Abstract: A three-phase flowmeter from Norway's Roxar Company was field tested at a condensate gas concentration treatment station in Jalalco. The three-phase flowmeter was installed on the front end of the Triassic metering separator, and the single-well oil and gas production was measured online in real time. The field test proved that the repeatability and accuracy of the MPFM1900 VI three-phase flow meter can meet the relevant technical requirements in the on-site test acceptance criteria, and can be applied to the high-pressure condensate gas well metering analysis and data acquisition work.
Keywords: Flow meter measuring phase fraction flow rate flow rate
1 device structure
The Roxar three-phase non-separation flowmeter consists of a gamma density meter, capacitance measurement and sensors, conductivity measurement and sensors, a venturi device, and a flow computer. The data acquisition system consists of a temperature transmitter, a pressure transmitter, a differential pressure transmitter, a gamma density meter, a capacitance sensor, a conductivity sensor, and a flow calculation system. Structure shown in Figure 1, Figure 2.
2 Measurement principle
Roxar three-phase non-separation flow meter measurement principle shown in Figure 3.
The single-bore oil and gas water mixture is assumed to be a four-phase fluid, ie, oil, water, discrete gas, and free gas. The large bubble flow rate is the same as the gas flow rate (large bubbles are discrete gases), the small bubble flow rate is the same as the liquid flow rate (small bubbles are free gases), and the oil phase flow rate and the water flow rate in the vertical measurement pipe section of the three-phase flow meter are the same. Suppose: Q is the volume flow rate; A is the volume phase fraction; v is the flow rate
Q=Av (1)
The volume phase fraction is equal to the product of the phase fraction and the cross-sectional area of ​​the measuring tube. Since the cross-sectional area of ​​the measuring tube is known, the calculation of the flow rate of each phase of oil and gas can be converted to the phase fraction and the flow rate of each phase.
(1) Calculation of phase fraction. Suppose: Ï oil is oil phase density; Ï water is water phase density; Ï gas is gas phase density (oil phase density, water phase density and gas phase density before measurement input); ε oil is oil phase permittivity; ε water is water phase Capacitance; ε gas is the gas phase permittivity (the oil phase permittivity is calculated by the flow computer according to the input fluid PVT parameter, the water phase permittivity is constant, approximately equal to 70, the gas phase permittivity is constant, approximately equal to 1); σ oil For the oil phase conductivity; σ water for the water phase conductivity; σ gas for the gas phase conductivity (water phase conductivity according to the input fluid PVT parameters obtained by the flow computer, the oil phase conductivity and gas phase conductivity are constant, numerical Tends to infinity; Ï mixture is the mixture density; ε mixture is the mixture permittivity; σ mixture is the mixture conductivity (mixture density can be measured with a gamma density meter, the mixture permittivity can be measured with a capacitance sensor, and the mixture conductivity is The conductivity sensor can be measured); α is the gas phase fraction; β is the water phase fraction; γ is the oil phase fraction (the gas phase fraction is the volume percentage of large and small bubbles in the mixture per unit time, water The fraction of the aqueous phase per unit of time representing the volume percentage in the mixture, the oil phase fraction of the unknown variables in the oil phase comprises a mixture volume percent, α, β and γ are the equations unit time).
The low-water content permittivity sensor works. The three equations of the permittivity equation, the density equation, and the normalization equation are used to solve the phase fractions of oil and water phases; the conductivity sensor works in the high water content phase, the conductivity equation, the density equation, and the normalization. The three equations of the equation are solved simultaneously for the phase fraction of oil and gas phases. (2) Calculation of flow rate and flow rate. The Roxar three-phase flowmeter distributes paired capacitance detection electrodes and conductance detection electrodes at two points of a known distance. When the same fluid passes through the detection electrode in sequence, the detection electrode will continuously collect two sets of electrical signals. The curves formed by the two sets of electrical signals are similar in shape, but are in different time segments. The cross-correlation calculations of the two sets of electrical signal curves can yield maxima. The corresponding time is T, which is the time required for the fluid to flow from electrode A to electrode B.
Assume that: V is the fluid flow rate; d is the electrode potential difference; T is the time required for the fluid to flow from electrode A to electrode B. then
V=d/T (6)
Among them: d is a known quantity, T can be obtained through cross-correlation calculation, and solving equation (5) can determine the flow rate (when the fluid passing through the electrode is a large bubble, the calculated flow rate is the gas flow rate; when passing through the electrode When the fluid is a small bubble, the calculated flow rate is the liquid flow rate).
Sometimes cross-correlation calculations cannot be maximal, and cross-correlation operations are considered to fail. Roxar three-phase flowmeter can set the minimum allowable success rate of cross-correlation calculation when calculating the flow rate. When it is lower than the set value, the result of cross-correlation operation is not obtained, and the venturi's calculated flow rate prevails.
Venturi device flow rate calculation formula
Where: M is the mass flow rate; dp is the venturi differential pressure; C is the flow coefficient, C=f(ReD, β); E is the compensation coefficient, E=1/ 
ReD is the Reynolds number; β is the ratio of the inner diameter to the outer diameter, Venturi throat diameter / inner diameter of the venturi; ε is the expansion factor, ε = f(dP/P, β, γ); γ is constant pressure heat capacity and constant volume heat The ratio of the volume, γ = CP / CV; A is the venturi through the pipe area.
The oil-gas-water phase fraction and the gas-liquid phase velocity are obtained. Solving equation 1 can calculate the volumetric flow rate of each phase of oil-gas-water.
(3) The main technical indicators. Operating range: 0 to 100% moisture content (WLR); 0 to 98% gas porosity (GVF); measurement accuracy: liquid phase relative error of 3% to 6%; water content (90% confidence) absolute error of 1.5 % to 4%; gas phase relative error of 6% to 8%; standard speed range: low GVF of 1.5 to 15m/s; high GVF of 3.5 to 35m/s; pipe size of 2 to 12inch (43 to 220mm); The pressure is 69000 kPa; the design temperature is 150°C (3028/).
(4) Field test. Three-phase flowmeters from Norway's Roxar Co., Ltd. were field tested at a condensate gas concentration treatment station in Jilaq. The three-phase flowmeters were installed on the front-end headers of the Triassic metering separator to measure real-time oil, gas and water production of individual wells online. The field test proved that the repeatability and accuracy of the MPFM1900 VI three-phase flow meter can meet the relevant technical requirements in the on-site test acceptance criteria, and can be applied to the high-pressure condensate gas well metering analysis and data acquisition work.
3 conclusions
The three-phase non-separation flowmeter does not need to be separated, mixed, and has no moving parts. It can accurately measure the oil, gas and water production of high-pressure condensate gas wells. The instrument has excellent long-term stability, accuracy and repeatability, and can meet the measurement requirements of condensate gas wells in the Tarim Oilfield. In summary, Roxar's three-phase non-separation flowmeter has a broad market prospect in the Tarim Oilfield.
Keywords: Flow meter measuring phase fraction flow rate flow rate
1 device structure
The Roxar three-phase non-separation flowmeter consists of a gamma density meter, capacitance measurement and sensors, conductivity measurement and sensors, a venturi device, and a flow computer. The data acquisition system consists of a temperature transmitter, a pressure transmitter, a differential pressure transmitter, a gamma density meter, a capacitance sensor, a conductivity sensor, and a flow calculation system. Structure shown in Figure 1, Figure 2.
Figure 1 Roxar three-phase flowmeter structure
Figure 2 Roxar three-phase non-separation flowmeter internal view
2 Measurement principle
Roxar three-phase non-separation flow meter measurement principle shown in Figure 3.
Figure 3 Roxar three-phase flow meter measurement principle
The single-bore oil and gas water mixture is assumed to be a four-phase fluid, ie, oil, water, discrete gas, and free gas. The large bubble flow rate is the same as the gas flow rate (large bubbles are discrete gases), the small bubble flow rate is the same as the liquid flow rate (small bubbles are free gases), and the oil phase flow rate and the water flow rate in the vertical measurement pipe section of the three-phase flow meter are the same. Suppose: Q is the volume flow rate; A is the volume phase fraction; v is the flow rate
Q=Av (1)
The volume phase fraction is equal to the product of the phase fraction and the cross-sectional area of ​​the measuring tube. Since the cross-sectional area of ​​the measuring tube is known, the calculation of the flow rate of each phase of oil and gas can be converted to the phase fraction and the flow rate of each phase.
(1) Calculation of phase fraction. Suppose: Ï oil is oil phase density; Ï water is water phase density; Ï gas is gas phase density (oil phase density, water phase density and gas phase density before measurement input); ε oil is oil phase permittivity; ε water is water phase Capacitance; ε gas is the gas phase permittivity (the oil phase permittivity is calculated by the flow computer according to the input fluid PVT parameter, the water phase permittivity is constant, approximately equal to 70, the gas phase permittivity is constant, approximately equal to 1); σ oil For the oil phase conductivity; σ water for the water phase conductivity; σ gas for the gas phase conductivity (water phase conductivity according to the input fluid PVT parameters obtained by the flow computer, the oil phase conductivity and gas phase conductivity are constant, numerical Tends to infinity; Ï mixture is the mixture density; ε mixture is the mixture permittivity; σ mixture is the mixture conductivity (mixture density can be measured with a gamma density meter, the mixture permittivity can be measured with a capacitance sensor, and the mixture conductivity is The conductivity sensor can be measured); α is the gas phase fraction; β is the water phase fraction; γ is the oil phase fraction (the gas phase fraction is the volume percentage of large and small bubbles in the mixture per unit time, water The fraction of the aqueous phase per unit of time representing the volume percentage in the mixture, the oil phase fraction of the unknown variables in the oil phase comprises a mixture volume percent, α, β and γ are the equations unit time).
Assume that: V is the fluid flow rate; d is the electrode potential difference; T is the time required for the fluid to flow from electrode A to electrode B. then
V=d/T (6)
Among them: d is a known quantity, T can be obtained through cross-correlation calculation, and solving equation (5) can determine the flow rate (when the fluid passing through the electrode is a large bubble, the calculated flow rate is the gas flow rate; when passing through the electrode When the fluid is a small bubble, the calculated flow rate is the liquid flow rate).
Sometimes cross-correlation calculations cannot be maximal, and cross-correlation operations are considered to fail. Roxar three-phase flowmeter can set the minimum allowable success rate of cross-correlation calculation when calculating the flow rate. When it is lower than the set value, the result of cross-correlation operation is not obtained, and the venturi's calculated flow rate prevails.
Venturi device flow rate calculation formula
ReD is the Reynolds number; β is the ratio of the inner diameter to the outer diameter, Venturi throat diameter / inner diameter of the venturi; ε is the expansion factor, ε = f(dP/P, β, γ); γ is constant pressure heat capacity and constant volume heat The ratio of the volume, γ = CP / CV; A is the venturi through the pipe area. The oil-gas-water phase fraction and the gas-liquid phase velocity are obtained. Solving equation 1 can calculate the volumetric flow rate of each phase of oil-gas-water.
(3) The main technical indicators. Operating range: 0 to 100% moisture content (WLR); 0 to 98% gas porosity (GVF); measurement accuracy: liquid phase relative error of 3% to 6%; water content (90% confidence) absolute error of 1.5 % to 4%; gas phase relative error of 6% to 8%; standard speed range: low GVF of 1.5 to 15m/s; high GVF of 3.5 to 35m/s; pipe size of 2 to 12inch (43 to 220mm); The pressure is 69000 kPa; the design temperature is 150°C (3028/).
(4) Field test. Three-phase flowmeters from Norway's Roxar Co., Ltd. were field tested at a condensate gas concentration treatment station in Jilaq. The three-phase flowmeters were installed on the front-end headers of the Triassic metering separator to measure real-time oil, gas and water production of individual wells online. The field test proved that the repeatability and accuracy of the MPFM1900 VI three-phase flow meter can meet the relevant technical requirements in the on-site test acceptance criteria, and can be applied to the high-pressure condensate gas well metering analysis and data acquisition work.
3 conclusions
The three-phase non-separation flowmeter does not need to be separated, mixed, and has no moving parts. It can accurately measure the oil, gas and water production of high-pressure condensate gas wells. The instrument has excellent long-term stability, accuracy and repeatability, and can meet the measurement requirements of condensate gas wells in the Tarim Oilfield. In summary, Roxar's three-phase non-separation flowmeter has a broad market prospect in the Tarim Oilfield.
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