Non-contact downhole high-temperature electromagnetic flowmeter and resonant excitation magnetic closed-loop control method

Abstract

The application relates to the technical field of magnetic sensors, and discloses a non-contact downhole high-temperature electromagnetic flowmeter and a resonant excitation magnetic closed-loop control method, which comprises the following steps: a ground processing unit is connected with a downhole measurement assembly through a data cable, the downhole measurement assembly comprises a control measurement nipple and a sensor nipple; the control measurement nipple comprises a resonant excitation magnetic circuit; the sensor nipple comprises an excitation coil and signal electrodes, the excitation coil is connected with the resonant excitation magnetic circuit; the signal electrodes are connected with the control measurement nipple; the signal electrodes transmit the collected induced voltage signals to the control measurement nipple, the signals are processed by the control measurement nipple, and then the processed signals are transmitted to the ground processing unit to calculate electromagnetic flow; wherein the resonant excitation magnetic circuit is used for generating a control signal to drive the excitation coil to generate an alternating magnetic field, monitoring the current phase error of the excitation coil, and dynamically adjusting the current phase error so that the circuit is in a resonant state. The application overcomes the problem of large zero drift of the traditional high-frequency excitation technology, and improves the precision and service life of the electromagnetic flowmeter.

Description

Technical Field

[0001] This invention relates to the field of magnetic sensor technology, specifically to a non-contact downhole high-temperature electromagnetic flowmeter and a resonant excitation closed-loop control method. Background Technology

[0002] As my country's oil development enters its later stages, research on water injection and polymer flooding technologies in oilfields has become an effective means to ensure the long-term stable development of oil and gas production. Currently, it has evolved from the original general injection to the stage of stratified and precise injection. Commonly used downhole flow meters for water injection include mechanical flow meters such as orifice plate flow meters and turbine flow meters. However, due to the fact that mechanical structures are easily jammed by impurities such as mud and sand, the measurement accuracy is affected. In particular, with the application of sewage reinjection technology, there is an urgent need to develop a flow meter that does not come into contact with the measured liquid.

[0003] In the process of realizing this invention, the inventors discovered the following problems in the prior art: Under high-pressure environments, the technological development of ultrasonic flowmeters is limited, currently mainly operating below 85°C. Furthermore, due to the absorption of sound waves by polymers, they are only suitable for measuring water injection flow. Downhole electromagnetic flowmeters currently all use contact electrodes. This type of electrode structure can cause polarization and corrosion, affecting measurement accuracy. The operating frequency is also limited, generally using an integer fraction of the power frequency. Moreover, when measuring polymers, it is similar to slurry flowing over the electrode surface, generating slurry noise and friction noise, severely affecting measurement accuracy. Electromagnetic flowmeters based on high-frequency excitation technology have fast measurement response speeds and can be applied to slurry measurement in real-world environments, but the zero-point stability of high-frequency excitation technology is poor. Downhole non-contact electromagnetic flowmeters for oil wells have instrument limitations; currently, there are no practical application products or use cases both domestically and internationally. Summary of the Invention

[0004] In view of this, embodiments of this application provide a non-contact downhole high-temperature electromagnetic flowmeter and a resonant excitation closed-loop control method to solve the problems of large zero-point drift and phase sensitivity error of traditional high-frequency excitation technology.

[0005] In a first aspect, one embodiment of this application provides a non-contact downhole high-temperature electromagnetic flowmeter, which includes: a surface processing unit; and a downhole measurement component connected via a data cable. The downhole measurement component includes a control measurement sub-section and a non-contact electromagnetic flow sensor sub-section. The control measurement sub-section includes a resonant excitation circuit. The non-contact electromagnetic flow sensor sub-section includes an excitation coil shielding electrode and a signal electrode, with the excitation coil connected to the resonant excitation circuit. Both the shielding electrode and the signal electrode are connected to the control measurement sub-section. The shielding electrode covers the signal electrode to enhance its noise immunity. The signal electrode transmits the acquired induced voltage signal to the control measurement sub-section, which processes the signal and then transmits it to the surface processing unit to calculate the electromagnetic flow. The resonant excitation circuit generates a control signal to drive the excitation coil to generate an alternating magnetic field, monitors the current phase error of the excitation coil, and dynamically adjusts the circuit based on the current phase error to maintain resonance.

[0006] In conjunction with the first aspect, in some implementations of the first aspect, the resonant excitation circuit further includes: an excitation current sampling circuit and an SPWM control circuit, wherein the excitation current sampling circuit is connected to the SPWM control circuit; the SPWM control circuit is connected to the excitation coil; the excitation current sampling circuit monitors the current phase error of the excitation coil, and if the current phase error is less than or equal to 5°, it is determined to be in a resonant state; if the current phase error is greater than 5°, the phase error is reduced by adjusting the output SPWM signal through the SPWM control circuit until a resonant state is achieved; if the current phase error is greater than 5° and the temperature is greater than 85°, and / or, the current phase error is greater than 5° and the noise frequency is greater than 100Hz, the phase error is reduced by performing dynamic temperature compensation and / or high-frequency noise suppression until a resonant state is achieved.

[0007] In conjunction with the first aspect, in some implementations of the first aspect, the resonant excitation circuit further includes a full-bridge drive circuit, which is connected to the SPWM control circuit and the excitation coil respectively; the SPWM control circuit generates an SPWM signal to drive the full-bridge drive circuit, which is used to drive the excitation coil to generate an alternating magnetic field, thereby generating current.

[0008] In conjunction with the first aspect, in some implementations of the first aspect, the control measurement section also includes a DSP core circuit, which is connected to the SPWM control circuit; the DSP core circuit generates a sinusoidal drive signal and controls the full-bridge drive circuit through the SPWM control circuit.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, the control measurement section further includes an analog signal conditioning circuit and an encoding conversion and coupling circuit; the analog signal conditioning circuit is connected to the DSP core circuit and the signal electrode respectively, and the DSP core circuit is connected to the encoding conversion and coupling circuit; the signal electrode is used to transmit the voltage signal of the non-contact electromagnetic flow sensor section to the analog signal conditioning circuit, the analog signal conditioning circuit receives the voltage signal of the signal electrode and converts the voltage signal into an analog flow signal, and the analog flow signal is transmitted to the ground processing unit to calculate the flow after signal processing by the DSP core circuit and the encoding conversion and coupling circuit.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, the control measurement section further includes a flow and excitation current synchronous digitization circuit and a signal power supply circuit. The flow and excitation current synchronous digitization circuit is connected to the DSP core circuit and is used to digitize the analog flow signal and the current signal of the excitation coil. The signal power supply circuit is connected to the flow and excitation current synchronous digitization circuit, the DSP core circuit, and the analog signal conditioning circuit, respectively, and is used to provide the various levels required by the flow and excitation current synchronous digitization circuit, the DSP core circuit, and the analog signal conditioning circuit.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the resonant excitation circuit further includes an excitation power supply circuit, a switching transistor, and a low-pass filter circuit; the excitation power supply circuit is connected to the full-bridge drive circuit, and is used to provide the high-voltage power supply and drive operating level for the full-bridge drive circuit; the switching transistor is connected to both the full-bridge drive circuit and the low-pass filter circuit, and is used to control the current switching on and off of the full-bridge drive circuit and the low-pass filter circuit; the low-pass filter circuit is connected to both the switching transistor and the excitation coil, and is used to filter out high-frequency signal components and output the fundamental frequency to excite the excitation coil; the analog signal conditioning circuit further includes: an interface circuit, a differential filter amplifier circuit, a DC blocking circuit, a programmable amplifier circuit, a first active rectifier filter circuit, and a second active rectifier. The system includes a filtering circuit; both the shielding electrode and the signal electrode are connected to an interface circuit, which in turn connects to a differential filter amplifier circuit. This differential filter amplifier circuit is connected to a DC blocking circuit and a second active rectifier filter circuit. The DC blocking circuit is connected to a programmable amplifier circuit, which in turn connects to a first active rectifier filter circuit. The first active rectifier filter circuit is connected to the DSP core circuit. The interface circuit is used for the initial transmission and matching of the voltage signal. The differential filter amplifier circuit is used for differential amplification and filtering out interference noise. The DC blocking circuit is used to isolate AC and DC signals. The programmable amplifier circuit is used to amplify the voltage signal, and the amplification factor is adjustable. The first and second active rectifier filter circuits are used to rectify and filter the voltage signal, outputting an analog flow signal.

[0012] Secondly, one embodiment of this application provides a resonant excitation closed-loop control method applied to a non-contact downhole high-temperature electromagnetic flowmeter. The flowmeter includes a surface processing unit and a downhole measurement component. The surface processing unit is connected to the downhole measurement component via a data cable. The downhole measurement component includes a control measurement section and a non-contact electromagnetic flow sensor section. The control measurement section includes a resonant excitation circuit, and the non-contact electromagnetic flow sensor section includes an excitation coil, a shielding electrode, and a signal electrode. The excitation coil is connected to the resonant excitation circuit. The shielding electrode and the signal electrode are both connected to the control measurement section. The method includes: the resonant excitation circuit generating a control signal to drive the excitation coil to generate an alternating magnetic field; monitoring the current phase error of the excitation current of the resonant excitation circuit; dynamically adjusting the circuit according to the current phase error to make the circuit resonant; receiving the induced voltage signal collected by the signal electrode; transmitting the collected induced voltage signal to the control measurement section, and after signal processing by the control measurement section, transmitting it to the surface processing unit to calculate the electromagnetic flow.

[0013] In conjunction with the second aspect, in some implementations of the second aspect, dynamic adjustment is performed based on the current phase error to bring the circuit into a resonant state, including: if the current phase error is less than or equal to 5°, it is determined to be in a resonant state; if the current phase error is greater than 5°, the phase error is reduced by adjusting the output control signal until a resonant state is achieved; the control signal is an SPWM signal; if the current phase error is greater than 5° and the temperature is greater than 85°, and / or, if the current phase error is greater than 5° and the noise frequency is greater than 100Hz, the phase error is reduced by performing dynamic temperature compensation and / or high-frequency noise suppression until a resonant state is achieved.

[0014] In conjunction with the second aspect, in some implementations of the second aspect, dynamic adjustment is performed based on the current phase error to bring the circuit into a resonant state. This includes: synchronous triggering of the ADC start signal and the rising edge of the SPWM carrier; acquiring flow signals and excitation current for several cycles; calculating the correlation coefficient function of the flow signal and the excitation current; adjusting the SPWM phase according to the correlation coefficient function to obtain the independent variable that maximizes the correlation coefficient function, with the potential value corresponding to the independent variable tending towards the corrected potential value, and the independent variable being a time delay parameter; outputting the corrected potential value; calculating the resistance value of the coil resistor, which is the equivalent resistance of the excitation coil; calculating the voltage compensation value of the coil resistor; performing a zero-flow calibration operation: turning off the resonant excitation circuit for 10 seconds, acquiring baseline noise, and storing the voltage compensation value; calculating the slurry center frequency; detecting the slurry center frequency, and if the slurry center frequency is within the range [100, 1000Hz], setting the notch filter frequency value equal to the slurry center frequency value.

[0015] The non-contact downhole high-temperature electromagnetic flowmeter provided in this invention transmits the collected induced voltage signal to the control and measurement sub-section via the signal electrode. After signal processing by the control and measurement sub-section, the signal is transmitted to the surface processing unit to calculate the electromagnetic flow. The resonant excitation circuit generates a control signal to drive the excitation coil to produce an alternating magnetic field and monitors the current phase error of the excitation coil. Dynamic adjustments are made based on the current phase error to keep the circuit in a resonant state, thus realizing the calculation of non-contact downhole high-temperature electromagnetic flow. Because a phase compensation algorithm with correlation coefficient ρ(τ) is used for resonant excitation closed-loop control, and dynamic temperature compensation and high-frequency noise suppression are employed to reduce phase error, the problem of large zero-point drift in traditional high-frequency excitation technology is overcome, improving the measurement accuracy of the electromagnetic flowmeter. Attached Figure Description

[0016] Figure 1 The diagram shown is a schematic diagram of the circuit structure of an electromagnetic flowmeter provided in an exemplary embodiment of this application.

[0017] Figure 2 The diagram shown is a schematic diagram of the resonant excitation closed-loop control of an electromagnetic flowmeter provided in an exemplary embodiment of this application.

[0018] Figure 3 The diagram shown is a schematic diagram illustrating the working principle of the control and measurement section of an electromagnetic flowmeter provided in an exemplary embodiment of this application.

[0019] Figure 4 The diagram shown is a schematic flowchart of a resonant excitation closed-loop control method provided in an exemplary embodiment of this application.

[0020] Figure 5 The diagram shown is an equivalent schematic diagram of resonant excitation provided in an exemplary embodiment of this application.

[0021] In the diagram: 1. Surface processing unit; 2. Data cable; 3. Downhole measurement assembly; 4. Non-contact electromagnetic flow sensor section; 5. Control and measurement section; 7A, 7B. Shielding electrodes; 8A, 8B. Signal electrodes; 9A, 9B. Excitation coil; 17. Interface circuit; 18. Differential filter amplifier circuit; 19. DC blocking circuit; 20. Programmable amplifier circuit; 21. First active rectifier filter circuit; 211. Second active rectifier filter circuit; 22. Excitation current sampling circuit; 23. SPWM control circuit; 24. Full-bridge drive circuit; 25. Excitation power supply circuit; 26. Flow and excitation current synchronous digitization circuit; 27. DSP core circuit; 28. Encoding conversion and coupling circuit; 29. ​​Signal power supply circuit; 30. Cable interface; 31. Analog signal conditioning circuit; 32. Resonant excitation circuit; 35. Switching transistor; 36. Low-pass filter circuit. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Figure 1 The diagram shown is a schematic representation of the circuit structure of an electromagnetic flowmeter provided in an exemplary embodiment of this application. Please refer to [link / reference]. Figure 1 This invention provides a non-contact downhole high-temperature electromagnetic flowmeter, comprising: a surface processing unit 1 for calibration, data playback, calculation, and recording of cumulative flow; and a downhole measurement assembly 3 connected via a data cable 2, the downhole measurement assembly 3 including a control measurement section 5 and a non-contact electromagnetic flow sensor section 4; the control measurement section 5 including a resonant excitation circuit 32; and the non-contact electromagnetic flow sensor section 4 including excitation coils 9A and 9B, shielding electrodes 7A and 7B, and signal electrodes 8A and 8B, the excitation coils 9A and 9B being connected to the resonant excitation circuit 32; the shielding electrodes 7A and 7B... B and signal electrodes 8A and 8B are both connected to the control and measurement subsection 5; shielding electrodes 7A and 7B cover the signal electrodes to enhance their noise immunity; signal electrodes 8A and 8B transmit the collected induced voltage signals to the control and measurement subsection 5, which then processes the signals and transmits them to the ground processing unit 1 to calculate the electromagnetic flow; the resonant excitation circuit 32 generates control signals to drive the excitation coils 9A and 9B to generate an alternating magnetic field, monitors the current phase error of the excitation coils 9A and 9B, and dynamically adjusts the circuit according to the current phase error to keep it in a resonant state.

[0024] For example, the non-contact electromagnetic flow sensor section 4 and the control and measurement section 5 can be combined as needed and connected by flexible wires or rigid wires to adapt to different application scenarios. When used alone as a well logging instrument, a rigid connection can be used; while when integrated into other instruments, such as water distributors, it can be used as a flow measurement unit, in which case a flexible connection can be used.

[0025] For example, the non-contact electromagnetic flow sensor section 4 in the downhole measurement assembly 3 includes a set of excitation coils 9A and 9B, a set of signal electrodes 8A and 8B, a set of shielding electrodes 7A and 7B, and an insulating pad; the sensor excitation coils 9A and 9B are made of high magnetic permeability materials, such as pure iron, ferrite, permalloy, etc., and are used as the core components of the magnetic field generator; the sensor signal electrodes 8A and 8B and the shielding electrodes 7A and 7B are all made of conductive materials with high conductivity but poor magnetic permeability; the signal electrodes 8A and 8B adopt a mesh or comb structure to reduce the influence of eddy currents.

[0026] For example, insulating pads are placed on signal electrodes 8A and 8B respectively, and then shielding electrodes 7A and 7B are laid on them respectively. Shielding electrodes 7A and 7B adopt an active shielding method to cover signal electrodes 8A and 8B and enhance noise immunity. Then, excitation coils 9A and 9B are wound and set on the assembly of shielding electrodes 7A and 7B, signal electrodes 8A and 8B, and insulating pads. At this time, the central axis of the assembly is perpendicular to the central axis of signal electrodes 8A and 8B, and the central axis of the assembly is perpendicular to the central axis of the liquid being measured. In the rectangular coordinate system, the vertical axis is consistent with the central axis of the assembly and represents the direction of the magnetic field; the horizontal axis of the rectangular coordinate system is consistent with the central axis of the liquid being measured and represents the direction of fluid movement; the vertical axis of the rectangular coordinate system is consistent with the central axis of signal electrodes 8A and 8B and shielding electrodes 7A and 7B and represents the direction of the generated induced electromotive force.

[0027] The non-contact downhole high-temperature electromagnetic flowmeter provided in this invention overcomes the problem of poor zero-point stability caused by excessive current phase error in traditional high-frequency excitation circuits by monitoring current phase error and making dynamic adjustments based on the current phase error, thereby improving the accuracy of the flowmeter.

[0028] Figure 2 The diagram shown is a schematic representation of the resonant excitation closed-loop control of an electromagnetic flowmeter according to an exemplary embodiment of this application. Please refer to [link / reference]. Figure 2 The non-contact downhole high-temperature electromagnetic flowmeter provided in this embodiment of the invention includes: a resonant excitation circuit 32 and a DSP core circuit 27; the resonant excitation circuit 32 includes excitation coils 9A and 9B, shielding electrodes 7A and 7B, signal electrodes 8A and 8B, an excitation current sampling circuit 22, an SPWM control circuit 23, a full-bridge drive circuit 24, an excitation power supply circuit 25, a switching transistor 35, and a low-pass filter circuit 36; the excitation coils 9A and 9B are connected to the excitation current sampling circuit 22; the excitation current sampling circuit 22 is connected to the SPWM control circuit. 23 and full-bridge drive circuit 24; shielding electrodes 7A, 7B and signal electrodes 8A, 8B are connected to DSP core circuit 27; voltage signals from signal electrodes 8A, 8B are transmitted to DSP core circuit 27; DSP core circuit 27 is connected to SPWM control circuit 23; SPWM control circuit 23 is connected to full-bridge drive circuit 24; full-bridge drive circuit 24 is connected to switching transistor 35; switching transistor 35 is connected to low-pass filter circuit 36; low-pass filter circuit 36 ​​is connected to excitation coils 9A, 9B; excitation power supply circuit 25 is connected to full-bridge drive circuit 24.

[0029] Among them, shielding electrodes 7A and 7B adopt an active driving method, and the voltage signals of signal electrodes 8A and 8B are transmitted to the DSP core circuit 27; the DSP core circuit 27 generates a fundamental frequency sine wave to control the signal of the resonant excitation circuit 32; the excitation current sampling circuit 22 monitors the current phase error of the excitation coils 9A and 9B; the SPWM control circuit 23 is equipped with a PID controller to adjust the output SPWM signal; the full-bridge drive circuit 24 generates a controllable sine wave working electromagnetic field; and the excitation power supply circuit 25 provides the high voltage power supply and drive working level for the full-bridge drive circuit 24.

[0030] Specifically, the DSP core circuit 27 starts working, generating a sinusoidal drive signal, which is output to the resonant excitation circuit 32. The SPWM control circuit 23 generates a complementary dead-time signal to drive the full-bridge drive circuit 24. Through level conversion, the switching transistor 35 is controlled to turn on and off according to a sinusoidal law, so that the output pulse width has a sinusoidal amplitude distribution. The low-pass filter circuit 36 ​​filters out high-frequency signal components and outputs the fundamental wave to excite the excitation coils 9A and 9B. During this period, the SPWM control circuit 23 samples the current flowing through the excitation coils 9A and 9B in real time through the excitation current sampling circuit 22, generating a high-frequency sinusoidal wave with a fixed frequency and a pulse width that varies with the current. After comparing it with the drive sinusoidal wave generated by the DSP core circuit 27, the control signal of the full-bridge drive circuit 24 is output to ensure the AC drive of the excitation coils 9A and 9B, generating a uniform alternating electromagnetic field between the coil frames. The magnetic field strength is set to B.

[0031] The resonant excitation closed-loop control provided in this embodiment of the invention solves the problems of excitation current phase shift, amplitude fluctuation and magnetic field instability caused by environmental factors by sampling the excitation current in real time, comparing it with the reference sine wave generated by the DSP, and dynamically adjusting the drive signal using the SPWM circuit of the built-in PID controller, thereby achieving the purpose of generating a highly stable, uniform and controllable alternating electromagnetic field.

[0032] Figure 3 The diagram shown illustrates the working principle of the control and measurement section of an electromagnetic flowmeter according to an exemplary embodiment of this application. Please refer to... Figure 3 The non-contact downhole high-temperature electromagnetic flowmeter provided in this embodiment of the invention further includes: an analog signal conditioning circuit 31, a resonant excitation circuit 32, a synchronous digital circuit for flow and excitation current 26, an encoding conversion and coupling circuit 28, a signal power supply circuit 29, and a cable interface 30.

[0033] The analog signal conditioning circuit 31 of the downhole instrument control and measurement section 5 includes an interface circuit 17, a differential filter amplifier circuit 18, a DC blocking circuit 19, a programmable amplifier circuit 20, a first active rectifier filter circuit 21, and a second active rectifier filter circuit 211. The voltage signal received by the sensor is amplified and / or filtered by the analog signal conditioning circuit 31 in sequence, and converted into an acquireable analog flow signal.

[0034] Specifically, shielding electrodes 7A and 7B and signal electrodes 8A and 8B are all connected to interface circuit 17. Interface circuit 17 is connected to differential filter amplifier circuit 18. Differential filter amplifier circuit 18 is connected to DC blocking circuit 19 and second active rectifier filter circuit 211. DC blocking circuit 19 is connected to programmable amplifier circuit 20. Programmable amplifier circuit 20 is connected to first active rectifier filter circuit 21. First active rectifier filter circuit 21 is connected to DSP core circuit 27. Interface circuit 17 is used to realize the initial transmission and matching of voltage signal. Differential filter amplifier circuit 18 is used for differential amplification and filtering out interference noise. DC blocking circuit 19 is used to isolate AC signal and DC signal. Programmable amplifier circuit 20 is used to amplify the voltage signal, and the amplification factor can be adjusted. First active rectifier filter circuit 21 and second active rectifier filter circuit 211 are used to rectify and filter voltage signal to output analog flow signal.

[0035] Specifically, the downhole instrument control measurement section 5 uses a synchronous digital circuit 26 to digitize both the analog flow signal and the current signals of the excitation coils 9A and 9B. The change in the excitation current reflects the change in the magnetic field, while the change in the flow signal reflects the real-time flow velocity. By combining these two digital quantities, the downhole measurement component 3 can be compensated and corrected.

[0036] Specifically, the digital signal processing device (DSP) core circuit 27 of the downhole instrument control and measurement section 5 has the following main functions: generating a fundamental frequency sine wave to control the excitation circuit signal, generating a multiplexer control signal, acquiring real-time flow signals, acquiring ADC signals after real-time acquisition of flow and excitation current signals, signal filtering and signal processing, and digital encoding of output data.

[0037] Specifically, the encoding conversion and coupling circuit 28 mainly converts the encoded signal into a preset level signal and transmits it to the ground through the cable interface 30; the signal power supply circuit 29 provides the various levels required for the operation of the analog signal conditioning circuit 31, the DSP core circuit 27 and the flow and excitation current synchronous digitization circuit 26.

[0038] The working principle of the control and measurement sub provided in this invention is to synchronously digitize and collect flow signals and excitation current signals that reflect the magnetic field state. The DSP core circuit performs real-time correlation processing, which solves the problem of magnetic field and flow velocity signal mismatch in high-temperature and noisy downhole environments and improves the response speed and anti-interference of resonant excitation closed-loop control.

[0039] Figure 4 The diagram shown is a schematic flowchart of a resonant excitation closed-loop control method provided in an exemplary embodiment of this application. Please refer to [link / reference]. Figure 4 The resonant excitation closed-loop control method provided in this embodiment of the invention includes:

[0040] In step S100, the resonant excitation circuit generates a control signal to drive the excitation coil to generate an alternating magnetic field.

[0041] Step S200: Monitor the current phase error of the excitation current in the resonant excitation circuit.

[0042] Step S300: Dynamically adjust the circuit based on the current phase error to bring it into a resonant state.

[0043] Specifically, the current phase error is monitored by the excitation current sampling circuit 22. If the current phase error is less than or equal to 5°, it is determined to be a resonance.

[0044] Step S400: Receive the induced voltage signal collected by the signal electrode.

[0045] In step S500, the collected induced voltage signal is transmitted to the control and measurement sub-section. After signal processing by the control and measurement sub-section, it is transmitted to the ground processing unit to calculate the electromagnetic flow.

[0046] Specifically, if the current phase error is greater than 5°, the output SPWM signal is adjusted by the PID controller set in the SPWM control circuit 23 until resonance is achieved; wherein, the PID parameters in the PID controller are Kp = 0.8, Ki = 0.05, and Kd = 0.01.

[0047] In practical applications, the zero-point stability process includes: performing dynamic temperature compensation and high-frequency noise suppression in high-temperature, high-frequency noise scenarios (temperature > 85°C, noise frequency > 100Hz); synchronously triggering the ADC start signal inside the DSP core circuit 27 with the rising edge of the SPWM carrier of the SPWM control circuit 23; and acquiring 256 cycles of flow signal: e(t) = B × d × v(t) and excitation current: i B (t)=I m sin(2πft+Φ); where v(t) is the real-time fluid velocity (m / s); I mΦ is the current amplitude; f is the excitation frequency; Φ is the phase angle; calculate the flow signal e(t) and the excitation current i. B The correlation coefficient ρ of (t) eliminates phase error; where... τ is the time delay parameter (s); T is the signal period; adjust the SPWM phase to maximize ρ(τ). max The tendency towards e corr (t)=e(t+τ max Output corrected potential e corr .

[0048] Furthermore, dynamic temperature compensation includes: calculating the coil resistance R. x Resistance value: R x (T)=R x0 [1+α(T-25)]; where R x0 The initial coil resistance R x The resistance value; α is the copper winding, and in this embodiment of the invention, α = 0.0039 / ℃ is assumed; coil resistance R x Voltage compensation value: V comp =V set ×[1+α(T-25)]; where V set The voltage is set at room temperature (25℃); zero flow calibration is performed every 30 minutes: the resonant excitation circuit 32 is turned off for 10 seconds, baseline noise is collected, and the voltage compensation value is stored in the DSP core circuit 27; the final flow signal is output: e final =e raw -e offset ; where e raw It is the original flow signal; e offset It is the flow signal after the excitation is turned off.

[0049] Furthermore, high-frequency noise suppression includes: calculating the center frequency of the slurry. Where K is the slurry stiffness; m is the slurry mass; the center frequency f0 of the slurry is detected, and if f0∈[100,1000Hz], the notch filter frequency of the DSP core circuit 27 is set to f0.

[0050] The resonant excitation closed-loop control method provided in this invention uses a phase compensation algorithm based on the correlation coefficient ρ(τ) to perform resonant excitation closed-loop control. It also assists with dynamic temperature compensation and high-frequency noise suppression to reduce phase error, overcoming the problem of large zero-point drift in traditional high-frequency excitation technology and improving the measurement accuracy of electromagnetic flowmeters.

[0051] Figure 5 The diagram shown is an equivalent schematic of resonant excitation provided in an exemplary embodiment of this application. Please refer to... Figure 5The non-contact downhole high-temperature electromagnetic flowmeter provided in this embodiment of the invention includes: selecting a resonant capacitor connected in series in the resonant excitation circuit 32, so that the resonant excitation circuit 32 reaches a resonant state at a specific excitation frequency, thereby reducing the loop impedance of the excitation coils 9A and 9B. Assume that the excitation coils 9A and 9B of the non-contact electromagnetic flow sensor section 4 can be equivalent to the coil resistance R. x and inductor L x In a series configuration, the excitation current angular frequency is ω1, and the resonant capacitor connected in series in the resonant excitation circuit 32 is C. x Its impedance expression is:

[0052]

[0053] Compensation capacitor C x for:

[0054]

[0055] For example, after compensating for the resonant capacitor, the impedance of the resonant excitation circuit 32 reaches its minimum at the excitation frequency ω1, at which point Z min =R x Taking a DN40 instrument as an example, when the excitation frequency f1 = 75Hz, if C is connected in series in the resonant excitation circuit 32... x A 20μF capacitor has an impedance amplitude of 75Ω; compared with an uncompensated capacitor, its impedance amplitude is reduced by 55Ω. Therefore, to generate an excitation current of 200mA, the excitation voltage amplitude required for resonant excitation is reduced by 11V compared to the uncompensated capacitor, significantly reducing the excitation voltage.

[0056] When the measured liquid flows through the alternating magnetic field region, its flow velocity is v. According to Faraday's law of electromagnetic induction, when a moving conductor passes through a magnetic field, an induced electromotive force e will be generated on both sides of the conductor. The direction of the electromotive force conforms to the right-hand rule with respect to the direction of the magnetic field and the direction of the conductor's motion. The fluid between signal electrodes 8A and 8B can be considered as a moving conductor, with the conductor length being the inner diameter of signal electrodes 8A and 8B, denoted as d. Due to the high dielectric constant of the measuring tube, a capacitance effect is formed at both ends of the conductor with the signal electrodes 8A and 8B, respectively. These can be considered as the two plates of a capacitor. According to the knowledge of capacitance, the charge between the two plates of a capacitor is the same, that is, the electromotive force is the same. At this time, the electromotive force voltage signal e is directly proportional to the flow velocity v of the measured fluid 12, that is:

[0057] e = Bdv;

[0058] Please see Figure 3 and Figure 5This electromotive force is the voltage signal output by the non-contact electromagnetic flow sensor section 4. This signal passes sequentially through the interface circuit 17 of the analog conditioning circuit 31, the differential filter amplifier circuit 18, the DC blocking circuit 19, the programmable amplifier circuit 20, and the first active rectifier filter circuit 21. The signal is then amplified to an acquireable level and sent to the analog signal acquisition port of the DSP core circuit 27 for acquisition. At the same time, the excitation current signal and the flow signal are input to the flow and excitation current synchronous digitization circuit 26, where they are quantized into digitally acquireable 0 or 1 levels and input to the digital signal acquisition port of the DSP core circuit 27 for acquisition.

[0059] Furthermore, after the acquired signal is filtered, calculated, and compensated in the DSP core circuit 27 program, it is output from the output port of the DSP core circuit 27 to the encoding conversion and coupling circuit 28 according to the encoding requirements. The encoded signal is coupled to the DC circuit and transmitted to the ground processing unit 1 through the data cable 2. The ground processing unit 1 decodes the encoded signal, records, saves and displays it, and at the same time compares the count data with the scale data to convert it into an instantaneous flow rate value. The flow rate is combined with time to calculate the instantaneous flow rate, and then the cumulative flow rate over a period of time can be calculated.

[0060] The electromagnetic flowmeter provided in this invention reduces the circuit impedance by connecting a capacitor in series in the excitation circuit, thus solving the heat generation problem caused by high circuit impedance. As a result, the impedance of the DN40 instrument is reduced by 55Ω, the excitation voltage is reduced by 11V, and the power consumption is reduced by 40% when it is excited at 75Hz.

[0061] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A non-contact downhole high temperature electromagnetic flowmeter characterized by, Comprise: Surface processing unit (1); Downhole measurement assembly (3) connected through data cable (2), the downhole measurement assembly (3) includes control measurement short section (5) and non-contact electromagnetic flow sensor short section (4); The control measurement short section (5) includes a resonant excitation magnetic circuit (32); The non-contact electromagnetic flow sensor short section (4) includes excitation coil (9A, 9B) shielding electrode (7A, 7B) and signal electrode (8A, 8B), the excitation coil (9A, 9B) is connected with the resonant excitation magnetic circuit (32);Shielding electrode (7A, 7B) and signal electrode (8A, 8B) are connected with the control measurement short section (5); The shielding electrode (7A, 7B) covers the signal electrode (8A, 8B) for enhancing the noise immunity of the signal electrode (8A, 8B);The signal electrode (8A, 8B) transmits the collected induced voltage signal to the control measurement short section (5), and after signal processing by the control measurement short section (5), the electromagnetic flow is transmitted to the surface processing unit (1) for calculation;Wherein, the resonant excitation magnetic circuit (32) is used to generate a control signal to drive the excitation coil (9A, 9B) to generate an alternating magnetic field, and monitor the current phase error of the excitation coil (9A, 9B), and dynamically adjust according to the current phase error, so that the circuit is in resonance state; The resonant excitation magnetic circuit (32) further comprises excitation current sampling circuit (22) and SPWM control circuit (23), the excitation current sampling circuit (22) is connected with the SPWM control circuit (23);The SPWM control circuit (23) is connected with the excitation coil (9A, 9B); The excitation current sampling circuit (22) monitors the current phase error of the excitation coil (9A, 9B), if the current phase error is less than or equal to 5°, it is determined that the resonance state is reached;If the current phase error is greater than 5°, the SPWM signal output by the SPWM control circuit (23) is adjusted to reduce the phase error until the resonance state is reached;If the current phase error is greater than 5° and the temperature is greater than 85°, and / or the current phase error is greater than 5° and the noise frequency is greater than 100Hz, then reduce the phase error by executing dynamic temperature compensation and / or high frequency noise suppression until the resonance state is reached.

2. A non-contact downhole high temperature electromagnetic flowmeter according to claim 1, wherein, The resonant excitation magnetic circuit (32) further comprises full-bridge drive circuit (24), the full-bridge drive circuit (24) is connected with the SPWM control circuit (23) and the excitation coil (9A, 9B) respectively;The SPWM control circuit (23) generates SPWM signal to drive the full-bridge drive circuit (24), and the full-bridge drive circuit (24) is used to drive the excitation coil (9A, 9B) to generate alternating magnetic field, and then generate current.

3. A non-contact downhole high temperature electromagnetic flowmeter according to claim 2, wherein, The control measurement short section (5) further comprises DSP core circuit (27), the DSP core circuit (27) is connected with the SPWM control circuit (23); The DSP core circuit (27) generates a sine wave driving signal and controls the full-bridge driving circuit (24) through the SPWM control circuit (23).

4. A non-contact downhole high temperature electromagnetic flowmeter according to claim 3, wherein, The control and measurement short section (5) further comprises an analog signal conditioning circuit (31) and a code conversion and coupling circuit (28); the analog signal conditioning circuit (31) is connected to the DSP core circuit (27) and the signal electrode (8A, 8B) respectively, and the DSP core circuit (27) is connected to the code conversion and coupling circuit (28); The signal electrode (8A, 8B) is used to transmit the voltage signal of the non-contact electromagnetic flow sensor short section (4) to the analog signal conditioning circuit (31), the analog signal conditioning circuit (31) receives the voltage signal of the signal electrode (8A, 8B) and converts the voltage signal into an analog flow signal, and the analog flow signal is transmitted to the ground processing unit (1) for flow calculation after signal processing by the DSP core circuit (27) and the code conversion and coupling circuit (28).

5. A non-contact downhole high temperature electromagnetic flowmeter according to claim 4, wherein, The control and measurement short section (5) further comprises a flow and excitation current synchronous digitizing circuit (26) and a signal power supply circuit (29); the flow and excitation current synchronous digitizing circuit (26) is connected to the DSP core circuit (27), and is used to digitize the analog flow signal and the current signal of the excitation coil (9A, 9B); the signal power supply circuit (29) is connected to the flow and excitation current synchronous digitizing circuit (26), the DSP core circuit (27) and the analog signal conditioning circuit (31) respectively, and is used to provide various levels required by the flow and excitation current synchronous digitizing circuit (26), the DSP core circuit (27) and the analog signal conditioning circuit (31).

6. A non-contact downhole high temperature electromagnetic flowmeter according to claim 5, wherein, The resonant excitation circuit (32) further comprises an excitation power supply circuit (25), a switch tube (35) and a low-pass filter circuit (36); the excitation power supply circuit (25) is connected to the full-bridge driving circuit (24), and is used to provide a high-voltage power supply and a driving working level for the full-bridge driving circuit (24); the switch tube (35) is connected to the full-bridge driving circuit (24) and the low-pass filter circuit (36) respectively, and is used to control the current on-off of the full-bridge driving circuit (24) and the low-pass filter circuit (36); the low-pass filter circuit (36) is connected to the switch tube (35) and the excitation coil (9A, 9B) respectively, and is used to output a fundamental wave to excite the excitation coil (9A, 9B) after filtering high-frequency signal components; The analog signal conditioning circuit (31) further comprises an interface circuit (17), a differential filter amplification circuit (18), a direct current isolation circuit (19), a program-controlled amplification circuit (20), a first active rectification filter circuit (21) and a second active rectification filter circuit (211). The shield electrode (7A, 7B) and the signal electrode (8A, 8B) are connected to the interface circuit (17), the interface circuit (17) is connected to the differential filter amplification circuit (18), the differential filter amplification circuit (18) is connected to the direct current isolation circuit (19) and the second active rectification filter circuit (211) respectively, the direct current isolation circuit (19) is connected to the program-controlled amplification circuit (20), the program-controlled amplification circuit (20) is connected to the first active rectification filter circuit (21), and the first active rectification filter circuit (21) is connected to the DSP core circuit (27); the interface circuit (17) is used for realizing preliminary transmission and matching of the voltage signal; the differential filter amplification circuit (18) is used for differential amplification and filtering of interference noise; the direct current isolation circuit (19) is used for isolating alternating current signals and direct current signals; the program-controlled amplification circuit (20) is used for amplifying the voltage signal, and the amplification multiple can be adjusted; and the first active rectification filter circuit (21) and the second active rectification filter circuit (211) are used for rectifying and filtering the voltage signal, and output the analog flow signal.

7. A resonant field magnetic closed loop control method, characterized by, The application is applied to a non-contact downhole high-temperature electromagnetic flowmeter, the flowmeter comprises a ground processing unit (1) and a downhole measurement assembly (3), the ground processing unit (1) is connected to the downhole measurement assembly (3) through a data cable (2), the downhole measurement assembly (3) comprises a control measurement short section (5) and a non-contact electromagnetic flow sensor short section (4), the control measurement short section (5) comprises a resonant excitation magnetic circuit (32), the non-contact electromagnetic flow sensor short section (4) comprises excitation coils (9A, 9B), shield electrodes (7A, 7B) and signal electrodes (8A, 8B), and the excitation coils (9A, 9B) are connected to the resonant excitation magnetic circuit (32); the shield electrodes (7A, 7B) and the signal electrodes (8A, 8B) are connected to the control measurement short section (5); and the method comprises: The resonant excitation magnetic circuit (32) generates a control signal to drive the excitation coils (9A, 9B) to generate an alternating magnetic field; A current phase error of an excitation current of the resonant excitation magnetic circuit (32) is monitored; If the current phase error is less than or equal to 5°, it is determined that the resonant state is reached; If the current phase error is greater than 5°, the phase error is reduced by adjusting the output control signal until the resonant state is reached; the control signal is an SPWM signal; If the current phase error is greater than 5° and the temperature is greater than 85°, and / or the current phase error is greater than 5° and the noise frequency is greater than 100 Hz, the phase error is reduced by performing dynamic temperature compensation and / or high-frequency noise suppression until the resonant state is reached; An induced voltage signal collected by the signal electrodes (8A, 8B) is received; The collected induced voltage signal is transmitted to the control measurement short section (5), and after signal processing by the control measurement short section (5), the signal is transmitted to the ground processing unit (1) to calculate the electromagnetic flow.

8. The method of claim 7, wherein the method further comprises: The reducing phase error until reaching a resonance state comprises: The ADC start signal is triggered synchronously with the rising edge of the SPWM carrier; Collecting flow signals and excitation currents of several cycles; Calculating a correlation coefficient function of the flow signals and the excitation currents; Adjusting the SPWM phase according to the correlation coefficient function to obtain an independent variable when the correlation coefficient function takes a maximum value, a potential value corresponding to the independent variable tends to a corrected potential value, and the independent variable is a time delay parameter; Outputting the corrected potential value; Calculating a resistance value of a coil resistance, the coil resistance being an equivalent resistance of the excitation coil; Calculating a voltage compensation value of the coil resistance; Performing a zero-flow calibration operation: turning off the resonant excitation circuit for 10 seconds, collecting baseline noise, and storing the voltage compensation value; Calculating a slurry center frequency; Detecting the slurry center frequency, and if the slurry center frequency is within the interval [100, 1000Hz], setting a notch frequency value equal to the slurry center frequency value.

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