Two-phase flow calculation method based on gas-liquid components

Abstract

The invention provides an online non-separation type two-phase flow accurate calculation method based on gas-liquid components. The online non-separation type two-phase flow accurate calculation method comprises the steps that the liquid content alpha or the gas content sigma of a section is monitored in real time through a gas-liquid component measuring unit installed in a measuring pipeline; then respectively calculating the gas-phase sectional area Ag and the liquid-phase sectional area Al of the fluid flowing through the measuring pipeline; directly or indirectly calculating a gas phase velocity Vg and a liquid phase velocity V1 by utilizing a fluid velocity measuring unit arranged in a measuring pipeline; and finally, the flow totalizer calculates the gas phase flow Qg and the liquid phase flow Ql according to the gas phase sectional area Ag, the liquid phase sectional area Al, the gas phase velocity Vg and the liquid phase velocity Vl of the fluid flowing through the measuring pipeline calculated by the flow totalizer. The gas-phase flow and the liquid-phase flow are finally calculated by easily and directly measuring the section holdup and matching with the gas-liquid velocity obtained through measurement or conversion, and compared with the prior art, the method has the advantages that the error introduced by a formula can be reduced, the application range is wider, and the practical application is more convenient.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas-liquid two-phase flow measurement, and relates to a two-phase flow calculation method based on gas-liquid components, specifically to an on-line non-separating two-phase flow calculation method based on gas-liquid components. Background Art

[0002] When a natural gas well is in operation, it is necessary to measure the flow rates of natural gas and water ejected from the well. Existing two-phase flow calculation methods based on gas-liquid components include a separating measurement method and an on-line non-separating measurement method; 1) The separating measurement method is: separating the gas-liquid two-phase fluid ejected from the well into a pure gas-phase fluid and a pure liquid-phase fluid for separate measurement. The existing method is the gravity sedimentation method. This solution requires a separating device, a gas-phase flowmeter, and a liquid-phase flowmeter. The disadvantages are large volume and high cost, which are not conducive to large-area popularization and use; 2) The on-line non-separating measurement method is: calculating the gas-phase flow rate and the liquid-phase flow rate by multiplying the total flow rate in the gas-liquid two-phase flow by the phase fraction. The phase fraction is difficult to directly measure and needs to be converted by methods such as the empirical method and the normalization fitting method. The calculated phase fraction itself has a theoretical measurement error. Summary of the Invention

[0003] In order to solve the problem that the phase fraction in the prior art is difficult to directly measure and there are errors in the converted and calculated phase fraction using methods such as the empirical method and the normalization fitting method, the present invention provides an accurate on-line non-separating two-phase flow calculation method based on gas-liquid components. The method is as follows:

[0004] Utilize the gas-liquid component measurement unit installed in the measurement pipeline to continuously monitor the liquid holdup α of the cross-section; calculate the gas-phase cross-sectional area A g and the liquid-phase cross-sectional area A l of the fluid flowing through the measurement pipeline respectively through the following formula:

[0005]

[0006] A l = A * α

[0007] wherein, the unit of the liquid holdup α of the cross-section is dimensionless, the unit of the cross-sectional area A of the measurement pipeline is m 2 , the unit of the gas-phase cross-sectional area A g is m 2 , and the unit of the liquid-phase cross-sectional area A l is m 2 ;

[0008] Then utilize the fluid velocity measurement unit set in the measurement pipeline to directly measure or indirectly calculate the gas-phase velocity V g and the liquid-phase velocity V l ;

[0009] Finally, the last flow integrator substitutes the directly measured or indirectly calculated gas-phase cross-sectional area A g and liquid-phase cross-sectional area A l , gas-phase velocity V g , and liquid-phase velocity V l into the following formula to calculate the gas-phase flow rate Q g and liquid-phase flow rate Q l respectively:

[0010] Q g = A g * V g

[0011] Q l = A l * V l

[0012] where the gas-phase flow rate Q g has the unit of m 3 / h, the liquid-phase flow rate Q l has the unit of m 3 / h, the gas-phase velocity V g has the unit of m / h; the liquid-phase velocity V l has the unit of m / h.

[0013] Preferably,

[0014] the directly measured fluid velocity measurement unit includes a velocity sensor, a temperature sensor, and a pressure sensor; the indirectly calculated fluid velocity measurement unit includes at least one throttling element and its differential pressure sensor, temperature sensor, and pressure sensor.

[0015] Preferably,

[0016] the indirectly calculated fluid velocity measurement unit adopts a differential pressure conversion fluid velocity measurement unit; the directly measured fluid velocity measurement unit adopts an ultrasonic fluid velocity measurement unit or a fluid velocity measurement unit for directly measuring the liquid and gas flow velocities in a two-phase fluid.

[0017] Preferably, the fluid velocity measurement unit adopts a differential pressure conversion fluid velocity measurement unit, and the method for calculating the gas-phase velocity V g and liquid-phase velocity V l includes:

[0018] The differential pressure conversion fluid velocity measurement unit adopts a differential pressure throttling element and measures the differential pressure value ΔP of the mixed phase in the measurement pipeline using it; assume:

[0019] ΔP g = ΔP * f(ΔP, ρ g , α, ε) gas

[0020] ΔP l = ΔP * f(ΔP, α) liquid

[0021] where the correction function f(ΔP, ρ g , α, ε) gas and f(ΔP, α) liquid are the functional relationships between ΔP, ρ g , α, ε, ρ l , A, C, β and the flow rate, that is, the functional relationships between ΔP and ΔP g , ΔP l respectively, which are obtained through experiments and calculations; among them, the mixed-phase differential pressure value ΔP, the gas-phase differential pressure value ΔP g , and the liquid-phase differential pressure value ΔP l are all in the unit of Pa; the correction functions f(ΔP, ρ g , α, ε) gas and f(ΔP, α) liquid are both in the unit of none;

[0022] Then the flow integrator substitutes the calculated gas-phase differential pressure value ΔP g and the liquid-phase differential pressure value ΔP l into the following formula to calculate the gas-phase velocity V g and the liquid-phase velocity V l respectively:

[0023]

[0024]

[0025] where C is the discharge coefficient, β is the diameter ratio, ε is the gas expansion coefficient, ρ g The unit of gas density is g / m 3 , ρ l The unit of liquid density is g / m 3 , and they are all known quantities; the unit of the gas-phase velocity V g is m / h; the unit of the liquid-phase velocity V l is m / h.

[0026] Preferably, the method for obtaining the correction functions f(ΔP, ρ g , α, ε) gas and f(ΔP, α) liquid includes:

[0027] Generate a two-phase fluid with known and constant gas-phase flow rate Q gas标准表 and liquid-phase flow rate Q liquid标准表 through a standard device, and this two-phase fluid will flow through the differential pressure throttling element of the gas-liquid component measurement unit and the differential pressure conversion fluid velocity measurement unit;

[0028] Record the ΔP and ρ in the differential pressure throttling element of the gas-liquid component measurement unit and the differential pressure conversion fluid velocity measurement unit in real time g , α, ε, ρ l , A, C, β and the flow rate Q in the standard device liquid标准表 , Q gas标准表 ;

[0029] Substitute the above ΔP, ρ g , α, ε, ρ l , A, C, β and the flow rate Q in the standard device liquid标准表 , Q gas标准表 data into the following formula to calculate the correction functions f(ΔP, ρ g , α, ε) gas , f(ΔP, α) liquid ;

[0030]

[0031]

[0032] Among them, the cross-sectional liquid holdup α has no unit, the cross-sectional area A of the test measurement pipeline has the unit of m 2 , C is the discharge coefficient, β is the diameter ratio, ε is the gas expansion coefficient, ρ g The gas density has the unit of g / m 3 , ρ l The liquid density has the unit of g / m 3 , the flow rate Q liquid标准表 has the unit of m 3 / h, Q gas标准表 has the unit of m 3 / h, and the mixed-phase differential pressure value ΔP has the unit of Pa;

[0033] Then repeat the above operations. By setting different gas-liquid flow rates, several groups of data are obtained; through multiple groups of data, the correction functions f(ΔP, ρ g , α, ε) gas , f(ΔP, α) liquid are obtained.

[0034] Preferably,

[0035] the ρ l liquid is water, and the density is about 1000 g / m 3 ; then ρ g the gas density is obtained by the following formula:

[0036]

[0037] Among them, M is the molar mass of the gas, with the unit of g / mol; R is the gas constant, with the unit of J / (mol*K); T is the thermodynamic temperature of the gas, with the unit of K (Kelvin), which is measured by the temperature sensor in the fluid velocity measurement unit calculated indirectly; P is the pressure of the gas, with the unit of Pa, which is measured by the pressure sensor in the fluid velocity measurement unit calculated indirectly.

[0038] Preferably,

[0039] The differential pressure throttling element is selected from a Venturi differential pressure throttling element, or an orifice plate differential pressure throttling element, or a nozzle differential pressure throttling element, or a wedge differential pressure throttling element, and the number thereof is at least one.

[0040] Preferably,

[0041] The differential pressure throttling element is selected from a Venturi tube differential pressure throttling element, and the gas expansion coefficient ε is obtained by the following formula:

[0042]

[0043] Among them, β is the diameter ratio, κ is the isentropic exponent, τ is the pressure ratio, and the calculation formulas for the pressure ratio τ and the diameter ratio β are as follows:

[0044]

[0045]

[0046] Among them, P 节流元件处绝压 is the absolute pressure at the differential pressure throttling element, with the unit of Pa; P 上游处绝压 is the absolute pressure upstream of the differential pressure throttling element, with the unit of Pa; d 节流元件内径 is the inner diameter of the differential pressure throttling element, with the unit of mm; D 管段内径 is the inner diameter of the measuring pipe section where the differential pressure throttling element is installed, with the unit of mm.

[0047] Preferably,

[0048] The gas-liquid component measurement unit adopts a microwave method, or a capacitance method, or a ray attenuation method, or an image method gas-liquid component measurement unit.

[0049] The present invention also provides another two-phase flow calculation method based on gas-liquid components. The method is as follows:

[0050] The cross-sectional gas holdup σ is monitored in real time by using the gas-liquid component measurement unit installed in the measurement pipeline; the gas cross-sectional area A g and the liquid cross-sectional area A l flowed through by the fluid in the measurement pipeline are calculated respectively through the following formula:

[0051] A l =A*(1 - σ)

[0052] A g = A * σ

[0053] wherein, the cross-sectional gas holdup σ has no unit, the cross-sectional area A of the measurement pipeline has the unit of m 2 , the cross-sectional area of the gas phase A g has the unit of m 2 , the cross-sectional area of the liquid phase A l has the unit of m 2 ;

[0054] Then, by using the fluid velocity measurement unit arranged in the measurement pipeline, the gas phase velocity V is directly measured or indirectly calculated g , and the liquid phase velocity V l ;

[0055] Finally, the flow integrator substitutes the directly measured or indirectly calculated cross-sectional area of the gas phase A g , the cross-sectional area of the liquid phase A l , the gas phase velocity V g , and the liquid phase velocity V l into the following formula to calculate the gas phase flow rate Q g and the liquid phase flow rate Q l respectively:

[0056] Q g = A g * V g

[0057] Q l = A l * V l

[0058] wherein, the gas phase flow rate Q g has the unit of m 3 / h, the liquid phase flow rate Q l has the unit of m 3 / h, the gas phase velocity V g has the unit of m / h; the liquid phase velocity V l has the unit of m / h.

[0059] Preferably,

[0060] the fluid velocity measurement unit for direct measurement includes a velocity sensor, a temperature sensor and a pressure sensor; the fluid velocity measurement unit for indirect calculation includes at least one throttle element and its differential pressure sensor, temperature sensor and pressure sensor.

[0061] Preferably,

[0062] The indirectly calculated fluid velocity measurement unit uses a differential pressure conversion fluid velocity measurement unit; the directly measured fluid velocity measurement unit uses an ultrasonic fluid velocity measurement unit, or a fluid velocity measurement unit that directly measures the flow rates of liquid and gas in a two-phase fluid.

[0063] Preferably, the fluid velocity measurement unit uses a differential pressure conversion fluid velocity measurement unit to calculate the gas phase velocity V g and the liquid phase velocity V l The method includes:

[0064] The differential pressure conversion fluid velocity measurement unit uses a differential pressure throttling element and measures the differential pressure value ΔP of the mixture in the measurement pipeline; assume:

[0065] ΔP g = ΔP * f(ΔP, ρ g , σ, ε) gas

[0066] ΔP l = ΔP * f(ΔP, σ) liquid

[0067] where the correction function f(ΔP, ρ g , σ, ε) gas and f(ΔP, σ) liquid are the functional relationships between ΔP, ρ g , σ, ε, ρ l , A, C, β and the flow rate, that is, the functional relationships between ΔP and ΔP g , ΔP l respectively, which are obtained through experiments and calculations; where the differential pressure value of the mixture ΔP, the differential pressure value of the gas phase ΔP g and the differential pressure value of the liquid phase ΔP l are all in Pa; the correction functions f(ΔP, ρ g , σ, ε) gas and f(ΔP, σ) liquid are all dimensionless;

[0068] Then the flow integrator substitutes the calculated differential pressure value of the gas phase ΔP g and the differential pressure value of the liquid phase ΔP l into the following formula to calculate the gas phase velocity V g and the liquid phase velocity V l respectively:

[0069]

[0070]

[0071] where C is the discharge coefficient, β is the diameter ratio, ε is the gas expansion coefficient, ρg The unit of gas density is g / m 3 , ρ l The unit of liquid density is g / m 3 , all of which are known quantities; the gas phase velocity V g has the unit of m / h; the liquid phase velocity V l has the unit of m / h.

[0072] Preferably, the method for obtaining the correction functions f(ΔP, ρ g , σ, ε) gas and f(ΔP, σ) liquid includes:

[0073] Generating a two-phase fluid with known gas phase flow rate Q gas标准表 and liquid phase flow rate Q gas标准表 and constant numerical values through a standard device. This two-phase fluid will flow through the differential pressure throttling element of the gas-liquid component measurement unit and the differential pressure conversion fluid velocity measurement unit;

[0074] Recording in real time the ΔP, ρ g , σ, ε, ρ l , A, C, β in the differential pressure throttling element of the gas-liquid component measurement unit and the differential pressure conversion fluid velocity measurement unit, as well as the flow rates Q liquid标准表 , Q gas标准表 ;

[0075] Substituting the above ΔP, ρ g , σ, ε, ρ l , A, C, β and the flow rates Q liquid标准表 , Q gas标准表 data into the following formula to calculate the correction functions f(ΔP, ρ g , σ, ε) gas and f(ΔP, σ) liquid ;

[0076]

[0077]

[0078] where the cross-sectional gas holdup σ has the unit of none, the cross-sectional area A of the test measurement pipeline has the unit of m 2 , C is the discharge coefficient, β is the diameter ratio, ε is the gas expansion coefficient, ρ g The unit of gas density is g / m 3 , ρ l The unit of liquid density is g / m 3 , the flow rate Q liquid标准表 has the unit of m 3 / h, Q gas标准表 has the unit of m 3 / h, and the unit of the mixed-phase differential pressure value ΔP is Pa for all;

[0079] Then repeat the above operations. By setting different gas-liquid flow rates, several groups of data are obtained; from the multiple groups of data, correction functions f(ΔP, ρ g , σ, ε) gas , f(ΔP, σ) liquid .

[0080] Preferably,

[0081] If the ρ l liquid is water, then the density is approximately 1000 g / m 3 ; then ρ g The gas density is obtained by the following formula:

[0082]

[0083] where M is the molar mass of the gas, with the unit g / mol; R is the gas constant, with the unit J / (mol*K); T is the gas thermodynamic temperature, with the unit K (Kelvin), which is measured by the temperature sensor in the fluid velocity measurement unit for indirect calculation; P is the pressure of the gas, with the unit Pa, which is measured by the pressure sensor in the fluid velocity measurement unit for indirect calculation.

[0084] Preferably,

[0085] The differential pressure throttling element is selected from a Venturi differential pressure throttling element, or an orifice plate differential pressure throttling element, or a nozzle differential pressure throttling element, or a wedge differential pressure throttling element, and the number thereof is at least one.

[0086] Preferably,

[0087] The differential pressure throttling element is selected as a Venturi tube differential pressure throttling element, and the gas expansion coefficient ε is obtained by the following formula:

[0088]

[0089] where β is the diameter ratio, κ is the isentropic exponent, τ is the pressure ratio, and the calculation formulas for the pressure ratio τ and the diameter ratio β are as follows:

[0090]

[0091]

[0092] where P 节流元件处绝压 is the absolute pressure at the differential pressure throttling element, with the unit Pa; P 上游处绝压 is the absolute pressure upstream of the differential pressure throttling element, with the unit Pa; d 节流元件内径 is the inner diameter of the differential pressure throttling element, with the unit mm; D 管段内径The inner diameter of the measuring pipe section for installing the differential pressure throttling element, with the unit of mm.

[0093] Preferably,

[0094] The gas-liquid component measurement unit adopts a microwave method, a capacitance method, a ray attenuation method or an image method for gas-liquid component measurement.

[0095] The present invention provides an online non-separating two-phase flow accurate calculation method based on gas-liquid components. By easily directly measuring the gas-liquid components and cooperating with the measured or converted gas-liquid velocities, the gas-phase flow rate and the liquid-phase flow rate are finally calculated. Compared with the prior art, it can reduce the measurement error introduced by the formula, has a wider application range, and is more convenient for practical applications. Description of the Drawings

[0096] Figure 1 This is a schematic block diagram of an online non-separating two-phase flow calculation system based on gas-liquid components provided by the present invention;

[0097] Figure 2 This is a schematic flow chart of an online non-separating two-phase flow calculation method based on gas-liquid components provided in Embodiment 1 of the present invention;

[0098] Figure 3 This is a schematic flow chart of an online non-separating two-phase flow calculation method based on gas-liquid components provided in Embodiment 2 of the present invention. Detailed Embodiments

[0099] The following further describes the present invention in detail with reference to the drawings. The following is an explanation of the present invention rather than a limitation.

[0100] As Figure 1 shown, the present invention provides an online non-separating two-phase flow calculation system based on gas-liquid components, including a gas-liquid component measurement unit, a flow integrator and a fluid velocity measurement unit, wherein:

[0101] The gas-liquid component measurement unit is used to measure the gas holdup or liquid holdup per unit cross-section in the pipeline;

[0102] The flow integrator is used to complete the logical operation of the data measured by the gas-liquid component measurement unit and the fluid velocity measurement unit and the human-machine operation interface;

[0103] The fluid velocity measurement unit is used to directly measure or indirectly calculate the gas-phase fluid velocity and liquid-phase fluid velocity in the two-phase flow within the measurement pipeline. The indirectly calculating fluid velocity measurement unit includes a throttling element, its differential pressure sensor, temperature sensor, and pressure sensor, such as a differential pressure conversion fluid velocity measurement unit; the directly calculating fluid velocity measurement unit includes a velocity sensor, temperature sensor, and pressure sensor, such as an ultrasonic fluid velocity measurement unit, or a fluid velocity measurement unit that directly measures the liquid and gas flow rates in the two-phase fluid.

[0104] Embodiment 1

[0105] As Figure 2 shown, the present invention provides a schematic flow diagram of an on-line non-separating two-phase flow calculation method based on gas-liquid components. The two-phase flow calculation method is as follows: (The following takes the indirectly calculating fluid velocity measurement unit and the gas-liquid component measurement unit measuring the liquid holdup of the cross-section as an example for illustration)

[0106] Using the microwave method gas-liquid component measurement unit, the liquid holdup α of the cross-section can be measured. The principle is that the dielectric constant of water in the gas-liquid is nearly 70 times different from that of natural gas, and thus the ratio of gas and liquid in the cross-section can be distinguished; given the pipeline cross-sectional area A, the gas-phase cross-sectional area A g and liquid-phase cross-sectional area A l flowing through the pipeline can be calculated through the following formula:

[0107] A g = A * (1 - α)

[0108] A l = A * α

[0109] wherein, the unit of the liquid holdup α of the cross-section is dimensionless, the unit of the measurement pipeline cross-sectional area A is mm 2 , the unit of the gas-phase cross-sectional area A g is mm 2 , and the unit of the liquid-phase cross-sectional area A l is mm 2 ;

[0110] Then, using the indirectly calculating fluid velocity measurement unit (differential pressure conversion fluid velocity measurement unit), a Venturi differential pressure throttling element, the gas-phase differential pressure value ΔP g and liquid-phase differential pressure value ΔP l are measured, and the gas-phase velocity V g and liquid-phase velocity V l are calculated. Among them, the gas-phase differential pressure value ΔP g and liquid-phase differential pressure value ΔP l are obtained by the following method: The differential pressure value ΔP that can measure the mixed-phase differential pressure value in the pipeline installed on the Venturi differential pressure throttling element is set as ΔP g = ΔP * f(ΔP, ρg , α, ε) gas , ΔP l = ΔP * f(ΔP, α) liquid .

[0111] Obtain the above correction function f(ΔP, ρ g , α, ε) gas , f(ΔP, α) liquid The test method is as follows:

[0112] Step 1: Generate a two-phase fluid with a known gas-phase flow rate Q gas标准表 , liquid-phase flow rate Q liquid标准表 and a constant value. This two-phase fluid will flow through the instrument to be corrected (i.e., the indirect calculation fluid velocity measurement unit and the microwave gas-liquid component measurement unit), and the generated flow rates Q gas标准表 , Q liquid标准表 The range can refer to the actual estimated flow rate output range of the wellhead where this instrument to be corrected is applied;

[0113] Step 2: Record ΔP, ρ g , α, ε, ρ l , A, C, β and the flow rate Q liquid标准表 , Q gas标准表 in the standard device. Usually, when the fluid to be measured by the flowmeter and its structure are determined, then A, C, β, ρ l will be determined, and the other parameters will vary with the actual working conditions, ΔP, ρ g , α, ε.

[0114] Step 3: Calculate the correction function f(ΔP, ρ g , α, ε) gas , f(ΔP, α) liquid ;

[0115] First, according to the following formula:

[0116]

[0117]

[0118] From the above formula, the following formula can be obtained through conversion:

[0119]

[0120]

[0121] Substitute the data obtained through the above test into the above two formulas.

[0122] Step 4: Repeat the above operations. By setting different gas-liquid flow rates, several groups of data can be obtained. From these multiple groups of data, correction functions f(ΔP, ρ g , α, ε) gas , f(ΔP, α) liquid can be obtained.

[0123] The standard device mentioned above is a device that can generate a two-phase fluid with known gas-phase flow rate and liquid-phase flow rate. Generally, there are multiple schemes for the composition of such devices. Commonly used is: generating high-pressure gas through an air compressor and high-pressure liquid through a water pump. The generated gas and liquid are first measured by the gas flow meter and liquid flow meter in the standard device to obtain the gas-phase flow rate, which is Q gas标准表 and the liquid-phase flow rate, which is Q liquid标准表 . Then they are mixed to form a two-phase fluid, and then the two-phase fluid passes through the instrument to be corrected (i.e., the indirect calculation fluid velocity measurement unit (differential pressure conversion fluid velocity measurement unit) and the microwave method gas-liquid component measurement unit), so as to know whether the flow rate calculated by the instrument to be corrected is accurate. The gas-phase and liquid-phase flow rates can be set by adjusting the valve opening, water pump frequency, and air compressor pressure.

[0124] If ΔP g , ΔP l , ρ g , α, ε, ρ l , A, C, β are known, then the flow rate can be directly calculated according to the formula. However, since ΔP g and ΔP l cannot be directly measured using a single differential pressure throttling element, it is necessary to find the relationship between ΔP, ρ g , α, ε, ρ l , A, C, β and the flow rate, that is, the relationship between ΔP and ΔP g , ΔP l . That is the desired function f(ΔP, ρ g , α, ε) gas , f(ΔP, α) liquid . And in the above experiment, Q liquid标准表 , Q gas标准表 and the calculated functions f(ΔP, ρ g , α, ε) gas , f(ΔP, α) liquid are known. This is equivalent to knowing the flow rate if there are determined ΔP, ρ g , α, ε, ρ l , A, C, β.

[0125] Then, based on the Q liquid标准表 , Q gas标准表 and the calculated functions f(ΔP, ρ g obtained from the above experiment,,α,ε) gas 、f(ΔP,α) liquid Data, and the determined ΔP, ρ g ,α,ε,ρ l , A, C, β, and use the following formula to calculate the gas phase velocity V g , liquid phase velocity V l :

[0126]

[0127]

[0128] Where C is the outflow coefficient, β is the diameter ratio, ε is the gas expansion coefficient, ρ g The unit of gas density is g / m 3 , g / m3, ρ l The unit of liquid density is g / m 3 , g / m3, are all known quantities. l If the liquid is water, its density is about 1000g / m 3 ρ g The gas density can be calculated using the ideal gas state equation:

[0129]

[0130] Wherein, M is the molar mass of the gas, in g / mol; R is the gas constant, in J / (mol*K); T is the thermodynamic temperature of the gas, in K, which is measured by the temperature sensor in the indirect fluid velocity measurement unit; P is the pressure of the gas, in Pa, which is measured by the pressure sensor in the indirect fluid velocity measurement unit.

[0131] The C outflow coefficient is mentioned in the national standard GB / T 2624 and can be obtained by manufacturing according to the standard or through testing.

[0132] The ε gas expansion coefficient has different calculation methods depending on the different differential pressure throttling elements selected (the calculation method of the ε gas expansion coefficient of other differential pressure throttling elements shall refer to the national standard GB / T 2624). Taking the Venturi tube differential pressure throttling element as an example, it can be calculated by the following formula:

[0133]

[0134] Where β is the diameter ratio, κ is the isentropic index, and τ is the pressure ratio. The calculation formula for the τ pressure ratio is as follows:

[0135]

[0136]

[0137] Among them, P 节流元件处绝压 is the absolute pressure at the throttling element, with the unit of Pa; P 上游处绝压 is the absolute pressure at the upstream, with the unit of Pa; d 节流件内径 is the inner diameter of the throttling element, with the unit of mm; D 管段内径 is the inner diameter of the pipe section where the throttling element is installed, with the unit of mm;

[0138] Finally, the gas-phase flow rate Q g and the liquid-phase flow rate Q l are calculated through the following formula:

[0139] Q g = A g * V g

[0140] Q l = A l * V l

[0141] Among them, the gas-phase flow rate Q g has the unit of m 3 / h, the liquid-phase flow rate Q l has the unit of m 3 / h, the gas-phase velocity V g has the unit of m / h; the liquid-phase velocity V l has the unit of m / h.

[0142] Embodiment 2

[0143] As Figure 3 shown, the present invention provides a schematic flow chart of an on-line non-separating two-phase flow rate calculation method based on gas-liquid components, and its two-phase flow rate calculation method is as follows: (The following takes the fluid velocity measurement unit and the gas-liquid component measurement unit for indirect calculation to measure the gas holdup at the cross section as an example for illustration)

[0144] Using the microwave method gas-liquid component measurement unit, the gas holdup σ at the cross section can be measured. The principle is that the dielectric constant of water in gas-liquid is nearly 70 times different from that of natural gas, so the ratio of gas and liquid in the cross section can be distinguished; Given the pipe cross-sectional area A, the gas-phase cross-sectional area A g and the liquid-phase cross-sectional area A l flowing through the fluid in the pipe can be calculated through the following formula:

[0145] A l = A * (1 - σ)

[0146] A g = A * σ

[0147] Among them, the gas holdup σ has the unit of none, the measured pipe cross-sectional area A has the unit of mm 2 , the gas-phase cross-sectional area A gUnit: mm 2 , the cross-sectional area of the liquid phase A l Unit: mm 2 ;

[0148] Then, using the indirect calculation fluid velocity measurement unit (differential pressure conversion fluid velocity measurement unit), a Venturi differential pressure throttling element, measure the gas-phase differential pressure value ΔP g , the liquid-phase differential pressure value ΔP l , and calculate the gas-phase velocity V g , the liquid-phase velocity V l , where the gas-phase differential pressure value ΔP g , the liquid-phase differential pressure value ΔP l The acquisition method is as follows: The one installed on the Venturi differential pressure throttling element can measure the mixed-phase differential pressure value ΔP in the pipeline. Let ΔP l =ΔP*f(ΔP,ρ g ,σ,ε) gas , ΔP g =ΔP*f(ΔP,σ) liquid .<�

[0149] The test method for obtaining the above correction functions f(ΔP,ρ g ,σ,ε) gas , f(ΔP,σ) liquid is as follows:

[0150] Step 1: Generate a two-phase fluid with a known gas-phase flow rate Q gas standard meter, liquid-phase flow rate Q liquid标准表 and a constant value. This two-phase fluid will flow through the instrument to be corrected (i.e., the indirect calculation fluid velocity measurement unit and the microwave method gas-liquid component measurement unit), and the generated flow rates Q gas标准表 , Q liquid标准表 The range can refer to the actual estimated flow rate output range of the wellhead where this instrument to be corrected is applied;

[0151] Step 2: Record ΔP, ρ g , σ, ε, ρ l , A, C, β in the two-phase flowmeter at this time, and the flow rates Q liquid标准表 , Q gas标准表 in the standard device. Usually, when the fluid to be measured by the flowmeter and its structure are determined, then A, C, β, ρ l will be determined, and the other parameters will change with the actual working conditions ΔP, ρ g , σ, ε.

[0152] Step 3: Calculate the correction functions f(ΔP,ρ g ,σ,ε) gas , f(ΔP,σ) liquid ;

[0153] First, according to the following formula:

[0154]

[0155]

[0156] The following formula can be obtained by conversion from the above formula:

[0157]

[0158]

[0159] Substitute the data obtained from the above experiments into the above two formulas.

[0160] Step 4: Repeat the above operations. By setting different gas-liquid flow rates, several groups of data can be obtained. Through multiple groups of data, correction functions f(ΔP, ρ g , σ, ε) gas , f(ΔP, σ) liquid can be obtained.

[0161] The standard device mentioned above is: a device that can generate a two-phase fluid with known gas phase flow rate and liquid phase flow rate. Generally, there are multiple schemes for the composition of such devices. Commonly used is: generating high-pressure gas through an air compressor and high-pressure liquid through a water pump. The generated gas and liquid are first measured by the gas flow meter and liquid flow meter in the standard device to obtain the gas phase flow rate, which is Q gas标准表 , and the liquid phase flow rate, which is Q liquid标准表 . Then, they are mixed to form a two-phase fluid, and then the two-phase fluid passes through the instrument to be corrected (i.e., the indirect calculation fluid velocity measurement unit and the microwave method gas-liquid component measurement unit), so as to know whether the flow rate calculated by the instrument to be corrected is accurate. The gas phase and liquid phase flow rates can be set by adjusting the valve opening, water pump frequency, and air compressor pressure.

[0162] If ΔP g , ΔP l , ρ g , σ, ε, ρ l , A, C, β are known, then the flow rate can be directly calculated according to the formula. However, since ΔP g , ΔP l cannot be directly measured using a single differential pressure throttling element, it is necessary to find the relationship between ΔP, ρ g , σ, ε, ρ , A, C, β and the flow rate, that is, the relationship between ΔP and ΔP l , ΔP g , ΔP l , which is the required correction function f(ΔP, ρ g , σ, ε)gas , f(ΔP, σ) liquid . And in the above test, Q is known liquid标准表 , Q gas标准表 , the calculated correction function f(ΔP, ρ g , σ, ε) gas , f(ΔP, σ) liquid data. It is equivalent to that if there are determined ΔP, ρ g , σ, ε, ρ g , A, C, β, the flow rate can be known

[0163] Then, based on the Q known in the above test liquid标准表 , Q gas标准表 , the calculated correction function f(ΔP, ρ g , σ, ε) gas , f(ΔP, σ) liquid data, as well as the determined ΔP, ρ g , σ, ε, ρ g , A, C, β, and use the following formula to calculate the gas velocity V g , the liquid velocity V l :

[0164]

[0165]

[0166] where C is the discharge coefficient, β is the diameter ratio, ε is the gas expansion coefficient, ρ g The unit of gas density is g / m 3 , grams per cubic meter, ρ l The unit of liquid density is g / m 3 , grams per cubic meter, and both are known quantities. Among them, ρ l If the liquid is water, the density is about 1000 g / m 3 ; ρ g The gas density can be obtained through the ideal gas state equation:

[0167]

[0168] where M is the molar mass of the gas, with the unit of g / mol; R is the gas constant, with the unit of J / (mol*K); T is the gas thermodynamic temperature, with the unit of K, measured by the temperature sensor in the fluid velocity measurement unit for indirect calculation; P is the pressure of the gas, with the unit of Pa, measured by the pressure sensor in the fluid velocity measurement unit for indirect calculation

[0169] The discharge coefficient C is mentioned in the national standard GB / T 2624 and can be manufactured according to the standard or obtained through tests

[0170] The ε gas expansion coefficient has different calculation methods according to different differential pressure throttling elements selected (for the calculation methods of the ε gas expansion coefficient of other differential pressure throttling elements, refer to the national standard GB / T 2624). Taking the Venturi tube differential pressure throttling element as an example, it can be obtained from the following formula:

[0171]

[0172] Among them, β is the diameter ratio, κ is the isentropic exponent, τ is the pressure ratio, and the calculation formula of the τ pressure ratio is as follows:

[0173]

[0174]

[0175] Among them, P 节流元件处绝压 is the absolute pressure at the throttling element, with the unit of Pa; P 上游处绝压 is the absolute pressure at the upstream, with the unit of Pa; d 节流件内径 is the inner diameter of the throttling element, with the unit of mm; D 管段内径 is the inner diameter of the pipe section where the throttling element is installed, with the unit of mm;

[0176] Finally, the gas-phase flow rate Q g and the liquid-phase flow rate Q l are calculated through the following formula:

[0177] Q g = A g * V g

[0178] Q l = A l * V l

[0179] Among them, the gas-phase flow rate Q g has the unit of m 3 / h, the liquid-phase flow rate Q l has the unit of m 3 / h, the gas-phase velocity V g has the unit of m / h; the liquid-phase velocity V l has the unit of m / h.

[0180] In the present invention, the gas-liquid component measurement unit described is not limited to the microwave method gas-liquid component measurement unit, and a capacitance method, a ray attenuation method, an image method, etc. gas-liquid component measurement unit can be adopted;

[0181] In the present invention, the differential pressure throttling element described is not limited to the Venturi differential pressure throttling element, and an orifice plate, a nozzle, a wedge, etc. differential pressure throttling element can be selected, and the number thereof is at least one.

[0182] In the present invention, the fluid velocity measurement unit is not limited to using a differential pressure conversion fluid velocity measurement unit, and an ultrasonic fluid velocity measurement unit can also be used, or a fluid velocity measurement unit that can directly measure the flow rates of liquid and gas in a two-phase fluid.

[0183] The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A two-phase flow calculation method based on gas-liquid components, characterized in that, The method is as follows: The liquid holdup α of the cross-section is monitored in real time by using a gas-liquid component measurement unit installed in the measurement pipeline; the gas-phase cross-sectional area A g and the liquid-phase cross-sectional area A l through which the fluid flows in the measurement pipeline are calculated respectively by the following formula: A g = A * (1 - α) A l = A * α Among them, the cross-sectional liquid holdup α has no unit, and the measured cross-sectional area A of the pipeline has the unit of m 2 , the cross-sectional area of the gas phase A g has the unit of m 2 , and the cross-sectional area of the liquid phase A l has the unit of m 2 ; Reuse the setting to directly measure or indirectly calculate the gas phase velocity V by a fluid velocity measuring unit in the measuring pipeline g and the liquid phase velocity V l ; Finally, the flow integrator substitutes the directly measured or indirectly calculated gas-phase cross-sectional area A g , liquid-phase cross-sectional area A l , gas-phase velocity V g , liquid-phase velocity V l into the following formula to calculate the gas-phase flow rate Q g , liquid-phase flow rate Q l respectively: Q g = A g * V g Q l = A l * V l Among them, the gas phase flow rate Q g is in the unit of m 3 / h, and the liquid phase flow rate Q l is in the unit of m 3 / h. The gas phase velocity V g is in the unit of m / h; the liquid phase velocity V l is in the unit of m / h.

2. The two-phase flow calculation method according to claim 1, characterized in that the directly measured fluid velocity measurement unit includes a velocity sensor, a temperature sensor, and a pressure sensor; the indirectly calculated fluid velocity measurement unit includes at least one throttling element and its differential pressure sensor, temperature sensor, and pressure sensor.

3. The two-phase flow calculation method according to claim 2, characterized in that the indirectly calculated fluid velocity measurement unit adopts a differential pressure conversion fluid velocity measurement unit; the directly measured fluid velocity measurement unit adopts an ultrasonic fluid velocity measurement unit, or a fluid velocity measurement unit that directly measures the flow velocities of liquid and gas in the two-phase fluid.

4. The two-phase flow calculation method according to claim 3, characterized in that The described fluid velocity measurement unit adopts a differential pressure conversion fluid velocity measurement unit to calculate the gas phase velocity V g and the liquid phase velocity V l The method includes: The differential pressure conversion fluid velocity measurement unit adopts a differential pressure throttling element and uses it to measure the differential pressure value ΔP of the mixture in the measurement pipeline; assume: ΔP g = ΔP * f(ΔP, ρ g , α, ε) gas ΔP l = ΔP * f(ΔP, α) liquid Among them, the correction functions f(ΔP, ρ g , α, ε) gas and f(ΔP, α) liquid are the functional relationships between ΔP, ρ g , α, ε, ρ l , A, C, β and the flow rate respectively, that is, the functional relationships between ΔP and ΔP g , ΔP l respectively, which are obtained through experiments and calculations; among them, the mixed-phase differential pressure value ΔP, the gas-phase differential pressure value ΔP g , and the liquid-phase differential pressure value ΔP l are all in Pa; the correction functions f(ΔP, ρ g , α, ε) gas and f(ΔP, α) liquid are all unitless; Then the flow integrator substitutes the calculated gas-phase differential pressure value ΔP g and the liquid-phase differential pressure value ΔP l into the following formula to calculate the gas-phase velocity V g and the liquid-phase velocity V l respectively as follows: Among them, C is the discharge coefficient, β is the diameter ratio, ε is the gas expansion coefficient, and ρ g The unit of gas density is g / m 3 , ρ l The unit of liquid density is g / m 3 , all of which are known quantities; the gas phase velocity V g The unit is m / h; the liquid phase velocity V l The unit is m / h.

5. The two-phase flow calculation method according to claim 4, characterized in that, The test obtains correction functions f(ΔP, ρ g , α, ε) gas , f(ΔP, α) liquid The method includes: Generate a known gas-phase flow rate Q through a standard device gas标准表 and a liquid-phase flow rate Q gas标准表 to form a two-phase fluid with a constant value. This two-phase fluid will flow through the gas-liquid component measurement unit and the differential pressure throttling element of the differential pressure conversion fluid velocity measurement unit; Record the ΔP, ρ in the differential pressure throttling element of the gas-liquid component measurement unit and the differential pressure conversion fluid velocity measurement unit in real time g , α, ε, ρ l , A, C, β and the flow rate Q in the standard device liquid标准表 , Q gas Standard meter; Substitute the above ΔP, ρ g , α, ε, ρ l , A, C, β and the flow rate Q in the standard device liquid标准表 , Q gas标准表 into the following formula to calculate the correction functions f(ΔP, ρ g , α, ε) gas , f(ΔP, α) liquid respectively; Among them, the cross-sectional liquid holdup α has no unit, and the cross-sectional area A of the test measurement pipeline has the unit of m 2 , C is the discharge coefficient, β is the diameter ratio, ε is the gas expansion coefficient, ρ g The unit of the gas density is g / m 3 , ρ l The unit of the liquid density is g / m 3 , the flow rate Q liquid标准表 has the unit of m 3 / h, Q gas标准表 has the unit of m 3 / h, and the differential pressure value ΔP of the mixed phase has the unit of Pa; Then repeat the above operations. By setting different gas-liquid flow rates, several groups of data are obtained; through multiple groups of data, correction functions f(ΔP,ρ g ,α,ε) gas , f(ΔP,α) liquid are obtained.

6. The two-phase flow calculation method according to claim 5, characterized in that The described ρ l If the liquid is water, the density is approximately 1000 g / m 3 ; then ρ g The gas density is obtained by the following formula: where M is the molar mass of the gas, with the unit g / mol; R is the gas constant, with the unit J / (mol*K); T is the thermodynamic temperature of the gas, with the unit K (Kelvin), which is measured by the temperature sensor in the indirectly calculated fluid velocity measurement unit; P is the pressure of the gas, with the unit Pa, which is measured by the pressure sensor in the indirectly calculated fluid velocity measurement unit.

7. The two-phase flow calculation method according to claim 4 or 5 or 6, characterized in that the differential pressure throttling element is selected from a Venturi differential pressure throttling element, or an orifice plate differential pressure throttling element, or a nozzle differential pressure throttling element, or a wedge differential pressure throttling element, and the number thereof is at least one.

8. The two-phase flow calculation method according to claim 7, characterized in that the differential pressure throttling element is selected from a Venturi tube differential pressure throttling element, and the gas expansion coefficient ε is obtained by the following formula: where β is the diameter ratio, κ is the isentropic index, τ is the pressure ratio, and the calculation formulas for the pressure ratio τ and the diameter ratio β are as follows: Among them, P 节流元件处绝压 is the absolute pressure at the differential pressure throttling element, with the unit of Pa; P 上游处绝压 is the absolute pressure upstream of the differential pressure throttling element, with the unit of Pa; d 节流元件内径 is the inner diameter of the differential pressure throttling element, with the unit of mm; D 管段内径 is the inner diameter of the measuring pipe section where the differential pressure throttling element is installed, with the unit of mm.

9. The two-phase flow calculation method according to claim 1 or 2 or 3 or 4 or 5 or 6, characterized in that the gas-liquid component measurement unit adopts a microwave method, or a capacitance method, or a ray attenuation method, or an image method gas-liquid component measurement unit.

10. A two-phase flow calculation method based on gas-liquid components, the method is characterized in that, The method is as follows: The gas-liquid component measurement unit installed in the measurement pipeline is used to monitor the gas holdup σ of the cross-section in real time; the gas-phase cross-sectional area A g and the liquid-phase cross-sectional area A l flowed through by the fluid in the measurement pipeline are calculated respectively by the following formula: A l = A * (1 - σ) A g = A * σ Among them, the cross-sectional gas holdup σ has no unit, the measured cross-sectional area A of the pipeline has the unit of m 2 , the cross-sectional area of the gas phase A g has the unit of m 2 , the cross-sectional area of the liquid phase A l has the unit of m 2 ; Reuse the setting to directly measure or indirectly calculate the gas phase velocity V by the fluid velocity measurement unit in the measurement pipeline g and the liquid phase velocity V l ; Finally, the flow integrator substitutes the directly measured or indirectly calculated gas-phase cross-sectional area A g and liquid-phase cross-sectional area A l , gas-phase velocity V g , and liquid-phase velocity V l into the following formula to separately calculate the gas-phase flow rate Q g and liquid-phase flow rate Q l : Q g = A g * V g Q l = A l * V l Among them, the gas phase flow rate Q g is in the unit of m 3 / h, and the liquid phase flow rate Q l is in the unit of m 3 / h. The gas phase velocity V g is in the unit of m / h; the liquid phase velocity V l is in the unit of m / h.

11. The two-phase flow calculation method according to claim 9, characterized in that the directly measured fluid velocity measurement unit includes a velocity sensor, a temperature sensor, and a pressure sensor; the indirectly calculated fluid velocity measurement unit includes at least one throttling element and its differential pressure sensor, temperature sensor, and pressure sensor.

12. The two-phase flow calculation method according to claim 11, characterized in that the indirectly calculated fluid velocity measurement unit adopts a differential pressure conversion fluid velocity measurement unit; the directly measured fluid velocity measurement unit adopts an ultrasonic fluid velocity measurement unit, or a fluid velocity measurement unit that directly measures the flow velocities of liquid and gas in the two-phase fluid.

13. The two-phase flow calculation method according to claim 12, characterized in that The described fluid velocity measurement unit adopts a differential pressure conversion fluid velocity measurement unit to calculate the gas phase velocity V g and the liquid phase velocity V l The method includes: the differential pressure conversion fluid velocity measurement unit adopts a differential pressure throttling element and uses it to measure the differential pressure value ΔP of the mixture in the measurement pipeline; assume: ΔP g = ΔP * f(ΔP, ρ g , σ, ε) gas ΔP l = ΔP * f(ΔP, σ) liquid Among them, the correction functions f(ΔP, ρ g , σ, ε) gas and f(ΔP, σ) liquid are the functional relationships between ΔP, ρ g , σ, ε, ρ l , A, C, β and the flow rate, that is, the functional relationships between ΔP and ΔP g and ΔP l respectively, which are obtained through experiments and calculations; among them, the mixed-phase differential pressure value ΔP, the gas-phase differential pressure value ΔP g , and the liquid-phase differential pressure value ΔP l are all in the unit of Pa; the correction functions f(ΔP, ρ g , σ, ε) gas and f(ΔP, σ) liquid are both unitless; Then the flow integrator substitutes the calculated gas-phase differential pressure value ΔP g , the liquid-phase differential pressure value ΔP l into the following formula to calculate the gas-phase velocity V g , the liquid-phase velocity V l respectively: Among them, C is the discharge coefficient, β is the diameter ratio, ε is the gas expansion coefficient, and ρ g The unit of gas density is g / m 3 , ρ l The unit of liquid density is g / m 3 , all of which are known quantities; the gas phase velocity V g The unit is m / h; the liquid phase velocity V l The unit is m / h.

14. The two-phase flow calculation method according to claim 13, wherein The test obtains correction functions f(ΔP, ρ g , σ, ε) gas , f(ΔP, σ) liquid The method includes: Generate a known gas-phase flow rate Q through a standard device gas标准表 and a liquid-phase flow rate Q gas标准表 to form a two-phase fluid with a constant value. The two-phase fluid will flow through the gas-liquid component measurement unit and the differential pressure throttling element of the differential pressure conversion fluid velocity measurement unit; Record the ΔP, ρ in the differential pressure throttling element of the gas-liquid component measurement unit and the differential pressure conversion fluid velocity measurement unit in real time g , σ, ε, ρ l , A, C, β and the flow rate Q in the standard device liquid标准表 , Q gas标准表 ; Substitute the above ΔP, ρ g , σ, ε, ρ l , A, C, β and the flow rate Q in the standard device liquid标准表 , Q gas标准表 into the following formula to calculate the correction functions f(ΔP, ρ g , σ, ε) gas , f(ΔP, σ) liquid respectively; Among them, the cross-sectional gas holdup σ has no unit, and the cross-sectional area A of the test measurement pipeline has a unit of m 2 , C is the discharge coefficient, β is the diameter ratio, ε is the gas expansion coefficient, ρ g The unit of gas density is g / m 3 , ρ l The unit of liquid density is g / m 3 , the flow rate Q liquid标准表 has a unit of m 3 / h, Q gas标准表 has a unit of m<00> 3 / h, and the mixed-phase differential pressure value ΔP has a unit of Pa; Then repeat the above operations. By setting different gas-liquid flow rates, several groups of data are obtained; through multiple groups of data, correction functions f(ΔP,ρ g ,σ,ε) gas , f(ΔP,σ) liquid are obtained.

15. The two-phase flow calculation method according to claim 14, wherein The described ρ l If the liquid is water, the density is approximately 1000 g / m 3 ; then ρ g The gas density is obtained by the following formula: where M is the molar mass of the gas, in g / mol; R is the gas constant, in J / (mol*K); T is the thermodynamic temperature of the gas, in K, Kelvin, which is measured by the temperature sensor in the fluid velocity measurement unit for indirect calculation; P is the pressure of the gas, in Pa, which is measured by the pressure sensor in the fluid velocity measurement unit for indirect calculation.

16. The two-phase flow calculation method according to claim 13 or 14 or 15, wherein the differential pressure throttling element is selected from a Venturi differential pressure throttling element, or an orifice plate differential pressure throttling element, or a nozzle differential pressure throttling element, or a wedge differential pressure throttling element, and the number thereof is at least one.

17. The two-phase flow calculation method according to claim 16, wherein the differential pressure throttling element is selected from a Venturi tube differential pressure throttling element, and the gas expansion coefficient ε is obtained by the following formula: where β is the diameter ratio, k is the isentropic exponent, τ is the pressure ratio, and the calculation formulas for the pressure ratio τ and the diameter ratio β are as follows: Among them, P 节流元件处绝压 is the absolute pressure at the differential pressure throttling element, with the unit of Pa; P 上游处绝压 is the absolute pressure upstream of the differential pressure throttling element, with the unit of Pa; d 节流元件内径 is the inner diameter of the differential pressure throttling element, with the unit of mm; D 管段内径 is the inner diameter of the measuring pipe section where the differential pressure throttling element is installed, with the unit of mm.

18. The two-phase flow calculation method according to claim 10 or 11 or 12 or 13 or 14 or 15, wherein the gas-liquid component measurement unit adopts a microwave method, or a capacitance method, or a ray attenuation method, or an image method for the gas-liquid component measurement unit.

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