RU2746167C1 - Multiphase flowmeter for the component-by-component determination of the flow rates of gas, hydrocarbon condensate and water in the products of gas condensate wells - Google Patents

Abstract

FIELD: measuring tech.

SUBSTANCE: invention relates to the field of measuring technology and can be used in gas wells or areas of primary gas processing. The multiphase flowmeter consists of a restriction device, measuring and reference resonators of the decimeter range, a filter that beats off the liquid phase, a gas volume meter that has passed through the filter, temperature and pressure control devices in the measuring and reference resonator, electrically controlled valves, electronic blocks - a flowmeter operation control unit and a block for processing information and calculating component costs. The restriction device is made in the form of a Venturi tube, on which the pressure drop ΔP is measured, which makes it possible to determine the gas-liquid flow rate. The density of the gas-liquid flow is measured by the frequency shift of the measuring resonator covering the throat of the Venturi tube.

EFFECT: operational determination of natural gas, hydrocarbon condensate and water consumption without preliminary separation of well production products into these components.

6 cl, 1 dwg

Description

The invention relates to the field of measuring technology and can be used in wells or primary gas treatment plants to determine the flow rate of gas, liquid hydrocarbon condensate and water without dividing the well production product into its constituent components.

There is a known method and device for determining the component-wise flow rate of a gas-liquid mixture (GZHM), based on the results of the interaction of GZHM with an electromagnetic field of the millimeter wavelength range, measurement of the Doppler frequency and the resonant frequency of a microwave resonator of the Fabry-Perot type filled with GZHM, calculation of the flow rate and cross-sectional areas occupied by the liquid and gas phase and the subsequent determination of the gas and liquid flow rates [1].

The disadvantages of the method and device are the impossibility of determining the ratio of the volume fractions of water and hydrocarbon condensate in a liquid, as well as a low upper limit of the water-gas factor (WGF) of ~ 100 cm ³ / nm ³ , while most wells have a WGF significantly exceeding this figure.

The disadvantages of the device are also the steep angles of the input narrowing device, the difference between the mirrors of the Fabry-Perot resonator (RFP) and flat ones, and the presence in the resonator volume of a plate that dampens parasitic oscillations, which creates a gas-dynamic resistance to the gas flow and causes instability of its spatial position, leading to sharp jumps signal from the resonator detector, which requires the use of complex static methods of signal processing and, in turn, necessitates the use of a powerful computing device.

Closest to the proposed flow meter is the device [2], selected for the prototype. It contains a measuring section built into the pipeline with transitions from a standard section of the pipeline to a narrowed section, which is covered by a measuring resonator of decimeter waves, a bypass line with a reference resonator built into it, identical to the measuring one, which is filled with gas that has passed through a filter that repels the liquid phase, and electronic blocks measuring the resonant frequencies and Q-factors of both resonators when the gas-liquid mixture flows through the main pipeline. By processing the data obtained from the resonators, the volume fractions of gas, water and hydrocarbon condensate coming from the well are established.

In this case, the constriction device plays an unimportant role in the reduced structure: it is only needed to mate the smaller diameter of the resonator through hole with the larger diameter of the working pipeline.

The disadvantage of the device, taken as a prototype, is the lack of a flow rate meter. In addition, due to the small pressure drop across the orifice and the sufficiently high gas-dynamic resistance of the filter, the gas flow through the reference resonator is extremely small. This leads to long delay times of the readings of the reference resonator in relation to the measuring one, which ultimately leads to an increase in the error in measuring the density of the gas-liquid mixture.

The next disadvantage of the device is the difficulty in regenerating the filter and removing droplet liquid from it.

The disadvantage of this method and device is also the need to calculate the compressibility factor when determining the density under operating conditions of pure (free from liquid phase) gas in the reference resonator.

The disadvantage of this method is the fact that the algorithm for obtaining information about the volume fraction of condensate C _{3 is} constructed in such a way that the fraction due to the pure gas is subtracted from the frequency shift of the measuring resonator, then the Q-factor of the resonator with a gas-liquid flow is measured, and the volume fraction of water C is found from the change in Q-factor. ₂ ; then the frequency shift attributable to it is subtracted from the frequency shift of the measuring resonator, and the volume fraction of the condensate is calculated from the remaining shift. In this case, since water is a dielectric with a dielectric constant (DP) significantly higher than the DP of condensate, even small errors in determining the proportion of water C ₂ strongly affect the value of C ₃ .

The disadvantage of the device is also the lack of sensors that record the speed and longitudinal size of water plugs, which are often found in gas condensate wells.

The technical result of the proposed invention is the ability to quickly determine the flow rate of the production products of a gas or gas condensate well - natural gas, hydrocarbon condensate and water - without dividing the well production product into its constituent components, as well as determining the volume fraction of condensate, water and gas in the flow of gas liquids with error.

The technical result is achieved by the fact that in a multiphase flow meter for the component-by-component determination of the flow rates of gas, hydrocarbon condensate and water in the products of production of gas condensate wells, consisting of a restriction device, measuring and reference resonators of the decimeter range, a filter that beats off the liquid phase, a gas volume meter passed through the filter , temperature and pressure control devices in the measuring and reference resonator, electrically controlled valves, electronic control units for the flow meter and information processing unit and for calculating component flow rates, inlet and outlet transition sections from the standard section of the pipeline to the narrowed section in the pipe measuring section are made in the form of a pipe Venturi, at which the differential pressure ΔP is measured, which makes it possible to determine the gas-liquid flow rate.

The technical result is also achieved by the fact that the gas outlet in the filter, which beats off the liquid phase, is made in a volume with low pressure (of the order of atmospheric pressure), which makes it possible to efficiently purge the filter.

The technical result is also achieved by the fact that the filter contains a heater that allows you to transfer the liquid phase to the vapor phase and, in the presence of a gas flow, to clean the filter from the stripped liquid.

The technical result is also achieved by the fact that the filter, which beats off the liquid phase, is made in the form of a cylindrical waveguide and is transmitted through millimeter-wave radio waves.

The technical result is also achieved by the fact that an electrically adjustable valve is installed in the bypass line, which makes it possible to change the pressure in the reference resonator and, according to the resonator's reaction to the gas pressure and temperature, to quickly determine the gas compressibility factor.

The technical result is also achieved by the fact that the measuring section contains a resistive or capacitive probe, which makes it possible to determine the time of the beginning of the passage of the water plug and the time of its end.

The drawing schematically depicts a multiphase flow meter for the component-wise determination of the flow rates of gas, hydrocarbon condensate and water in the products of the production of gas condensate wells. The multiphase flowmeter includes: a standard pipeline 1, a restriction device - a Venturi tube 2, a measuring resonator of the decimeter range 3, a reference resonator 4 identical to it, a filter 5 stripping the liquid phase, a heater 6, a probe for sampling 7, horns for transmitting the filter with millimeter waves range - emitting 8 and receiving 9, millimeter wave generator 10, ferrite valve 11, detector 12, electrically controlled valves 13, 14, 15 and 34, gas volume meter in operating conditions 16, meters of thermobaric parameters of the gas-liquid mixture in the resonator 3 -pressure 17 and temperature 18, pressure meter 19 and gas temperature 20 in resonator 4, flow meter operation control unit 21, computing device 22, data transfer device to the upper level 23, pressure drop meter across Venturi tube 24, millimeter wave generator power supply from control unit 25, output from the millimeter-wave detector to the computing device at 26, input and output of the filter heater spiral 27 and 28, communication cable 29 between blocks 21 and 22, power supply 30 to resonator 3, output to the detector from resonator 3-31, power supply to resonator 4-32, output from the detector resonator 4-33, gas outlet to a low pressure volume (~ 1 atm) per candle or catalytic combustion - 35. Designations 13 *, 14 *, 15 * ... 32 * - outputs of the control unit to the corresponding sensors or inputs from sensors to the computational device.

The operation of a multiphase flow meter is as follows. The control unit supplies the measuring resonator 3 and the reference resonator 4 with a voltage linearly varying in frequency in the decimeter wave range so that the resonators 3 and 4 (they are made identical) are excited on the TM ₀₁₀ mode (the frequency corresponding to this mode in the absence of flux is denoted by ƒ ₀ ). At the same time, the millimeter-wave generator 10 is started, producing a microwave signal stabilized in frequency and amplitude, which is recorded by the detector 12. The ferrite valve 11 serves to prevent the filter from affecting the generator 10.

When the product of the well production appears in the pipeline 1, the resonator 3 is filled with a flow of gas mixture. In this case, its resonant frequency ƒ ₀ is shifted due to the appearance of gas, condensate and water in it and becomes equal to ƒ _Σ . In this case, the equality is fulfilled:

Here Δƒ ₁ = ƒ ₀ - ƒ ₁ ; Δƒ ₂ = ƒ ₀ - ƒ ₂ ; Δƒ ₃ = ƒ ₀ - ƒ ₃ , where ƒ ₁ , ƒ ₂ and ƒ ₃ are the resonant frequencies of the resonator when individual flow components are introduced into it, namely: only gas (ƒ ₁ ), only water (ƒ ₂ ), and only condensate ( ƒ ₃ ) in those volumes and at those temperatures and pressures in which they are present in the gas-liquid mixture flow. Those. Δƒ ₁ , Δƒ ₂ , Δƒ ₃ are the partial shifts of the resonator frequency due to the introduction of gas, water and condensate into its volume, and Δƒ _Σ = ƒ ₀ - ƒ _Σ is the total frequency shift [3].

The contributions of Δƒ ₁ , Δƒ ₂ and Δƒ ₃ to the total frequency shift are unknown and are to be determined further. First, determine the value of Δƒ ₁ .

сдвиги частоты.To do this, by command from the control unit 21 for some time Δt = t ₂ - t ₁ (where t ₁ and t ₂ are the opening and closing times), valves 34, 14 and 15 are opened. After that, a small fraction of the flow of the gas mixture (10 ^-3 … 10 ^-4 ) begins to fill the bypass line through the intake opening. In this case, the liquid fraction of the flow - hydrocarbon condensate and water - are captured by the filter 5, and the gas, free from the droplet-liquid aerosol, fills the resonator 4 up to the working pressure 3 at the working temperature T. The frequency of the resonator 4 - ƒ _{1 is} measured, the absolute Δƒ _{1 is} calculated and relative

frequency shifts.

Then determine the relative partial shift given by the water aerosol. To do this, measure the value of the signal from the detector before and after closing the valves 34, 14 and 15 - U ₀ and U _1, respectively, and simultaneously measure the volume (under operating conditions) of the gas that has passed through the bypass line with the gas meter 16.

Since the condensate has a small tangent of the loss angle at millimeter waves, the entire attenuation of the signal passed through the filter 5 is due only to the water fraction collected in it.

Then calculate the mass of water trapped by the filter m _in . To do this, use the ratio:

in which the coefficient k _in is determined in advance. Then calculate the volume of water V _in :

where ρ _in is the density of water.

Knowing the volume of the gas V _byp passed through the filter and the volume of water V _in , the volume fraction of water in the mixture of the gas-liquid flow is found:

After that, the relative frequency shift due to the water fraction is calculated according to the ratio:

- действительная и мнимая части диэлектрической постоянной воды на частоте ƒ₀; С₂ - объемная доля воды в резонаторе 3.Where

- real and imaginary parts of the dielectric constant of water at a frequency ƒ ₀ ; С ₂ - volume fraction of water in resonator 3.

резонатора 3, обязанный только углеводородному конденсату:Further, from relation (1), the frequency shift is found

resonator 3, owing only to hydrocarbon condensate:

, находят объем конденсата V_к из соотношения:Knowing

, find the volume of condensate V _to from the ratio:

here V _o is the volume of resonator 3; ε _k is the dielectric constant of the condensate under operating conditions, η is a form factor that takes into account the fact that the resonator is not completely filled with a dielectric [3], [4]. The value of η is preliminarily set experimentally.

After that, the volume V _to is determined and the volume fraction of condensate in the gas liquids flow is calculated:

Knowing the volume fraction of water C ₂ and condensate C ₃ , find the volume fraction of gas C ₁ :

C ₁ = 1 - (C ₂ + C ₃ )

After determining the volume fractions of the components of the gas mixture, the gas from the resonator 4 is vented onto the candle (or disposed of in some other way). After venting the gas, gas remains in the bypass line at a pressure of P ≈ 1 atm. Measure the values of P = P ₁ , T = T ₁ and the frequency of the resonator 4 ƒ ₀ . These data will be further used to calculate the compressibility factor K.

Next, proceed to the determination of partial volumetric flow rates under operating conditions: gas - Q ₁ , water - Q ₂ and condensate - Q ₃ . At the beginning, the flow rate of the gas-liquid mixture Q _{gzhs is determined} .

The basis of the formula for determining the volumetric flow _{rate of gas mixture Q cm is} taken from the classical formula [5] for measuring the flow rate of dry gas, corrected for the presence of liquid in the aerosol phase in the gas flow. This accounting is carried out by the function ψ, depending on the gas velocity and the percentage of the liquid phase in it.

where S is the cross-sectional area of the Venturi pipe, E is the inlet coefficient, C is the outflow coefficient, β is the expansion coefficient, ρ _cm is the density of the mixture under operating conditions, ΔP _cm is the pressure drop across the Venturi tube, ψ is a correction factor that takes into account the effect of liquid phases per flow rate. The function ψ is either determined in advance on the experimental bench, or is calculated based on published literature data, for example, from [6]. In what follows, we will assume that it is known. The coefficients S, E, C, β are calculated in advance [5]: the pressure drop ΔP _cm is measured by the device 24. The density of the mixture ρ _cm in the flow formula is calculated based on the volume fractions of the components.

where ρ ₁ , ρ ₂ and ρ ₃ are the density of gas, water and condensate under operating conditions.

The density of water under operating conditions is assumed to be 1.0 kg / dm ³ , the density of unstable hydrocarbon condensate ρ _{3 is} reported by the laboratory of the gas company that owns the well.

The gas density at operating conditions ρ _{1 is} calculated based on the gas density at standard conditions ρ _с , thermobaric parameters Р, Т and compressibility factors at standard Z _c and operating Z conditions:

The value of the density under standard conditions ρ _{c is} known - it is calculated based on the composition of the gas (the composition is provided by the chemical laboratory of the enterprise):

here a _i - volume fractions of gas components.

, в настоящее время всегда только рассчитывают, исходя из состава газа [7], пробу которого берут не чаще 1 раза в сутки. В нашем случае имеется возможность оперативно отслеживать величину

, проводя ее измерение резонатором 4, что способствует понижению погрешности измерения расхода Q_см. При этом делается два измерения частоты: одно при Р₁ ≈ Р = 0,1 МПа и температуре газа T₁, а второе - при рабочем давлении Р и температуре Т.Compressibility factor K, defined as the ratio of compressibility factors

, at present they are always only calculated based on the composition of the gas [7], the sample of which is taken no more than 1 time per day. In our case, it is possible to quickly track the value

, carrying out its measurement by resonator 4, which helps to reduce the error in measuring the flow rate Q _cm . In this case, two measurements of frequency are made: one at Р ₁ ≈ Р = 0.1 MPa and gas temperature T ₁ , and the second at operating pressure Р and temperature T.

The values of Р and Т are measured by devices 17, 18. The compressibility factor is calculated according to the ratio [8]:

- сдвиг частоты резонатора 4 в стандартных условиях. Величина

известна из проведенных выше измерений; величина

вычисляется из измерений давления Р₁, температуры T₁ и частоты резонатора ƒ_о, которые проводились после выпуска газа из байпаской линии в объем с низким (близким к атмосферному) давлением (см. выше):Here

- frequency shift of resonator 4 under standard conditions. The quantity

known from the above measurements; magnitude

is calculated from measurements of pressure Р ₁ , temperature T ₁ and resonator frequency ƒ _о , which were carried out after the gas was released from the bypass line into a volume with low (close to atmospheric) pressure (see above):

Where:

After determining the density ρ _cm and measuring ΔP _{cm, the} gas flow rate Q _{cm is} calculated. Component costs are carried out according to the ratios:

here Q ₁ , Q ₂ , Q ₃ - flow rates of gas, water and condensate, respectively; the coefficients η ₁ , η ₂ , η ₃ characterize the difference in the velocities of the gas and aerosol phases. They are preliminarily determined experimentally on a specially created stand or by comparing the flow rates Q ₁ , Q ₂ , Q ₃ with the flows measured at the control separator. As a rule, these coefficients η _i are small and amount to values η ₁ ≈ 1.0; η ₂ ≈ η ₃ = 0.95 ... 0.98. In the event that the flow of GZHM in the pipeline is accompanied by water plugs, then the volume of water V _pr carried by them is also taken into account: it is calculated based on the speed of the water plug υ _pr and the time of its flow through the pipeline:

t₁ - время начала появления пробки на зонде 29; t₂ - время начала появления пробки на зонде 36; t₃ - время окончания пробки на зонде 29; L - расстояние между зондами 29 и 36.Where

t ₁ - the time of the beginning of the appearance of the plug on the probe 29; t ₂ - the time of the beginning of the appearance of the plug on the probe 36; t ₃ is the end time of the plug on the probe 29; L is the distance between probes 29 and 36.

After the completion of the measurement cycle and preparation for the next cycle, the filter 5 is cleaned from the droplet-liquid phase. For this, valve 34 is closed, heater 6 is turned on, valve 13 is opened; in this case, the liquid that has turned into steam is vented for disposal (or into a drainage tank). The cleaning process is controlled by a signal from the detector 12 and continues until the signal U ₁ increases to the initial value U _about .

The operation of the flow meter in its main point - determining the density of the gas mixture - was tested in laboratory conditions on air gas-liquid mixtures at atmospheric pressure. A medical compressor aerosol generator for physiotherapy Boreal was used as a source of the gas-liquid mixture, giving an air flow with a known volumetric liquid content in the dispersed phase. A panoramic VSWR meter of the decimeter range P2-102 was used as a device supplying resonators 3 and 4 and measuring their frequency. The measuring and reference resonators had the following dimensions: diameter 2a = 130 mm, height h = 100 mm, and the bore diameter was 40 mm. Fluoroplastic-4 was used as a dielectric filling the cavity of the resonator. The operating frequency of the resonators on the TM ₀₁₀ mode in the absence of gas was ƒ _o = 1450 MHz (λ ≈ 20 cm), the quality factor Q _o ≈ 850.

Instead of natural gas, air was used, instead of condensate, screwLub compressor oil with a dielectric constant ε = 2.05, almost equal to that of stable condensate. Before spraying in the Boreal apparatus, a water-oil emulsion with a known ratio of water volume to oil volume was prepared on a special vibration stand.

A panoramic VSWR meter of the P2-65 range was used as a millimeter wave generator and an attenuation meter. The filter cartridge was a cylinder with a diameter of 10 mm and a length of 95 mm, filled with quartz sand and Petryanov's cloth, taken in a ratio of 2: 1 by the volume of the filter.

The method of on-line determination of the compressibility coefficient was previously described in [8] and later tested in [9]. The experiment was carried out on carbon dioxide; the maximum working pressure was 50 atm.

The experiments carried out confirmed the correctness of the initial relations (1), (2) and (3), which were the basis for calculating the volumetric contents of gas, water and condensate (in the dispersed phase).

Literature.

1. RF patent No. 2164340 dated 20.03.2001. Method for determining the component-wise flow rate of a gas-liquid mixture of gas-oil production products in a pipeline and a device for its implementation. Authors: Orekhov Yu.I., Moskalev I.N., Kostyukov V.E., Khokhrin L.P., Remizov V.V., Bityukov VS, Filonenko A.S., Rylov E.N., Vyshivanyi I. G., Filippov A.G.

2. RF patent No. 2289808 dated 02.28.2005. Method and device for determining the volume fractions of liquid hydrocarbon condensate and water in a flow of a gas-liquid mixture of natural gas. Authors: Vyshivany I.G., Kostyukov V.E., Moskalev I.N., Orekhov Yu.I., Tikhonov A.B., Belyaev V.B.

3. Moskalev I.N., Kostyukov V.E. "Microwave Methods of Operational Analysis of Natural Gas and Occansate" in 3 volumes - Sarov: FSUE "RFNC-VNIIEF", 2013 T.I.420 p.

4. Brandt A.A. Study of dielectrics at ultrahigh frequencies. - M .: Gosud. Publishing house of physical and mathematical literature, 1963, 403 p.

5. GOST 8.586.5-2005 Measurement of flow and quantity of liquids and gases using standard orifice devices. Part 5. Measurement technique.

6. Rudometova A.V., Klapchuk O.V. Investigation of the regularities of the flow of gas-liquid flows through flow meter diaphragms // Magistralny transport of natural gas. - M .: VNIIGaz, 1990.94-113.

7. GOST 30319.1-96 Natural gas. Methods for calculating physical properties. Determination of the physical properties of natural gas, its components and products of its processing.

8. RF patent No. 2478195 IPC G 01 9/00 (2006.1). A method for the on-line determination of the compressibility factor of gases and their mixtures. Authors: Moskalev I.N., Kostyukov V.E., Volkov V.V. and other inventions. Utility Models - 2013 - No. 9.

9. Grishin D.V., Golod G.S., Moskalev I.N. and other Method and technique of continuous determination of the coefficient of compressibility of gases. Automation, telemechanization and communication in the oil industry M .; JSC "VNIOENT", 2016 - No. 1 - p. 11-19.

Claims (6)

1. A multiphase flow meter for the component-wise determination of the flow rates of gas, hydrocarbon condensate and water in the products of production of gas condensate wells, consisting of a restriction device, a measuring resonator of the decimeter range, a reference resonator of the decimeter range, installed in the bypass line between a filter that beats the liquid phase and a gas volume meter passed through the filter, temperature and pressure control devices in the measuring and reference resonator, electrically controlled valves installed in the bypass line, electronic control units for the flow meter and information processing unit and for calculating component flow rates, characterized in that the input and output transition sections from the standard cross-section The pipelines to the narrowed section covered by the measuring resonator in the measuring tube section are made in the form of a Venturi tube, on which the pressure drop ΔP is measured. 2. A flow meter according to claim 1, characterized in that for efficient filter purging, the gas outlet in the filter stripping the liquid phase is made into a volume with low pressure (of the order of atmospheric pressure). 3. A flow meter according to claim 1, characterized in that the filter contains a heater that allows the liquid phase to be converted into a vapor phase and, in the presence of a gas flow, to clean it from the stripped liquid. 4. The flow meter according to claim 1, characterized in that the filter, which beats off the liquid phase, is made in the form of a cylindrical waveguide and is transmitted through millimeter-wave radio waves to determine the mass content of water in it. 5. A flow meter according to claim 1, characterized in that an electrically adjustable valve is installed in the bypass line, which allows to change the pressure in the reference resonator and to quickly determine the gas compressibility factor. 6. A flow meter according to claim 1, characterized in that the measuring section contains a resistive or capacitive probe, which makes it possible to determine the time of the beginning of the passage of the water plug and the time of its end.

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