A dual-frequency microwave sensor, an oil-water two-phase water content measurement device and method

Abstract

This invention proposes a dual-frequency microwave sensor, an oil-water two-phase water cut measurement device and method, relating to the field of petroleum testing technology. The dual-frequency microwave sensor includes a sensor pipe, a shielding layer, and various detection probes. The sensor pipe is cylindrical, with flange interfaces at both ends for connection to oil well pipe flanges. The detection probes include a high-frequency excitation probe, a high-frequency measurement probe, a low-frequency excitation probe, and a low-frequency measurement probe. The high-frequency excitation probe and the high-frequency measurement probe penetrate radially along the sensor pipe in a double parallel line structure, symmetrical about the sensor pipe axis, and are located at the upper part of the sensor pipe. The low-frequency excitation probe and the low-frequency measurement probe also penetrate radially along the sensor pipe in a double parallel line structure, symmetrical about the sensor pipe axis, and are located at the lower part of the sensor pipe. This application helps improve the completeness and accuracy of water cut detection.

Description

Technical Field

[0001] This invention relates to the field of petroleum detection technology, and in particular to a dual-frequency microwave sensor, an oil-water two-phase water content measurement device and method. Background Technology

[0002] Oil water cut refers to the ratio of the volume of associated water in oil to the total volume of the oil-water mixture, and is one of the important parameters for oil extraction, processing, and research. With the long-term water injection extraction of crude oil from oil wells in my country, the need for high water cut measurement has become commonplace. High-resolution measurement of oil water cut under high water cut conditions is of great significance for extending oil well life, subsequent chemical processing, and crude oil storage, transportation, and sales.

[0003] Chinese Patent CN107288627B discloses a method for measuring high water content in oil-water two-phase flow using a dual parallel-line microwave resonant cavity sensor. This method measures the stratified interface morphology of two-phase flows with conductivity differences. The parallel-line array sensor comprises two sets of parallel-line electrodes: one set distributed on the same cross-section of the upstream pipe, serving as excitation electrodes; and the other set distributed on the same cross-section of the downstream pipe, serving as receiving electrodes. The excitation and receiving electrodes, positioned opposite each other, form a pair of line electrodes. Each electrode is fixed to a fixture and passes through a horizontal measuring pipe. The measurement method includes: determining the geometric dimensions of the parallel-line array sensor without disrupting the oil-water stratification interface morphology; sequentially measuring each pair of line electrodes to acquire a frame of measurement data; and calibrating the measurement response of the parallel-line array sensor using the stratified gas-water two-phase distribution within the stationary horizontal measuring pipe. However, the calibration process relies on the stratified two-phase flow distribution under static conditions, and the calibration results are difficult to reflect the true electromagnetic response characteristics of the oil-water mixture under flow conditions, thus easily leading to systematic errors in actual online measurements. Therefore, it is essential to provide a dual-frequency microwave sensor, an oil-water two-phase water content measurement device and method to improve the integrity and accuracy of water content detection. Summary of the Invention

[0004] In view of this, the present invention proposes a dual-frequency microwave sensor, an oil-water two-phase water content measurement device and method.

[0005] This invention provides a dual-frequency microwave sensor, which includes a sensor tube, a shielding layer, and various detection probes, wherein...

[0006] The sensor pipe is cylindrical, and flange interfaces for connecting to oil well pipe flanges are provided at opposite ends of the sensor pipe so that the oil-water mixture flows through the dual-frequency microwave sensor. The shielding layer is coaxially arranged with the sensor pipe and covers the outside of the sensor pipe.

[0007] The detection probe includes a high-frequency excitation probe, a high-frequency measurement probe, a low-frequency excitation probe, and a low-frequency measurement probe. The high-frequency excitation probe and the high-frequency measurement probe penetrate radially along the sensor pipe in a double parallel line structure, and the high-frequency excitation probe and the high-frequency measurement probe are symmetrically arranged about the axis of the sensor pipe at the upper part of the sensor pipe.

[0008] The low-frequency excitation probe and the low-frequency measurement probe are arranged radially along the sensor pipe in a double parallel line structure, and the low-frequency excitation probe and the low-frequency measurement probe are symmetrically arranged about the axis of the sensor pipe at the lower part of the sensor pipe.

[0009] Based on the above technical solutions, preferably, multiple sets of polyetheretherketone spiral ribs are arranged along the axial direction of the sensor pipe. The polyetheretherketone spiral ribs are used to break up the oil-water emulsion layer and promote the uniform distribution of the mixture. The inner wall of the sensor pipe is coated with a Teflon coating.

[0010] Based on the above technical solutions, preferably, the high-frequency excitation probe, the high-frequency measurement probe, the low-frequency excitation probe, and the low-frequency measurement probe all adopt a monopole probe structure, and each excitation probe includes a coaxial radio frequency cable, an insulating layer, and a radiating arm, wherein...

[0011] One end of the radiating arm is electrically connected to the center conductor of the coaxial radio frequency cable, and the other end of the radiating arm extends radially into the interior of the sensor pipe along the sensor pipe.

[0012] The radiating arm is located between any two adjacent polyetheretherketone spiral ribs, and the axis of the radiating arm is coaxial with the axis of the coaxial radio frequency cable.

[0013] The insulating layer covers the outside of the coaxial radio frequency cable and the radiating arm, and the insulating layer penetrates the sensor pipe and the shielding layer radially along the sensor pipe.

[0014] More preferably, the periphery of the radiating arm of the detection probe extending into the sensor tube is coated with a polytetrafluoroethylene-ceramic composite coating.

[0015] More preferably, the high-frequency excitation probe and the low-frequency excitation probe are located on the same side of the sensor pipe, and the high-frequency excitation probe and the low-frequency excitation probe are arranged in parallel. The high-frequency measurement probe and the low-frequency measurement probe are located on the same side of the sensor pipe, and the high-frequency measurement probe and the low-frequency measurement probe are arranged in parallel.

[0016] A second aspect of this application provides an oil-water two-phase water content measuring device, which includes a microwave generator, a microwave receiver, a signal processing device, and the aforementioned dual-frequency microwave sensor, wherein...

[0017] The microwave generator is connected to the dual-frequency microwave sensor and the signal processing device respectively, and the microwave generator is used to generate dual-frequency microwave signals.

[0018] The dual-frequency microwave sensor is connected to the microwave receiving device, and the dual-frequency microwave sensor performs microwave transmission measurement on the oil-water mixture flowing through the dual-frequency microwave sensor through the dual-frequency microwave signal.

[0019] The microwave receiving device is connected to the signal processing device. The microwave receiving device is used to detect and rectify the detection microwave signal output from the dual-frequency microwave sensor, and to acquire a DC voltage signal corresponding to the microwave amplitude attenuation in the detection microwave signal.

[0020] The signal processing device is used to sample the DC voltage signal and switch the detection mode corresponding to the dual-frequency microwave sensor according to the DC voltage signal to calculate the water content of the oil-water mixture.

[0021] A third aspect of this application provides a method for measuring the water content of an oil-water two-phase system, implemented using the aforementioned oil-water two-phase water content measuring device, the method comprising:

[0022] Oil-water mixtures with different water contents are introduced into a dual-frequency microwave sensor, allowing the oil-water mixtures to flow through the sensor's pipes.

[0023] High-frequency microwave signals and low-frequency microwave signals are generated in a microwave generator, and the dual-frequency microwave signals are radiated into the sensor pipe through the high-frequency excitation probe and the low-frequency excitation probe respectively set in the dual-frequency microwave sensor, so that the dual-frequency microwave signals are transmitted through the oil-water mixture.

[0024] The high-frequency measurement probe and the low-frequency measurement probe of the dual-frequency microwave sensor respectively receive the measurement microwave signals transmitted at the corresponding frequencies, and send the measurement microwave signals to the microwave receiving device.

[0025] The measured microwave signal is subjected to envelope detection and voltage doubler rectification in the microwave receiving device to obtain a DC voltage signal corresponding to the amplitude attenuation of the transmitted microwave, and the DC voltage signal is input to the signal processing device.

[0026] The signal processing device continuously samples the transmitted voltage corresponding to the DC voltage signal, compares the transmitted voltage with a pre-calibrated first threshold voltage and a second threshold voltage, switches the measurement mode of the dual-frequency microwave sensor, and calculates the water content of the oil-water mixture.

[0027] More preferably, the method further includes:

[0028] Water and crude oil are mixed in various volumes to prepare oil-water mixtures with different water contents, including 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%.

[0029] Oil-water mixtures with varying water contents are sequentially introduced into the dual-frequency microwave sensor. Multiple measurements are performed on each oil-water mixture using various detection probes. The average voltage and voltage attenuation of the DC voltage signal are calculated to obtain high-frequency calibration curves, low-frequency calibration curves, a first threshold voltage, and a second threshold voltage.

[0030] More preferably, the expressions for the high-frequency calibration curve and the low-frequency calibration curve are:

[0031]

[0032]

[0033] in, The high-frequency calibration curve function representing the high-frequency channel voltage attenuation with respect to moisture content. This represents the stable value at which the high-frequency calibration curve eventually stabilizes as the moisture content increases. This represents the total vertical span of the voltage attenuation change in the high-frequency calibration curve as the moisture content changes from 0% to 100%. This represents the sensitivity coefficient of the high-frequency calibration curve to changes in moisture content near the inflection point. This represents the water content variable under high-frequency mode. This indicates the moisture content at the inflection point of the high-frequency calibration curve. The low-frequency calibration curve function represents the low-frequency channel voltage attenuation with respect to moisture content. This represents the stable value at which the low-frequency calibration curve eventually stabilizes as the moisture content increases. This represents the sensitivity coefficient of the low-frequency calibration curve to changes in moisture content near the inflection point. This represents the water content variable under low-frequency mode. This indicates the moisture content at the inflection point of the low-frequency calibration curve.

[0034] More preferably, comparing the transmitted voltage with a pre-calibrated first threshold voltage and a second threshold voltage to switch the measurement mode of the dual-frequency microwave sensor specifically includes:

[0035] If the transmitted voltage is greater than the first threshold voltage, the dual-frequency microwave sensor is switched to a low water content measurement mode, and the water content of the oil-water mixture is calculated based only on the high-frequency signal.

[0036] If the transmitted voltage is less than the second threshold voltage, the dual-frequency microwave sensor is switched to high water content measurement mode, and the water content of the oil-water mixture is calculated based only on the low-frequency signal.

[0037] If the transmission voltage is greater than or equal to the second threshold voltage and the transmission voltage is less than or equal to the first threshold voltage, the dual-frequency microwave sensor is switched to the medium water content measurement mode, and the water content of the oil-water mixture is calculated by weighting based on the high-frequency signal and the low-frequency signal.

[0038] The dual-frequency microwave sensor, oil-water two-phase water content measurement device and method provided by this invention have the following advantages over the prior art:

[0039] (1) By setting the shielding layer coaxially with the sensor pipe and covering the outside, external electromagnetic interference can be effectively isolated, electromagnetic leakage can be suppressed, and the electromagnetic field distribution inside the sensor can be stabilized, thereby improving the signal-to-noise ratio and repeatability of the measurement signal. Furthermore, two sets of excitation probes and measurement probes, one high-frequency and one low-frequency, are set up so that the sensor can detect oil-water mixtures at different frequency bands. The high-frequency signal is more sensitive to changes in dielectric constant and is suitable for characterizing the proportion of oil-water components and changes in fine structure. The low-frequency signal has strong penetration ability and is less affected by flow fluctuations, which is beneficial for obtaining overall water content information. The dual-frequency joint measurement improves the integrity and accuracy of water content detection. At the same time, the high-frequency probe and the low-frequency probe are both set with a double parallel line structure and are symmetrical about the axis of the sensor pipe, which helps to form a symmetrical and stable electromagnetic field distribution inside the pipe and reduce the measurement error caused by flow pattern bias or uneven local phase distribution.

[0040] (2) By performing envelope detection and voltage doubler rectification on the transmitted microwave signal, the high-frequency microwave signal is converted into a stable DC voltage signal, reducing the impact of noise and transient fluctuations on the measurement results. Furthermore, the signal processing device continuously samples the transmitted voltage and compares it with the pre-calibrated first and second threshold voltages. It can automatically switch the measurement mode of the dual-frequency microwave sensor according to the actual water content of the oil-water mixture, avoiding the problem of insufficient sensitivity of a single frequency in a specific water content range, and improving the measurement accuracy and stability in different water content ranges. At the same time, by combining the real-time acquired transmitted voltage signal with the pre-calibrated data model to calculate the water content, it can effectively reduce the impact of flow fluctuations, flow pattern changes and other factors on the measurement results, and improve the repeatability and consistency of the measurement results. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the structure of the dual-frequency microwave sensor provided by the present invention;

[0043] Figure 2 This is a cross-sectional schematic diagram of the dual-frequency microwave sensor provided by the present invention;

[0044] Figure 3 A schematic diagram of the frame of the oil-water two-phase water content measuring device provided by the present invention.

[0045] Explanation of reference numerals in the attached drawings: 1. Dual-frequency microwave sensor; 11. Sensor conduit; 12. Shielding layer; 13. Detection probe; 131. Coaxial radio frequency cable; 132. Radiation arm; 133. Insulation layer; 14. Flange interface; 15. Polyetheretherketone spiral rib; 2. Microwave generator; 3. Microwave receiver; 4. Signal processing device. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] refer to Figure 1This invention provides a dual-frequency microwave sensor 1, comprising a sensor channel 11, a shielding layer 12, and various detection probes 13, wherein...

[0048] The sensor pipe 11 is cylindrical, and flange interfaces 14 connected to oil well pipe flanges are provided at opposite ends of the sensor pipe 11 so that the oil-water mixture flows through the dual-frequency microwave sensor 1. The shielding layer 12 is coaxially arranged with the sensor pipe 11 and covers the outside of the sensor pipe 11.

[0049] Multiple sets of polyetheretherketone spiral ribs 15 are arranged along the axial direction of the sensor pipe 11. The polyetheretherketone spiral ribs 15 are used to break the oil-water emulsion layer and promote the uniform distribution of the mixture. The inner wall of the sensor pipe 11 is coated with Teflon coating.

[0050] The detection probe 13 includes a high-frequency excitation probe, a high-frequency measurement probe, a low-frequency excitation probe, and a low-frequency measurement probe. The high-frequency excitation probe and the high-frequency measurement probe are arranged radially along the sensor pipe 11 in a double parallel line structure, and the high-frequency excitation probe and the high-frequency measurement probe are symmetrically arranged about the axis of the sensor pipe 11 at the upper part of the sensor pipe 11.

[0051] The low-frequency excitation probe and the low-frequency measurement probe are arranged radially along the sensor pipe 11 in a double parallel line structure, and the low-frequency excitation probe and the low-frequency measurement probe are symmetrically arranged about the axis of the sensor pipe 11 at the lower part of the sensor pipe 11.

[0052] The high-frequency excitation probe and the low-frequency excitation probe are located on the same side of the sensor pipe 11, and the high-frequency excitation probe and the low-frequency excitation probe are arranged in parallel. The high-frequency measurement probe and the low-frequency measurement probe are located on the same side of the sensor pipe 11, and the high-frequency measurement probe and the low-frequency measurement probe are arranged in parallel. The radiating arm 132 of the detection probe 13, which extends into the sensor pipe 11, is coated with a polytetrafluoroethylene-ceramic composite coating on all sides.

[0053] In this embodiment, the high-frequency excitation probe and the low-frequency excitation probe are positioned on the same side of the sensor pipe 11 and parallel to each other. Similarly, the high-frequency measurement probe and the low-frequency measurement probe are positioned on the same side and parallel to each other. This ensures that the high-frequency and low-frequency microwaves have similar incident directions and propagation paths within the sensor pipe 11, thereby guaranteeing that the spatial regions affected by microwaves of different frequencies in the oil-water mixture are essentially consistent. This improves the comparability between high-frequency and low-frequency measurement results and reduces system errors caused by differences in probe spatial distribution. The parallel arrangement of the excitation and measurement probes facilitates control of the electromagnetic field direction and field distribution, reduces unwanted coupling and crosstalk between the high- and low-frequency probes, thereby improving the effective radiation efficiency of the excitation signal into the pipe, enhancing the stability and repeatability of the received signal, and improving the measurement reliability under conditions of simultaneous operation of dual-frequency microwaves.

[0054] The probes are concentrated on the same side of the pipeline, which helps to form a relatively stable and predictable non-uniform electromagnetic field distribution. Combined with a dual-frequency measurement mechanism, the dielectric properties of the oil-water mixture can be complementaryly sensed at different frequency bands, thereby reducing the impact of complex flow patterns such as oil-water stratification and agglomeration on the water cut measurement results. The radiating arm 132 of the detection probe 13, which extends into the sensor pipeline 11, is coated with a polytetrafluoroethylene-ceramic composite coating. This effectively isolates the metal probe from corrosive media in the oil-water mixture, improving its corrosion resistance in high-water-content, high-salinity oil well environments. Furthermore, the polytetrafluoroethylene-ceramic composite coating has a low dielectric constant, low dielectric loss, and good dielectric stability. Without significantly weakening the microwave radiation capability, it reduces the dielectric loading effect on the probe surface, stabilizes the equivalent electrical length and impedance characteristics of the probe, and improves the consistency between microwave transmission and received signals, thereby enhancing the accuracy of water cut calculation.

[0055] Furthermore, the high-frequency excitation probe, high-frequency measurement probe, low-frequency excitation probe, and low-frequency measurement probe all adopt a monopole probe structure, and each excitation probe includes a coaxial RF cable 131, an insulating layer 133, and a radiating arm 132, wherein...

[0056] One end of the radiating arm 132 is electrically connected to the center conductor of the coaxial radio frequency cable 131, and the other end of the radiating arm 132 extends radially into the interior of the sensor pipe 11 along the sensor pipe 11.

[0057] The radiating arm 132 is located between any two adjacent polyetheretherketone spiral ribs 15, and the axis of the radiating arm 132 is coaxial with the axis of the coaxial radio frequency cable 131.

[0058] The insulating layer 133 covers the outside of the coaxial radio frequency cable 131 and the radiating arm 132, and the insulating layer 133 penetrates the sensor pipe 11 and the shielding layer 12 radially along the sensor pipe 11.

[0059] In this embodiment, the high-frequency excitation probe, high-frequency measurement probe, low-frequency excitation probe, and low-frequency measurement probe all adopt a monopole probe structure, which can form a stable radial electromagnetic radiation field inside the sensor pipe 11, thereby improving the coupling efficiency of microwave energy into the oil-water mixture, enhancing the intensity of transmitted microwave signals, and improving the effectiveness of received signals. One end of the radiation arm 132 is directly electrically connected to the center conductor of the coaxial radio frequency cable 131, and the axis of the radiation arm 132 and the coaxial radio frequency cable 131 are kept coaxial, which helps to maintain the electrical continuity and symmetry of the probe structure, reduce signal reflection and transmission loss, improve the impedance matching characteristics between the probe and the microwave transmission line, and improve the accuracy and repeatability of microwave signal amplitude measurement.

[0060] The radiating arm 132 is positioned between any two adjacent polyetheretherketone (PEEK) spiral ribs 15. The ribs limit and protect the radiating arm 132, effectively preventing it from shifting or vibrating under high-speed flow of oil-water mixture. The PEEK spiral ribs 15 have excellent mechanical strength, wear resistance, and corrosion resistance. Positioning the radiating arm 132 between them reduces fluid erosion and direct impact from solid particles. The insulating layer 133 covers the coaxial RF cable 131 and the outer side of the radiating arm 132, and radially penetrates the sensor pipe 11 and the shielding layer 12. This provides reliable electrical isolation between the probe and the sensor pipe 11 and the shielding layer 12, preventing leakage and short circuits, improving the insulation safety of the probe in high humidity and high water content environments, enhancing the overall sealing performance of the sensor, and preventing oil-water mixture from seeping into the probe connection area.

[0061] In one example, the probe employs a monopole probe structure, consisting of a stainless steel radiating arm 132, a polyetheretherketone (PEEK) insulating support (insulating layer 133), and an RG-178 coaxial radio frequency cable 131. The probe surface is coated with a polytetrafluoroethylene-ceramic composite coating. Anti-oil waxing and scaling enhance the coating's wear resistance and prevent coating detachment caused by downhole crude oil erosion.

[0062] In one example, such as Figure 2 As shown, the shielding layer 12 is also a cylindrical tubular structure, wrapped around the outside of the sensor pipe 11, and coaxial with the sensor pipe 11. The shielding layer 12 is made of brass and grounded to shield against the influence of external interference signals. Ferrite absorbing material is attached to the inside of the shielding layer 12 to absorb stray radiation from the antenna itself and reduce interference to the sensor pipe 11. The high-frequency microwave excitation measurement probe is located above the sensor pipe 11, and the low-frequency microwave excitation measurement probe is located below the sensor pipe 11. Each pair of excitation and measurement probes has a double parallel line structure, perpendicular to the axis of the sensor pipe 11, passing through the sensor pipe 11, and symmetrical about the cross-sectional diameter of the sensor pipe 11. In addition, two sets of polyetheretherketone spiral ribs 15 are designed along the cavity axis to break up the oil-water emulsion layer, promote uniform distribution of the mixture, and avoid uneven dielectric constant distribution caused by oil bubble accumulation. The inner wall of the cavity is coated with Teflon to reduce the influence of the conduction current of the high-mineralization water on the microwave characteristics of the cavity and reduce energy loss.

[0063] In this embodiment, the shielding layer 12 is coaxially arranged with the sensor pipe 11 and covers the outside, which can effectively isolate external electromagnetic interference, suppress electromagnetic leakage, and stabilize the electromagnetic field distribution inside the sensor, thereby improving the signal-to-noise ratio and repeatability of the measurement signal. Furthermore, two sets of excitation probes and measurement probes, one high-frequency and one low-frequency, are set up so that the sensor can detect oil-water mixtures at different frequency bands. The high-frequency signal is more sensitive to changes in dielectric constant and is suitable for characterizing the proportion of oil and water components and changes in fine structure. The low-frequency signal has strong penetration ability and is less affected by flow fluctuations, which is beneficial for obtaining overall water content information. The dual-frequency joint measurement improves the integrity and accuracy of water content detection. At the same time, both the high-frequency probe and the low-frequency probe are arranged with a double parallel line structure and are symmetrical about the axis of the sensor pipe 11, which helps to form a symmetrical and stable electromagnetic field distribution inside the pipe and reduce measurement errors caused by flow pattern bias or uneven local phase distribution.

[0064] Based on the aforementioned dual-frequency microwave sensor 1, this application discloses an oil-water two-phase water content measuring device, with reference to... Figure 3 The oil-water two-phase water content measuring device includes a microwave generator 2, a microwave receiver 3, a signal processing device 4, and the aforementioned dual-frequency microwave sensor 1.

[0065] The microwave generator 2 is connected to the dual-frequency microwave sensor 1 and the signal processing device 4 respectively. The microwave generator 2 is used to generate dual-frequency microwave signals.

[0066] The dual-frequency microwave sensor 1 is connected to the microwave receiving device 3. The dual-frequency microwave sensor 1 performs microwave transmission measurement on the oil-water mixture flowing through the dual-frequency microwave sensor 1 through the dual-frequency microwave signal.

[0067] The microwave receiving device 3 is connected to the signal processing device 4. The microwave receiving device 3 is used to detect and rectify the detection microwave signal output from the dual-frequency microwave sensor 1, and to acquire the DC voltage signal corresponding to the microwave amplitude attenuation in the detection microwave signal.

[0068] The signal processing device 4 is used to sample the DC voltage signal and switch the detection mode corresponding to the dual-frequency microwave sensor 1 according to the DC voltage signal in order to calculate the water content of the oil-water mixture.

[0069] Furthermore, the microwave generator 2 is a dual-frequency signal generator, which outputs low-frequency (1.8 GHz) and high-frequency (2.5 GHz) microwave signals through an RF chip, and amplifies the signals emitted by the microwave signal source through a low-noise amplifier circuit. The amplifier is designed with an "L"-shaped adjustable matching circuit, which adjusts the adjustable capacitor and inductor in real time through the RF chip to match the output impedance of the signal source and reduce microwave signal reflection loss.

[0070] Microwave receiver 3 is an envelope detector circuit. It converts the signal from the probe into a DC signal through voltage doubler rectification and sends it to the signal processing module to improve signal sensitivity. The signal processing module uses an MCU as the core of the measurement device. The MCU continuously samples via an ADC and updates the transmitted voltage value. After each ADC acquisition, the MCU automatically switches the measurement mode state machine according to its internally designed voltage threshold and calculates the water content using voltage data from different antennas based on the current state machine. After each measurement, the MCU displays the current state, the voltage value obtained from the dual probes, and the obtained water content on an LCD screen and transmits the data to the host computer via serial communication.

[0071] In one example, microwave generator 2 generates and amplifies a microwave voltage signal, which is then connected to the excitation probe of dual-frequency microwave sensor 1 via an RF line. The high-frequency and low-frequency excitation probes receive the voltage signal from microwave generator 2 and emit high and low-frequency microwave signals, respectively. The microwave signal from the excitation probes is transmitted through crude oil from the well in sensor conduit 11, and the transmitted microwave signal is then transmitted to the high-frequency measurement probe and the low-frequency excitation probe. Microwave receiver 3 extracts the signal from the measurement probes, and then the signal processing device 4 samples it to obtain measurement data.

[0072] For further information, please refer to [link / reference]. Figure 1 and Figure 2 High-frequency excitation probes and high-frequency measurement probes are symmetrically distributed on both sides of the sensor pipe 11, as are low-frequency excitation probes and low-frequency measurement probes. The high-frequency excitation probes and high-frequency measurement probes are located on the upper side of the sensor pipe 11, while the low-frequency excitation probes and low-frequency measurement probes are located on the lower side of the sensor pipe 11. The high-frequency excitation probes and high-frequency measurement probes operate at a frequency of 2.5 GHz, while the low-frequency excitation probes and low-frequency measurement probes operate at a frequency of 1.8 GHz. All detection probes 13 employ a monopole antenna structure. Each probe consists of a radiating arm 132, an insulating support, and a feeding structure. The radiating arm 132 is the core working part of the antenna, made of a 316L stainless steel rod with a diameter of approximately 2 mm. Its length is optimized according to the operating frequency and is connected to a capacitor and inductor for impedance matching. The radiating arm 132 is fixed by a cylindrical polyetheretherketone (PEEK) insulator and electrically isolated from the metal wall of the sensor pipe 11. An RG-178 coaxial RF cable 131 passes through the wall of the sensor pipe 11 and the insulating support. The center conductor of the cable is firmly welded to the root of the radiating arm 132, while its outer shielding layer 12 forms good electrical contact with the inner wall of the sensor pipe 11 and is grounded together.

[0073] This feeding method allows the radiating arm 132 extending into the cavity to form a monopole antenna radiation system together with the large-area metal cavity wall. The entire radiating arm 132 extending into the cavity and the feeding connection point are completely covered by the aforementioned "PTFE-ceramic composite coating". Each probe is connected to the microwave generator 2 via an RF cable at the other end of the radiating arm 132 measuring probe, and to the microwave receiver 3 via an RF cable at the other end of the excitation probe.

[0074] Due to the drastic increase in microwave attenuation under high water content conditions, the energy loss caused by water molecules becomes even more pronounced for higher frequency microwave signals. Therefore, two microwave signal transmission frequencies were chosen to measure oil-water mixtures with different water contents. At lower water contents, the amplitude attenuation of high-frequency signals is more pronounced than at lower frequencies, resulting in higher resolution; however, at higher water contents, the amplitude attenuation of high-frequency signals decreases sharply, even approaching complete absorption. Low-frequency signals have higher penetrating power and exhibit less amplitude attenuation at higher water contents; however, they have lower resolution at lower water contents and are susceptible to interference from oil phase inhomogeneity and salinity at low water contents. Therefore, two frequency signals were used for measurement: high-frequency signals for low water content and low-frequency signals for high water content. This invention sets 2.5 GHz as the high frequency and 1.8 GHz as the low frequency. More accurate multiphase flow parameters are obtained through measurements using two different microwave signal frequencies. When microwaves are transmitted through the oil-water mixture in sensor pipe 11, the polarization of water molecules consumes the energy of the microwaves, causing changes in the amplitude and phase of the transmitted microwave signal.

[0075] Based on the aforementioned oil-water two-phase water content measuring device, this application discloses a method for measuring the water content of an oil-water two-phase system. The method includes:

[0076] S1, introduce oil-water mixtures with different water contents into the dual-frequency microwave sensor 1, so that the oil-water mixtures flow through the sensor pipe 11;

[0077] In this step, water and crude oil are mixed in volume ratios to prepare measurement samples with water contents of 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%.

[0078] S2, high-frequency microwave signal and low-frequency microwave signal are generated in microwave generator 2, and the dual-frequency microwave signal is radiated into sensor pipe 11 through high-frequency excitation probe and low-frequency excitation probe respectively set in dual-frequency microwave sensor 1, so that the dual-frequency microwave signal is transmitted through oil-water mixture.

[0079] S3, receive the measurement microwave signals transmitted at the corresponding frequencies from the high-frequency measurement probe and the low-frequency measurement probe in the dual-frequency microwave sensor 1, and send the measurement microwave signals to the microwave receiving device 3;

[0080] In this step, the high-frequency measurement probe and high-frequency excitation probe of the dual-frequency microwave sensor 1 are used to measure the sample for each moisture content. For each moisture content, 50 microwave signal voltage amplitudes obtained through transmission are measured, and data that deviates significantly from the mean are discarded. The mean of each group of 50 voltage amplitudes is then calculated.

[0081] Then, the measurement was performed on each moisture content sample using the low-frequency measurement probe and low-frequency excitation probe of the dual-frequency microwave sensor 1. For each moisture content, 50 microwave signal voltage amplitudes were measured after transmission, and data significantly deviating from the mean were discarded. The mean of each group of 50 voltage amplitudes was calculated. After calculating all the mean values, the average high and low frequency voltage attenuation values ​​were calculated based on the measurement at 0% moisture content. and The attenuation values ​​of 100 sets of voltages were obtained by combining the high-frequency amplitude attenuation and the low-frequency amplitude attenuation. Am The corresponding expression is:

[0082]

[0083]

[0084] in, Indicates the first i The high-frequency amplitude attenuation of a high-frequency calibration sample. Indicates the first i The average transmission voltage of a high-frequency calibration sample. This represents the average high-frequency transmission voltage corresponding to a standard calibration sample with a moisture content of 0%. Indicates the first i The low-frequency amplitude attenuation of each low-frequency calibration sample Indicates the first i The average transmission voltage of a low-frequency calibration sample. This refers to the average low-frequency transmission voltage corresponding to a standard calibration sample with a water content of 0%. The calibration sample itself is an oil-water mixture prepared by volume ratio with several water contents (e.g., 0%, 10%, ..., 100%). High-frequency calibration sample data refers to the set of "high-frequency measurement data" corresponding to a sample with a certain water content, obtained by repeatedly measuring the transmission voltage at a high-frequency channel (e.g., 2.5 GHz) using a high-frequency excitation / measurement probe. Low-frequency calibration sample data refers to the set of transmission voltage data obtained and averaged at a low-frequency channel (e.g., 1.8 GHz) using a low-frequency probe for the same water content sample. The physical samples are the same; the only difference is whether the data is measured using a high-frequency or low-frequency channel, used to fit two calibration curves, one for high frequency and one for low frequency.

[0085] In one example, water and crude oil are mixed in various volumes to prepare oil-water mixtures with different water contents, including 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%.

[0086] Oil-water mixtures with different water contents are sequentially introduced into the dual-frequency microwave sensor 1. Multiple measurements are performed on each oil-water mixture using various detection probes 13, and the average voltage and voltage attenuation corresponding to the DC voltage signal are calculated to obtain the high-frequency calibration curve, the low-frequency calibration curve, the first threshold voltage, and the second threshold voltage.

[0087] S4, the microwave signal being measured is subjected to envelope detection and voltage doubler rectification in the microwave receiving device 3 to obtain a DC voltage signal corresponding to the amplitude attenuation of the transmitted microwave, and the DC voltage signal is input to the signal processing device 4;

[0088] S5, the signal processing device 4 continuously samples the DC voltage signal corresponding to the transmitted voltage, compares the transmitted voltage with the pre-calibrated first threshold voltage and second threshold voltage, switches the measurement mode of the dual-frequency microwave sensor 1, and calculates the water content of the oil-water mixture.

[0089] In this embodiment, based on moisture content With voltage attenuation The properties are obtained through nonlinear least squares curve fitting, based on the Sigmoid function. First, set the parameters. , , and The initial guess value is then continuously adjusted until the minimum error is obtained.

[0090] The expressions for the high-frequency calibration curve and the low-frequency calibration curve are as follows:

[0091]

[0092]

[0093] in, The high-frequency calibration curve function representing the high-frequency channel voltage attenuation with respect to moisture content. This represents the stable value at which the high-frequency calibration curve eventually stabilizes as the moisture content increases. This represents the total vertical span of the voltage attenuation change in the high-frequency calibration curve as the moisture content changes from 0% to 100%. This represents the sensitivity coefficient of the high-frequency calibration curve to changes in moisture content near the inflection point. This represents the water content variable under high-frequency mode. This indicates the moisture content at the inflection point of the high-frequency calibration curve. The low-frequency calibration curve function represents the low-frequency channel voltage attenuation with respect to moisture content. This represents the stable value at which the low-frequency calibration curve eventually stabilizes as the moisture content increases. This represents the sensitivity coefficient of the low-frequency calibration curve to changes in moisture content near the inflection point. This represents the water content variable under low-frequency mode. This indicates the moisture content at the inflection point of the low-frequency calibration curve.

[0094] The voltage threshold under high-frequency conditions can be expressed as:

[0095]

[0096]

[0097] in, Indicates the first threshold voltage. Indicates the second threshold voltage. This indicates the threshold moisture content that distinguishes between low and medium moisture content. The threshold moisture content that distinguishes between medium and high moisture content can be represented by... and Set at 70% and 85%.

[0098] The root mean square error (RMSE) of each model can be expressed as:

[0099] ; ,

[0100] in, This represents the root mean square error of the high-frequency calibration model. This represents the root mean square error of the low-frequency calibration model. Indicates the firsti The average attenuation of high-frequency amplitude of a high-frequency calibration sample. Indicates the first i The average attenuation of low-frequency amplitude of each low-frequency calibration sample.

[0101] The weighted algorithm under moisture content conditions can be expressed as:

[0102]

[0103]

[0104]

[0105] in, This represents the weighted average moisture content measurement value. This represents the high-frequency moisture content estimate. This represents the low-frequency moisture content estimate. This represents the weighting coefficient of the high-frequency channel. This represents the root mean square error of the high-frequency calibration model. This represents the root mean square error of the low-frequency calibration model. This represents the weighting coefficient for the low-frequency channel.

[0106] Furthermore, the dual-frequency microwave sensor 1 has three operating modes: low moisture content measurement mode, medium moisture content measurement mode, and high moisture content measurement mode. First, a coarse measurement is performed, and the operating mode is switched based on the measurement result. By default, a high-frequency 2.5GHz signal with significant amplitude attenuation is used for measurement. The amplitude attenuation is measured by the signal receiving module, and the result is fed back to the MCU in the processing module. The MCU then switches the program's state machine based on the measurement result.

[0107] If the transmitted voltage is greater than the first threshold voltage, the dual-frequency microwave sensor 1 is switched to the low water content measurement mode, and the water content of the oil-water mixture is calculated only based on the high-frequency signal.

[0108] If the transmitted voltage is less than the second threshold voltage, the dual-frequency microwave sensor 1 is switched to the high water content measurement mode, and the water content of the oil-water mixture is calculated based only on the low-frequency signal.

[0109] If the transmitted voltage is greater than or equal to the second threshold voltage and less than or equal to the first threshold voltage, the dual-frequency microwave sensor 1 is switched to the medium water content measurement mode, and the water content of the oil-water mixture is calculated by weighting based on the high-frequency signal and the low-frequency signal.

[0110] Crude oil from an oil well is fed into sensor pipe 1, and the amplitude voltage is measured using a high-frequency microwave probe. ;

[0111] MCU according to The state machine switches based on the value. When switching to low moisture content measurement mode, the high-frequency probe is used to measure according to the high-frequency calibration curve. Measure moisture content; when Switch to high moisture content mode and use a low-frequency probe based on the low-frequency calibration curve. Measure moisture content; when Switch to medium moisture content mode, measure simultaneously with two probes, and obtain the moisture content through a weighted algorithm. The calculated moisture content is then output to the host computer.

[0112] In one example, when the water content is below 70%, the dual-frequency microwave sensor 1 operates in low water content mode. In this mode, the water content of the crude oil is measured by measuring the attenuation value of the 2.5 GHz high-frequency signal. When the water content is above 85%, the dual-frequency microwave sensor 1 operates in high water content mode. In this mode, the water content of the crude oil is measured by measuring the attenuation value of the 1.8 GHz low-frequency signal. When the water content is between 70% and 85%, the dual-frequency microwave sensor 1 operates in medium water content mode. In this mode, the dual-frequency microwave sensor 1 simultaneously acquires the amplitude attenuation values ​​of both the low-frequency and high-frequency signals and calculates the water content using a weighted algorithm.

[0113] In this embodiment, high-frequency and low-frequency microwave signals are generated simultaneously in the microwave generator 2 and applied to the oil-water mixture respectively. This allows the measurement process to simultaneously acquire response information of the dielectric properties of oil and water at different frequency bands. By utilizing the sensitivity of high-frequency microwaves to changes in dielectric constant, the resolution capability for medium-to-high water content range is enhanced. By utilizing the strong penetration capability and good stability of low-frequency microwaves, the measurement reliability under low water content or complex flow patterns is improved. Through the complementary use of dual-frequency information, the water content measurement range is effectively broadened and the overall measurement accuracy is improved. By performing envelope detection and voltage doubler rectification on the transmitted microwave signal, the high-frequency microwave signal is converted into a stable DC voltage signal, reducing the impact of noise and transient fluctuations on the measurement results. Furthermore, the signal processing device 4 continuously samples the transmitted voltage and compares it with the pre-calibrated first and second threshold voltages. It can automatically switch the measurement mode of the dual-frequency microwave sensor 1 according to the actual water content of the oil-water mixture, avoiding the problem of insufficient sensitivity of a single frequency in a specific water content range, and improving the measurement accuracy and stability in different water content ranges. At the same time, by combining the real-time acquired transmitted voltage signal with the pre-calibrated data model to calculate the water content, the influence of factors such as flow fluctuations and flow pattern changes on the measurement results can be effectively reduced, improving the repeatability and consistency of the measurement results.

[0114] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An oil-water two-phase water content measuring device, comprising a microwave generator (2), a microwave receiver (3), a signal processing device (4), and a dual-frequency microwave sensor (1), wherein, The microwave generator (2) is connected to the dual-frequency microwave sensor (1) and the signal processing device (4) respectively. The microwave generator (2) is used to generate dual-frequency microwave signals. The dual-frequency microwave sensor (1) is connected to the microwave receiving device (3), and the dual-frequency microwave sensor (1) performs microwave transmission measurement on the oil-water mixture flowing through the dual-frequency microwave sensor (1) through the dual-frequency microwave signal; The microwave receiving device (3) is connected to the signal processing device (4). The microwave receiving device (3) is used to detect and rectify the detection microwave signal output from the dual-frequency microwave sensor (1) and obtain a DC voltage signal corresponding to the microwave amplitude attenuation in the detection microwave signal. The signal processing device (4) is used to sample the DC voltage signal and switch the detection mode corresponding to the dual-frequency microwave sensor (1) according to the DC voltage signal to calculate the water content of the oil-water mixture; The voltage thresholds corresponding to the switching of the DC voltage signal include: The expressions for the high-frequency calibration curve and the low-frequency calibration curve are as follows: ； ； in, The high-frequency calibration curve function representing the high-frequency channel voltage attenuation with respect to moisture content. This represents the stable value at which the high-frequency calibration curve eventually stabilizes as the moisture content increases. This represents the total vertical span of the voltage attenuation change in the high-frequency calibration curve as the moisture content changes from 0% to 100%. This represents the total vertical span of the voltage attenuation change in the low-frequency calibration curve as the moisture content changes from 0% to 100%. This represents the sensitivity coefficient of the high-frequency calibration curve to changes in moisture content near the inflection point. This represents the water content variable under high-frequency mode. This indicates the moisture content at the inflection point of the high-frequency calibration curve. The low-frequency calibration curve function represents the low-frequency channel voltage attenuation with respect to moisture content. This represents the stable value at which the low-frequency calibration curve eventually stabilizes as the moisture content increases. This represents the sensitivity coefficient of the low-frequency calibration curve to changes in moisture content near the inflection point. This represents the water content variable under low-frequency mode. The moisture content at the inflection point of the low-frequency calibration curve. Indicates moisture content; The voltage threshold under high-frequency conditions is expressed as: ； ； in, Indicates the first threshold voltage. Indicates the second threshold voltage. This indicates the threshold moisture content that distinguishes between low and medium moisture content. This indicates the threshold moisture content that distinguishes between medium and high moisture content. This represents the average low-frequency transmission voltage corresponding to a standard calibration sample with a moisture content of 0%. This represents the average high-frequency transmission voltage corresponding to a standard calibration sample with a moisture content of 0%. The dual-frequency microwave sensor (1) includes a sensor tube (11), a shielding layer (12), and various detection probes (13), wherein, The sensor pipe (11) is cylindrical, and the sensor pipe (11) is provided with flange interfaces (14) at both ends of the sensor pipe (11) for connection with the oil well pipe flange, so that the oil-water mixture flows through the dual-frequency microwave sensor (1). The shielding layer (12) is coaxially arranged with the sensor pipe (11), and the shielding layer (12) covers the outside of the sensor pipe (11). The detection probe (13) includes a high-frequency excitation probe, a high-frequency measurement probe, a low-frequency excitation probe and a low-frequency measurement probe. The high-frequency excitation probe and the high-frequency measurement probe are arranged in a double parallel line structure to penetrate radially along the sensor pipe (11). The high-frequency excitation probe and the high-frequency measurement probe are symmetrical about the axis of the sensor pipe (11) and are arranged at the upper part of the sensor pipe (11). The low-frequency excitation probe and the low-frequency measurement probe are arranged in a double parallel line structure and penetrate radially along the sensor pipe (11). The low-frequency excitation probe and the low-frequency measurement probe are symmetrical about the axis of the sensor pipe (11) and are located at the lower part of the sensor pipe (11).

2. The oil-water two-phase water content measuring device as described in claim 1, characterized in that, Multiple sets of polyetheretherketone spiral ribs (15) are arranged along the axial direction of the sensor pipe (11). The polyetheretherketone spiral ribs (15) are used to break the oil-water emulsion layer and promote the uniform distribution of the mixture. The inner wall of the sensor pipe (11) is coated with Teflon coating.

3. The oil-water two-phase water content measuring device as described in claim 2, characterized in that, The high-frequency excitation probe, the high-frequency measurement probe, the low-frequency excitation probe, and the low-frequency measurement probe all adopt a monopole probe structure, and each excitation probe includes a coaxial radio frequency cable (131), an insulating layer (133), and a radiating arm (132). One end of the radiating arm (132) is electrically connected to the center conductor of the coaxial radio frequency cable (131), and the other end of the radiating arm (132) extends radially into the interior of the sensor pipe (11) along the sensor pipe (11); The radiating arm (132) is located between any two adjacent polyetheretherketone spiral ribs (15), and the axis of the radiating arm (132) is coaxial with the axis of the coaxial radio frequency cable (131). The insulating layer (133) covers the outside of the coaxial radio frequency cable (131) and the radiating arm (132), and the insulating layer (133) penetrates the sensor pipe (11) and the shielding layer (12) radially along the sensor pipe (11).

4. The oil-water two-phase water content measuring device as described in claim 3, characterized in that, The periphery of the radiation arm (132) of the detection probe (13) extending into the sensor pipe (11) is coated with a polytetrafluoroethylene-ceramic composite coating.

5. The oil-water two-phase water content measuring device as described in claim 1, characterized in that, The high-frequency excitation probe and the low-frequency excitation probe are located on the same side of the sensor pipe (11), and the high-frequency excitation probe and the low-frequency excitation probe are arranged in parallel. The high-frequency measurement probe and the low-frequency measurement probe are located on the same side of the sensor pipe (11), and the high-frequency measurement probe and the low-frequency measurement probe are arranged in parallel.

6. A method for measuring the water content of an oil-water two-phase system, implemented using the oil-water two-phase water content measuring device as described in claim 1, characterized in that, The method includes: Oil-water mixtures with different water contents are introduced into the dual-frequency microwave sensor (1) so that the oil-water mixtures flow through the sensor pipe (11); High-frequency microwave signals and low-frequency microwave signals are generated in the microwave generator (2), and the high-frequency excitation probe and low-frequency excitation probe respectively are set in the dual-frequency microwave sensor (1) to radiate the dual-frequency microwave signals into the sensor pipe (11), so that the dual-frequency microwave signals are transmitted through the oil-water mixture. The high-frequency measurement probe and the low-frequency measurement probe in the dual-frequency microwave sensor (1) respectively receive the measurement microwave signals transmitted at the corresponding frequencies, and send the measurement microwave signals to the microwave receiving device (3); In the microwave receiving device (3), the measured microwave signal is subjected to envelope detection and voltage doubler rectification to obtain a DC voltage signal corresponding to the amplitude attenuation of the transmitted microwave, and the DC voltage signal is input to the signal processing device (4). The signal processing device (4) continuously samples the transmitted voltage corresponding to the DC voltage signal, compares the transmitted voltage with the pre-calibrated first threshold voltage and second threshold voltage, switches the measurement mode of the dual-frequency microwave sensor (1), and calculates the water content of the oil-water mixture.

7. The method for measuring the water content of an oil-water two-phase system as described in claim 6, characterized in that, The method further includes: Water and crude oil are mixed in various volumes to prepare oil-water mixtures with different water contents, including 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 75%, 80%, 85%, 90%, 95%, and 100%. Oil-water mixtures with different water contents are sequentially introduced into the dual-frequency microwave sensor (1). Multiple measurements are performed on each oil-water mixture using various detection probes (13), and the average voltage and voltage attenuation corresponding to the DC voltage signal are calculated to obtain the high-frequency calibration curve, the low-frequency calibration curve, the first threshold voltage, and the second threshold voltage.

8. The method for measuring the water content of an oil-water two-phase system as described in claim 7, characterized in that, The step of comparing the transmitted voltage with a pre-calibrated first threshold voltage and a second threshold voltage to switch the measurement mode of the dual-frequency microwave sensor (1) specifically includes: If the transmitted voltage is greater than the first threshold voltage, the dual-frequency microwave sensor (1) is switched to low water content measurement mode, and the water content of the oil-water mixture is calculated only based on the high-frequency signal. If the transmitted voltage is less than the second threshold voltage, the dual-frequency microwave sensor (1) is switched to high water content measurement mode, and the water content of the oil-water mixture is calculated based only on the low-frequency signal. If the transmission voltage is greater than or equal to the second threshold voltage and the transmission voltage is less than or equal to the first threshold voltage, then the dual-frequency microwave sensor (1) is switched to the medium water content measurement mode, and the water content of the oil-water mixture is calculated by weighting based on the high-frequency signal and the low-frequency signal.

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