WO2017166367A1

WO2017166367A1 - Device for metering flow rates of two phases of gas and liquid in wet natural gas

Info

Publication number: WO2017166367A1
Application number: PCT/CN2016/080894
Authority: WO
Inventors: 张丛
Original assignee: 深圳市樊溪电子有限公司
Priority date: 2016-04-01
Filing date: 2016-05-03
Publication date: 2017-10-05
Also published as: WO2017166258A1

Abstract

A device for metering the flow rates of two phases of gas and liquid in wet natural gas, comprising a differential pressure collection unit (20) for collecting the differential pressure between the pressures before and after the wet natural gas flows through an orifice plate many times within a pre-defined cycle; and a flow rate calculation unit (21) for calculating the mass flow rate of the liquid phase and the mass flow rate of the gas phase. The real-time online metering of gas yield and liquid yield without separation is achieved by means of collecting the differential pressure between the pressures before and after the wet natural gas flows through the orifice plate many times in conjunction with a multiphase flow calculation algorithm.

Description

Wet natural gas gas-liquid two-phase flow metering device

Technical field

The invention relates to the technical field of fluid flow measurement, in particular to a wet natural gas gas-liquid two-phase flow metering method and a metering device.

Background technique

In the process of natural gas production, the gas production and production volume of gas wells is one of the important data for gas field production and management. It is not only an important basis for formulating production processes, determining production processes and production management methods, but also optimizing gas field production and ensuring rational gas reservoirs. Basic data.

With the rapid development of the natural gas industry, relevant institutions at home and abroad began to study the on-line measurement technology of wet natural gas gas-liquid two-phase non-separation, and made significant progress. Throughout the domestic and international wet gas gas-liquid two-phase on-line measurement technology, the following two measurement methods are mainly used. One is to use two or more single-volume flowmeters in series combination, according to the virtual high-frequency characteristics of the single-phase flowmeter for wet natural gas measurement. Two or more relational equations are established, and the gas-liquid two-phase flow is obtained by the simultaneous solution; the second is to obtain the gas-liquid two-phase flow by using a single flowmeter combined with microwave, radiation and the like.

Both of the above-mentioned measurement methods have high cost problems, and are mainly applied to the measurement of wet natural gas in large-scale gas wells such as oceans and deserts abroad, which cannot meet the requirements of low domestic gas well production and low development cost, and are not suitable for domestic use. Business application environment.

Summary of the invention

In order to solve the problem that the wet natural gas gas-liquid two-phase on-line measurement method in the prior art is costly, cannot meet the domestic gas well production situation, and is not suitable for the domestic commercial application environment, the embodiment of the present invention provides a wet natural gas gas-liquid two-phase flow measurement. Method and metering device, the technical scheme is as follows:

In one aspect, an embodiment of the present invention provides a wet natural gas gas-liquid two-phase flow metering method, and a wet natural gas gas-liquid two-phase flow metering method, wherein the method comprises:

The differential pressure ΔP _i before and after the wet natural gas flows through the orifice plate is collected multiple times in a predefined cycle.

The liquid phase mass flow rate G _d and the gas phase mass flow rate G _{c are} calculated based on the following formula:

among them,

The statistical average of the square root of the differential pressure,

For statistical variance, R is the relative statistical variance, ρ _c is the gas phase density, ρ _d is the liquid phase density, θ is the empirical constant, X _d is the liquid mass content ratio, and G is the total mass flow of natural gas, C For the outflow coefficient of the orifice plate, β is the orifice ratio of the orifice device, d is the orifice diameter of the orifice, D is the inner diameter of the metering tube, and ε is the coefficient of expansion of the wet natural gas.

Further, before the collecting the differential pressure ΔP _i before and after the wet natural gas flows through the orifice plate, the method further comprises: collecting the pipeline pressure before the wet natural gas flows through the orifice plate; sampling and testing the wet natural gas, The gas phase operating density ρ _c and the liquid phase operating density ρ _{d are} determined in conjunction with the line pressure.

Further, after calculating the mass flow rate of the liquid phase and the gas phase mass flow rate G _d G _c, said method further comprising: deriving the volume flow of the wet gas through the gas equation of state of gas, the gas volume flow and in accordance with the The liquid phase volumetric flow rate is calculated by the liquid phase operating density.

Preferably, the frequency of the differential pressure ΔP _i before and after the collection of the wet natural gas flowing through the orifice plate is at least 20 times per second.

Further, before the collecting the differential pressure ΔP _i before and after the wet natural gas flows through the orifice plate, the method further comprises: collecting the temperature value of the wet natural gas.

In another aspect, an embodiment of the present invention further provides a wet natural gas gas-liquid two-phase flow metering device, the device comprising:

Differential acquisition means for collecting a plurality of times before and after differential pressure △ wet gas flowing through orifice plate P _i within a predefined period;

a flow calculation unit for calculating a liquid phase mass flow rate G _d and a gas phase mass flow rate G _c based on the following formula:

among them,

The statistical average of the square root of the differential pressure,

Further, the apparatus further includes: a pressure collecting unit, configured to collect a pipeline pressure before the wet natural gas flows through the orifice plate before the differential pressure ΔP _i before and after the collecting of the wet natural gas flows through the orifice plate; And a calculating unit for sampling and testing the wet natural gas, and determining the gas phase working density ρ _c and the liquid phase working density ρ _d according to the line pressure.

Further, the flow calculation unit is further configured to: after the calculating the liquid phase mass flow rate G _d and the gas phase mass flow rate G _c , deriving a gas phase volume flow rate of the wet natural gas by a gas state equation, according to the gas phase volume The liquid phase volume flow is calculated from the flow rate and the liquid phase operating density.

Preferably, the differential pressure collecting unit collects a differential pressure ΔP _i of the wet natural gas flowing through the orifice plate at least 20 times per second.

Further, the apparatus further includes: a temperature collecting unit configured to collect a temperature value of the wet natural gas before the differential pressure ΔP _i before and after the collected wet natural gas flows through the orifice plate.

The beneficial effects of the technical solutions provided by the embodiments of the present invention are:

By collecting the differential pressure before and after the wet natural gas flows through the orifice plate, combined with the multiphase flow calculation algorithm, the real-time online measurement of gas production and liquid production is realized, and the measurement method is relatively simple and the cost is low.

DRAWINGS

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

FIG. 1 is an application scenario diagram provided by an embodiment of the present invention;

2 is a phase separation effect diagram of a two-phase flow provided on the orifice plate according to Embodiment 1 of the present invention;

3 is a liquid phase flow model diagram of a two-phase flow of an annular flow type according to Embodiment 1 of the present invention;

4 is a schematic diagram of a vapor-water two-phase flow experimental system according to Embodiment 1 of the present invention;

Figure 5 is a graph showing the relationship between the liquid phase flow rate and the statistical variance of the differential pressure square of the orifice plate provided in Example 1 of the present invention;

Figure 6 is a view showing the first embodiment of the present invention

A graph of the relative statistical variance R of the differential pressure square root;

Figure 7 is a view of the first embodiment of the present invention

with

Relationship diagram;

FIG. 8 is an autocorrelation function diagram and a linear spectrum diagram of differential pressure noise under three operating conditions according to Embodiment 1 of the present invention.

Figure 9 is a basic flow diagram of a horizontal tube two-phase flow according to Embodiment 1 of the present invention;

FIG. 10 is a structural diagram of a wet natural gas gas-liquid two-phase flow metering device according to Embodiment 2 of the present invention.

detailed description

The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

The application scenario of the embodiment of the present invention is briefly described below. Referring to FIG. 1, the natural gas produced by the gas well 101 is stored and used after being passed through the gas production line 102. An emergency shut-off valve 103 and a shut-off valve 104 are generally disposed on the gas production line 102. The natural gas produced by the gas well 101 is wet natural gas, and the wet natural gas mainly includes a gas phase and a liquid phase. In order to formulate a production process, determine a production process, and a production management mode, a wet natural gas flow meter 105 is usually disposed on the gas recovery pipeline 102. The gas phase and liquid phase flow rates of the wet natural gas are measured.

It should be noted that the types of the devices, the connection relationships, and the connection manners are not limited herein.

Example 1

Embodiments of the present invention provide a wet natural gas gas-liquid two-phase flow metering method, including the following steps:

S1: collecting the differential pressure ΔP _{i of the} wet natural gas flowing through the orifice plate multiple times in a predefined cycle;

Specifically, the wet natural gas comprises gas-liquid two phases, and the gas-liquid two phases are filled with interphase momentum, energy and mass exchange during the flow through the orifice plate, and the gas phase and the liquid phase are spatially and temporally distributed. Random. When the two-phase flow passes through the orifice plate, there is differential pressure noise, that is, differential pressure pulsation, and the differential pressure noise is the difference between the real-time measured value of the differential pressure and the actual value or the measured average value. The traditional measurement theory believes that this noise is the interference to the measurement and is eliminated by filtering. Modern measurement theory considers noise as the inherent physical characteristic of two-phase flow, and is the information carrier of two-phase flow state and parameters. The analysis of the noise mechanism, the statistical filtering model of the noise is established, and the relevant parameters of the two-phase flow can be obtained.

S2: Calculating the liquid phase mass flow rate G _d and the gas phase mass flow rate G _c based on the following formula:

among them,

The statistical average of the square root of the differential pressure,

For statistical variance, R is the relative statistical variance, ρ _c is the gas phase density, ρ _d is the liquid phase density, θ is the empirical constant, X _d is the liquid mass content ratio, and G is the total mass flow of natural gas, C For the outflow coefficient of the orifice plate, β is the orifice ratio of the orifice device, d is the orifice diameter of the orifice, D is the inner diameter of the metering tube, and ε is the expansion coefficient of the wet natural gas.

Specifically, the value of the outflow coefficient C can be obtained according to "8.4.2.1" in the standard "Measurement of natural gas flow by standard orifice plate GB/T 21446-2008", and the appendix of the standard can also be adopted if the accuracy requirement is not high. A "Table A.1 Outflow coefficient C value table" lookup table; the value of the expansion coefficient ε can be obtained according to the standard "GB.T. .

Further, before collecting the differential pressure ΔP _i before and after the wet natural gas flows through the orifice plate, the method further comprises: collecting the pipeline pressure before the wet natural gas flows through the orifice plate; sampling and testing the wet natural gas, determining the gas phase in combination with the pipeline pressure; Working condition density ρ _c and liquid phase working density ρ _d .

Specifically, in this embodiment, an orifice plate is used to assist in measuring the flow rate of the wet natural gas, and the pressure of the wet natural gas in the pipeline changes after the wet natural gas flows through the orifice plate, where the wet natural gas flows through the orifice. The line pressure in front of the plate is to facilitate metering the gas phase density and liquid phase density of the wet natural gas.

Specifically, for a gas well in a certain area, the natural gas component (gas phase) and the produced liquid component (liquid phase) produced by the gas well do not change much in a certain period of time. Because the density of the liquid phase is basically unaffected by the pressure, it can be obtained by on-site sampling and testing; when the gas phase density is greatly affected by the pressure, the gas density of the standard condition is obtained by sampling analysis, combined with the pressure collected by the pressure transmitter. The gas phase operating density is calculated.

Further, after calculating the mass flow rate of the liquid phase and the gas phase mass flow rate G _d G _c, the method further comprising: deriving the equation of state of gas by the gas volume flow of wet natural gas, the gas volume flow is calculated according to a liquid phase and a liquid phase density conditions Volume flow.

Preferably, the frequency of the differential pressure ΔP _i before and after the flow of the wet natural gas through the orifice plate is at least 20 times per second.

Further, before collecting the differential pressure ΔP _i before and after the wet natural gas flows through the orifice plate, the method further comprises: collecting the temperature value of the wet natural gas.

Specifically, the temperature value of the wet natural gas is used to calculate the gas phase working density ρ _c and the liquid phase working density ρ _d in the foregoing sampling assay, and the temperature value is also used as the parameter of the gas state equation for calculating the gas phase volume flow. .

The above relevant formula for measuring the gas-liquid two-phase flow rate of wet natural gas needs to be deduced and experimentally verified by the theoretical model. The specific process is as follows:

First, establish a theoretical mathematical model of gas-liquid two-phase flow metering

1. Two-phase separation flow ideal model

The formula for measuring the flow of a single-phase flow using an orifice plate is:

In the gas-liquid two-phase flow, it is assumed that the two phases flow through the orifice plate respectively, there is no momentum exchange between phases, no phase change process, and the adiabatic condition is satisfied, thereby obtaining an ideal model of the two-phase separation flow of the orifice plate:

Where G represents the mass flow rate, X represents the mass flow ratio of the phase, and V represents the volume of the phase.

The so-called ideal model refers to the "slip" phenomenon in which the two-phase flow exists completely under the above-mentioned assumptions, but it is actually impossible to not exist.

2. Disturbance model

In the gas-liquid two-phase flow, it is assumed that the two-phase flow flows through the orifice plate in an annular flow; as shown in Fig. 2, the gas phase flows freely, and the liquid phase is blocked, accumulated, and then discharged by the orifice plate; It is shown that there is no droplet in the gas phase, and no liquid phase flows through the orifice plate during the retardation and accumulation phases, and the accumulated liquid is sprayed in the form of a pulse. The liquid phase transient pulse is G _dP =G _d T/τ. When the liquid phase is retarded, only the gas phase flows through the orifice plate, then:

When the liquid phase flows through the orifice:

X _cp =G _c /(G _c +G _cp )=1/(1+T/τ·X _d ) (Equation 6)

Under the condition of no momentum exchange:

From equations (5-2), (5-4) and (5-5):

In the middle

The peak and valley values of the differential pressure root are respectively determined as the differential pressure root pulsation amplitude:

Defining the phase separation coefficient θ ₁ =T/(2τ) characterizing the phase separation effect gives:

Equation 10 shows that the magnitude of the differential pressure square root noise is proportional to the liquid phase flow.

3. Statistical model

In addition to the above two hypothetical models, it is assumed that the statistical variance of the concentration distribution of the dispersed phase (dilute phase, here liquid phase) is proportional to the average phase concentration of the phase; in the fully developed two-phase flow, the continuous phase (here The flow rate for the gas phase is constant, which is approximately true when the dispersed phase is a dilute phase. then

It can be seen as a constant quantity, and the relationship between the differential pressure ΔP(t) and the dispersed phase concentration V _d (t) obtained by the random variable of Equation 4:

Considering that the relative fluctuation is small, the statistical variance of ΔP(t) and V _d (t) can be approximated by the following formula:

Substituting formula 12 into:

Considering that the liquid phase is a dilute phase, 1-V _d ≈1, by assuming σ(V _d )=θ ₂ ·V _d , we can obtain:

Substituting Equation 2 and Formula 3 into Equation 14 yields:

Equation 15 shows that when the dispersed phase is a dilute phase, the statistical variance of the differential pressure square root is approximately proportional to the dispersed phase flow. This is identical in form to Equation 10 derived from the perturbation model. In the disturbance model, the discharge of the liquid is random and there is no fixed amplitude. Therefore, in the formula 10

And formula 15

There is no difference in essence, but the method of representation is different. Of course, the statistical model is no longer dependent on the disturbance effect of the barrier, not only for the orifice plate, but also for other throttling devices, or even a set of pipe segments. For convenience, θ is used instead of θ ₁ or θ ₂ .

4. Two-phase two-parameter theoretical model for gas-liquid two-phase differential pressure noise measurement

Definition: The relative statistical variance of the square root of the differential pressure is:

Substituting Equation 3 into Equation 14 yields:

Substituting Equation 17 into Equation 2 gives:

Equations 17 and 18 are theoretical models for two-phase flow two-parameter measurement using the statistical mean and relative statistical variance of the two-phase flow differential pressure square of the orifice plate. The form is very simple and the physical meaning is very clear. The first item after the split 18

Is the flow estimate for the continuous phase, where

It is a two-phase differential pressure, so this estimate is high. the third item

It is a correction to the first high estimate. second section

The estimated flow rate for the dispersed phase.

Theoretical analysis shows that the ratio of the two-phase flow density and the diameter ratio of the orifice plate may be the influence factors of the proportional coefficient θ, and the two-phase density ratio may be the main factor. The experimental study to determine the proportional coefficient θ and its influencing factors is indispensable for the development of practical empirical models for two-phase flow two-phase flow measurement of orifice plates.

(II) Experimental verification of theoretical model for differential pressure noise measurement of orifice plate

1, the experimental system description

The indoor experiment uses a vapor-water two-phase flow. The basic requirement of the experiment of measuring the vapor-water two-phase flow of the orifice plate is to generate a stable two-phase flow of known pressure, temperature and phase flow through the test orifice plate. The device and process are shown in Figure 4, where T ₁ and T ₂ are first-class standard mercury thermometers, P, P ₁ and P ₂ are pressure transmitters, and ΔP, ΔP ₁ and ΔP ₂ are differential pressure transmitters. Device. The steam-water two-phase flow of the direct current boiler (total mass flow, dryness, and pressure adjustable) is used to measure the differential pressure of the vapor-water two-phase flow through the test orifice, and simultaneously measure the pressure at the high pressure side of the orifice before passing through the orifice plate. pressure. The vapor-water two-phase stream then flows through the mixer and is thoroughly mixed with a cold water to form subcooled water (where the flow, pressure and temperature of the supercooled water are metered).

All flow metering orifice plates are flanged pressure-standard standard sharp-edged orifice plates designed and processed according to GB-2624-81, and together with their straight pipe sections (upper and downstream ≥30D) are all calibrated by Chongqing Automation, in line with national standards. . Pressure transmitters, differential pressure transmitters (take the 1151 series, time constant 0.2 seconds) and mercury thermometers are required to be qualified after calibration. The test orifice plate is installed horizontally, and the orifice plate dimensions are as follows:

The mass flow and dryness of the vapor-water two-phase flow (saturated water vapor) flowing through the test orifice are obtained by the continuity equation and the energy balance equation:

G=G ₂ -G ₁ (Equation 19)

X _c =(G ₂ i ₂ '-G ₁ i ₁ ' _- (G ₂ -G ₁ )i'+Q)/((G ₂ -G ₁ )(i"-i')) (Equation 20)

In the formula, Q is the heat loss, which is measured by the experiment and its quantity is extremely small. Two-phase flow of steam and water enthalpy i "and i ', and the enthalpy of cold water, mixed water is i _1' and i ₂ 'according to their respective pressure and temperature values determined look-up table.

The output signals of the pressure transmitter and differential pressure transmitter are metered and printed by a high-precision digital voltmeter with a sampling speed of 20 points/s.

For the six different sized orifice plates in the above table, the tests were carried out under different pressure, flow and dry conditions. The experimental parameters range is: operating pressure: 0.58 - 12.1 MPa; dryness: 0.05 - 0.95; flow: 1580 - 7400 Kg / h;

Assume

For the differential pressure square root sample value, the statistical average of the orifice two-phase flow differential root

Statistical variance

The relative statistical variance R is calculated by Equation 21, Equation 22, and Equation 23:

During the experiment, adjust the boiler outlet flow (by adjusting the water supply) and dryness (by adjusting the oil supply) and adjust the cold water flow to ensure that the mixed water is supercooled. However, the degree of subcooling should not be too low, otherwise the two-phase flow error will increase.

2. Experimental results and analysis

(1) Experimental results

As shown in Figure 5, G _d /F is described

(ie, estimating the liquid phase flow by statistical variance), indicating that the liquid phase flow is approximately proportional to the statistical variance of the differential pressure square root of the orifice.

As shown in Figure 6, described

The relationship between the statistical variance R (ie, Equation 17) and the differential pressure root.

As shown in Figure 7, described

with

(ie, the relationship of Equation 18).

It can be seen from the experimental data and Figures 5 to 7:

1 experimental data is in good agreement with the theoretical model;

2 The influence of two-phase density ratio and orifice diameter ratio on the value of θ is not obvious;

3 Taking the average value of the experimental data θ as the proportional coefficient of the practical model, the mean square deviation of the estimated flow and dryness is 9.0% and 6.5%, respectively. This error is comparable to the error of the existing combined two-phase flow measurement methods;

4 Theoretical derivation assumes 1-V _d ≈1, which shows that the low dryness is far from the straight line, which is consistent with the theoretical analysis.

(2) Model analysis

The orifice plate has differential pressure noise in the two-phase flow, that is, differential pressure pulsation, which is an inherent characteristic of the two-phase flow, and thus the characteristics of the noise are necessarily related to the two-phase flow. As shown in Fig. 8, the autocorrelation function and linear spectrum of differential pressure noise under three different operating conditions are described. As can be seen from the figure:

In the 1a working condition, the autocorrelation function is in the form of δ function, and the linear spectrum has multiple peaks between 0.5-3HZ, which indicates that the differential pressure noise signal is approximately band-limited white noise, and the random distribution law of phase concentration dominates. Figure 10 shows that the a condition is intermittent;

Under the condition of 2b, the autocorrelation function has a plurality of peaks in addition to one main peak, and there is a distinct main peak on the linear spectrum, indicating that the phase separation effect plays a major role. At this time, the two-phase flow belongs to the annular flow (refer to Figure 10), which is consistent with the theoretical assumption of the disturbance model;

Under the condition of 3c, the autocorrelation function and the linear spectral boundary between a and b, phase separation and randomness work simultaneously. Referring to Figure 9, the c operating condition may be a fog annular flow that transitions from a batch flow to an annular flow.

The orifice two-phase flow differential pressure noise is caused by two factors, the separation effect and the random fluctuation of the phase concentration distribution. As the flow conditions change, sometimes the former is the dominant factor, and sometimes the latter plays a major role, sometimes both, and its frequency characteristics change. In fact, even under the annular flow, the "spray" is random and there is no fixed amplitude. Therefore, in data processing, the statistical variance of the differential pressure square root is generally used. In the derivation of the theoretical model, the same conclusion is reached under two different assumptions that do not depend on frequency. In the gas well production process, there is no mechanical vibration, so there is no wavy flow, and the gas produced by the gas well is mainly in the gas phase. Therefore, the gas-liquid two-phase flow state of the horizontal pipe section in the gas well production process mainly appears misty according to the liquid-gas ratio from small to large. The flow, annular flow, and laminar flow regimes are applicable to the gas-liquid two-phase flow in the horizontal section of the gas well.

According to the above theoretical analysis and experimental verification, the following practical experience model can be obtained:

The gas-liquid two-phase flow can be divided into two types according to the composition of the material. The gas-liquid two-phase flow consisting of two phases of the same component is called a one-component gas-liquid two-phase flow, such as water vapor and water in the experiment. The two-phase flow is composed; the two-phase flow composed of two phases of different components is called a two-component two-phase flow, such as a gas well wet natural gas gas-liquid two-phase flow. The same mathematical model is applied to the one-component gas-liquid two-phase flow and the two-component gas-liquid two-phase flow without phase change. Therefore, the model of Equation 24 is also applicable to the wet natural gas gas-liquid two-phase flow metering, that is, the metering method model of the embodiment of the present invention.

The wet natural gas flow metering method provided by the embodiment of the invention collects the differential pressure before and after the flow of the wet natural gas through the orifice plate, and combines the multiphase flow calculation algorithm to realize the real-time on-line measurement of the gas production and the liquid production volume without separation. Relatively simple The method is simple and cost-effective. At the same time, the theoretical mathematical model derivation and experimental verification are respectively performed for the two-phase flow of the plurality of flow patterns, so that the measurement method provided by the embodiment is more rigorous and accurate.

Example 2

As shown in FIG. 10, an embodiment of the present invention further provides a wet natural gas gas-liquid two-phase flow metering device, which uses the method as described in Embodiment 1 to measure a gas-liquid two-phase flow rate of wet natural gas, and the device includes:

The differential pressure collecting unit 20 is configured to collect the differential pressure ΔP _{i of the} wet natural gas flowing through the orifice plate multiple times in a predefined period;

The flow calculation unit 21 is configured to calculate the liquid phase mass flow rate G _d and the gas phase mass flow rate G _c based on the following formula:

among them,

The statistical average of the square root of the differential pressure,

Further, the apparatus further includes: a pressure collecting unit 22, configured to collect the pipeline pressure before the wet natural gas flows through the orifice plate before collecting the differential pressure ΔP _i before and after the wet natural gas flows through the orifice plate; the density calculation unit 23, for sampling and testing wet natural gas, combined with pipeline pressure to obtain gas phase density ρ _c and liquid phase density ρ _d .

Further, the flow calculation unit 21 is further configured to: after calculating the liquid phase mass flow rate G _d and the gas phase mass flow rate G _c , deriving the gas phase volume flow rate of the wet natural gas by the gas state equation, according to the gas phase volume flow rate and the liquid phase working density Calculate the liquid volume flow rate.

Preferably, the differential pressure collecting unit 20 collects the differential pressure ΔP _i of the wet natural gas before and after flowing through the orifice plate to at least 20 times per second.

Further, the apparatus further includes: a temperature collecting unit 24 configured to collect the temperature value of the wet natural gas before collecting the differential pressure ΔP _i before and after the wet natural gas flows through the orifice plate.

The wet natural gas flow metering device provided by the embodiment of the invention collects the differential pressure before and after the wet natural gas flows through the orifice plate by using the differential pressure collecting unit, and uses the flow calculating unit to combine the multiphase flow algorithm to realize the gas production amount and the liquid production amount. The real-time online measurement is not separated, and the measurement method is relatively simple and low in cost.

The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalents, improvements, etc., which are within the spirit and scope of the present invention, should be included in the protection of the present invention. Within the scope.

Claims

A wet natural gas gas-liquid two-phase flow metering device, characterized in that the device comprises:

Differential acquisition means for collecting a plurality of times before and after differential pressure △ wet gas flowing through orifice plate P i within a predefined period;

a flow calculation unit for calculating a liquid phase mass flow rate G d and a gas phase mass flow rate G c based on the following formula:

among them,
The statistical average of the square root of the differential pressure,
For statistical variance, R is the relative statistical variance, ρ c is the gas phase density, ρ d is the liquid phase density, θ is the empirical constant, X d is the liquid mass content ratio, and G is the total mass flow of natural gas, C For the orifice coefficient of the orifice plate, β is the orifice ratio of the orifice device, d is the orifice diameter of the orifice, D is the inner diameter of the metering tube, and ε is the coefficient of expansion of the wet natural gas.
The device of claim 1 further comprising:

a pressure collecting unit, configured to collect a pipeline pressure before the wet natural gas flows through the orifice plate before the differential pressure ΔP i before and after the collecting of the wet natural gas flows through the orifice plate;

And a density calculation unit for sampling and testing the wet natural gas, and determining the gas phase working density ρ c and the liquid phase working density ρ d according to the line pressure.
The device according to claim 1, wherein the flow calculation unit is further configured to:

After the calculation of the mass flow rate of the liquid phase and the gas phase mass flow rate G d G c, is derived through the gas equation of state of gas volume flow rate of the wet natural gas, is calculated based on the liquid and gas volume flow of the liquid phase density conditions Volume flow.
The apparatus according to claim 1, wherein said differential pressure collecting unit collects a frequency of differential pressure ΔP i before and after the flow of wet natural gas through the orifice plate is at least 20 times per second.
The device according to any one of claims 1 to 4, wherein the device further comprises:

Temperature collecting means for collecting the front differential pressure △ gas before and after passing through the wet orifice plate P i, collecting said wet gas temperature.