阅读说明：本技术 基于连续相导电特性补偿的油气水三相流持气率测量方法 (Oil-gas-water three-phase flow gas holdup measuring method based on continuous phase conductive characteristic compensation ) 是由 翟路生 王雨青 杨杰 金宁德 于 2020-11-26 设计创作，主要内容包括：本发明提供一种基于连续相导电特性补偿的油气水三相流持气率测量方法,测量管道为竖直向上管道,所述的三相流为油气水三相流,所采用的传感器为电导网格传感器和分布式同轴电导传感器；所述的电导网格传感器包括激励电极和接收电极,电导网格传感器采用循环激励模式,当完成一次循环激励后,电导网格传感器输出一帧数据,对应油气水三相流中气相分布的一幅图像。分布式同轴电导传感器包括三个同轴电导传感器；三个同轴电导传感器均匀地安装在测量管道同一个径向截面的周围,每个同轴电导传感器的前端设置有液体延拓区,该液体延拓区被设计为斜向上,与测量管道径向截面呈30°夹角。(The invention provides an oil-gas-water three-phase flow holdup gas rate measuring method based on continuous phase conductive characteristic compensation, wherein a measuring pipeline is a vertically upward pipeline, three-phase flow is oil-gas-water three-phase flow, and adopted sensors are a conductive grid sensor and a distributed coaxial conductive sensor; the electric conduction grid sensor comprises an exciting electrode and a receiving electrode, the electric conduction grid sensor adopts a circulation exciting mode, and after one circulation exciting is completed, the electric conduction grid sensor outputs one frame of data corresponding to one image of gas phase distribution in the oil-gas-water three-phase flow. The distributed coaxial conductivity sensor comprises three coaxial conductivity sensors; the three coaxial conductivity sensors are uniformly arranged around the same radial section of the measuring pipeline, and the front end of each coaxial conductivity sensor is provided with a liquid extension area which is designed to be inclined upwards and form an included angle of 30 degrees with the radial section of the measuring pipeline.)

1. A gas-oil-water three-phase flow holdup gas rate measuring method based on continuous phase conductive characteristic compensation is characterized in that a measuring pipeline is a vertical upward measuring pipeline, three-phase flow is oil-gas-water three-phase flow, one sensor is a conductive grid sensor, and the other sensor is a distributed coaxial conductive sensor; the conductivity grid sensor comprises excitation electrodes and receiving electrodes, wherein the excitation electrodes are parallel to each other and are positioned on the same radial section of the measuring pipeline, the receiving electrodes are parallel to each other and are positioned on the other radial section of the measuring pipeline, the conductivity grid sensor adopts a circulating excitation mode, and after one-time circulating excitation is completed, the conductivity grid sensor outputs one frame of data corresponding to one image of gas phase distribution in the oil-gas-water three-phase flow. It is characterized in that the preparation method is characterized in that,

the distributed coaxial conductivity sensor is used for dynamically monitoring the change of continuous phase conductivity characteristics and realizing the real-time correction of the imaging result of the conductivity grid sensor, and comprises three coaxial conductivity sensors; the three coaxial conductivity sensors are uniformly arranged around the same radial section of the measuring pipeline, and the front end of each coaxial conductivity sensor is provided with a liquid continuation area which is designed to be obliquely upward and form an included angle of 30 degrees with the radial section of the measuring pipeline; the method for measuring the gas holdup rate of oil-gas-water three-phase flow by using the conductive grid sensor and the coaxial conductive sensor comprises the following steps:

1) aiming at oil-gas-water three-phase flow, obtaining output signal V of electric conduction grid sensor_m,1,V_m,2,…,V_m,10And a marking signal V_Mark(ii) a For data of the k frame, at V_MarkCalculating the jth receiving electrode signal V in the time interval between two adjacent rising edges_m,j(k) The extreme difference of (D) is marked as V_m(i, j, k), wherein i is the excitation electrode number;

2) filling air into the measuring pipeline, and measuring output signal V of the electric conductance grid sensor_g,1,V_g,2,…,V_g,10(ii) a To V_g,1,V_g,2,…,V_g,10By performing the treatment, a very different V can be obtained_g(i, j, k); calculating the range V of different data frames_gAverage value V of (i, j, k)_g(i,j)；

3) Filling the measuring pipeline with water phase, and measuring output signal V of the electric conductance grid sensor_w,1,V_w,2,…,V_w,10(ii) a To V_g,1,V_g,2,…,V_g,10Processing to obtain range difference signal V_w(i, j, k), calculating the polar difference V under different data frames_wAverage value V of (i, j, k)_w(i,j)；

4) From the results in steps 1), 2) and 3), on signal V_m(i, j, k) carrying out normalization processing to obtain normalized signalWherein N is the number of frames;

5) obtaining a measurement signal U of a distributed coaxial conductivity sensor aiming at oil-gas-water three-phase flow_m,1，U_m,2，U_m,3For the k frame data, the average value U of the measurement signals of No. 1, No. 2 and No. 3 coaxial conductivity sensors is calculated_m,p(k)；

6) Filling air into the measuring pipeline to obtain the distributed coaxial conductivity sensorMeasurement signal U_g,1，U_g,2，U_g,3(ii) a Calculating the average value U of the measurement signal of the No. p coaxial conductivity sensor_g,p(k) (ii) a Then, calculating U under different data frames_g,p(k) Average value of U_g,p；

7) Filling the measuring pipeline with water phase to obtain a measuring signal U of the distributed coaxial conductivity sensor_w,1，U_w,2，U_w,3(ii) a Calculating the average value U of the measurement signal of the No. p coaxial conductivity sensor_w,p(k) Then calculating U under different data frames_w,p(k) Average value of U_w,p；

8) For the normalized signal V obtained in step 4)_N(i, j, k) performing a correction: calculating the conductivity correction coefficient of a single coaxial conductivity sensor to the continuous phase in the oil-gas-water three-phase flowCalculating an average value delta (k) of the three conductivity correction coefficients; obtaining a normalized signal V_N(i, j, k) correction results

9) Obtaining the measurement result of the gas holdup of the oil-gas-water three-phase flow of the electric conduction grid sensor according to the correction result of the step 8)

10) And (3) processing signals aiming at the abnormal condition of bubble invasion in the extended area of the distributed coaxial conductivity sensor: calculating the average value U of the measuring signals of the coaxial conductivity sensors under each frame of data_m,p(k) P is 1,2, 3; k is 1,2, …, N, and its standard deviation σ_p(ii) a Judging the U corresponding to the kth frame data_m,p(k) Whether there is an abnormality, ifIf it is, then U_m,p(k) No exception, if the above formula does not hold, then U_m,p(k) There is an abnormality in whichRepresents U_m,p(k) Average value of (d); when U is turned_m,p(k) When there is an abnormality, let U_m,p(k)＝U_m,p(k'), wherein U_m,p(k') is with U_m,p(k) Nearest neighbor non-anomalous data, U_m,p(k ') the number of frames corresponding to k';

11) when abnormal conditions occur, the normalized signal V is compared_N(i, j, k) performing a correction: calculating the conductivity correction factor in the abnormal situation according to step 8)Calculating a normalized signal V_N(i, j, k) correction results

12) Obtaining the measurement result of the oil-gas-water three-phase flow gas holdup rate of the electric conduction grid sensor under the abnormal condition according to the result of the step 11)

Technical Field

The invention relates to an oil-gas-water three-phase flow gas holdup measuring method based on continuous phase conductive characteristic compensation.

Background

The flow phenomenon of oil-gas-water three-phase flow widely exists in the production process of petroleum, chemical industry and other important industries. The accurate measurement of the oil-gas-water gas holdup rate has important significance for production safety and economic benefit improvement. However, most multiphase flow measurement systems are designed based on a single measurement mode, such as dielectric constant or conductivity, which has significant limitations for complex oil, gas, and water three-phase flow measurements.

At present, the method widely used for measuring the flow parameters of the three-phase flow is bimodal measurement, namely two physical properties of the three-phase flow are measured simultaneously to distinguish three different media. Qiu et al (FlowMeasurement & Instrumentation,2007,18: 247-. However, this type of system is not suitable for measuring multiphase mixed fluids with a strongly evolving structure, since the two sensors are placed at different locations of the pipe. Sun et al (Measurement,2015,6: 150-. In addition, because ECT itself is used as a soft measurement scheme, higher spatial resolution cannot be achieved, and its use also has certain limitations.

The conductive grid sensor as an emerging fluid visualization technology has certain advantages in the aspect of researching flow parameters of complex multiphase flow. The sensor was originally proposed by Prasser et al (FlowMeasurement & Instrumentation,1998,9(2): 111-. The conductivity grid sensor is sensitive to the change of the conductivity at the intersection point of the two layers of electrodes, so that the measurement of a gas-liquid or oil-water two-phase flow structure and the local phase separation holding rate can be realized. Previous scholars have primarily utilized conductive grid sensors to measure flow parameters in two-phase flow. In recent years, researchers have applied two excitation signals of different frequencies to a grid sensor to achieve simultaneous measurement of resistance and capacitance at the intersection, but at present this approach is only applicable to simple testing of stratified flow of oil, gas and water three-phase flow under static experimental conditions (measurementcience & Technology,2015,26: 105302).

FIG. 1 is a schematic diagram of a typical gas-liquid two-phase flow and oil-gas-water three-phase flow pipeline radial cross-section phase distribution. According to the typical phase distribution of the gas-liquid two-phase flow shown in fig. 1(a), when only two media, namely gas and water, exist in the pipeline, the gas mainly exists in two forms: dispersed air bubbles and taylor bubbles of larger size, like bullets. Oil-gas-water three-phase flow can be divided into two types according to different continuous phases: firstly, water is a continuous phase (figure 1 (b)); secondly, the low oil content oil-water emulsion is a continuous phase (fig. 1 (c)). For the case of fig. 1(b), since the oil droplet size is much smaller than the spatial resolution of the grid sensor, the dispersed oil droplets do not affect the measurement of the gas holdup by the conductive grid sensor. For the case of fig. 1(c), when the oil-water emulsion is a continuous phase, the oil content may affect the conductivity of the continuous liquid phase, so that the conductive grid sensor cannot accurately measure the gas holdup, and an effective real-time monitoring means for the conductivity of the oil-water emulsion and an effective measurement response correction method for the grid sensor are required.

Disclosure of Invention

The invention provides an oil-gas-water three-phase flow gas holdup measuring method based on continuous phase conductive characteristic compensation. A combined measuring system of a conductivity grid sensor and a coaxial conductivity sensor is designed, the coaxial conductivity sensor adopts a special distributed non-invasive structure, and can monitor the conductivity of a continuous phase (oil-water emulsion) in an oil-gas-water three-phase flow in real time, so that the imaging result of the gas phase distribution in the oil-gas-water three-phase flow of the conductivity grid sensor is corrected, and the accurate gas holdup rate of the oil-gas-water three-phase flow is finally provided. The technical scheme is as follows:

a gas-oil-water three-phase flow holdup gas rate measuring method based on continuous phase conductive characteristic compensation is characterized in that a measuring pipeline is a vertical upward measuring pipeline, three-phase flow is oil-gas-water three-phase flow, one sensor is a conductive grid sensor, and the other sensor is a distributed coaxial conductive sensor; the conductivity grid sensor comprises excitation electrodes and receiving electrodes, wherein the excitation electrodes are parallel to each other and are positioned on the same radial section of the measuring pipeline, the receiving electrodes are parallel to each other and are positioned on the other radial section of the measuring pipeline, the conductivity grid sensor adopts a circulating excitation mode, and after one-time circulating excitation is completed, the conductivity grid sensor outputs one frame of data corresponding to one image of gas phase distribution in the oil-gas-water three-phase flow. It is characterized in that the preparation method is characterized in that,

the distributed coaxial conductivity sensor is used for dynamically monitoring the change of continuous phase conductivity characteristics and realizing the real-time correction of the imaging result of the conductivity grid sensor, and comprises three coaxial conductivity sensors; the three coaxial conductivity sensors are uniformly arranged around the same radial section of the measuring pipeline, and the front end of each coaxial conductivity sensor is provided with a liquid continuation area which is designed to be obliquely upward and form an included angle of 30 degrees with the radial section of the measuring pipeline; the method for measuring the gas holdup rate of oil-gas-water three-phase flow by using the conductive grid sensor and the coaxial conductive sensor comprises the following steps:

1) aiming at oil-gas-water three-phase flow, obtaining output signal V of electric conduction grid sensor_m,1,V_m,2,…,V_m,10And a marking signal V_Mark(ii) a For data of the k frame, at V_MarkCalculating the jth receiving electrode signal V in the time interval between two adjacent rising edges_m,j(k) The extreme difference of (D) is marked as V_m(i, j, k), wherein i is the excitation electrode number;

2) filling air into the measuring pipeline, and measuring output signal V of the electric conductance grid sensor_g,1,V_g,2,…,V_g,10(ii) a To V_g,1,V_g,2,…,V_g,10By performing the treatment, a very different V can be obtained_g(i, j, k); calculating the range V of different data frames_gAverage value V of (i, j, k)_g(i,j)；

3) Filling the measuring pipeline with water phase, and measuring output signal V of the electric conductance grid sensor_w,1,V_w,2,…,V_w,10(ii) a To V_g,1,V_g,2,…,V_g,10Processing to obtain range difference signal V_w(i, j, k), calculating the polar difference V under different data frames_wAverage value V of (i, j, k)_w(i,j)；

4) From the results in steps 1), 2) and 3), on signal V_m(i, j, k) carrying out normalization processing to obtain normalized signalWherein N is the number of frames;

5) obtaining a measurement signal U of a distributed coaxial conductivity sensor aiming at oil-gas-water three-phase flow_m,1，U_m,2，U_m,3For the k frame data, the average value U of the measurement signals of No. 1, No. 2 and No. 3 coaxial conductivity sensors is calculated_m,p(k)；

6) Filling air into the measuring pipeline to obtain a measuring signal U of the distributed coaxial conductivity sensor_g,1，U_g,2，U_g,3(ii) a Calculating the average value U of the measurement signal of the No. p coaxial conductivity sensor_g,p(k) (ii) a Then, calculating U under different data frames_g,p(k) Average value of U_g,p；

7) Filling the measuring pipeline with water phase to obtain a measuring signal U of the distributed coaxial conductivity sensor_w,1，U_w,2，U_w,3(ii) a Calculating the average value U of the measurement signal of the No. p coaxial conductivity sensor_w,p(k) Then calculating U under different data frames_w,p(k) Average value of U_w,p；

8) For the normalized signal V obtained in step 4)_N(i, j, k) performing a correction: calculating the conductivity correction coefficient of a single coaxial conductivity sensor to the continuous phase in the oil-gas-water three-phase flowCalculating an average value delta (k) of the three conductivity correction coefficients; obtaining a normalized signal V_N(i, j, k) correction results

9) Obtaining the measurement result of the gas holdup of the oil-gas-water three-phase flow of the electric conduction grid sensor according to the correction result of the step 8)

10) And (3) processing signals aiming at the abnormal condition of bubble invasion in the extended area of the distributed coaxial conductivity sensor: calculating the average value U of the measuring signals of the coaxial conductivity sensors under each frame of data_m,p(k),p＝1,2,3；k is 1,2, …, N, and its standard deviation σ_p(ii) a Judging the U corresponding to the kth frame data_m,p(k) Whether there is an abnormality, ifIf it is, then U_m,p(k) No exception, if the above formula does not hold, then U_m,p(k) There is an abnormality in whichRepresents U_m,p(k) Average value of (d); when U is turned_m,p(k) When there is an abnormality, let U_m,p(k)＝U_m,p(k'), wherein U_m,p(k') is with U_m,p(k) Nearest neighbor non-anomalous data, U_m,p(k ') the number of frames corresponding to k';

11) when abnormal conditions occur, the normalized signal V is compared_N(i, j, k) performing a correction: calculating the conductivity correction factor in the abnormal situation according to step 8)Calculating a normalized signal V_N(i, j, k) correction results

12) Obtaining the measurement result of the oil-gas-water three-phase flow gas holdup rate of the electric conduction grid sensor under the abnormal condition according to the result of the step 11)

Due to the adoption of the technical scheme, the invention has the following advantages:

(1) the invention provides a novel distributed non-invasive structure of a coaxial conductivity sensor, aiming at a flow structure of vertical oil-gas-water three-phase flow. Based on the distributed non-invasive structure, the coaxial conductivity sensor can monitor the change of the conductive property of the continuous phase in the oil-gas-water three-phase flow in real time.

(2) The invention provides a real-time correction method for a gas-phase distribution imaging result of a conductive grid sensor based on the continuous phase conductive characteristic of an oil-gas-water three-phase flow output by a coaxial conductive sensor, which can effectively improve the measurement precision of the conductive grid sensor on the gas holdup rate of the oil-gas-water three-phase flow.

(3) The invention provides a processing method for abnormal response signals of a distributed coaxial conductivity sensor, which solves the problem of measurement errors caused by bubbles entering a sensitive area of the sensor, and thus obtains a more accurate result of the gas holdup rate of oil-gas-water three-phase flow.

Drawings

FIG. 1 is a schematic view of the radial cross-section phase distribution of a vertical rising gas-liquid two-phase flow and a typical oil-gas-water three-phase flow pipeline

FIG. 2 is a schematic diagram of a gas holdup measurement sensing system for oil-gas-water three-phase flow: (a) a conductive grid sensor structure diagram;

(b) a front view and a side view of the coaxial conductivity sensor; (c) a piping installation schematic of a single coaxial conductivity sensor; (d) pipeline installation diagrams of three distributed coaxial conductivity sensors; (e) conductive grid sensor and pipeline installation diagram of coaxial conductive sensor

FIG. 3 is a schematic diagram of output signals of a conductivity grid sensor and distributed coaxial conductivity sensors

FIG. 4 is a flow chart of conductance grid sensor output signal processing

FIG. 5 is a flow chart of distributed coax conductance sensor output signal processing

Fig. 6 shows output signals of the oil-gas-water three-phase flow distributed coaxial conductivity sensor: (a) normal conditions; (b) abnormal situation

FIG. 7 is a flow chart of a process for measuring signals of a distributed coax conductivity sensor under abnormal conditions

FIG. 8 is a flow chart of measuring the gas holdup of oil-gas-water three-phase flow by the conductive grid sensor

FIG. 9 shows the three-dimensional imaging result (U) of the gas phase distribution in the three-phase flow of oil, gas and water by the conductive grid sensor_sg＝0.055m/s，U_sl＝1.179m/s)：(a)f_o0.05, uncorrected; (b) f. of_o0.05, correcting; (c) f. of_o0.15, uncorrected; (d) f. of_o0.15, correction

FIG. 10 is oil, gas and water of a conductivity grid sensorThree-phase flow gas holdup measurement (f)_o＝0.05)

The reference numerals are explained below:

1 a circular central excitation electrode; 2 an intermediate insulating material; 3 an outer annular receiving electrode; 4 a fluid continuation zone; 5, pipe wall; 6 vertical pipe central axis

Detailed Description

The invention is described in detail below with reference to the figures and examples. The invention comprises the following steps:

(1) the sensing system is designed as shown in fig. 2. The system includes a conductive grid sensor, a distributed coaxial conductivity sensor, and a measurement circuit. Grid sensor with excitation electrode (E)₁To E₁₀) And a receiving electrode (R)₁To R₁₀) Composition, as shown in FIG. 2 (a). All the excitation electrodes are parallel to each other and are positioned on the same radial section of the pipeline; the receiving electrodes are parallel to each other and are located at the other radial section of the pipeline. The sensor adopts a cyclic excitation mode, and only the ith excitation electrode E in a certain time period_iIs excited (connected to an excitation source), and the excitation electrode E can be measured_iAnd all receiving electrodes R_j(j ═ 1,2, …,10) fluid conductivity information at the intersection; when completing E in sequence₁To E₁₀When the electrodes are excited, the fluid conductivity information at all the intersection points on the radial section of the pipeline can be obtained.

The coaxial conductivity sensor is composed of a circular central exciting electrode, an intermediate insulating material and an outer annular receiving electrode, as shown in fig. 2 (b). In order to ensure that the change of the conductive characteristic of the continuous phase is obtained on the premise of no turbulent flow and no influence of taylor bubbles in the pipeline, a liquid extension area is designed in front of the coaxial conductivity sensor, as shown in fig. 2 (c). The extended zone is designed to be angled obliquely upwards at an angle of 30 ° to the radial cross-section of the pipe. The depth of the upper edge of the extension area embedded into the pipeline is 3.6 mm. When the continuous phase (oil-water emulsion) of the oil-gas-water three-phase flow enters the continuation zone, the amplitude of the output signal of the coaxial conductivity sensor can reflect the change of the conductive characteristic of the continuous phase. In order to ensure that the conductivity of the continuous phase at different positions is obtained, the coaxial conductivity sensors are distributed, and as shown in fig. 2(d), three coaxial conductivity sensors are uniformly distributed around the pipeline.

The positions of the conductive grid sensors and the coaxial conductive sensors mounted on the pipeline are shown in fig. 2 (e). For oil-gas-water three-phase flow in a pipeline, the output voltage signal V of the electric conduction grid sensor_m,1,V_m,2,…,V_m,10And a marking signal V_Mark(ii) a Output voltage signal U of distributed coaxial conductivity sensor_m,1、U_m,2、U_m,3And the voltage signals are simultaneously recorded on an upper computer through a data acquisition card.

(2) The conductance grid sensor and distributed coaxial conductance sensor output signals are shown in fig. 3. Marking signal V output by conductive grid sensor_MarkIs square wave and is used for indicating the electrode E₁,E₂,…,E₁₀The order of excitation (Zhai et al,2019, I2MTC, DOI:10.1109/I2 MTC.2019.8827063; Zhai et al,2020, DOI: 10.1109/I2MTC43012.2020.9129032). Marking signal V_MarkThe first rising edge of (D) represents E₁Is activated and the second rising edge represents E₂Is excited, and so on, and circulates back and forth. Marking signal V_MarkEvery ten rising edges of (a) correspond to one frame of data, and the number of frames can be represented by k. For the k frame data, the output signal of the conductance grid sensor is V_m,1(k),V_m,2(k),…,V_m,10(k) The output signal of the coaxial conductivity sensor is U_m,1(k)，U_m,2(k)，U_m,3(k)。

(3) For oil-gas-water three-phase flow, the electric conduction grid sensor outputs a signal V_m,1To V_m,10The processing is performed according to the flow shown in FIG. 4. First reading the marking signal V_MarkAnd retrieves its rising edge, the ith rising edge indicating that the ith actuation electrode is actuated at that time. Then, for the k frame data, at V_MarkCalculating the jth receiving electrode signal V in the time interval between two adjacent rising edges_m,j(k) The extreme difference of (D) is marked as V_m(i,j,k)。

(4) Filling the detection field of the conductive grid sensor with air, and outputting a signal V by the measuring circuit_g,1,V_g,2,…,V_g,10. Using the flow shown in FIG. 4 for V_g,1,V_g,2,…,V_g,10By performing the treatment, a very different V can be obtained_g(i, j, k). V under different data frames_gThe average of (i, j, k) can be expressed as:

filling the detection field of the conductivity grid sensor with water, and outputting a signal V by the measuring circuit_w,1,V_w,2,…,V_w,10. Using the flow shown in FIG. 4 for V_w,1,V_w,2,…,V_w,10By performing the treatment, a very different V can be obtained_w(i, j, k). V under different data frames_wThe average of (i, j, k) can be expressed as:

(5) to V_m(i, j, k) to obtain normalized signal V_N(i,j,k)：

(6) For oil-gas-water three-phase flow, the distributed coaxial conductivity sensor measures the signal U_m,1，U_m,2，U_m,3The process flow of (2) is shown in FIG. 5. First, a mark signal V is read_MarkAnd retrieving each rising edge thereof; then, for the k frame data, the average value of the p number coaxial conductance sensor measurement signals is calculated and recorded as U_m,p(k)

(7) Filling the coaxial conductive sensor with air in the detection field, and outputting signal U by the measuring circuit_g,1，U_g,2，U_g,3(ii) a Signal U is paired according to the flow shown in FIG. 5_g,1、U_g,2、U_g,3Processing to obtain the average value of the p-th coaxial conductivity sensor measurement signal, and recording the average value as U_g,p(k) In that respect Calculating U under different data frames_g,p(k) Average value of U_g,p。

Filling the coaxial conductivity sensor with water in the detection field, and outputting signal U from the measuring circuit_w,1，U_w,2，U_w,3(ii) a Signal U is paired according to the flow shown in FIG. 5_w,1、U_w,2、U_w,3Processing to obtain the average value of the p-th coaxial conductivity sensor measurement signal, and recording the average value as U_w,p(k) In that respect Calculating U under different data frames_w,_p(k) Average value of U_w,p。

(8) Calculating the conductivity correction coefficient delta of continuous phase in oil-gas-water three-phase flow_p(k)：

The average of the conductivity correction factors for the three in-line conductivity sensors can be expressed as:

(9) for the normalized signal V in equation (3)_N(i, j, k) corrected to give:

(10) oil-gas-water three-phase flow gas holdup measured by electric conduction grid sensorCan be expressed as:

(11) the invention carries out signal processing aiming at the abnormal condition that bubbles invade in the continuation area of the distributed coaxial conductivity sensor. Under normal conditions, the voltage signals obtained by the distributed coaxial conductivity sensor are stable, and the average value is related to the oil contentThe higher the oil content, the higher the average value of the voltage signal, as shown in fig. 6 (a). Wherein U is_sgAnd U_slRespectively representing the apparent flow rates of the gas phase and the continuous liquid phase, f_oThe content of the oil phase in the liquid phase is shown. When bubbles invade the extension area of the coaxial conductivity sensor (abnormal condition), the voltage signal has abnormal fluctuation. As shown in fig. 6(b), when a bubble enters the continuation region of the coaxial conductivity sensor 2, the response signal of the sensor fluctuates abnormally. When the abnormal response signal appears, the conductivity correction coefficient of the continuous phase in the oil-gas-water three-phase flow can generate errors.

The processing procedure of the distributed coaxial conductance sensor measurement signal for the above abnormal situation is shown in fig. 7. First, the average value U of the measurement signals of the coaxial conductivity sensors in each frame of data is calculated according to the flow shown in FIG. 5_m,p(k) (p-1, 2, 3; k-1, 2, …, N) and their standard deviations

If the following expression (9) is satisfied, U corresponding to the k-th frame data is described_m,p(k) No abnormality

WhereinRepresents U_m,p(k) Average value of (a). If equation (9) does not hold, U is indicated_m,p(k) And belongs to abnormal data. At this time, the order of:

U_m,p(k)＝U_m,p(k') (10)

wherein U is_m,p(k') is with U_m,p(k) Nearest neighbor non-anomalous data, U_m,pThe number of frames corresponding to (k ') is k'.

Substituting the formula (10) into the formula (4) and the formula (5) to obtain the conductivity correction coefficient when the abnormal condition occursBy usingFor the normalized signal V in equation (3)_N(i, j, k) corrected to give:

the oil-gas-water three-phase flow gas holdup rate when abnormal conditions occur can be obtained by using the formula (11)

The implementation process of the system for measuring the gas holdup of the oil-gas-water three-phase flow is described in the following with the accompanying drawings:

the flow of the conductivity grid sensor for measuring the gas holdup of oil-gas-water three-phase flow is shown in fig. 8, and the specific process is as follows:

(1) the conductivity grid sensor and the distributed coaxial conductivity sensor were mounted on a pipe with an internal diameter of 20mm in the relative spatial positions shown in fig. 2. The conductive grid sensor excitation electrodes and the receiving electrodes form a 10 x 10 grid. The diameter of the exciting electrode and the diameter of the receiving electrode are both 0.2 mm. The distance between the radial section of the pipeline where the excitation electrode is located and the radial section of the pipeline where the receiving electrode is located is 2 mm; the distance between two adjacent excitation electrodes is 2mm, and the distance between two adjacent receiving electrodes is 2 mm. The diameter of the central exciting electrode of the coaxial conductivity sensor is 1.5mm, the thickness of the middle insulating material is 0.5mm, and the thickness of the outer annular receiving electrode is 1 mm. The distributed coaxial conductivity sensor was mounted 2030mm from the inlet and the conductive grid sensor was mounted 2230mm from the inlet.

(2) And (5) carrying out a vertical oil-gas-water three-phase flow experiment. Gas phase apparent flow rate U in experiment_sgIn the range of 0.055 to 0.663

m/s, liquid phase (oil phase and water phase) mixed apparent flow rate U_slIn the range of 0.037 to 1.179m/s, the oil content f of the liquid phase_oRespectively accounting for 0%, 5%, 10% and 15%, and the specific experimental conditions are shown in Table 1. In the experimental process, under the oil content of a certain liquid phase, a scheme of fixing the gas phase apparent flow rate and gradually increasing the liquid phase mixed apparent flow rate is adopted. A total of four runs were performed, each run containing 64 sets of operating conditions. Recording output voltage signal V of conductance grid sensor by data acquisition card_m,1,V_m,2,…,V_m,10And a marking signal V_Mark(ii) a Simultaneously, recording output voltage signals U of the distributed coaxial conductivity sensors_m,1，U_m,2，U_m,3。

TABLE 1 vertical oil-gas-water three-phase flow experiment working condition table (unit m/s)

(3) And (5) carrying out calibration experiments on the conductivity grid sensor and the distributed coaxial conductivity sensor. In the experiment, the pipeline is filled with air, and the output voltage signal V of the electric conduction grid sensor is recorded by using a data acquisition card_g,1,V_g,2,…,V_g,10Simultaneously recording output voltage signal U of distributed coaxial conductivity sensor_g,1、U_g,2、U_g,3. Then, the pipeline is filled with full water, and the output voltage signal V of the conductivity grid sensor is recorded by using a data acquisition card_w,1,V_w,2,…,V_w,10Simultaneously recording output voltage signal U of distributed coaxial conductivity sensor_w,1、U_w,2、U_w,3。

(4) The data of the conductivity grid sensor collected in the oil-gas-water three-phase flow experiment and calibration experiment are processed according to the flow shown in FIG. 4 to obtain a signal V_m(i,j,k)，V_g(i, j) and V_w(i, j); the data of the distributed coaxial conductivity sensor collected in the oil-gas-water three-phase flow experiment and calibration experiment are processed according to the flow shown in fig. 5 to obtain a signal U_m,p(k)，U_g,pAnd U_w,p。

(5) For signal V according to equation (3)_m(i, j, k) normalizing to obtain a normalized signal V_N(i, j, k); push button

Equation (4) and equation (5) for U_m,p(k) Normalization and averaging are carried out, and for the distributed coaxial conductivity sensor with or without abnormality, the formula (5) respectively outputs conductivity correction coefficients delta (k) and delta (k)

(6) The correction factors δ (k) and δ (k) are respectively corrected by the conductivity according to the formula (6) and the formula (11)To one another

Change signal V_N(i, j, k) to obtain a correction signalAnd

(7) will correct the signalAndsubstituting into formula (7) and formula (12) to obtain corrected oil-gas-water three-phase flow gas holdupAnd

experimental verification and results:

FIG. 9 shows the oil content f when the liquid phase is used_oAnd when the flow rate is 0.05 and 0.15, the conductance grid sensor is used for three-dimensional imaging of the gas phase distribution in the oil-gas-water three-phase flow. FIG. 9(a) is a schematic view of a semiconductor device manufactured byThe conductivity grid sensor measurement data was obtained directly without correction with continuous phase conductivity properties, resulting in a longer continuous gas phase structure observed at the liquid slug (0.93-0.95s) and large bubble tail (0.99-1s), which is not consistent with the actual flow structure. In fig. 9(b), it can be observed that after the continuous phase conductive characteristic is corrected, the longer continuous gas phase structure disappears, the gas plug and the liquid plug structure in the pipeline can be clearly observed, and the imaging effect is greatly improved. The advantage of the conductive grid sensor with compensation of the conductivity properties for imaging three phase flow can also be seen by comparing fig. 9(c) and 9 (d).

Oil content f_oWhen the average gas holdup of the oil-gas-water three-phase flow of the radial section of the pipeline is 0.05, the average gas holdup of the oil-gas-water three-phase flow of the radial section of the pipeline is shown in figure 10. When the apparent flow velocity of the liquid phase is fixed, the average gas holding rate of the radial section of the pipeline measured by the electric conduction grid sensor continuously increases along with the increase of the apparent flow velocity of the gas phase. For the same gas phase superficial flow rate, as the liquid phase superficial flow rate increases, the average gas holdup decreases.