulation module 2; when the pipeline is blocked or the pipeline is self-cleaned regularly, the backwash motor drives the transfer tube to rotate, and cleaning path one or cleaning path two can be selected, so that the cleaning liquid flows directly from the liquid inlet to the liquid outlet, thereby cleaning the pipeline.

[0108] like Fig.10Before the system is used, the housing module 6 and other components are installed as a whole on the Christmas tree by an underwater robot.

[0109] An operation control method of the underwater chemical reagent adaptive injection metering system as described above comprises the following steps:

[0110] Step 1: System self-check

[0111] Before using the system, use the monitoring module 5 to check whether the fluid pipeline interface and the electrical connection interface are connected properly;

[0112] Step 2: Calculation of chemical reagent adaptive injection volume

[0113] Adopting the adaptive analysis module 1 to calculate the injection amount of chemical reagents, and obtaining the value of the methanol injection amount Mcd or the ethylene glycol injection amount Ecd;

[0114] Step 3: Chemical reagent injection operation

[0115] The value of the methanol injection amount Mcd or the ethylene glycol injection amount Ecd is provided to the metering and regulating module 2 and the control module 3; and the following judgment is made:

[0116] When one of the change in oil and gas free water content ΔW, wellhead pressure change ΔP, and wellhead temperature change ΔT exceeds a set threshold (a value between 1% and 3%, set according to actual site conditions), the coarse control mode is executed: the methanol injection amount Mcd and ethylene glycol injection amount Ecd calculated by the adaptive analysis module 1 are selected as the chemical reagent injection amount, and provided to the metering and regulation module 2 and the control module 3, and the system performs chemical reagent injection amount adjustment;

[0117] When the change in oil and gas free water content ΔW, wellhead pressure change ΔP, and wellhead temperature change ΔT do not exceed the set threshold (a value between 1% and 3%, set according to the actual situation on site), the precision control mode is executed: the injection volume is calculated using the adaptive analysis module 1, and the result is provided to the metering and regulation module 2 and the control module 3. A closed-loop control strategy is adopted to jointly control the accuracy of the chemical injection volume through the metering and regulation module 2 and the control module 3, including the following steps:

[0118] Step 310: The control module 3 monitors the flow of the flow regulating valve in real time through the ultrasonic flow meter 25, records the flow value, and thus determines the flow error value and the flow error change rate;

[0119] Step 320: Input the flow error value and the flow error change rate into the fuzzy PID controller of the control module 3, and output the flow control amount; the details are as follows:

[0120] S321: Determine the fuzzy controller structure and use the differential algorithm to improve the fuzzy PID controller;

[0121] Definition: r(t) represents the flow setting value of the flow control valve, y(t) represents the measured flow value of the flow control valve, e(t) represents the error between the flow setting value and the measured flow value, that is, the flow error value e, de(t) / dt represents the flow error change rate ec, u(t) represents the output of the fuzzy PID controller, that is, the valve control amount, Kp, Ki, Kd represent the proportional coefficient setting value, integral coefficient setting value and differential coefficient setting value respectively;

[0122] The fuzzy PID controller structure satisfies:

[0123] E(t)=r(t)-y(t); (1)

[0124]

[0125] The differential optimization algorithm is used to optimize the parameters of the fuzzy PID so that Kp, Ki, and Kd converge to the minimum value;

[0126] S322: define the fuzzy distribution of input and output; define the range of input e, ec and output ΔKp, ΔKi, ΔKd as the domain [-6,6], select the seven-level fuzzy subset {NB, NM, NS, ZO, PS, PM, PB}, where N represents negative, P represents positive, B represents large, M represents medium, S represents small, and ZO represents 0;

[0127] S323: Establish fuzzy rules and find corresponding fuzzy rules according to fuzzy subsets; establish fuzzy rules and find corresponding fuzzy rules according to fuzzy subsets; according to preset fuzzy subsets, use triangle membership function to divide the values ​​on the standard domain into the fuzzy subsets.

[0128] S324: Convert the outputted fuzzy value into a clear value through defuzzification processing:

[0129] The fuzzy controller defuzzifies the fuzzy quantity of the PID coefficient and outputs the PID coefficient adjustment value; when making fuzzy subset decisions, the centroid method is used to map the actual domain to map the adjustment value of the PID coefficient to the actual domain; the PID coefficient setting value is obtained according to the following formula:

[0130]

[0131] Among them, K p0 , K i0 , K d0They represent the preset value of proportional coefficient, the preset value of integral coefficient and the preset value of differential coefficient respectively, ΔKp, ΔKi and ΔKd represent the adjustment value of proportional coefficient, the adjustment value of integral coefficient and the adjustment value of differential coefficient respectively, Kp, Ki and Kd represent the setting value of proportional coefficient, the setting value of integral coefficient and the setting value of differential coefficient respectively;

[0132] Step 330: The control module adjusts the opening of the needle valve by driving the motor 2310 according to the flow control amount, thereby controlling the flow;

[0133] Step 340: The system automatically implements the cycle of steps 310 to 330 until the dosage meets the requirement. When the control module 3 controls the system to stop running, the flow regulation automatically stops.

[0134] During the execution of step three, when the system has a flow metering error exceeding the range of ±5%, the monitoring module is used to monitor and determine whether the pipeline is blocked. If the pipeline is blocked, the chemical reagent injection operation is suspended and the cleaning and maintenance control operation is started. After cleaning, the chemical reagent injection operation is continued. If the system still has a flow metering error exceeding the range of ±5%, an alarm is prompted.

[0135] The above-mentioned embodiments are only illustrative of the principles and effects of the invention, as well as some embodiments of its application, and are not intended to limit the invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept of the invention, and all of these belong to the protection scope of the invention.

Claims

1. An underwater Christmas tree chemical reagent adaptive injection metering system, comprising an adaptive analysis module (1) located in an above-water main control station, and a housing module (6) arranged underwater, wherein the housing module (6) comprises a housing and a Christmas tree connection interface (61) and an underwater robot interface (62) arranged on the housing; a metering and regulating module (2) and a control module (3) are arranged in the housing; Features: It also includes a wellhead free water content detector (36), a wellhead pressure sensor (37), and a wellhead temperature sensor (38) electrically connected to the control module (3); the adaptive analysis module (1) provides the control module (3) with an adaptive injection amount of a chemical reagent of the oil tree based on the detection data of the wellhead free water content detector (36), the wellhead pressure sensor (37), and the wellhead temperature sensor (38); the control module (3) is used to control the metering and regulating module (2) to complete the adaptive injection of the chemical reagent; The metering and regulating module (2) comprises a fluid inflow pipeline (21), a flow regulating valve (22), a buffer chamber 1 (24), an ultrasonic flow meter (25), a buffer chamber 2 (26), and a fluid outflow pipeline (27) which are arranged in sequence in a housing module (6); the fluid inflow pipeline (21) is connected to a reagent inlet pipe, and the fluid outflow pipeline (27) is connected to a reagent outlet pipe. A valve needle (222) driving mechanism (23) which cooperates with the regulating flow valve is arranged in the housing; the ultrasonic flow meter (25) is electrically connected to the control module (3); The flow regulating valve (22) comprises a valve housing (220), the valve housing (220) being provided with a liquid inlet hole, the valve housing (220) being provided with a liquid inlet joint (2211) and a locking nut (2212) for locking the liquid inlet joint (2211) on the liquid inlet hole, a valve seat (221) being provided at one end of the valve housing (220), a valve body (229) being provided at the other end of the valve housing (220), a valve hole penetrating through the valve body (229), and a valve hole extending through the valve body (229) being provided on the valve body (229) away from the valve housing (220). ) is provided with a liquid outlet joint (2210) at one end, an annular liquid inlet groove is provided on the outer periphery of one side of the valve seat (221) close to the valve body (229), a plurality of liquid holes are provided on the groove wall of the liquid inlet groove on the valve seat (221) and are communicated with the inner cavity of the valve housing (220), a valve stem is passed through the valve seat (221), a boss portion is provided on the valve stem and matches with the wall of the liquid inlet groove, an end of the valve stem passing through the valve hole is in a conical shape, and an end sealing device is provided on the valve seat (221) at the end of the valve stem passing through. The valve stem driving mechanism comprises a base connecting flange (232) arranged on the valve housing (220), a connecting seat (233) being provided on the base connecting flange (232), a guide rail (234) being provided on the connecting seat (233), a sliding block (235) moving parallel to the valve stem being provided on the guide rail (234), a driving rack (237) being provided on the sliding block (235), a valve needle connecting block (2313) being provided at the end of the driving rack (237), the valve needle connecting block (2313) being connected to the end of the valve stem passing through the valve seat (221), a motor fixing seat (239) being provided on the mounting seat, a driving motor (2310) being provided on the motor fixing seat (239), a driving gear (236) meshing with the driving rack (237) being provided on the output shaft of the driving motor (2310), and the driving motor (2310) being electrically connected to the control module (3).

2. The self-adaptive injection metering system of chemical reagents for underwater oil trees according to claim 1, characterized in that: The self-cleaning module (4) is also included; the self-cleaning module (4) includes a flushing liquid supply device and two switching modules respectively arranged on the reagent inlet pipe and the reagent outlet pipe, the two switching modules are connected via a flushing pipeline, the outlet of the flushing liquid supply device is connected to the switching module on the reagent outlet pipe via the flushing pipeline, and the switching module on the reagent inlet pipe is connected to the flushing liquid discharge pipe; the switching module includes a module body and a backwashing motor, the module body is provided with a connecting hole connected to the pipe mouth of the fluid inlet pipe (21) or the fluid outflow pipe (27), a through hole connected to the reagent inlet pipe or the reagent outlet pipe, and a through hole connected to the reagent inlet pipe or the reagent outlet pipe. The module body is provided with an inner cavity with a central hole, in which a T-shaped adapter is movably provided, and the middle part of the T-shaped adapter is connected with the output shaft of the backwashing motor extending into the module body, and the backwashing motor drives the T-shaped adapter to switch between the medication position and the flushing position; end face sealing rings are respectively provided on the two end openings of the T-shaped tube; the middle opening of the T-shaped adapter is connected with the connecting hole; when in the medication position, one end opening of the T-shaped adapter is connected with the medicine hole, and the other end opening of the T-shaped adapter forms a seal with the inner cavity wall of the module body; when in the flushing position, the two end openings of the T-shaped adapter are respectively connected with a pair of flushing holes.

3. The self-adaptive injection metering system of chemical reagents for underwater oil trees according to claim 2, characterized in that: The ultrasonic flow meter (25) comprises a π-shaped pipe, wherein two curved pipe ends of the π-shaped pipe are respectively used to connect the buffer chamber 1 (24) and the buffer chamber 2 (26), and ultrasonic transducers (251) are respectively provided at the two ends of the straight pipe section of the π-shaped pipe, and the ultrasonic transducer (251) is electrically connected to the control module (3).

4. The self-adaptive injection metering system of chemical reagents for underwater oil trees according to claim 2, characterized in that: It also comprises a remotely arranged monitoring module (5) located in the main control station on the water, and the control module (3) communicates with the monitoring module (5) to realize remote monitoring and reliability simulation of connection with external equipment.

5. The self-adaptive injection metering system of chemical reagents for underwater oil trees according to claim 2, characterized in that: The first buffer chamber (24) is provided with two buffer plates, and the two buffer plates are provided with through holes with different axes; the second buffer chamber (26) is provided with two buffer plates, and the two buffer plates are provided with through holes with different axes.

6. The self-adaptive injection metering system of chemical reagents for underwater oil trees according to claim 2, characterized in that: It also includes an internal pressure balancing mechanism (29) arranged in the shell; the internal pressure balancing mechanism (29) includes at least one leather bag (290) arranged on the shell and the inner cavity of which is connected to the outside.

7. An operation control method of the underwater chemical reagent adaptive injection metering system as claimed in any one of claims 2 to 6, comprising the following steps: Step 1: System self-check Before using the system, the monitoring module (5) is used to check whether the fluid pipeline interface and the electrical connection interface are properly connected; Step 2: Calculation of chemical reagent adaptive injection volume Adopting the adaptive analysis module (1) to calculate the injection amount of chemical reagents, and obtaining the value of the methanol injection amount Mcd or the ethylene glycol injection amount Ecd; Step 3: Chemical reagent injection operation The value of the methanol injection amount Mcd or the ethylene glycol injection amount Ecd is provided to the metering and regulating module (2) and the control module (3); and the following judgment is made: When one of the change in free water content ΔW of oil and gas, the change in wellhead pressure ΔP, and the change in wellhead temperature ΔT exceeds the set threshold, the rough control mode is executed: the methanol injection amount Mcd and the ethylene glycol injection amount Ecd calculated by the adaptive analysis module (1) are selected as the chemical reagent injection amount, and provided to the metering and regulation module (2) and the control module (3), and the system performs chemical reagent injection amount regulation; When the change in free water content ΔW of oil and gas, the change in wellhead pressure ΔP, and the change in wellhead temperature ΔT do not exceed the set threshold, the precision control mode is executed: the injection volume is calculated using the adaptive analysis module (1), and the result is provided to the metering and regulation module (2) and the control module (3). A closed-loop control strategy is adopted to jointly control the precision of the chemical injection volume through the metering and regulation module (2) and the control module (3); the details are as follows: Step 310: the control module (3) monitors the flow of the flow control valve (22) in real time through the ultrasonic flow meter (25), records the flow value, and thus determines the flow error value and the flow error change rate; Step 320: Input the flow error value and the flow error change rate into the fuzzy PID controller of the control module (3) and output the flow control amount; including: S321: Determine the fuzzy controller structure and use the differential algorithm to improve the fuzzy PID controller; Definition: r(t) represents the flow setting value of the flow control valve (22), y(t) represents the flow measured value of the flow control valve (22), e(t) represents the error between the flow setting value and the flow measured value, that is, the flow error value e, de(t) / dt represents the flow error change rate ec, u(t) represents the output of the fuzzy PID controller, that is, the valve control amount, Kp, Ki, Kd represent the proportional coefficient setting value, the integral coefficient setting value and the differential coefficient setting value respectively; The fuzzy PID controller structure satisfies: E(t)=r(t)-y(t); (1) The differential optimization algorithm is used to optimize the parameters of the fuzzy PID so that Kp, Ki, and Kd converge to the minimum value; S322: define the fuzzy distribution of input and output quantities, define the range of input quantities e, ec and output quantities ΔKp, ΔKi, ΔKd as the domain [-6, 6], select the seven-level fuzzy subset {NB, NM, NS, ZO, PS, PM, PB}, where N represents negative, P represents positive, B represents large, M represents medium, S represents small, and ZO represents 0; S323: Establish fuzzy rules and find corresponding fuzzy rules according to fuzzy subsets; S324: Convert the outputted fuzzy value into a clear value through defuzzification processing: The fuzzy controller defuzzifies the fuzzy quantity of the PID coefficient and outputs the PID coefficient adjustment value; when making fuzzy subset decisions, the centroid method is used to map the actual domain to map the adjustment value of the PID coefficient to the actual domain; the PID coefficient setting value is obtained according to the following formula: Among them, K p0 , K i0 , K d0 They represent the preset value of proportional coefficient, the preset value of integral coefficient and the preset value of differential coefficient respectively, ΔKp, ΔKi and ΔKd represent the adjustment value of proportional coefficient, the adjustment value of integral coefficient and the adjustment value of differential coefficient respectively, Kp, Ki and Kd represent the setting value of proportional coefficient, the setting value of integral coefficient and the setting value of differential coefficient respectively; Step 330: the control module (3) adjusts the opening of the needle valve through the driving motor (2310) according to the flow control amount, thereby controlling the flow; Step 340: The system automatically implements the cycle of steps 310 to 330 until the dosage meets the requirement. When the control module (3) controls the system to stop running, the flow regulation automatically stops.

8. The operation control method of the underwater chemical reagent adaptive injection metering system according to claim 7, characterized in that: In the step S323, according to the preset fuzzy subsets, the values ​​on the standard domain are divided into the fuzzy subsets using a triangle membership function.

9. The operation control method of the underwater chemical reagent adaptive injection metering system according to claim 7, characterized in that: It also includes cleaning and maintenance control; during cleaning and maintenance, the backwash motors on the two switching modules drive the T-shaped tube to rotate to the flushing position, and then the cleaning liquid of the flushing liquid supply device enters the switching module on the reagent outlet pipe in one way, directly flows through the switching module on the reagent inlet pipe, and is discharged from the flushing liquid discharge pipe; the other way enters the switching module on the reagent outlet pipe, passes through the flowmeter and the regulating valve, and then is discharged from the flushing liquid discharge pipe through the switching module on the reagent inlet pipe.

10. The operation control method of the underwater chemical reagent adaptive injection metering system according to claim 7, characterized in that: In the step three, the threshold values ​​of the change in oil and gas free water content ΔW, the change in wellhead pressure ΔP, and the change in wellhead temperature ΔT are set to values ​​between 1% and 3%.

11. The operation control method of the underwater chemical reagent adaptive injection metering system according to claim 9, characterized in that: In the step 3, when the system has a flow metering error exceeding the range of ±5%, the monitoring module (5) is used to monitor and determine whether a pipeline blockage occurs. If a pipeline blockage occurs, the chemical reagent injection operation is suspended and a cleaning maintenance control operation is started. After cleaning, the chemical reagent injection operation is continued. If the system still has a flow metering error exceeding the range of ±5%, an alarm is issued.

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