CN116106373A - Dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement system and method - Google Patents

Abstract

A dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement system and a method relate to the technical field of sensors and detection. The invention solves the problem of poor accuracy in the existing measurement process of the water content and the mineralization degree of crude oil. According to the invention, resistance and capacitance information can be obtained through digital demodulation signals, the change of conductivity is reflected through voltage change caused by the demodulation of the resistance value in the obtained oil-water two-phase flow, the change of water content is reflected through the voltage change caused by the demodulation of the capacitance value in the obtained oil-water two-phase flow, and a gear switching circuit is adopted, so that the wide-range span of water content and mineralization degree is realized, and the application range and application occasions are improved. The invention is suitable for measuring physical property parameters of crude oil.

Description

Dual-frequency phase-sensitive demodulation crude oil physical parameter measurement system and method

Technical Field

The invention relates to the field of sensors and detection technology.

Background Art

At present, crude oil extraction mainly adopts the method of high-pressure water injection, which leads to too high water content in the extracted crude oil. The increase in water content will increase the capacity of the oil transportation pipeline, wasting a lot of resources. It will also affect the subsequent treatment of oil such as distillation and catalytic cracking. In addition, there are inorganic salt components in the water phase of crude oil, which will cause great harm to subsequent storage and transportation, refining and processing, oil quality and equipment maintenance. Therefore, accurately measuring the water content and conductivity of the extracted crude oil is a key task in this field, and its precise measurement is of great significance to the quality assessment and extraction planning of oil fields.

The capacitance method is a commonly used method for measuring the water content and mineralization of crude oil. It has the advantages of small mechanical loss, simple structure, stability and reliability. However, it has the problem that the measurement error is extremely large or it cannot be measured at all when the crude oil is in a medium-high water content state or a medium-high salt content state. In addition, when processing the measurement data, most of them use data linear fitting. Since the equivalent dielectric constant of two-phase flow is an empirical formula with errors, linear fitting further increases the error. At the same time, there is currently no equipment on the market that can simultaneously measure the water content and conductivity of crude oil online. Existing research usually uses C/V conversion chips, charge and discharge methods, and AC excitation methods to measure the capacitance in the equivalent model as accurately as possible. In terms of high water content measurement, the method of applying an insulating layer on the inner side of the electrode is mainly adopted to solve the measurement problem under medium-high water content or medium-high salt content. For example, the application publication number is CN109596675A, and the name is a three-electrode crude oil water content sensor measurement device. It adopts a fixed single-frequency AC excitation method. The AC sinusoidal signal outputs a signal containing a water content signal through an inverting amplifier circuit composed of a single feedback resistor, and is sent to the single-chip microcomputer for processing through a signal processing module. The disadvantages of this invention are: due to the small dielectric constant of the insulating material, the equivalent capacitance of the sensor will inevitably be reduced, the measurement difficulty will be increased, and the aging of the insulating layer over time will cause measurement errors; in addition, its single feedback resistor will limit the measurement range, and when the water content range is large, the measurement will fail; at the same time, its single frequency can only be used to measure water content detection, and its crude oil residual physical parameters cannot be measured. For example, in the paper on the measurement method of high water content of crude oil based on the capacitance method, it uses the charge and discharge method to measure the equivalent capacitance, and uses a temperature sensor to measure and compensate the temperature, and sends the measurement information to the single-chip microcomputer for processing to obtain the water content parameters. In terms of data processing, it performs a secondary linear fit on the basis of a primary linear fit to improve the measurement accuracy. The disadvantage of this invention is that the charge-discharge method does not have the ability to measure with high resolution in terms of weak capacitance measurement, which reduces the measurement accuracy. In addition, although the capacitance value and the equivalent dielectric constant are linearly related, the dielectric constant of each phase of the two-phase flow is unstable, so the linear fit of the water content by the equivalent dielectric constant has inherent defects, which makes its accuracy inherently limited. Another example is the development of a new remote online detection system for the water content of crude oil in the paper. The detection system designed in the paper uses a flat electrode capacitance sensor, in which the C/V conversion uses a CAV444 chip, and the information is directly collected and sent to the stm32 microcontroller for processing, and then displayed by the host computer. The disadvantage of this design is that the measurement range of the CAV444 chip is 10pf~10nf, which makes it lose its measurement ability under low water content conditions, and the charge-discharge measurement principle of the chip also makes it impossible to use it under high water content conditions.

Summary of the invention

The purpose of the present invention is to solve the problem of poor accuracy in the existing measurement process of crude oil water content and salinity, and proposes a dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement device.

The dual-frequency phase-sensitive demodulation crude oil physical parameter measurement system of the present invention comprises: a signal generation module, two measuring electrodes, a gear switching circuit, an I/V conversion operational amplifier, a temperature sensor, an ADC sampling circuit, a main controller and a host computer;

The signal output end of the signal generating module is connected to a measuring electrode, and the dual-frequency AC superposition signal is loaded to the one measuring electrode. The other measuring electrode is connected to the signal input end of the I/V conversion operational amplifier. The dual-frequency AC superposition signal is a superposition of two signals with different frequencies and amplitudes.

One end of the two measuring electrodes is disposed in the mixed solution to be measured, and a gap is left between the two measuring electrodes;

The I/V conversion operational amplifier is connected in parallel with the gear switching circuit;

The signal output end of the I/V conversion operational amplifier is connected to the signal input end of the ADC sampling circuit, and the temperature sensor is used to collect the temperature of the mixed liquid to be tested and transmit the collected temperature signal to the signal input end of the ADC sampling circuit;

The signal output end of the ADC sampling circuit is connected to the signal input end of the main controller, and the signal input end of the main controller is also connected to the signal output end of the signal generating module;

The main controller multiplies the signal output by the signal generating module and the signal output by the ADC sampling circuit, performs low-pass filtering, obtains two DC voltage signals, and uploads the two DC voltage signals to the host computer. The host computer uses the two DC voltage signals to obtain equivalent resistance and capacitance information of the mixed solution to be tested, and uses the BP neural network algorithm, combined with the equivalent resistance and capacitance information, the gear position of the gear switching circuit and the temperature of the liquid to be tested, to calculate and obtain the water content and conductivity information of the mixed solution to be tested.

Furthermore, in the present invention, the signal generation module includes a signal generator, two signal amplifiers, two low-pass filters and an inverse adder;

The signal generating module outputs two sinusoidal excitation signals, which are amplified by the signal amplifier and respectively input into two low-pass filters. The two low-pass filters respectively perform low-pass filtering on the two amplified sinusoidal excitation signals. The two signals after low-pass filtering are simultaneously input into the reverse adder. The reverse adder reversely adds the two signals after low-pass filtering and outputs a dual-frequency AC superposition signal.

Furthermore, in the present invention, the main controller includes two signal processing circuits, each signal processing circuit includes a digital multiplier and a low-pass filter, the two digital multipliers respectively receive the output signal of the ADC sampling circuit and the output signal of the signal generating module, the two digital multipliers respectively multiply the received signals with the corresponding reference signals and send them to the corresponding low-pass filters, the two low-pass filters respectively low-pass filter the received signals, obtain two DC voltage signals, and send the two DC voltage signals to the host computer.

Furthermore, in the present invention, the two measuring electrodes are coaxially arranged as two cylinders, wherein one measuring electrode is sleeved on the outside of the other measuring electrode, and the measuring electrode located on the outside is a hollow cylindrical structure, wherein the radius of the measuring electrode located on the inside is smaller than the radius of the measuring electrode located on the outside.

Furthermore, in the present invention, the gear switching circuit includes a relay and a plurality of feedback resistors with different resistance values, and the relay is used to control the resistance value of the feedback resistor connected in parallel with the I/V conversion operational amplifier.

The dual-frequency phase-sensitive demodulation crude oil physical parameter measurement method is based on the dual-frequency phase-sensitive demodulation crude oil physical parameter measurement system, and the specific steps are as follows:

Step 1: two measuring electrodes are placed in the mixed solution to be tested, with a gap between the two measuring electrodes;

Step 2: Use a signal generator to output two sinusoidal excitation signals, amplify and low-pass filter the two sinusoidal excitation signals, and then add them in reverse to obtain a dual-frequency AC superposition signal;

Step 3: The dual-frequency AC superposition signal is transmitted to one measuring electrode, and the other measuring electrode is connected to an I/V conversion operational amplifier, and the dual-frequency AC superposition signal of the mixed liquid to be measured is transmitted to the I/V conversion operational amplifier, and an ADC sampling circuit is used to sample the temperature signal of the mixed liquid to be measured and the output signal of the I/V conversion operational amplifier;

Step 4: The main controller uses two digital multipliers to multiply the signal output by the ADC sampling circuit and the signal output by the signal generating module with the corresponding reference signal, and then performs low-pass filtering to obtain two DC voltage signals;

Step 5: Using a host computer, using the two DC voltage signals, obtain the equivalent resistance and capacitance information of the mixed solution to be tested, and using a BP neural network algorithm, combining the equivalent resistance and capacitance information, the gear position of the gear switching circuit and the temperature of the liquid to be tested, to obtain the water content and conductivity information of the mixed solution to be tested.

Furthermore, in the present invention, in step 1, the equivalent resistance-capacitance expression of the two measuring electrodes is:

Wherein, σ _m is the conductivity of the oil-water mixture; ε _o is the vacuum dielectric constant; ε _m is the equivalent dielectric constant of the oil-water two-phase flow; R is the inner diameter of the outer electrode; r is the outer diameter of the inner electrode; l is the electrode length of the sensor;

The equivalent dielectric constant of oil-water two-phase flow is:

Where, ε _o is the relative dielectric constant of the oil phase, ε _w is the relative dielectric constant of water, and α is the water content of the two-phase flow;

It is deduced that:

Furthermore, in the present invention, in step 1, the signal generator outputs two sinusoidal excitation signals as follows:

为信号的相角，k₁、k₂分别为两路正弦激励信号的角频率，ω为角速度，V₁、V₂分别为分别为两路正弦激励信号。Where _A1 and _A2 are the signal amplitudes at two frequencies respectively.

is the phase angle of the signal, k ₁ and k ₂ are the angular frequencies of the two sinusoidal excitation signals, ω is the angular velocity, and V ₁ and V ₂ are the two sinusoidal excitation signals.

Furthermore, in the present invention, in step 2, the dual-frequency AC superposition signal is:

V _i =V ₁ +V ₂ =A ₁ sin(k ₁ ωt)+A ₂ sin(k ₂ ωt)

Among them, _Vi is a dual-frequency AC superposition signal.

Furthermore, in the present invention, the signal output by the ADC sampling circuit is:

Wherein, V _O is the ADC output signal, n corresponds to the value range of 0 to N-1, N is the number of sampling points; _RX is the equivalent resistance of the mixed solution to be tested, _CX is the equivalent capacitance of the mixed solution to be tested, and _Rf is the feedback resistor of the I/V conversion operational amplifier.

Further, in the present invention, in step 4, the reference signal of the two signal digital multipliers is:

Where _VfR (n) is the resistor excitation reference signal, and _VfC (n) is the capacitor excitation reference signal.

Further, in the present invention, in step 4, the main controller uses two digital multipliers to multiply the signal output by the ADC sampling circuit and the signal output by the signal generating module with the corresponding reference signal to obtain the signal:

Where V _OR (n) is the capacitor output voltage signal, and V _Oc (n) is the resistor output voltage signal.

Furthermore, in the present invention, in step 4, the two DC voltage signals are:

Wherein, _Vo'C is the capacitor DC voltage signal, _{and Vo'R} is _the resistor DC voltage signal.

Furthermore, in the present invention, in step 5, the equivalent resistance and capacitance information of the mixed solution to be tested is obtained as follows:

Among them, _RX is the equivalent resistance to be measured. _CX is the equivalent capacitance to be measured.

The dual-frequency phase-sensitive demodulation crude oil physical parameter measurement device described in the present invention is applied to the oil-water two-phase flow measurement system containing conductive water phase. The resistance and capacitance information can be obtained through the digital demodulation signal, and the change of conductivity is reflected by the voltage change caused by the resistance value in the oil-water two-phase flow obtained by demodulation, and the change of water content is reflected by the voltage change caused by the capacitance value in the oil-water two-phase flow obtained by demodulation. At the same time, a gear switching circuit is adopted to achieve a large range span of water content and mineralization, thereby improving its scope of application and applicable occasions. A temperature sensor is used to collect the temperature of the mixed liquid to be measured, realize temperature compensation, and take into account the influence of temperature on the measurement of physical parameters, thereby further improving the accuracy of measurement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a block diagram of the dual-frequency phase-sensitive demodulation crude oil physical parameter measurement system of the present invention;

FIG2 is a structural block diagram of a dual-frequency phase-sensitive demodulation crude oil physical parameter measurement system according to a specific embodiment;

FIG3 is a schematic diagram of an equivalent model of oil-water two-phase flow;

FIG4 is a sensitivity diagram of the outer electrode at different radii, in which D represents the radius of the outer electrode;

FIG5 is a sensitivity diagram of the inner electrode at different radii, where d represents the radius of the inner electrode;

FIG6 is a sensitivity diagram of electrodes of different lengths; in the figure, L represents the length of the electrode;

FIG7 is a flow chart of gear control;

Fig. 8 is a conductivity measurement error diagram;

Fig. 9 is a diagram of moisture content measurement error;

FIG10 is a time curve diagram of the actual measured moisture content;

FIG. 11 is a time curve diagram of the actual measured conductivity.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

Specific implementation method 1: The following describes this implementation method in conjunction with FIG. 1 and FIG. 2. The dual-frequency phase-sensitive demodulation crude oil physical parameter measurement system described in this implementation method includes: a signal generating module 1, two measuring electrodes 2, a gear switching circuit 3, an I/V conversion operational amplifier 4, a temperature sensor 5, an ADC sampling circuit 6, a main controller 7 and a host computer 8;

The signal output end of the signal generating module 1 is connected to a measuring electrode 2, and a dual-frequency AC superposition signal is loaded to the one measuring electrode 2. The other measuring electrode 2 is connected to the signal input end of the I/V conversion operational amplifier 4. The dual-frequency AC superposition signal is a superposition of two signals with different frequencies and amplitudes.

One end of the two measuring electrodes 2 is disposed in the mixed solution to be measured, and a gap is left between the two measuring electrodes 2;

The I/V conversion operational amplifier 4 is connected in parallel with the gear switching circuit 3;

The signal output end of the I/V conversion operational amplifier 4 is connected to the signal input end of the ADC sampling circuit 6. The temperature sensor 5 is used to collect the temperature of the mixed liquid to be tested and transmit the collected temperature signal to the signal input end of the ADC sampling circuit 6.

The signal output end of the ADC sampling circuit 6 is connected to the signal input end of the main controller 7, and the signal input end of the main controller 7 is also connected to the signal output end of the signal generating module 1;

The main controller 7 multiplies the signal output by the signal generating module 1 and the signal output by the ADC sampling circuit 6, and then performs low-pass filtering to obtain two DC voltage signals, and uploads the two DC voltage signals to the host computer 8. The host computer 8 uses the two DC voltage signals to obtain the equivalent resistance and capacitance information of the mixed solution to be tested, and uses the BP neural network algorithm, combined with the equivalent resistance and capacitance information, the gear position of the gear switching circuit 3 and the temperature of the liquid to be tested, to calculate and obtain the water content and conductivity information of the mixed solution to be tested.

Furthermore, in this embodiment, the signal generating module 1 includes a signal generator 101, two signal amplifiers 102, two low-pass filters 103 and an inverse adder 104;

The signal generating module 1 outputs two sinusoidal excitation signals, which are amplified by the signal amplifier 102 and input into two low-pass filters 103 respectively. The two low-pass filters 103 respectively perform low-pass filtering on the two amplified sinusoidal excitation signals. The two signals after low-pass filtering are simultaneously input into the reverse adder 104. The reverse adder 104 reversely adds the two signals after low-pass filtering and outputs a dual-frequency AC superposition signal.

Furthermore, in this embodiment, the main controller 7 includes two signal processing circuits, each signal processing circuit includes a digital multiplier and a low-pass filter, the two digital multipliers respectively receive the output signal of the ADC sampling circuit 6 and the output signal of the signal generating module 1, the two digital multipliers respectively multiply the received signal with the corresponding reference signal and send it to the corresponding low-pass filter, the two low-pass filters respectively low-pass filter the received signal, obtain two DC voltage signals, and send the two DC voltage signals to the host computer 8.

Furthermore, in the present embodiment, the two measuring electrodes 2 are coaxially arranged as two cylinders, wherein one measuring electrode is sleeved on the outside of the other measuring electrode, and the measuring electrode located on the outside is a hollow cylindrical structure, wherein the radius of the measuring electrode located on the inside is smaller than the radius of the measuring electrode located on the outside, and the measurement sensitivity diagrams of the measuring electrode located on the inside and the measuring electrode located on the outside under different geometric dimensions are shown in Figures 4 to 6.

Furthermore, in this embodiment, the gear switching circuit includes a relay and a plurality of feedback resistors with different resistance values, and the relay is used to control the resistance value of the feedback resistor connected in parallel with the I/V conversion operational amplifier 4.

The equivalent resistance and capacitance are calculated at a water content of 0-40% and a conductivity of 0ms/m-100ms/m. The equivalent capacitance ranges from about 13.96pf to 122.26pf, corresponding to 20kΩ to 200Ω. Therefore, the 6-position feedback resistance switching circuit is designed with feedback resistances of 500Ω, 1.5kΩ, 2.2kΩ, 3.48kΩ, 5kΩ, and 10kΩ, respectively, so that it meets the measurement requirements of equivalent capacitance of 27.5pf to 300pf and equivalent resistance of 200Ω to 20kΩ. This embodiment is illustrated in conjunction with FIG. 7. FIG. 7 is a specific process for controlling the gear switching circuit. The reasonable range of resistance and capacitance described in the figure is whether it is between the set maximum and minimum values. In order to determine the measurement benchmark, the feedback resistance is manually matched with the resistance and capacitance to be measured to obtain the output when the impedance and capacitive reactance are the same as the feedback resistance at different gears. The DC output value range of the resistor is 280±3, and the DC output value of the capacitor is 360±2.7. To facilitate the subsequent gear control, the reasonable range of impedance and capacitive reactance output values is 140~560, 180~720, that is, the resistance to be measured is 0.5~2 times the feedback resistance. In this case, the maximum difference between impedance and capacitive reactance is 4 times, and the maximum error brought about is 1%, which meets the equipment requirements, as shown in Figures 8 to 11.

The dual-frequency phase-sensitive demodulation crude oil physical parameter measurement method is based on the dual-frequency phase-sensitive demodulation crude oil physical parameter measurement system, and the specific steps are as follows:

Step 1: two measuring electrodes 2 are arranged in the mixed solution to be measured, and a gap is provided between the two measuring electrodes 2;

Step 2: using the signal generator 101 to output two sinusoidal excitation signals, amplifying and low-pass filtering the two sinusoidal excitation signals, and then adding them in reverse to obtain a dual-frequency AC superposition signal;

Step 3: The dual-frequency AC superposition signal is transmitted to a measuring electrode 2, and the other measuring electrode 2 is connected to the signal input end of the I/V conversion operational amplifier 4, and the dual-frequency AC superposition signal of the mixed liquid to be measured is transmitted to the I/V conversion operational amplifier, and the ADC sampling circuit 6 is used to sample the temperature signal of the mixed liquid to be measured and the output signal of the I/V conversion operational amplifier;

Step 4, main controller The main controller 7 uses two digital multipliers to respectively multiply the signal output by the ADC sampling circuit 6 and the signal output by the signal generating module 1 with the corresponding reference signal and then performs low-pass filtering to obtain two DC voltage signals;

Step 5: Using the host computer 8, using the two DC voltage signals, obtain the equivalent resistance and capacitance information of the mixed solution to be tested, and using the BP neural network algorithm, combining the equivalent resistance and capacitance information, the gear position of the gear switching circuit 3 and the temperature of the liquid to be tested, to obtain the water content and conductivity information of the mixed solution to be tested.

Furthermore, in this embodiment, in step 1, the equivalent resistance-capacitance expression of the two measuring electrodes 2 is:

Wherein, σ _m is the conductivity of the oil-water mixture; ε _o is the vacuum dielectric constant; ε _m is the equivalent dielectric constant of the oil-water two-phase flow; R is the inner diameter of the outer electrode; r is the outer diameter of the inner electrode; l is the electrode length of the sensor, R _x is the equivalent resistance of the mixed liquid to be measured, and C _x is the equivalent capacitance of the mixed liquid to be measured;

The equivalent dielectric constant of oil-water two-phase flow is:

Where, ε _o is the relative dielectric constant of the oil phase, ε _w is the relative dielectric constant of water, and α is the water content of the two-phase flow;

It is deduced that:

Furthermore, in this implementation, in step 1, the signal generator 101 outputs two sinusoidal excitation signals as follows:

为信号的相角，k₁、k₂分别为两路正弦激励信号的角频率，ω为角速度，V₁、V₂分别为分别为两路正弦激励信号，t为时间。Where _A1 and _A2 are the signal amplitudes at two frequencies respectively.

is the phase angle of the signal, k ₁ and k ₂ are the angular frequencies of the two sinusoidal excitation signals, ω is the angular velocity, V ₁ and V ₂ are the two sinusoidal excitation signals, and t is the time.

Further, in this implementation, in step 2, the dual-frequency AC superposition signal is:

V _i =V ₁ +V ₂ =A ₁ sin(k ₁ ωt)+A ₂ sin(k ₂ ωt)

Among them, _Vi is a dual-frequency AC superposition signal.

Furthermore, in this embodiment, the signal output by the ADC sampling circuit 6 is:

Where, V _O is the ADC output signal, n corresponds to the value range of 0 to N-1, N is the number of sampling points; R _f is the feedback resistor of the I/V conversion operational amplifier.

Furthermore, in this implementation, in step 4, the reference signal of the two-signal digital multiplier is:

Where _VfR (n) is the resistor excitation reference signal, and _VfC (n) is the capacitor excitation reference signal.

Further, in this embodiment, in step 4, the main controller 7 uses two digital multipliers to respectively multiply the signal output by the ADC sampling circuit 6 and the signal output by the signal generating module 1 with the corresponding reference signal to obtain the signal:

Where V _OR (n) is the capacitor output voltage signal, and V _Oc (n) is the resistor output voltage signal.

Furthermore, in this implementation, in step 4, the two DC voltage signals are:

Wherein, _Vo'C is the capacitor DC voltage signal, _{and Vo'R} is _the resistor DC voltage signal.

Further, the present embodiment is described in conjunction with FIG. 3 . In the present embodiment, in step 5, the equivalent resistance-capacitance information of the mixed solution to be tested is obtained as follows:

Wherein, _Rx is the equivalent resistance of the mixed solution to be tested, and _Cx is the equivalent capacitance of the mixed solution to be tested.

The dual-frequency phase-sensitive demodulation crude oil physical parameter measurement device described in the present invention is applied to the oil-water two-phase flow measurement system containing conductive water phase. The resistance and capacitance information can be obtained through the digital demodulation signal, and the change of conductivity is reflected by the voltage change caused by the resistance value in the oil-water two-phase flow obtained by demodulation, and the change of water content is reflected by the voltage change caused by the capacitance value in the oil-water two-phase flow obtained by demodulation. At the same time, a gear switching circuit is adopted to achieve a large range span of water content and mineralization, thereby improving its scope of application and applicable occasions. A temperature sensor is used to collect the temperature of the mixed liquid to be measured to achieve temperature compensation, and the influence of temperature on the measurement of physical parameters is taken into account, thereby further improving the accuracy of measurement.

Specific implementation and error verification:

The resistance and capacitance to be measured are measured using a 6.5-digit digital multimeter DM3068 as the measurement standard. The measurement data and errors are as follows:

Table 1 RC measurement results and errors

As can be seen from the table above, only in terms of resistance and capacitance measurement, it can meet the error requirements during design, verifying the reliability and accuracy of the measurement method, and highlighting the system's ability to measure weak capacitance.

In order to verify the measurement accuracy, two-phase flow measurement liquids with different conductivity and water content were prepared, and the existing water content measuring instrument and crude oil conductivity measuring instrument were used as the verification standards for water content and conductivity measurement. Conductivity calibration liquids with conductivity of 1.288us/m, 11.13ms/m, 14.13ms/m, 14.6ms/m, and 128.8ms/m were used as the conductive water phase, 10# white oil was used as the oil phase, 21 groups of oil-water two-phase flows with different water content and conductivity were prepared, and the corresponding 0.8% ratio of demulsifier Span80 was added, and the high-speed shearing machine was used to stir at 6000rad/min for 10 minutes, and the measurement was carried out until the measuring liquid was in a uniform state.

The measurement results and actual measurement data are shown in the following table:

Table 2 Water content and conductivity measurement results and errors

Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims (10)

1. The system for measuring physical property parameters of the dual-frequency phase-sensitive demodulation crude oil is characterized by comprising the following components: the device comprises a signal generation module (1), two measuring electrodes (2), a gear switching circuit (3), an I/V conversion operational amplifier (4), a temperature sensor (5), an ADC sampling circuit (6), a main controller (7) and an upper computer (8);

the signal output end of the signal generation module (1) is connected with a measuring electrode (2), a double-frequency alternating current superposition signal is loaded to the measuring electrode (2), the other measuring electrode (2) is connected with the signal input end of the I/V conversion operational amplifier (4), and the double-frequency alternating current superposition signal is superposition of two signals with different frequencies and amplitudes;

one ends of the two measuring electrodes (2) are arranged in the mixed liquid to be measured, and a gap is reserved between the two measuring electrodes (2);

the I/V conversion operational amplifier (4) is connected with the gear switching circuit (3) in parallel;

the signal output end of the I/V conversion operational amplifier (4) is connected with the signal input end of the ADC sampling circuit (6), and the temperature sensor (5) is used for collecting the temperature of the mixed liquid to be tested and transmitting the collected temperature signal to the signal input end of the ADC sampling circuit (6); the signal output end of the ADC sampling circuit (6) is connected with the signal input end of the main controller (7), and the signal input end of the main controller (7) is also connected with the signal output end of the signal generation module (1);

the main controller (7) multiplies the signal output by the signal generating module (1) and the signal output by the ADC sampling circuit (6) and then carries out low-pass filtering to obtain two direct-current voltage signals, the two direct-current voltage signals are uploaded to the upper computer (8), the upper computer (8) obtains equivalent resistance-capacitance information of the mixed solution to be detected by utilizing the two direct-current voltage signals, and calculates and obtains the water content and conductivity information of the mixed solution to be detected by utilizing BP neural network algorithm and combining the equivalent resistance-capacitance information, the gear of the gear switching circuit (3) and the temperature of the liquid to be detected.

2. The dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement system according to claim 1, wherein the signal generation module (1) comprises a signal generator (101), two signal amplifiers (102), two low-pass filters (103) and an inverse adder (104);

the signal generation module (1) outputs two sine excitation signals, the two sine excitation signals are amplified by the signal amplifier (102) and then are respectively input into the two low-pass filters (103), the two low-pass filters (103) respectively carry out low-pass filtering on the two amplified sine excitation signals, the two signals after the low-pass filtering are simultaneously input into the reverse adder (104), and the reverse adder (104) carries out reverse addition on the two signals after the low-pass filtering and outputs a double-frequency alternating current superposition signal.

3. The dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement system according to claim 1 or 2, wherein the main controller (7) comprises two signal processing circuits, each signal processing circuit comprises a digital multiplier and a low-pass filter, the two digital multipliers respectively receive the output signal of the ADC sampling circuit (6) and the output signal of the signal generation module (1), the two digital multipliers respectively multiply the received signals with corresponding reference signals and then send the multiplied signals to the corresponding low-pass filters, and the two low-pass filters respectively low-pass filter the received signals to obtain two direct-current voltage signals and send the two direct-current voltage signals to the upper computer (8).

4. The dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement system according to claim 1 or 2, wherein two measurement electrodes (2) are coaxially arranged in two cylinders, one measurement electrode is sleeved outside the other measurement electrode, the measurement electrode positioned on the outer side is of a hollow cylindrical structure, and the radius of the measurement electrode positioned on the inner side is smaller than that of the outer measurement electrode.

5. The dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement system according to claim 1 or 2, wherein the gear switching circuit comprises a relay and a plurality of feedback resistors with different resistance values, and the relay is used for controlling the resistance value of the feedback resistor connected in parallel with the I/V conversion operational amplifier (4).

6. The method for measuring the physical property parameters of the double-frequency phase-sensitive demodulation crude oil is realized based on the system for measuring the physical property parameters of the double-frequency phase-sensitive demodulation crude oil according to any one of claims 1 to 5, and is characterized by comprising the following specific steps:

step one, arranging two measuring electrodes (2) in mixed liquid to be measured, wherein a gap is arranged between the two measuring electrodes (2);

step two, outputting two paths of sine excitation signals by using a signal generator (101), amplifying the two paths of sine excitation signals, carrying out low-pass filtering, and then reversely adding to obtain a double-frequency alternating current superposition signal;

transmitting the double-frequency alternating current superposition signal to one measuring electrode (2), connecting the other measuring electrode (2) with an I/V conversion operational amplifier (4), transmitting the double-frequency alternating current superposition signal of the mixed solution to be tested to the I/V conversion operational amplifier, and sampling the temperature signal of the mixed solution to be tested and the output signal of the I/V conversion operational amplifier by adopting an ADC sampling circuit (6);

step four, multiplying the signal output by the ADC sampling circuit (6) and the signal output by the signal generating module (1) by the main controller (7) by two digital multipliers respectively, and then performing low-pass filtering to obtain two direct-current voltage signals;

and fifthly, acquiring equivalent resistance-capacitance information of the mixed solution to be detected by using the two direct-current voltage signals and acquiring the water content and conductivity information of the mixed solution to be detected by using a BP neural network algorithm and combining the equivalent resistance-capacitance information, the gear of the gear switching circuit (3) and the temperature of the liquid to be detected.

7. The method for measuring physical properties parameters of dual-frequency phase-sensitive demodulation crude oil according to claim 6, wherein in the first step, the equivalent resistance-capacitance expression of the two electrodes (2) is:

in sigma _m Is the conductivity of the oil-water mixture; epsilon _o Is vacuum dielectric constant; epsilon _m Is the equivalent dielectric constant of the oil-water two-phase flow; r is the inner diameter of the outer electrode; r is the outside of the inner electrode; l is the electrode length of the sensor, R _x Is the equivalent resistance of the mixed solution to be measured, C _x The equivalent capacitance of the mixed solution to be measured;

the equivalent dielectric constant of the oil-water two-phase flow is as follows:

wherein ε _o Epsilon is the relative permittivity of the oil phase _w The water is water with a dielectric constant, and alpha is the water content of the two-phase flow;

the deduction is carried out:

8. the method for measuring physical properties of crude oil by double frequency phase sensitive demodulation according to claim 6 or 7, wherein in the first step, the signal generator (101) outputs two paths of sine excitation signals as follows:

wherein A is ₁ 、A ₂ Respectively are provided withFor the signal amplitude at two frequencies,

for phase angle, k of signal ₁ 、k ₂ Angular frequency, omega is angular velocity, V of two paths of sine excitation signals respectively ₁ 、V ₂ Two paths of sine excitation signals are respectively adopted, and t is time.

9. The method for measuring physical properties parameters of dual-frequency phase-sensitive demodulation crude oil according to claim 8, wherein the signals output by the ADC sampling circuit (6) are:

wherein V is _O For the ADC output signal, N is 0-N-1, N is the number of sampling points; r is R _f Is the feedback resistance of the I/V conversion operational amplifier.

10. The method for measuring physical properties of dual-frequency phase-sensitive demodulated crude oil according to claim 9, wherein in the fourth step, two direct-current voltage signals are:

wherein V is _o ' _C Is a capacitor direct current voltage signal, V _o ' _R Is a resistive direct current voltage signal.

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