CN116106373A - Dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement system and method - Google Patents
Dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement system and method Download PDFInfo
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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
Technical Field
The invention relates to the technical field of sensors and detection.
Background
At present, the crude oil is extracted mainly by adopting a high-pressure water injection method, the method leads to the excessive water content of the extracted crude oil, the increase of the water content can lead to the increase of the capacity of a petroleum transportation pipeline, and a large amount of resources are wasted. And also affects subsequent treatments of the petroleum such as distillation, catalytic cracking, etc. In addition, inorganic salt components exist in the crude oil water phase, and the inorganic salt components cause great harm to subsequent storage and transportation, refining processing, oil quality and equipment maintenance. Therefore, accurate measurement of the water content and the conductivity of the extracted crude oil is a key task in the field, and accurate measurement of the water content and the conductivity is of great significance to quality evaluation and extraction planning of oil fields.
The capacitance method is a common method for measuring the water content and the mineralization degree of crude oil, has the advantages of small mechanical loss, simple structure, stability, reliability and the like, but has the problem that the measurement error is extremely large or cannot be measured at all when the crude oil is in a medium-high water content state or in a medium-high salt content state, and the data linear fitting is mostly adopted when the measurement data is processed at present, and the error is further increased due to the fact that the equivalent dielectric constant of the two-phase flow is the error of an empirical formula. Meanwhile, no equipment capable of simultaneously measuring the water content and the conductivity of crude oil on line exists in the market at present. In the prior art, a C/V conversion chip is generally adopted in measurement, and the capacitance in the equivalent model is measured as accurately as possible by a charge-discharge method and an alternating current excitation method. In the aspect of high water content measurement, an insulating layer is mainly smeared on the inner side of an electrode to solve the measurement problem in a medium-high water content or medium-high salt content state, for example, the application publication number is CN109596675A, the three-electrode type crude oil water content sensor measuring device is named, a fixed single-frequency alternating current excitation method is adopted, an alternating current sinusoidal signal outputs a signal containing a water content signal through an inverting amplifying circuit formed by a single feedback resistor, and the signal is sent to a singlechip for processing through a signal processing module. The invention has the following defects: because the dielectric constant of the insulating material is smaller, the equivalent capacitance of the sensor is inevitably reduced, the measurement difficulty is increased, and the aging of the insulating layer can bring about measurement errors; in addition, the single feedback resistance can limit the measurement range, and the measurement can be disabled when the water content change range is large; meanwhile, the single frequency can only be suitable for measuring the water content detection, and the crude oil residue parameters cannot be measured. In the paper of a crude oil high water content measuring method based on a capacitance method, an equivalent capacitance is measured by adopting a charging and discharging method, temperature is measured and compensated by a temperature sensor, and measurement information is sent into a singlechip for processing to obtain water content parameters. In terms of data processing, the method performs secondary linear fitting on the basis of primary linear fitting so as to improve measurement accuracy. The invention has the following defects: the charge-discharge method does not have the capability of high-resolution measurement in the aspect of weak capacitance measurement, so that the measurement accuracy is reduced. In addition, the capacitance value and the equivalent dielectric constant are in a linear relation, but the dielectric constants of the phases of the two-phase flow have instability, so that the water content is linearly fitted by the equivalent dielectric constants, and the accuracy is inherently limited. And as another research and development of a novel remote online detection system for the water content of crude oil, the detection system designed in the paper adopts a flat electrode capacitance sensor, wherein a CAV444 chip is adopted for C/V conversion, and information is directly collected and sent into a stm32 singlechip for processing and is displayed through an upper computer. The disadvantage of this design is that: the CAV444 chip has a measurement range of 10 pf-10 nf, so that the CAV444 chip can lose measurement capability under the condition of low water content, and meanwhile, the measurement principle of the charge-discharge method of the chip can not be used under the condition of high water content.
Disclosure of Invention
The invention aims to solve the problem of poor accuracy in the existing crude oil water content and mineralization degree measurement process, and provides a double-frequency phase-sensitive demodulation crude oil physical property parameter measurement device.
The invention relates to a dual-frequency phase-sensitive demodulation crude oil physical property parameter measurement system, which comprises: the device 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 an upper computer;
the signal output end of the signal generation module is connected with a measuring electrode, a double-frequency alternating current superposition signal is loaded to the measuring electrode, the other measuring electrode is connected with the signal input end of the I/V conversion operational amplifier, 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 are arranged in the mixed liquid to be measured, and a gap is reserved between the two measuring electrodes;
the I/V conversion operational amplifier is connected with the gear switching circuit in parallel;
the signal output end of the I/V conversion operational amplifier is connected with the signal input end of the ADC sampling circuit, and the temperature sensor 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;
the signal output end of the ADC sampling circuit is connected with the signal input end of the main controller, and the signal input end of the main controller is also connected with the signal output end of the signal generation module;
the main controller multiplies the signal output by the signal generating module and the signal output by the ADC sampling circuit 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, the upper computer 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 and the temperature of the liquid to be detected.
Further, in the present invention, the signal generating module includes a signal generator, two signal amplifiers, two low-pass filters and an inverse adder;
the signal generation module outputs two sine excitation signals, the two sine excitation signals are amplified by the signal amplifier and then are respectively input into the two low-pass filters, the two low-pass filters 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, and the reverse adder carries out reverse addition on the two signals after the low-pass filtering and outputs a double-frequency alternating current superposition signal.
Further, in the invention, the main controller comprises two paths of signal processing circuits, each path of signal processing circuit comprises a digital multiplier and a low-pass filter, the two digital multipliers respectively receive the output signals of the ADC sampling circuit and the output signals of the signal generating module, 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.
Further, in the invention, the two measuring electrodes are coaxially arranged in two cylinders, wherein one measuring electrode is sleeved outside the other measuring electrode, the measuring electrode positioned at the outer side is of a hollow cylindrical structure, and the radius of the measuring electrode positioned at the inner side is smaller than that of the measuring electrode positioned at the outer side.
Further, in the invention, the gear switching circuit comprises a relay and a plurality of feedback resistors with different resistance values, wherein the relay is used for controlling the resistance value of the feedback resistor connected with the I/V conversion operational amplifier in parallel.
The method for measuring the physical property parameters of the dual-frequency phase-sensitive demodulation crude oil is realized based on a dual-frequency phase-sensitive demodulation crude oil physical property parameter measuring system and comprises the following specific steps of:
step one, arranging two measuring electrodes in mixed liquid to be measured, wherein a gap is arranged between the two measuring electrodes;
step two, outputting two paths of sine excitation signals by using a signal generator, 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;
step three, transmitting the double-frequency alternating current superposition signal to one measuring electrode, connecting the other measuring electrode with an I/V conversion operational amplifier, 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;
step four, multiplying the signal output by the ADC sampling circuit and the signal output by the signal generating module by the main controller by the corresponding reference signal by adopting 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 by using an upper computer, 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 and the temperature of the liquid to be detected.
Further, in the first step of the present invention, the equivalent resistance-capacitance expression of the two measuring electrodes 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;
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:
further, in the first step of the present invention, the signal generator outputs two paths of sinusoidal excitation signals as follows:
wherein A is 1 、A 2 The signal amplitudes at the two frequencies are respectively,
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.
Further, in the second step of the present invention, the dual-frequency ac superimposed signal is:
V i ＝V 1 +V 2 ＝A 1 sin(k 1 ωt)+A 2 sin(k 2 ωt)
wherein V is i Is a double-frequency alternating current superposition signal.
Further, in the present invention, the signal output by the ADC sampling circuit is:
wherein V is O For the ADC output signal, N is 0-N-1, N is the number of sampling points; r is R X Is the equivalent resistance of the mixed solution to be measured, C X R is the equivalent capacitance of the mixed solution to be measured f Is the feedback resistance of the I/V conversion operational amplifier.
Further, in the fourth step of the present invention, the reference signals of the two signal digital multipliers are:
wherein V is fR (n) is a resistive excitation reference signal, V fC And (n) is a capacitively stimulated reference signal.
In the fourth step of the present invention, the signals obtained by multiplying the signals output by the ADC sampling circuit and the signals output by the signal generating module by the main controller with the corresponding reference signals by using two digital multipliers are:
wherein V is OR (n) is a capacitor output voltage signal, V Oc And (n) is a resistor output voltage signal.
Further, in the fourth step of the present invention, the two dc 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.
Further, in the fifth step of the present invention, the obtained equivalent resistance-capacitance information of the mixed solution to be measured is:
wherein R is X The equivalent resistance to be measured. C (C) X Is the equivalent capacitance to be measured.
The device for measuring the physical property parameters of the dual-frequency phase-sensitive demodulated crude oil is applied to a system for measuring the oil-water two-phase flow containing the conductive water phase. The 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, and the change of water content is reflected through voltage change caused by the demodulation of the capacitance value in the obtained oil-water two-phase flow. Meanwhile, a gear switching circuit is adopted, so that the wide-range span of the water content and the mineralization degree is realized, and the application range and the application occasion are improved. The temperature sensor is adopted to collect the temperature of the mixed liquid to be measured, so that temperature compensation is realized, and the influence of the temperature on the measurement of physical parameters is considered, wherein the measurement accuracy is further improved.
Drawings
FIG. 1 is a block diagram of a system for measuring physical properties parameters of dual-frequency phase-sensitive demodulation crude oil according to the invention;
FIG. 2 is a block diagram of a system for measuring physical properties of a dual-frequency phase-sensitive demodulated crude oil according to an embodiment;
FIG. 3 is a schematic diagram of an equivalent model of an oil-water two-phase flow;
FIG. 4 is a graph of sensitivity of the outer electrode at different radii, where D represents the outer electrode radius;
FIG. 5 is a graph of sensitivity of the inner electrode at different radii, where d represents the inner electrode radius;
FIG. 6 is a graph of sensitivity for different lengths of electrodes; in the figure, L represents the length of the electrode;
FIG. 7 is a gear control flow chart;
FIG. 8 is a graph of conductivity measurement error;
FIG. 9 is a graph of water cut measurement error;
FIG. 10 is a graph of actual measured moisture content versus time;
fig. 11 is a graph of actual measured conductivity versus time.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The first embodiment is as follows: the following describes a system for measuring physical properties of a dual-frequency phase-sensitive demodulated crude oil according to the present embodiment with reference to fig. 1 and 2, including: 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 one measuring electrode 2, a double-frequency alternating current superposition signal is loaded to the one 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, 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.
Further, in the present 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 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 to the two low-pass filters 103, the two low-pass filters 103 respectively low-pass filter the two amplified sine excitation signals, the two signals after the low-pass filtering are simultaneously input to the inverse adder 104, and the inverse adder 104 reversely adds the two signals after the low-pass filtering and outputs a double-frequency alternating current superposition signal.
Further, in this embodiment, the main controller 7 includes two signal processing circuits, each of which 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 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 dc voltage signals and send the two dc voltage signals to the host computer 8.
Further, in this embodiment, the two measuring electrodes 2 are coaxially arranged in two columns, wherein one measuring electrode is sleeved on the outer side of the other measuring electrode, the measuring electrode located on the outer side is in a hollow cylindrical structure, the radius of the measuring electrode located on the inner side is smaller than that of the measuring electrode located on the outer side, and the measuring sensitivity diagrams of the measuring electrode located on the inner side and the measuring electrode located on the outer side under different geometric dimensions are shown in fig. 4 to 6.
Further, in the present embodiment, the shift switching circuit includes a relay for controlling the resistance value of a feedback resistor connected in parallel with the I/V conversion operational amplifier 4, and a plurality of feedback resistors of different resistance values.
And (3) carrying out equivalent resistance-capacitance calculation under the condition that the water content is 0-40% and the conductivity is 0-100 ms/m. The equivalent capacitance is about 13.96pf to 122.26pf and corresponds to 20k omega to 200 k omega, so that the 6-gear feedback resistance switching circuit is designed to have resistance feedback resistances of 500 k omega, 1.5k omega, 2.2k omega, 3.48k omega, 5k omega and 10k omega respectively, so that the equivalent capacitance of 27.5pf to 300pf and the equivalent resistance measurement requirement of 200 omega to 20k omega are met. In the present embodiment, fig. 7 is a specific process of controlling the shift switching circuit, and a reasonable range of the resistor and the capacitor is between the set maximum value and the set minimum value. In order to determine a measurement reference, the feedback resistor and the resistance-capacitance to be measured are manually matched to obtain the output when the impedance and the capacitance are the same as the feedback resistor in 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. The method is convenient for the control of the subsequent gear, the reasonable range of the impedance and capacitance output value setting is 140-560, 180-720 respectively, namely the resistance to be measured is 0.5-2 times of the feedback resistance. In this case, the maximum difference between the impedance and the capacitive reactance is 4 times, and the error is 1% at the maximum, so as to meet the requirements of the apparatus, as shown in fig. 8 to 11.
The method for measuring the physical property parameters of the dual-frequency phase-sensitive demodulation crude oil is realized based on a dual-frequency phase-sensitive demodulation crude oil physical property parameter measuring system and comprises the following specific steps of:
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;
step three, transmitting the double-frequency alternating current superposition signal to one measuring electrode 2, wherein the other measuring electrode 2 is connected with the signal input end of the 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, the main controller 7 of the main controller adopts two digital multipliers to 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 respectively, and then carries out 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.
Further, in the present embodiment, in the first step, the equivalent resistance-capacitance expression of the two measurement 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 outer diameter 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:
further, in the present embodiment, in the first step, the signal generator 101 outputs two paths of sinusoidal excitation signals as follows:
wherein A is 1 、A 2 The signal amplitudes at the two frequencies are respectively,
for phase angle, k of signal 1 、k 2 The angular frequencies of the two paths of sine excitation signals are respectively, omega is the angular velocity,V 1 、V 2 two paths of sine excitation signals are respectively adopted, and t is time.
Further, in the second embodiment, the dual-frequency ac superimposed signal is:
V i ＝V 1 +V 2 ＝A 1 sin(k 1 ωt)+A 2 sin(k 2 ωt)
wherein V is i Is a double-frequency alternating current superposition signal.
Further, in the present embodiment, the signal output from the ADC sampling circuit 6 is:
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.
Further, in the fourth embodiment, the reference signals of the two signal digital multipliers are:
wherein V is fR (n) is a resistive excitation reference signal, V fC And (n) is a capacitively stimulated reference signal.
Further, in the fourth embodiment, in the step, the signals obtained by multiplying the signals output by the ADC sampling circuit 6 and the signals output by the signal generating module 1 by the two digital multipliers respectively by the main controller 7 and the corresponding reference signals are:
wherein V is OR (n) is a capacitor output voltage signal, V Oc And (n) is a resistor output voltage signal.
Further, in the fourth embodiment, the two dc 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.
Further, in the present embodiment, referring to fig. 3, in the fifth embodiment, the obtained equivalent resistance-capacitance information of the mixed solution to be tested is:
wherein R is x Is the equivalent resistance of the mixed solution to be measured, C x Is the equivalent capacitance of the mixed liquid to be measured.
The device for measuring the physical property parameters of the dual-frequency phase-sensitive demodulated crude oil is applied to a system for measuring the oil-water two-phase flow containing the conductive water phase. The 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, and the change of water content is reflected through voltage change caused by the demodulation of the capacitance value in the obtained oil-water two-phase flow. Meanwhile, a gear switching circuit is adopted, so that the wide-range span of the water content and the mineralization degree is realized, and the application range and the application occasion are improved. The temperature sensor is adopted to collect the temperature of the mixed liquid to be measured, so that temperature compensation is realized, the influence of the temperature on the measurement of physical parameters is considered, and the measurement accuracy is further improved.
Specific embodiments and error verification:
the resistance-capacitance to be measured adopts a 6-bit half-digital multimeter DM3068 as a measurement standard, and the measurement data and the error are as follows:
TABLE 1 resistance-capacitance measurement results and errors
As can be seen from the table, the system can meet the error requirement in design only by resistance-capacitance measurement, verify the reliability and accuracy of the measurement method, and simultaneously highlight the measurement capability of the system in weak capacitance
In order to verify the measurement accuracy, two-phase flow measuring liquids with different conductivities and water contents are proportioned, and the water content and the conductivity measuring standard are verified by adopting the existing water content measuring instrument and the crude oil conductivity measuring instrument as verification standards respectively. The conductivity calibration solutions with the conductivities of 1.288us/m, 11.13ms/m, 14.13ms/m, 14.6ms/m and 128.8ms/m are respectively adopted as conductive water phases, 10# white oil is adopted as an oil phase, 21 groups of two-phase flows with different water contents and conductivity oil-water are proportioned, a demulsifier Span80 with the corresponding proportion of 0.8% is added, the mixture is stirred for 10min at 6000rad/min by a high-speed shearing machine, and the liquid to be measured is in a uniform state for measurement.
The measurement results and actual measurement data are shown in the following table:
TABLE 2 Water content and conductivity measurements and errors
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative 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 different dependent claims and the features described herein may be combined in ways other than as described in the original claims. It is also to be understood that features described in connection with separate 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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