Blowout preventer remote automatic grease injection system based on PID control and control method

Abstract

The invention discloses a blowout preventer remote automatic grease injection system based on PID control and a control method, and relates to the technical field of grease injection, and the control method comprises the following steps: an initialization stage: automatically matching the specification of a choke tube according to the diameter of a cable, and preheating sealing grease to a set temperature; in the dynamic control stage, wellhead pressure and grease injection pressure are monitored in real time, pressure errors are calculated, the flow of a grease injection pump is adjusted according to a PID algorithm, and when the cable lowering speed suddenly changes, pressure fluctuation is inhibited in advance through a differential link; and according to the safety redundancy mechanism, when the main PID controller fails, the standby PID controller is automatically switched, and emergency locking is triggered when the wellhead pressure exceeds the limit. The flow of a grease injection pump is adjusted in real time through an incremental PID algorithm and a self-adaptive adjustment method, the grease injection amount is accurately controlled, pressure fluctuation is reduced, sudden change of the cable lowering speed is predicted through a differential link, the response precision is improved, stable operation of the system is ensured through a redundant controller and an emergency locking function, PID output is corrected through a dynamic temperature-viscosity model, and the reliability of the system is improved. The system service life is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of grease injection, and specifically relates to a remote automatic grease injection system and control method for a blowout preventer based on PID control. Background Art

[0002] A blowout preventer is an important device used to prevent blowout accidents in offshore and onshore oil drilling operations. A blowout accident refers to a situation during drilling where the wellhead pressure is too high to be effectively controlled, resulting in the overflow of well fluid and even catastrophic accidents such as fires and explosions. The blowout preventer can close the wellhead by applying pressure to prevent the overflow of oil and gas. Therefore, the control system of the blowout preventer needs to have precise pressure regulation capabilities to ensure that the wellhead pressure is within a safe range. The role of the grease injection system in the blowout preventer is to maintain the lubrication of the blowout preventer's sealing system to ensure its reliability. To optimize the control of the grease injection system and improve safety, an automatic grease injection system based on PID control is adopted. The PID controller adjusts the flow rate of the grease injection pump to achieve real-time regulation of the wellhead pressure and the grease injection pressure, thereby maintaining the balance between the two. Traditional PID control systems have certain limitations, such as response lag and overregulation, and it is difficult to cope with instantaneous pressure fluctuations.

[0003] To solve these problems, the remote automatic grease injection system for the blowout preventer based on PID control adopts an incremental PID control algorithm and combines the monitoring and dynamic adjustment mechanism of the cable lowering speed to achieve a more efficient and reliable control strategy. In addition, the system also introduces a safety redundancy mechanism to improve the reliability and fault tolerance of the system. Summary of the Invention

[0004] To solve the above technical problems, a remote automatic grease injection system and control method for a blowout preventer based on PID control are provided, and this technical solution solves the above problems.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A remote automatic grease injection system for a blowout preventer based on PID control, comprising:

[0007] A grease injection execution unit, including a double plunger grease injection pump, a grease injection head, and a sealing grease storage tank. Among them, the grease injection pump adjusts the grease injection volume through a PID controller, and the grease injection head adopts a choke tube and a diversion groove structure;

[0008] A sensing and feedback unit, including a pressure sensor, a temperature sensor, and a speed sensor, which are respectively used to monitor the wellhead pressure, the grease injection pressure, the sealing grease temperature, the cable lowering speed, and the acceleration;

[0009] A PID control unit, which adjusts the flow rate of the grease injection pump through an incremental PID algorithm and adjusts the control parameters in real time according to the changes in the cable movement and the wellhead pressure;

[0010] A remote communication unit that implements two-way encrypted communication based on the TLCP protocol and real-time displays the pressure curve, grease injection volume, and alarm log through a human-machine interface.

[0011] Preferably, the PID controller adopts an incremental PID algorithm, and the parameter tuning range is Kp = 0.8 - 1.5, Ti = 0.5 - 2.0 seconds, Td = 0.1 - 0.3 seconds.

[0012] Preferably, a diversion groove and a PTFE-coated choke tube are provided inside the grease injection head, and the clearance tolerance is ±0.02 mm.

[0013] Preferably, the PID control unit includes a main controller and a standby controller, and automatically switches to the standby controller when the main controller fails.

[0014] Preferably, the system further includes a safety redundancy mechanism. When the wellhead pressure exceeds 10% of the design value, the blowout preventer is triggered to lock emergently.

[0015] Preferably, the PID control unit of the system corrects the PID control output through a dynamic temperature-viscosity model to cope with the influence of the change in the viscosity of the sealing grease with temperature.

[0016] A remote automatic grease injection control method for a blowout preventer based on PID control, including the following steps:

[0017] In the initialization stage, the choke tube specification is automatically matched according to the cable diameter, and the sealing grease is preheated to the set temperature;

[0018] In the dynamic control stage, the wellhead pressure and the grease injection pressure are monitored in real time, the pressure error is calculated, and the flow rate of the grease injection pump is adjusted according to the PID algorithm. When the cable lowering speed changes suddenly, the pressure fluctuation is suppressed in advance through the differential link;

[0019] Safety redundancy mechanism, automatically switches to the standby PID controller when the main PID controller fails, and triggers an emergency lock when the wellhead pressure exceeds the limit.

[0020] Preferably, in the initialization stage, the specific steps of automatically matching the choke tube specification according to the cable diameter and preheating the sealing grease to the set temperature include:

[0021] Based on the cable sensor, the diameter of the cable is obtained, and the preset matching relationship between the cable diameter and the choke tube specification is used to select the choke tube specification;

[0022] Set the preheating temperature to be between 60 - 80 °C, start the sealing grease heating device, and adjust the heating power according to the PID control algorithm to gradually increase the temperature of the sealing grease;

[0023] Use a temperature sensor to monitor the temperature of the sealing grease in real time. According to the temperature feedback, use a PID controller to adjust the heating power to ensure that the temperature of the sealing grease gradually approaches the target set temperature;

[0024] When the sealing grease reaches the set temperature, the heating system stops working and maintains this temperature until the grease injection process starts;

[0025] Ensure that the preheating of the choke tube and the sealing grease is completed normally and conduct inspections. The inspections include whether the temperature of the sealing grease and the specifications of the choke tube match;

[0026] After the initialization stage is completed, the system is ready to enter the dynamic control stage, start real-time monitoring of the wellhead pressure and the grease injection pressure parameters, and perform PID control adjustments.

[0027] Preferably, in the dynamic control stage, the wellhead pressure and the grease injection pressure are monitored in real time, the pressure error is calculated, and the flow rate of the grease injection pump is adjusted according to the PID algorithm. When the cable lowering speed changes suddenly, the pressure fluctuation is suppressed in advance through the differential link, specifically including:

[0028] Based on the sensors, the wellhead pressure and the grease injection pressure are obtained in real time, and the sensor data is transmitted to the control system in real time through the data acquisition system;

[0029] The control system collects the data of the wellhead pressure and the grease injection pressure through high-frequency data acquisition sensors. The output signal of the sensor is converted into a digital signal and transmitted to the control system to calculate the error between the wellhead pressure and the grease injection pressure. Among them, the calculation formula is:

[0030] E(t)=P W (t)-P G (t)

[0031] In the formula, E(t) is the pressure error at the current moment, P W (t) is the real-time pressure of the wellhead, P G (t) is the real-time pressure of the grease injection system;

[0032] The pressure error is used as the input signal and transmitted to the PID controller to adjust the flow rate of the grease injection pump according to the PID algorithm;

[0033] The PID controller calculates the output signal for adjusting the flow rate of the grease injection pump by calculating the pressure error feedback. Among them, the PID control formula is:

[0034]

[0035] In the formula, F(t) is the adjusted flow rate of the grease injection pump, K p 、K i and K d are the proportional, integral, and differential gains of the PID controller, is the integral part of the error, is the differential part of the error;

[0036] According to the control signal output by PID, the flow rate of the grease injection pump is adjusted to minimize the pressure error and maintain the balance between the wellhead pressure and the grease injection pressure;

[0037] By installing a cable lowering speed sensor to monitor the cable lowering speed in real time, the system detects sudden changes in the cable lowering speed to determine whether a sudden change has occurred;

[0038] When the cable lowering speed changes suddenly, the control system predicts and suppresses the pressure fluctuation in advance through the differential link;

[0039] Predict the risk of choke tube wear or cable breakage by analyzing the grease injection pressure waveform, perform Fourier transform on the grease injection pressure signal, convert the pressure waveform in the time domain into the frequency domain, and identify the frequency components in the signal;

[0040] Whether there is a frequency component greater than 5 Hz in the spectrum analysis signal obtained by Fourier transform, if the frequency component above 5 Hz is strong, there may be a risk of wear and wire breakage, where the analysis formula is:

[0041] R=∑ f＞5hz |X(f)|

[0042] Where R is the risk factor, f represents the frequency component of the signal in the frequency domain analysis, and |X(f)| represents the spectrum amplitude at the frequency f;

[0043] A threshold is set based on historical data. When the risk factor exceeds the threshold, the system is judged to have the risk of choke tube wear and cable breakage, and the system triggers an alarm.

[0044] The differential link responds to sudden changes in cable speed, calculates the rate of change of cable speed, and uses it as an input signal to affect the differential part of the PID controller;

[0045] The differential adjustment signal of the cable speed change rate is added to the differential part of the PID controller, and the PID controller makes flow adjustment in advance when the cable lowering speed changes suddenly;

[0046] Adopting adaptive adjustment method to optimize control parameters, so as to minimize the pressure fluctuation of the system during the cable lowering process;

[0047] The system monitors the PID adjustment effect in real time to ensure that the grease injection pump flow and wellhead pressure always remain within the set range.

[0048] Preferably, the safety redundancy mechanism automatically switches to the standby PID controller when the main PID controller fails and triggers an emergency lock when the wellhead pressure exceeds the limit, which specifically includes:

[0049] Monitor the working status of the main PID controller in real time. By collecting the output signal of the controller, calculating the response time of the controller, and detecting the stability of the controller, a health check mechanism is set up to detect whether there is any abnormality in the main PID controller in each control cycle.

[0050] If the PID control output exceeds the predetermined range, immediately trigger the switching mechanism and switch to the standby PID controller.

[0051] During the switching process, the system performs a health check to confirm its normal operation by testing the error between the output of the standby controller and the set value.

[0052] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0053] The present invention adjusts the flow rate of the grease injection pump in real time through the incremental PID algorithm and the adaptive adjustment method, accurately controls the grease injection amount, reduces pressure fluctuations, predicts sudden changes in the cable lowering speed through the differential link, improves the response accuracy, the redundant controller and the emergency locking function ensure the stable operation of the system, the dynamic temperature-viscosity model corrects the PID output to adapt to different temperature environments, the remote communication unit monitors the system status in real time to improve the management efficiency, intelligently matches the cable diameter with the choke tube specifications to ensure stability, pre-heats the sealing grease to improve the automation level, and extends the service life of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is the system framework diagram of the present invention;

[0055] Figure 2 is the step flow framework diagram of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0056] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations.

[0057] Refer to Figure 1 As shown, the remote automatic grease injection system for blowout preventers based on PID control is characterized by including:

[0058] The grease injection execution unit includes a double-plunger grease injection pump, a grease injection head, and a sealing grease storage tank. Among them, the grease injection pump adjusts the grease injection amount through a PID controller, and the grease injection head adopts a choke tube and a diversion groove structure;

[0059] The sensing and feedback unit includes a pressure sensor, a temperature sensor, and a speed sensor, which are respectively used to monitor the wellhead pressure, the grease injection pressure, the sealing grease temperature, the cable lowering speed, and the acceleration;

[0060] The PID control unit adjusts the flow rate of the grease injection pump through the incremental PID algorithm and adjusts the control parameters in real time according to the changes in the cable movement and the wellhead pressure;

[0061] The remote communication unit realizes two-way encrypted communication based on the TLCP protocol and displays the pressure curve, the grease injection volume, and the alarm log in real time through the human-machine interface;

[0062] This system adopts an advanced PID control algorithm, which can perform real-time feedback adjustment according to the changes in the wellhead pressure and the cable lowering speed, ensuring accurate and stable grease injection volume. Through the remote communication unit, the system can transmit data in real time, ensuring that the operator can immediately grasp the dynamic conditions of the wellhead and the grease injection pressure, reducing manual intervention, and improving the automation and intelligent level of the grease injection process.

[0063] The PID controller adopts the incremental PID algorithm, and the parameter tuning range is Kp = 0.8 - 1.5, Ti = 0.5 - 2.0 seconds, Td = 0.1 - 0.3 seconds;

[0064] Compared with the traditional PID algorithm, the incremental PID algorithm is more suitable for dynamic regulation and real-time control. In the actual application of the system, the incremental PID algorithm can effectively reduce the overshoot phenomenon in the control process, improve the response speed and stability, and ensure the accurate regulation of the flow rate of the grease injection pump.

[0065] The grease injection head is internally provided with a diversion groove and a PTFE-coated flow-blocking tube, and the clearance tolerance is ±0.02 mm;

[0066] By optimizing the design of the grease injection head, adopting a PTFE-coated flow-blocking tube and a precise diversion groove structure, the friction coefficient can be effectively reduced, ensuring the smooth injection of the fluid. At the same time, the fine tolerance control ensures the stability and high efficiency of the system during high-precision grease injection, thereby improving the injection effect of the sealing grease and the performance of the blowout preventer.

[0067] The PID control unit includes a main controller and a standby controller, and automatically switches to the standby controller when the main controller fails.

[0068] The system further includes a safety redundancy mechanism. When the wellhead pressure exceeds 10% of the design value, the blowout preventer is triggered to be emergently locked;

[0069] A redundant control unit is designed to enhance the reliability of the system. Through the switching mechanism between the main controller and the standby controller, it can be instantly switched to the standby controller when the main controller fails, ensuring the continuity and stability of the system, thus effectively reducing the risks brought by faults and enhancing the reliability and safety of the system.

[0070] The PID control unit of the system corrects the PID control output through a dynamic temperature-viscosity model to cope with the influence of the viscosity of the sealing grease changing with temperature.

[0071] The viscosity of the sealing grease changes with temperature, which may affect the accuracy of the grease injection process. This control unit introduces a dynamic temperature-viscosity model to adjust the PID control output in real time, ensuring that the system can always accurately control the grease injection volume under different temperature conditions and maintain the stable performance of the blowout preventer.

[0072] Refer to Figure 2 As shown, a remote automatic grease injection control method for a blowout preventer based on PID control includes the following steps:

[0073] In the initialization stage, the choke tube specification is automatically matched according to the cable diameter, and the sealing grease is preheated to the set temperature.

[0074] In the dynamic control stage, the wellhead pressure and the grease injection pressure are monitored in real time, the pressure error is calculated, and the flow rate of the grease injection pump is adjusted according to the PID algorithm. When the cable lowering speed changes suddenly, the pressure fluctuation is suppressed in advance through the differential link.

[0075] In the safety redundancy mechanism, when the main PID controller fails, it automatically switches to the standby PID controller, and triggers an emergency lock when the wellhead pressure exceeds the limit.

[0076] In the initialization stage, automatically matching the choke tube specification according to the cable diameter and preheating the sealing grease to the set temperature specifically includes:

[0077] Based on the cable sensor, the diameter of the cable is obtained, and the preset matching relationship between the cable diameter and the choke tube specification is used to select the choke tube specification.

[0078] Set the preheating temperature to be between 60 - 80 °C, start the sealing grease heating device, and adjust the heating power according to the PID control algorithm to gradually increase the temperature of the sealing grease.

[0079] Use the temperature sensor to monitor the temperature of the sealing grease in real time. According to the temperature feedback, use the PID controller to adjust the heating power to ensure that the temperature of the sealing grease gradually approaches the target set temperature.

[0080] When the sealing grease reaches the set temperature, the heating system stops working and maintains this temperature until the grease injection process starts.

[0081] Ensure that the preheating of the choke tube and sealant is completed properly and conduct inspections, including checking the sealant temperature and whether the choke tube specifications match;

[0082] After the initialization phase is completed, the system is ready to enter the dynamic control phase, starting to monitor the wellhead pressure and grease injection pressure parameters in real time and performing PID control adjustments;

[0083] This method not only includes the traditional grease injection control process but also innovatively introduces a differential link for sudden changes in the cable lowering speed, which can predict and suppress pressure fluctuations in advance, thus avoiding the impact of pressure instability on the blowout preventer. This innovation greatly enhances the system's response ability under extreme conditions.

[0084] During the dynamic control phase, the wellhead pressure and grease injection pressure are monitored in real time, the pressure error is calculated, and the flow rate of the grease injection pump is adjusted according to the PID algorithm. When there is a sudden change in the cable lowering speed, the pressure fluctuation is suppressed in advance through the differential link, which specifically includes:

[0085] Based on sensors, the wellhead pressure and grease injection pressure are obtained in real time, and the sensor data is transmitted to the control system in real time through the data acquisition system;

[0086] The control system collects the data of the wellhead pressure and grease injection pressure through high-frequency data acquisition sensors. The output signal of the sensor is converted into a digital signal and transmitted to the control system to calculate the error between the wellhead pressure and the grease injection pressure. The calculation formula is as follows:

[0087] E(t) = P W (t) - P G (t)

[0088] In the formula, E(t) is the pressure error at the current moment, P W (t) is the real-time pressure at the wellhead, P G (t) is the real-time pressure of the grease injection system;

[0089] The pressure error is used as the input signal and transmitted to the PID controller to adjust the flow rate of the grease injection pump according to the PID algorithm;

[0090] The PID controller calculates the output signal for adjusting the flow rate of the grease injection pump by feedback of the pressure error. The PID control formula is as follows:

[0091]

[0092] In the formula, F(t) is the adjusted flow rate of the grease injection pump, K p 、K i and K d are the proportional, integral, and differential gains of the PID controller, is the integral part of the error, is the differential part of the error;

[0093] According to the control signal output by the PID, adjust the flow rate of the grease injection pump to minimize the pressure error and maintain the balance between the wellhead pressure and the grease injection pressure;

[0094] By installing a cable lowering speed sensor to monitor the cable lowering speed in real time, the system detects the sudden change of the cable lowering speed to judge whether a mutation occurs;

[0095] When the cable lowering speed mutates, the control system predicts and suppresses the pressure fluctuation in advance through the differential link;

[0096] Through the analysis of the grease injection pressure waveform, predict the risk of choke tube wear or cable broken wires, perform Fourier transform on the grease injection pressure signal, convert the pressure waveform in the time domain to the frequency domain, and identify the frequency components in the signal;

[0097] Check whether there are frequency components greater than 5Hz in the spectrum analysis signal obtained through Fourier transform. If the frequency components above 5Hz are strong, there may be risks of wear and broken wires. The analysis formula is:

[0098] R = ∑ f＞5hz |X(f)|

[0099] In the formula, R is the risk factor, f represents the frequency component of the signal in the frequency domain analysis, and |X(f)| represents the spectrum amplitude at frequency f;

[0100] Set a threshold according to historical data. When the risk factor exceeds this threshold, it is judged that there is a risk of choke tube wear and cable broken wires in the system, and the system triggers an alarm;

[0101] The differential link responds to the sudden change of the cable speed, calculates the cable speed change rate, and uses it as an input signal to affect the differential part in the PID controller;

[0102] Add the differential adjustment signal of the cable speed change rate to the differential part of the PID controller. The PID controller adjusts the flow rate in advance when the cable lowering speed mutates;

[0103] Adopt an adaptive adjustment method to optimize the control parameters to minimize the pressure fluctuation during the cable lowering process;

[0104] The system monitors the PID adjustment effect in real time to ensure that the flow rate of the grease injection pump and the wellhead pressure are always within the set range;

[0105] During the dynamic control phase, the system adopts a high-frequency data acquisition system and a PID algorithm, which can accurately adjust the flow rate of the grease injection pump. This innovative design improves the system's response ability to pressure changes, ensures the stability of pressure under various operating conditions, and provides real-time feedback to adjust the grease injection volume, guaranteeing the efficiency and accuracy of grease injection.

[0106] The safety redundancy mechanism automatically switches to the standby PID controller when the main PID controller fails and triggers an emergency lock when the wellhead pressure exceeds the limit. Specifically, it includes:

[0107] Real-time monitoring of the working status of the main PID controller. By collecting the output signal of the controller, calculating the response time of the controller, and detecting the stability of the controller, a health check mechanism is set up to detect whether there are any abnormalities in the main PID controller in each control cycle.

[0108] If the PID control output exceeds the predetermined range, immediately trigger the switching mechanism and switch to the standby PID controller.

[0109] During the switching process, the system conducts a health check to confirm its normal operation by testing the error between the output of the standby controller and the set value.

[0110] This safety redundancy mechanism not only ensures that the main controller can be quickly switched to the standby controller when a failure occurs, maintaining the stable operation of the system, but also ensures that the system can automatically trigger an emergency lock under abnormal conditions by real-time monitoring of the wellhead pressure, thus improving the safety of the system and avoiding potential risks caused by control system failures.

[0111] In summary, the advantages of the present invention are as follows:

[0112] Through the incremental PID algorithm and the adaptive adjustment method, the system can adjust the flow rate of the grease injection pump in real time, thereby accurately controlling the grease injection volume. The PID controller can automatically adjust the control parameters according to the pressure error, temperature, and the change of the cable lowering speed to ensure that the wellhead pressure and the grease injection pressure are maintained within the set range, reducing pressure fluctuations and system instability.

[0113] The system predicts the sudden change of the cable lowering speed through the differential link, adjusts the flow rate in advance, and suppresses the pressure fluctuation caused by the sudden change. This predictive control method improves the response speed and accuracy of the system to dynamic changes.

[0114] The system has a redundant configuration of the main controller and the standby controller. When the main controller fails, the standby controller automatically takes over to ensure the continuous operation of the system. In addition, when the wellhead pressure exceeds the limit, the system can trigger an emergency lock to protect the equipment from damage or accidents.

[0115] By correcting the PID control output through a dynamic temperature-viscosity model, the system can effectively cope with the influence of the viscosity of the sealing grease changing with temperature, ensuring the stable operation of the grease injection system under different working environments;

[0116] Through the remote communication unit, the system can display the pressure curve, grease injection volume, and alarm log in real time. Operators can monitor the system status in real time through the human-machine interface. This remote control ability improves the convenience of operation and management efficiency;

[0117] The grease injection head adopts a flow guiding groove and a PTFE-coated flow blocking tube structure to ensure stable flow under high-pressure environments, reduce mechanical wear, and extend the service life of the system. The system ensures the stability and efficiency of the grease injection process by intelligently matching the cable diameter with the flow blocking tube specifications;

[0118] The system automatically matches the cable diameter with the flow blocking tube specifications and pre-heats the sealing grease before grease injection to ensure that the temperature and fluidity of the sealing grease meet the working requirements. This process can reduce human operation errors and improve the automation level of the system.

[0119] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. The remote automatic grease injection system for BOP based on PID control is characterized by: include: The grease injection execution unit includes a double-plunger grease injection pump, a grease injection head and a sealing grease storage tank, wherein the grease injection pump adjusts the grease injection amount through a PID controller, and the grease injection head adopts a choke tube and a guide groove structure; The sensing and feedback unit includes a pressure sensor, a temperature sensor, and a speed sensor, which are used to monitor the wellhead pressure, the injection pressure, the sealing grease temperature, the cable lowering speed, and the acceleration respectively; PID control unit, which adjusts the flow rate of the grease injection pump through the incremental PID algorithm and adjusts the control parameters in real time according to the cable movement and the change of wellhead pressure; The remote communication unit realizes two-way encrypted communication based on the TLCP protocol, and displays the pressure curve, fat injection amount and alarm log in real time through the human-machine interface.

2. The remote automated grease injection system for a blowout preventer based on PID control according to claim 1 is characterized in that: The PID controller adopts an incremental PID algorithm, and the parameter setting range is Kp=0.8-1.5, Ti=0.5-2.0 seconds, and Td=0.1-0.3 seconds.

3. The remote automatic grease injection system for blowout preventer based on PID control according to claim 2 is characterized in that: The grease injection head is provided with a guide groove and a PTFE-coated flow-blocking tube, and the clearance tolerance is ±0.02 mm.

4. The remote automated grease injection system for a blowout preventer based on PID control according to claim 3 is characterized in that: The PID control unit includes a main controller and a standby controller, and automatically switches to the standby controller when the main controller fails.

5. The remote automatic grease injection system for blowout preventer based on PID control according to claim 4 is characterized in that: The system further includes a safety redundancy mechanism, which triggers emergency shutdown of the blowout preventer when the wellhead pressure exceeds 10% of the design value.

6. The remote automated grease injection system for blowout preventers based on PID control according to claim 5 is characterized in that: The PID control unit of the system corrects the PID control output through a dynamic temperature-viscosity model to cope with the influence of the viscosity of the sealing grease changing with temperature.

7. A remote automated grease injection control method for a blowout preventer based on PID control, characterized in that: The following steps are involved: In the initialization stage, the specifications of the choke tube are automatically matched according to the cable diameter, and the sealing grease is preheated to the set temperature; In the dynamic control stage, the wellhead pressure and grease injection pressure are monitored in real time, the pressure error is calculated, and the grease injection pump flow is adjusted according to the PID algorithm. When the cable lowering speed changes suddenly, the pressure fluctuation is suppressed in advance through the differential link; The safety redundancy mechanism automatically switches to the backup PID controller when the main PID controller fails, and triggers emergency shutdown when the wellhead pressure exceeds the limit.

8. According to the PID-controlled remote automatic grease injection control method for a blowout preventer according to claim 7, in the initialization stage, automatically matching the choke tube specifications according to the cable diameter and preheating the sealing grease to a set temperature specifically includes: Based on the cable diameter obtained by the cable sensor, the specification of the choke tube is selected using the matching relationship between the preset cable diameter and the choke tube specification; Set the preheating temperature to between 60-80°C, start the sealing grease heating device, adjust the heating power according to the PID control algorithm, and gradually increase the temperature of the sealing grease; Use a temperature sensor to monitor the temperature of the sealing grease in real time. Based on the temperature feedback, use a PID controller to adjust the heating power to ensure that the sealing grease temperature gradually approaches the target set temperature. When the sealing grease reaches the set temperature, the heating system stops working and maintains the temperature until the grease injection process begins; Ensure that the preheating of the choke tube and the sealing grease is completed normally and an inspection is performed, including whether the sealing grease temperature and the choke tube specifications match; After the initialization phase is completed, the system is ready to enter the dynamic control phase and start real-time monitoring of wellhead pressure and injection pressure parameters to make PID control adjustments.

9. According to the method for remote automatic grease injection control of a blowout preventer based on PID control in claim 8, in the dynamic control stage, real-time monitoring of wellhead pressure and grease injection pressure, calculation of pressure error and adjustment of grease injection pump flow rate according to PID algorithm, when the cable lowering speed changes suddenly, pressure fluctuation is suppressed in advance through differential link, specifically including: Based on the real-time acquisition of wellhead pressure and injection pressure by sensors, the sensor data is transmitted to the control system in real time through the data acquisition system; The control system collects data on wellhead pressure and injection pressure through high-frequency data acquisition sensors. The sensor output signal is converted into a digital signal and transmitted to the control system to calculate the error between the wellhead pressure and the injection pressure. The calculation formula is: E(t)=P W (t)-P G (t) Where E(t) is the pressure error at the current moment, P W (t) is the real-time pressure at the wellhead, P G (t) is the real-time pressure of the grease injection system; The pressure error is used as an input signal and sent to the PID controller to adjust the grease injection pump flow rate according to the PID algorithm; The PID controller outputs the grease pump flow adjustment signal by calculating the pressure error feedback, where the PID control formula is: Where F(t) is the adjusted grease pump flow rate, K p , K i and K d are the proportional, integral and derivative gains of the PID controller, is the integral part of the error, is the differential part of the error; According to the control signal output by PID, the flow rate of the grease injection pump is adjusted to minimize the pressure error and maintain the balance between the wellhead pressure and the grease injection pressure; By installing a cable lowering speed sensor to monitor the cable lowering speed in real time, the system detects sudden changes in the cable lowering speed to determine whether a sudden change has occurred; When the cable lowering speed changes suddenly, the control system predicts and suppresses the pressure fluctuation in advance through the differential link; Predict the risk of choke tube wear or cable breakage by analyzing the grease injection pressure waveform, perform Fourier transform on the grease injection pressure signal, convert the pressure waveform in the time domain into the frequency domain, and identify the frequency components in the signal; Whether there is a frequency component greater than 5 Hz in the spectrum analysis signal obtained by Fourier transform, if the frequency component above 5 Hz is strong, there may be a risk of wear and wire breakage, where the analysis formula is: R=∑ f>5hz |X(f)| Where R is the risk factor, f represents the frequency component of the signal in the frequency domain analysis, and |X(f)| represents the spectrum amplitude at the frequency f; A threshold is set based on historical data. When the risk factor exceeds the threshold, the system is judged to have the risk of choke tube wear and cable breakage, and the system triggers an alarm. The differential link responds to sudden changes in cable speed, calculates the rate of change of cable speed, and uses it as an input signal to affect the differential part of the PID controller; The differential adjustment signal of the cable speed change rate is added to the differential part of the PID controller, and the PID controller makes flow adjustment in advance when the cable lowering speed changes suddenly; Adopting adaptive adjustment method to optimize control parameters, so as to minimize the pressure fluctuation of the system during the cable lowering process; The system monitors the PID adjustment effect in real time to ensure that the grease injection pump flow and wellhead pressure always remain within the set range.

10. According to the method for remote automatic grease injection control of a blowout preventer based on PID control in claim 9, the safety redundancy mechanism automatically switches to a backup PID controller when the main PID controller fails, and triggers emergency shutoff when the wellhead pressure exceeds the limit, specifically comprising: Monitor the working status of the main PID controller in real time. By collecting the output signal of the controller, calculating the response time of the controller and detecting the stability of the controller, a health check mechanism is set up to detect whether there is any abnormality in the main PID controller in each control cycle. If the PID control output exceeds the predetermined range, the switching mechanism is immediately triggered to switch to the backup PID controller; During the switchover process, the system performs a health check to confirm that the backup controller is operating normally by testing the error between the output and the set point.

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