Anti-corrosion control system for surface pipelines and downhole pipes based on cathodic protection

Abstract

The present invention relates to the technical field of oil production pipeline anti-corrosion, and provides a surface pipeline and downhole pipe anti-corrosion control system based on the cathodic protection method. A sensor unit and a historical data acquisition unit in a data acquisition module respectively acquire real-time corrosion rate and historical corrosion and cathodic protection parameter data of the downhole pipe and the surface pipeline. A corrosion prediction module predicts corrosion trend and rate according to corrosion rate combined with time series. A decision generation module generates cathodic protection control strategies for the surface pipeline and the downhole pipe according to the prediction results and generates a collaborative control strategy based on the strategies. A cathodic protection execution module adjusts current and potential according to the collaborative control strategy. A monitoring and management module provides display and data input functions for users to view and operate. The present invention realizes accurate coordination and efficient anti-corrosion of cathodic protection of surface pipelines and downhole pipes by acquiring corrosion data, predicting corrosion trends, generating a cathodic protection collaborative control strategy with multiple strategies, and executing adjustments.

Description

Technical Field

[0001] The invention relates to the technical field of oil production pipeline anticorrosion, in particular to a surface pipeline and downhole pipe anticorrosion control system based on a cathode protection method. Background Art

[0002] During the oil extraction process, the surface pipelines and downhole pipes are in a harsh corrosive environment for a long time. On the one hand, the water in the formation contains various minerals, dissolved oxygen, hydrogen sulfide and other corrosive media, which will cause electrochemical corrosion to the metal pipes and pipelines. For example, hydrogen sulfide reacts with metal to generate sulfide, which destroys the protective film on the metal surface and accelerates the corrosion process; dissolved oxygen promotes the oxidation reaction of the metal, causing the metal to gradually wear out. On the other hand, the soil is also corrosive to the surface pipelines, and factors such as the soil's pH, humidity, and salt content will affect the corrosion rate of the pipeline.

[0003] As oil production continues to deepen, the corrosion problem of pipelines and pipe strings becomes more and more serious, which not only leads to frequent maintenance and replacement operations, increases production costs and downtime, but may also cause leakage accidents, pollute the environment and endanger the safety of surrounding personnel.

[0004] Traditional anti-corrosion methods such as coating anti-corrosion have the limitation of protection failure after coating damage. Cathodic protection, as an active electrochemical anti-corrosion method, applies cathodic current to the protected metal structure to make its potential lower than the corrosion potential in the surrounding environment, thereby inhibiting the corrosion reaction of the metal.

[0005] However, the existing background technology still has the following disadvantages:

[0006] In terms of cathodic protection parameter control and adjustment, when the corrosion rate of the downhole tubing increases due to changes in production conditions and the cathodic protection current and potential need to be changed quickly, it is difficult to coordinate in real time with the cathodic protection control system of the surface pipeline. The cathodic protection of the surface pipeline may be unbalanced due to the adjustment of the downhole tubing; for example, some areas of the surface pipeline may be under-protected due to interference in current distribution, increasing the risk of corrosion. Similarly, if the surface pipeline is reconnected to the system after a section of the pipeline is repaired, the cathodic protection current distribution is readjusted to lower the overall potential, and the downhole tubing may be under-protected due to insufficient protection current.

[0007] At the same time, when dealing with complex working conditions, it is impossible to ensure that the cathodic protection of the ground pipeline and the downhole pipe can transition synchronously and adaptively. The environment in which the ground pipeline is located is relatively changeable. Factors such as the surrounding soil environment, electromagnetic interference, and climatic conditions will have a complex impact on its corrosion condition. The working conditions of the downhole pipe change frequently during the mining process, making the corrosion condition of the downhole pipe change rapidly. Ultimately, the two control strategies cannot be well coordinated, reducing the overall anti-corrosion effect and pipeline service life, greatly affecting the safety and continuity of oilfield production. Summary of the invention

[0008] In order to solve the above-mentioned technical problems, the present invention provides a ground pipeline and downhole tubing anti-corrosion control system based on the cathodic protection method. By collecting corrosion data, predicting corrosion trends, generating cathodic protection collaborative control strategies with multiple strategies and executing adjustments, precise coordination and efficient anti-corrosion of cathodic protection of ground pipelines and downhole tubings are achieved to solve the problems in the prior art.

[0009] A surface pipeline and downhole pipe anti-corrosion control system based on cathodic protection method, comprising:

[0010] A data acquisition module, the data acquisition module includes a sensor unit and a historical data acquisition unit, the historical data acquisition unit collects historical corrosion data, including corrosion rate data at different historical moments and cathodic protection parameter adjustment records at corresponding moments;

[0011] The sensor unit is composed of probes and sensors, including resistance probes and AC impedance probes, and downhole multiphase flow corrosion sensors, which are used to collect the corrosion of downhole pipes in real time and calculate the corrosion rate; it also includes a buried pipeline corrosion rate tester, an electrochemical sensor based on linear polarization resistance technology, and a sensor based on an inductance probe, which are used to collect the corrosion of ground pipelines in real time and calculate the corrosion rate;

[0012] A corrosion prediction module, wherein the corrosion prediction module is connected to the data acquisition module, and a prediction model based on a grayscale prediction algorithm is constructed according to the corrosion rate collected by the data acquisition module in combination with the time series, and the prediction model is optimized by the least square method, and then the future corrosion rate is predicted according to the real-time corrosion rate;

[0013] A decision generation module, wherein the decision generation module is data-connected with the corrosion prediction module, and based on the corrosion rates of the surface pipeline and the downhole tubing respectively predicted by the corrosion prediction module, an initial control strategy for the cathodic protection current and potential of the surface pipeline and the downhole tubing is synchronously generated, and then a collaborative control strategy is generated based on the initial control strategy of the surface pipeline and the downhole tubing through a dynamic weighted average method, so as to ensure that the collaborative control strategy simultaneously performs anti-corrosion protection on the surface pipeline and the downhole tubing without affecting each other;

[0014] A cathodic protection execution module, which is data-connected to the decision-making module and adjusts the cathodic protection current and potential by using the protected downhole tubular and surface pipeline as cathodes according to the collaborative control strategy generated by the decision-making module;

[0015] The monitoring and management module is connected to the data acquisition module, the corrosion prediction module, the decision-making module, and the cathodic protection execution module to provide users with display functions and data input functions. Users can view the calculation results of each module of the system anytime and anywhere.

[0016] Preferably, the specific prediction process of the corrosion prediction module is as follows:

[0017] Assume that the time series of the surface pipeline corrosion rate is ,in represents the observed corrosion rate at the tth time point, and m is the length of the time series;

[0018] First, the time series Perform a first-order accumulation generation operation to obtain a new sequence ;

[0019]

[0020] Among them, the purpose of the first-order accumulation generation operation is to weaken the randomness of the original sequence and enhance the regularity;

[0021] Constructing grey prediction model, The adjacent sequence generated by the adjacent mean of is , the elements of the sequence next to the mean are calculated by the average of the two adjacent terms in the sequence generated by the first-order accumulation, and the calculation formula is as follows:

[0022]

[0023] The differential equation of the grey prediction model is:

[0024]

[0025] Among them, a is the development grayscale, which is used to reflect the development trend of the system, and u is the endogenous control grayscale, which represents the internal driving factor of the system. The parameter vector of parameters a and u is solved by the least squares method. , after obtaining the parameters, solving the differential equation can get the prediction model:

[0026]

[0027] Among them, e is a natural constant. After determining the parameters a and u, enter a new real-time corrosion rate observation value , and update the time series , if the original historical sequence length is m, then the updated sequence is ;

[0028] The updated time series is calculated according to the prediction model to obtain a new prediction value, and the prediction value is cumulatively reduced to obtain the original corrosion rate prediction value:

[0029]

[0030] Among them, y represents the predicted value, and the output The future The predicted value of the surface pipeline corrosion rate at a certain point in time. Similarly, by continuously inputting new real-time corrosion rate data sequences of downhole pipes, the future corrosion rate of downhole pipes can be predicted. .

[0031] Preferably, the decision generation module includes a surface pipeline strategy unit, a downhole string strategy unit and a collaborative control strategy generation unit;

[0032] The ground pipeline strategy unit adopts single neuron adaptive control, calculates the error and difference based on the predicted corrosion rate, calculates the current adjustment amount according to the learning rate and the neuron weight coefficient, and then determines the potential adjustment amount according to the current and potential relationship curve initially set for the ground pipeline, and obtains the initial control strategy for the ground pipeline regarding the current and potential adjustment amount;

[0033] The downhole string strategy unit uses PID control to calculate the error according to the predicted corrosion rate, and obtains the initial control strategy of the downhole string regarding the current and potential adjustment amount by calculating the proportional, integral and differential terms;

[0034] The collaborative control strategy generation unit adopts a dynamic weighted average method to calculate a comprehensive performance index based on the corrosion inhibition and cost indicators when the ground pipeline and the downhole pipe string make separate decisions, and then calculates the collaborative coefficient based on the comprehensive performance index to obtain the final current and potential adjustment amount as the collaborative control strategy.

[0035] Preferably, the surface pipeline strategy unit obtains the current and potential control strategy for cathodic protection based on single neuron adaptive control. The specific process is as follows:

[0036] Assume that the input data is the corrosion rate of the ground pipeline predicted at the tth time point ;

[0037] Assume that the expected corrosion rate of the surface pipeline is , infinitely approaches 0, then the error at the tth time point is:

[0038]

[0039] The input of a single neuron is ,in, Including error , the first-order difference of the error The second difference of the error ;

[0040] The output of a single neuron is the cathodic protection current adjustment at the tth time point , and its calculation formula is:

[0041]

[0042] Among them, K is the learning rate coefficient, which affects the single neuron according to the input information Adjust the output cathodic protection current The speed or amplitude of j represents the input The index of is 1, 2 and 3. is the neuron weight coefficient, which determines the input Adjustment of output cathodic protection current The relative importance of , , , the update formula of the weight coefficient is:

[0043]

[0044] in The step size for weight learning determines the amount of adjustment based on the error and current output each time the weight is updated. For the amplitude of weight adjustment, the particle swarm optimization algorithm or genetic algorithm is used to search for the optimal parameter combination that makes the corrosion rate of the ground pipeline approach 0 after adjustment through the historical corrosion rate data of the ground pipeline and the corresponding cathodic protection current and potential adjustment data, including the values ​​of the learning rate coefficient, weight coefficient and learning step size; then the cathodic protection current of the ground pipeline , cathodic protection potential Determined based on the current and potential relationship curve initially set for the ground pipeline.

[0045] Preferably, the specific process of the current and potential control strategy for cathodic protection obtained by the downhole tubing strategy unit based on PID control is as follows:

[0046] Assume that the expected corrosion rate of the downhole tubing is , infinitely close to 0; suppose the input data is the corrosion rate of the downhole string predicted at the tth time point , then the error is:

[0047]

[0048] Proportional term P: ,in It is a proportional coefficient, which can quickly reflect the size of the error and make preliminary adjustments to the cathodic protection current and potential according to the current error;

[0049] Integral term Q:

[0050]

[0051] Among them, d is the differential operator in the differential operation, and the sampling time step interval is , in the discrete case, that is, each If all are equal:

[0052]

[0053] in, is the integral coefficient, which is used to eliminate the steady-state error of the system and accumulate the previous error information so that the control strategy tends to eliminate corrosion more accurately;

[0054] Differential term C:

[0055]

[0056] In the discrete case:

[0057]

[0058] in, is the differential coefficient, which can adjust the control parameters in advance according to the error change rate to cope with the impact of rapid changes in the underground environment on corrosion; among them, the proportional coefficient , integral coefficient and the differential coefficient Based on the historical corrosion rate data of the downhole tubular at different times and the cathodic protection parameter adjustment records at the corresponding times, the PID parameters are obtained by calculating the variance of the corrosion rate and the average convergence time index under different PID parameter settings, and then establishing the relationship model between the PID parameters and these performance indicators through the data fitting method;

[0059] The cathodic protection current of the downhole pipe string is , cathodic protection potential ,in and It is the initial setting of the cathodic protection current and potential reference value of the downhole tubing.

[0060] Preferably, the collaborative control strategy generation unit first calculates the performance indicators of the surface pipeline and the downhole pipe string when making separate decisions;

[0061] For ground pipelines, the corrosion rate inhibition effect index when they are controlled separately is set as for:

[0062]

[0063] in, is the predicted corrosion rate before adjustment, is the actual measured corrosion rate after adjustment; at the same time, the control cost index based on power consumption per unit time is set for:

[0064]

[0065] here and is the adjustment amount of the current and potential of the ground pipeline, then its comprehensive performance index :

[0066]

[0067] in and It is the weight coefficient of the comprehensive performance index of the ground pipeline, which is used to balance the proportion of the suppression effect and the control cost, and can be set by the staff;

[0068] Similarly, according to the above calculation method for the surface pipeline, the comprehensive performance index of the downhole pipe string is obtained. ;

[0069] Calculate the synergy adjustment coefficient and ; The final coordinated control current and potential adjustment is:

[0070] Ground pipeline:

[0071]

[0072] Downhole pipe string:

[0073]

[0074] The cathodic protection current of the ground pipeline is , potential ; Cathodic protection current of downhole tubing , potential .

[0075] Preferably, the comprehensive performance index of the downhole tubular string is The specific calculation process is as follows:

[0076] For the downhole tubing, the corrosion rate inhibition effect index when it is controlled separately is set as for:

[0077]

[0078] in, is the predicted corrosion rate before adjustment, is the actual measured corrosion rate after adjustment; at the same time, the control cost index based on power consumption per unit time is set for:

[0079]

[0080] here and is the adjustment amount of the current and potential of the downhole string, then its comprehensive performance index :

[0081]

[0082] in and It is the weight coefficient of the comprehensive performance index of the downhole tubing, which is used to balance the proportion of the suppression effect and the control cost, and can be set by the staff;

[0083] Preferably, in the data input function provided by the monitoring and management module for the user, the input data includes the learning rate coefficient and learning step size in the ground pipeline strategy unit, the proportional coefficient, integral coefficient and differential coefficient required in the downhole tubing strategy unit, and the weight coefficient in the collaborative control strategy generation unit.

[0084] Preferably, the cathodic protection execution module adjusts the cathodic protection current and potential by adjusting a variable resistor, a rectifier output, changing the number or size of anodes, controlling the power output of a power supply, or adjusting a potential controller.

[0085] Compared with the prior art, the present invention has the following beneficial effects:

[0086] 1. The present invention predicts the corrosion trend of the ground pipeline and the downhole pipe string by combining the data of the corrosion prediction module with the data of the data acquisition module, provides a basis for the decision-making generation module, realizes the advance planning of the cathodic protection parameter adjustment strategy, and ensures that the cathodic protection of the ground pipeline and the downhole pipe string can be synchronously and adaptively transitioned when complex working conditions are converted, thereby reducing the risk of pipeline corrosion during working condition switching.

[0087] 2. The present invention can accurately calculate the current adjustment amount and determine the potential adjustment according to the corrosion rate of the ground pipeline based on the single neuron adaptive control through the ground pipeline strategy unit, which solves the problem of complex causes of ground pipeline corrosion. The downhole tubing strategy unit uses PID control to quickly respond and adjust the current and potential according to the corrosion rate of the downhole tubing, which solves the problem of changeable corrosion conditions of the downhole tubing. Finally, the collaborative control strategy generation unit uses the dynamic weighted average method to calculate the collaborative coefficient to achieve collaborative control of the ground pipeline and the downhole tubing when the cathodic protection parameters are adjusted, thereby avoiding imbalance in ground pipeline protection due to changes in the working conditions of the downhole tubing, ensuring the overall anti-corrosion effect and pipeline service life, and improving the safety and continuity of oil field production. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 It is a schematic diagram of the working process of the system of the present invention;

[0089] Figure 2 It is a schematic diagram of the prediction flow of the corrosion prediction module of the present invention;

[0090] Figure 3 It is a schematic diagram of the workflow of the decision-making generation module of the present invention. DETAILED DESCRIPTION

[0091] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0092] The present invention provides a surface pipeline and downhole pipe anti-corrosion control system based on the cathodic protection method, comprising:

[0093] A data acquisition module, the data acquisition module includes a sensor unit and a historical data acquisition unit, the historical data acquisition unit collects historical corrosion data, including corrosion rate data at different historical moments and cathodic protection parameter adjustment records at corresponding moments;

[0094] The sensor unit is composed of probes and sensors, including resistance probes and AC impedance probes, and downhole multiphase flow corrosion sensors, which are used to collect the corrosion of downhole pipes in real time and calculate the corrosion rate; it also includes a buried pipeline corrosion rate tester, an electrochemical sensor based on linear polarization resistance technology, and a sensor based on an inductance probe, which are used to collect the corrosion of ground pipelines in real time and calculate the corrosion rate;

[0095] A corrosion prediction module, wherein the corrosion prediction module is connected to the data acquisition module, and a prediction model based on a grayscale prediction algorithm is constructed according to the corrosion rate collected by the data acquisition module in combination with the time series, and the prediction model is optimized by the least square method, and then the future corrosion rate is predicted according to the real-time corrosion rate;

[0096] A decision generation module, wherein the decision generation module is data-connected with the corrosion prediction module, and based on the corrosion rates of the surface pipeline and the downhole tubing respectively predicted by the corrosion prediction module, an initial control strategy for the cathodic protection current and potential of the surface pipeline and the downhole tubing is synchronously generated, and then a collaborative control strategy is generated based on the initial control strategy of the surface pipeline and the downhole tubing through a dynamic weighted average method, so as to ensure that the collaborative control strategy simultaneously performs anti-corrosion protection on the surface pipeline and the downhole tubing without affecting each other;

[0097] A cathodic protection execution module, which is data-connected to the decision-making module and adjusts the cathodic protection current and potential by using the protected downhole tubular and surface pipeline as cathodes according to the collaborative control strategy generated by the decision-making module;

[0098] The monitoring and management module is connected to the data acquisition module, the corrosion prediction module, the decision-making module, and the cathodic protection execution module to provide users with display functions and data input functions. Users can view the calculation results of each module of the system anytime and anywhere.

[0099] Embodiment 1:

[0100] like Figure 1-Figure 3 As shown, in this embodiment, an oil field has an extensive surface pipeline network and downhole pipe string facilities, which have long faced serious corrosion problems, which not only threatens the integrity of the pipeline system, but also poses a major challenge to the safety and continuity of oil field production.

[0101] In addition, the environment is complex, and factors such as surrounding soil properties, water content, and stray current all affect the corrosion of pipelines. The traditional regular inspection method is difficult to accurately grasp the real-time changes in corrosion rate, so this system is introduced.

[0102] After the system was introduced, the buried pipeline corrosion rate tester and electrochemical sensor in the sensor unit continuously monitored the corrosion rate of the ground pipeline with high precision. At the same time, the historical data acquisition unit collected the corrosion data of the pipeline in different seasons and operating conditions over the past years, as well as the corresponding cathodic protection parameter records.

[0103] After the corrosion prediction module obtains these data, it analyzes the time series of the corrosion rate of the ground pipeline. The specific analysis process is as follows:

[0104] Assume that the time series of the surface pipeline corrosion rate is ,in represents the observed corrosion rate at the tth time point, and m is the length of the time series;

[0105] First, the time series Perform a first-order cumulative generation operation to obtain a new sequence ;

[0106]

[0107] Among them, the purpose of the first-order cumulative generation operation is to weaken the randomness of the original sequence and enhance the regularity;

[0108] Construct a grey prediction model. Let The adjacent sequence generated by the adjacent mean of , and the elements of the adjacent mean sequence are calculated by the average value of two adjacent terms in the sequence generated by the first-order cumulative generation. The calculation formula is as follows:

[0109]

[0110] The differential equation of the grey prediction model is:

[0111]

[0112] Among them, a is the development grey degree, which is used to reflect the development trend of the system, and u is the endogenous control grey degree, which represents the internal driving factor of the system; By using the least squares method to solve the parameter vector about parameters a and u, after obtaining the parameters, solving the differential equation can obtain the prediction model:

[0113]

[0114] Among them, e is the natural constant. After determining the parameters a and u, input a new real-time corrosion rate observation value , and update the time series . If the length of the original historical sequence is m, the updated sequence is ;

[0115] Calculate the new predicted value according to the prediction model for the updated time series, and perform cumulative subtraction reduction on the predicted value to obtain the predicted value of the original corrosion rate:

[0116]

[0117] Among them, y represents the predicted value, and the output is the predicted value of the ground pipeline corrosion rate at the future time point. Similarly, by continuously inputting the new real-time corrosion rate data sequence of the downhole string, predict the corrosion rate of the future downhole string .

[0118] For example, the corrosion rate observations of the past 50 consecutive time points, which can be days or weeks, are used as basic data to perform a first-order accumulation generation operation to obtain a new sequence. On this basis, a gray prediction model is constructed, and the development gray and endogenous control gray parameters in the model are solved through a rigorous least squares method, thereby determining an accurate prediction model.

[0119] In actual operation, whenever a new real-time corrosion rate observation is input, the system immediately updates the time series. For example, after a rainstorm, the sensor detects an abnormal fluctuation in the corrosion rate, and the new data is quickly incorporated into the time series for recalculation.

[0120] The predicted value obtained by the prediction model is restored through cumulative reduction, accurately predicting the trend of corrosion rate changes of the surface pipeline in the future. According to the prediction results, before the period when the corrosion rate may rise rapidly, the oilfield maintenance team prepares protective operations in advance, effectively avoiding pipeline leakage accidents that may be caused by increased corrosion, ensuring the safe and stable operation of the surface oil pipeline, reducing the risk of production interruption caused by sudden corrosion problems, and providing strong technical support for the normal production and operation of the oilfield.

[0121] Embodiment 2:

[0122] like Figure 1-Figure 3 As shown, in this embodiment, after an adjustment of downhole operations in a certain oil field in Example 1, the corrosion rate increases sharply due to changes in the working conditions of the downhole tubing, and it is necessary to quickly change the cathodic protection current and potential of the downhole tubing to prevent further corrosion of the downhole tubing. However, due to the lack of an effective coordinated control mechanism, the adjustment of the downhole tubing seriously interferes with the current distribution of the surface pipeline, resulting in under-protection in some areas of the surface pipeline, increasing the risk of corrosion, and may cause certain economic losses and production interruptions.

[0123] The corrosion prediction module first predicts that the corrosion rate of the downhole tubing will continue to increase based on the corrosion rate change data collected by the downhole tubing sensor units, such as the resistance probe and the AC impedance probe, combined with the historical data, and passes this information to the decision generation module.

[0124] The downhole string strategy unit in the decision generation module uses the PID control strategy;

[0125] Assume that the expected corrosion rate of the downhole tubing is , infinitely close to 0; suppose the input data is the corrosion rate of the downhole string predicted at the tth time point , then the error is:

[0126]

[0127] Proportional term P: ,in It is the proportionality coefficient, which can quickly reflect the size of the error and make preliminary adjustments to the cathodic protection current and potential according to the current error;

[0128] Integral term Q:

[0129]

[0130] Among them, d is the differential operator in the differential operation, and the sampling time step interval is , in the discrete case, that is, each If all are equal:

[0131]

[0132] in, is the integral coefficient, which is used to eliminate the steady-state error of the system and accumulate the previous error information so that the control strategy tends to eliminate corrosion more accurately;

[0133] Differential term C:

[0134]

[0135] In the discrete case:

[0136]

[0137] in, is the differential coefficient, which can adjust the control parameters in advance according to the error change rate to cope with the impact of rapid changes in the underground environment on corrosion; among them, the proportional coefficient , integral coefficient and the differential coefficient Based on the corrosion rate data of the downhole tubing at different historical moments and the cathodic protection parameter adjustment records at the corresponding moments, the PID parameters are obtained by calculating the variance of the corrosion rate and the average convergence time indicators under different PID parameter settings, and then establishing the relationship model between the PID parameters and these performance indicators through the data fitting method.

[0138] The cathodic protection current of the downhole pipe string is , cathodic protection potential ,in and It is the initial setting of the cathodic protection current and potential reference value of the downhole tubing.

[0139] At the same time, the ground pipeline strategy unit adopts single neuron adaptive control; the input data is used to predict the corrosion rate of the ground pipeline at the tth time point ;

[0140] Assume that the expected corrosion rate of the surface pipeline is , infinitely approaches 0, then the error at the tth time point is:

[0141]

[0142] The input of a single neuron is ,in, Including error , the first-order difference of the error The second difference of the error ;

[0143] The output of a single neuron is the cathodic protection current adjustment at the tth time point , and its calculation formula is:

[0144]

[0145] Among them, K is the learning rate coefficient, which affects the single neuron according to the input information Adjust the output cathodic protection current The speed or amplitude of j represents the input The index of is 1, 2, and 3. is the neuron weight coefficient, which determines the input Adjustment of output cathodic protection current The relative importance of , , , the update formula of the weight coefficient is:

[0146]

[0147] in The step size for weight learning determines the amount of adjustment based on the error and current output each time the weight is updated. For the amplitude of weight adjustment, the particle swarm optimization algorithm or genetic algorithm is used to search for the optimal parameter combination that makes the corrosion rate of the ground pipeline approach 0 after adjustment through the historical corrosion rate data of the ground pipeline and the corresponding cathodic protection current and potential adjustment data, including the values ​​of the learning rate coefficient, weight coefficient and learning step size; then the cathodic protection current of the ground pipeline , cathodic protection potential Determined based on the current and potential relationship curve initially set for the ground pipeline.

[0148] The collaborative control strategy generation unit adopts the dynamic weighted average method to first calculate the performance indicators of the surface pipeline and the downhole pipe string when making separate decisions;

[0149] For ground pipelines, the corrosion rate inhibition effect index when they are controlled separately is set as for:

[0150]

[0151] in is the predicted corrosion rate before adjustment, is the actual measured corrosion rate after adjustment; at the same time, the control cost index based on power consumption per unit time is set for:

[0152]

[0153] here and is the adjustment amount of the current and potential of the ground pipeline, then its comprehensive performance index :

[0154]

[0155] in and It is the weight coefficient of the comprehensive performance index of the ground pipeline, which is used to balance the proportion of the suppression effect and the control cost, and can be set by the staff;

[0156] If the oil field currently pays more attention to the long-term stability and safety of the pipeline system, that is, focuses on the corrosion inhibition effect, it can be appropriately increased. value, reduce The value of makes the collaborative control strategy more inclined to strengthen the protection against corrosion, even if it may increase a certain control cost.

[0157] On the contrary, if the oil field is in a critical period of cost control, the cost can be increased while ensuring the basic anti-corrosion requirements. value, reduce The value of should be prioritized to reduce cost factors such as energy consumption and equipment loss during cathodic protection, so as to balance the overall operating cost and pipeline anti-corrosion needs.

[0158] Similarly, for downhole tubulars, the comprehensive performance index of downhole tubulars is calculated based on the calculation method for surface pipelines. ; About the comprehensive performance indicators of downhole tubing The specific calculation process is as follows:

[0159] For the downhole tubing, the corrosion rate inhibition effect index when it is controlled separately is set as for:

[0160]

[0161] in is the predicted corrosion rate before adjustment, is the actual measured corrosion rate after adjustment; at the same time, the control cost index based on power consumption per unit time is set for:

[0162]

[0163] here and is the adjustment amount of the current and potential of the downhole string, then its comprehensive performance index :

[0164]

[0165] in and It is the weight coefficient of the comprehensive performance index of the downhole tubing, which is used to balance the proportion of the suppression effect and the control cost, and can be set by the staff;

[0166] Calculate the synergy adjustment coefficient and ; The final coordinated control current and potential adjustment is:

[0167] Ground pipeline:

[0168]

[0169] Downhole pipe string:

[0170]

[0171] The cathodic protection current of the ground pipeline is , potential ; Cathodic protection current of downhole tubing , potential .

[0172] Based on these coordinated control strategies, the cathodic protection execution module increases the protection current of the downhole tubing by adjusting the rectifier output, adjusts the current distribution of the surface pipeline by changing the resistance of the variable resistor, and uses the potential controller to accurately control the potential of the surface pipeline and the downhole tubing.

[0173] During the entire process, the monitoring and management module displays the calculation results and equipment operating parameters of each module in real time. The staff can check them at any time and fine-tune the correlation coefficients through the data input function when necessary to ensure that the system operates in the best condition.

[0174] Through this collaborative control mechanism, the negative impact of increased corrosion of downhole tubing due to changes in operating conditions on surface pipeline protection was successfully avoided, the integrity and stability of the entire oilfield pipeline system was ensured, safety hazards and production interruptions caused by corrosion problems were reduced, the efficiency and economic benefits of oilfield production were improved, the service life of surface pipelines and downhole tubing was extended, and a solid foundation for the sustainable development of the oilfield was laid.

[0175] The embodiments of the present invention are provided for the purpose of illustration and description. Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A surface pipeline and downhole pipe anti-corrosion control system based on cathodic protection method, characterized in that: include: A data acquisition module, the data acquisition module includes a sensor unit and a historical data acquisition unit, the historical data acquisition unit collects historical corrosion data, including corrosion rate data at different historical moments and cathodic protection parameter adjustment records at corresponding moments; The sensor unit is composed of probes and sensors, including resistance probes and AC impedance probes, and downhole multiphase flow corrosion sensors, which are used to collect the corrosion of downhole pipes in real time and calculate the corrosion rate; it also includes a buried pipeline corrosion rate tester, an electrochemical sensor based on linear polarization resistance technology, and a sensor based on an inductance probe, which are used to collect the corrosion of ground pipelines in real time and calculate the corrosion rate; A corrosion prediction module, wherein the corrosion prediction module is connected to the data acquisition module, and a prediction model based on a grayscale prediction algorithm is constructed according to the corrosion rate collected by the data acquisition module in combination with the time series, and the prediction model is optimized by the least square method, and then the future corrosion rate is predicted according to the real-time corrosion rate; A decision generation module, wherein the decision generation module is data-connected with the corrosion prediction module, and based on the corrosion rates of the surface pipeline and the downhole tubing respectively predicted by the corrosion prediction module, an initial control strategy for the cathodic protection current and potential of the surface pipeline and the downhole tubing is synchronously generated, and then a collaborative control strategy is generated based on the initial control strategy of the surface pipeline and the downhole tubing through a dynamic weighted average method, so as to ensure that the collaborative control strategy simultaneously performs anti-corrosion protection on the surface pipeline and the downhole tubing without affecting each other; A cathodic protection execution module, which is data-connected to the decision-making module and adjusts the cathodic protection current and potential by using the protected downhole tubular and surface pipeline as cathodes according to the collaborative control strategy generated by the decision-making module; The monitoring and management module is connected to the data acquisition module, the corrosion prediction module, the decision-making module, and the cathodic protection execution module to provide users with display functions and data input functions. Users can view the calculation results of each module of the system anytime and anywhere.

2. A surface pipeline and downhole pipe anti-corrosion control system based on cathodic protection method as claimed in claim 1, characterized in that: The specific prediction process of the corrosion prediction module is as follows: Assume that the time series of the surface pipeline corrosion rate is ,in represents the observed corrosion rate at the tth time point, and m is the length of the time series; First, the time series Perform a first-order accumulation generation operation to obtain a new sequence ; Among them, the purpose of the first-order accumulation generation operation is to weaken the randomness of the original sequence and enhance the regularity; Constructing grey prediction model, The adjacent sequence generated by the adjacent mean of is , the elements of the sequence next to the mean are calculated by the average of the two adjacent terms in the sequence generated by the first-order accumulation, and the calculation formula is as follows: The differential equation of the grey prediction model is: Among them, a is the development grayscale, which is used to reflect the development trend of the system, and u is the endogenous control grayscale, which represents the internal driving factor of the system. The parameter vector of parameters a and u is solved by the least squares method. , after obtaining the parameters, solving the differential equation can get the prediction model: Among them, e is a natural constant. After determining the parameters a and u, enter a new real-time corrosion rate observation value , and update the time series , if the original historical sequence length is m, then the updated sequence is ; The updated time series is calculated according to the prediction model to obtain a new prediction value, and the prediction value is cumulatively reduced to obtain the original corrosion rate prediction value: Among them, y represents the predicted value, and the output The future The predicted value of the surface pipeline corrosion rate at a certain point in time. Similarly, by continuously inputting new real-time corrosion rate data sequences of downhole pipes, the future corrosion rate of downhole pipes can be predicted. .

3. The anti-corrosion control system for ground pipelines and downhole pipes based on cathodic protection as claimed in claim 1, characterized in that: The decision generation module includes a surface pipeline strategy unit, a downhole pipe string strategy unit and a collaborative control strategy generation unit; The ground pipeline strategy unit adopts single neuron adaptive control, calculates the error and difference based on the predicted corrosion rate, calculates the current adjustment amount according to the learning rate and the neuron weight coefficient, and then determines the potential adjustment amount according to the current and potential relationship curve initially set for the ground pipeline, and obtains the initial control strategy for the ground pipeline regarding the current and potential adjustment amount; The downhole string strategy unit uses PID control to calculate the error according to the predicted corrosion rate, and obtains the initial control strategy of the downhole string regarding the current and potential adjustment amount by calculating the proportional, integral and differential terms; The collaborative control strategy generation unit adopts a dynamic weighted average method to calculate a comprehensive performance index based on the corrosion inhibition and cost indicators when the ground pipeline and the downhole pipe string make separate decisions, and then calculates the collaborative coefficient based on the comprehensive performance index to obtain the final current and potential adjustment amount as the collaborative control strategy.

4. A surface pipeline and downhole pipe anti-corrosion control system based on cathodic protection method as claimed in claim 3, characterized in that: The specific process of the ground pipeline strategy unit obtaining the current and potential control strategy for cathodic protection based on single neuron adaptive control is as follows: Assume that the input data is the corrosion rate of the ground pipeline predicted at the tth time point ; Assume that the expected corrosion rate of the surface pipeline is , infinitely approaches 0, then the error at the tth time point is: The input of a single neuron is ,in, Including error , the first-order difference of the error The second difference of the error ; The output of a single neuron is the cathodic protection current adjustment at the tth time point , and its calculation formula is: Among them, K is the learning rate coefficient, which affects the single neuron according to the input information Adjust the output cathodic protection current The speed or amplitude of j represents the input The index of is 1, 2, and 3. is the neuron weight coefficient, which determines the input Adjustment of output cathodic protection current The relative importance of , , , the update formula of the weight coefficient is: in The step size for weight learning determines the amount of adjustment based on the error and current output each time the weight is updated. For the amplitude of weight adjustment, the particle swarm optimization algorithm or genetic algorithm is used to search for the optimal parameter combination that makes the corrosion rate of the ground pipeline approach 0 after adjustment through the historical corrosion rate data of the ground pipeline and the corresponding cathodic protection current and potential adjustment data, including the values ​​of the learning rate coefficient, weight coefficient and learning step size; then the cathodic protection current of the ground pipeline , cathodic protection potential Determined based on the current and potential relationship curve initially set for the ground pipeline.

5. A surface pipeline and downhole pipe anti-corrosion control system based on cathodic protection method as claimed in claim 4, characterized in that: The specific process of the current and potential control strategy for cathodic protection obtained by the downhole tubing strategy unit based on PID control is as follows: Assume that the expected corrosion rate of the downhole tubing is , infinitely close to 0; suppose the input data is the corrosion rate of the downhole string predicted at the tth time point , then the error is: Proportional term P: ,in It is a proportional coefficient, which can quickly reflect the size of the error and make preliminary adjustments to the cathodic protection current and potential according to the current error; Integral term Q: Among them, d is the differential operator in the differential operation, and the sampling time step interval is , in the discrete case, that is, each If all are equal: in, is the integral coefficient, which is used to eliminate the steady-state error of the system and accumulate the previous error information so that the control strategy tends to eliminate corrosion more accurately; Differential term C: In the discrete case: in, is the differential coefficient, which can adjust the control parameters in advance according to the error change rate to cope with the impact of rapid changes in the underground environment on corrosion; among them, the proportional coefficient , integral coefficient and the differential coefficient Based on the historical corrosion rate data of the downhole tubular at different times and the cathodic protection parameter adjustment records at the corresponding times, the PID parameters are obtained by calculating the variance of the corrosion rate and the average convergence time index under different PID parameter settings, and then establishing the relationship model between the PID parameters and these performance indicators through the data fitting method; The cathodic protection current of the downhole pipe string is , cathodic protection potential ,in and It is the initial setting of the cathodic protection current and potential reference value of the downhole tubing.

6. A surface pipeline and downhole pipe anti-corrosion control system based on cathodic protection method as claimed in claim 5, characterized in that: The collaborative control strategy generation unit first calculates the performance indicators of the surface pipeline and the downhole pipe string when making separate decisions; For ground pipelines, the corrosion rate inhibition effect index when they are controlled separately is set as for: in is the predicted corrosion rate before adjustment, is the actual measured corrosion rate after adjustment; at the same time, the control cost index based on power consumption per unit time is set for: here and is the adjustment amount of the current and potential of the ground pipeline, then its comprehensive performance index : in and It is the weight coefficient of the comprehensive performance index of the ground pipeline, which is used to balance the proportion of the suppression effect and the control cost, and can be set by the staff; Similarly, according to the above calculation method for the surface pipeline, the comprehensive performance index of the downhole pipe string is obtained. ; Calculate the synergy adjustment coefficient and ; The final coordinated control current and potential adjustment is: Ground pipeline: Downhole pipe string: The cathodic protection current of the ground pipeline is , potential ; Cathodic protection current of downhole tubing , potential .

7. A surface pipeline and downhole pipe anti-corrosion control system based on cathodic protection method as claimed in claim 6, characterized in that: The comprehensive performance index of downhole tubing The specific calculation process is as follows: For the downhole tubing, the corrosion rate inhibition effect index when it is controlled separately is set as for: in is the predicted corrosion rate before adjustment, is the actual measured corrosion rate after adjustment; at the same time, the control cost index based on power consumption per unit time is set for: here and is the adjustment amount of the current and potential of the downhole pipe string, then its comprehensive performance index : in and It is the weight coefficient of the comprehensive performance index of the downhole tubing, which is used to balance the proportion of suppression effect and control cost and can be set by the staff.

8. The anti-corrosion control system for ground pipelines and downhole pipes based on cathodic protection as claimed in claim 1, characterized in that: The cathode protection execution module adjusts the cathode protection current and potential by adjusting the variable resistor, the rectifier output, changing the number or size of anodes, controlling the power output of the power supply or adjusting the potential controller.

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