An oil-gas-water three-phase flow online measurement method and system

Abstract

The application discloses an oil-gas-water three-phase flow online measurement system and method, and relates to the technical field of multiphase flow parameter measurement. The measurement system comprises a differential pressure flow measurement device and a phase content rate measurement device. The differential pressure flow measurement device comprises a Venturi throttling element, a pressure sensor, a first differential pressure sensor, a second differential pressure sensor and a temperature sensor. The water phase content rate is obtained by the phase content rate measurement device, the inlet flow pressure in the measurement pipeline, the fluid temperature in the measurement pipeline, the differential pressure between the upstream pressure taking point and the throat pressure taking point of the Venturi throttling element, and the pressure loss between the upstream pressure taking point and the downstream pressure taking point of the Venturi throttling element are obtained by the differential pressure flow measurement device, and then the oil, gas and water three-phase flow is determined online according to the above parameters. The application has the advantages of simple structure, small volume, high precision, low cost and the like.

Description

Technical Field

[0001] This invention relates to the field of multiphase flow parameter measurement technology, and in particular to an online method and system for measuring the flow of three phases: oil, gas, and water. Background Technology

[0002] Multiphase flow is widely present in power, chemical, petroleum, refrigeration, and aerospace industries. Without accurate measurement of the parameters involved in this flow process, the reliable operation of related equipment cannot be guaranteed. With the emergence of the concept of smart oil and gas fields, research on online measurement of multiphase flow parameters has become urgent, attracting significant attention from researchers worldwide. Due to the complex characteristics of multiphase flow, online measurement of its parameters currently faces challenges such as high difficulty, poor accuracy, and high measurement costs. Currently, there is a lack of instruments capable of directly measuring the flow rates of the three phases of oil, gas, and water.

[0003] Currently, there are two main categories of methods for measuring the flow rate of three-phase oil, gas, and water: separation methods and online measurement. Separation methods involve passing the multiphase flow through a three-phase separator to separate it into oil, gas, and water phases, and then using single-phase flow meters to measure each phase separately. This method offers high accuracy but cannot achieve online measurement, and the separators involved are bulky, time-consuming, and labor-intensive. Online measurement methods generally combine phase inclusion measurement devices with total flow measurement devices, using mathematical models to calculate the flow rate of each phase. Currently, multiphase flow meters from various manufacturers, such as the MPMF three-phase flow meter from FRAMO (Norway), the MPFM1900 three-phase flow meter from Fluent, the FR three-phase flow meter from Muti-Fluid, the MFI three-phase flow meter from ROXAR (Norway), and the MFM2000 three-phase flow meter from Haimo Technologies, all use radioactive devices to measure multiphase density or phase inclusion. However, these methods suffer from complex structures, difficult maintenance and management, and high costs. Summary of the Invention

[0004] The purpose of this invention is to provide an online method and system for measuring the three-phase flow of oil, gas and water, so as to realize the online measurement of the three-phase flow of oil, gas and water, and simplify the system structure.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] An online three-phase flow measurement system for oil, gas, and water, the system comprising: a differential pressure flow measurement device and a phase content measurement device; the differential pressure flow measurement device comprising: a Venturi throttling element, a pressure sensor, a first differential pressure sensor, a second differential pressure sensor, and a temperature sensor;

[0007] The Venturi throttling element is located inside the measuring pipe and is arranged along the flow direction of the multiphase fluid; the pressure sensor is located upstream of the Venturi throttling element; the temperature sensor is located downstream of the Venturi throttling element; the first differential pressure sensor is located between the upstream pressure tap and the throat pressure tap of the Venturi throttling element; the second differential pressure sensor is located between the upstream pressure tap and the downstream pressure tap of the Venturi throttling element; the phase content measuring device is located upstream of the differential pressure flow measuring device and is connected to the inlet end of the measuring pipe.

[0008] The pressure sensor is used to measure the incoming flow pressure in the measuring pipe; the temperature sensor is used to measure the fluid temperature in the measuring pipe; the first differential pressure sensor is used to measure the differential pressure between the upstream pressure tap and the throat pressure tap of the Venturi throttling element; the second differential pressure sensor is used to measure the pressure loss between the upstream pressure tap and the downstream pressure tap of the Venturi throttling element; the phase content measuring device is used to measure the water phase content of the multiphase fluid.

[0009] The incoming flow pressure, the fluid temperature, the differential pressure, the pressure loss, and the water phase content are used to determine the gas phase mass flow rate, gas phase content, oil phase content, oil phase mass flow rate, and water phase mass flow rate of the multiphase fluid.

[0010] Optionally, the phase content measurement device includes: a capacitance probe sensor and a capacitance probe base;

[0011] The capacitive probe base is located upstream of the differential pressure flow measurement device and is connected to the inlet end of the measurement pipeline; the capacitive probe sensor is located on the capacitive probe base;

[0012] The capacitive probe sensor is used to measure the aqueous phase content of the multiphase fluid.

[0013] Optionally, the measurement system further includes: a processor;

[0014] The processor is connected to the pressure sensor, the first differential pressure sensor, the second differential pressure sensor, the temperature sensor, and the phase content measurement device, respectively.

[0015] The processor is used to determine the gas phase mass flow rate, gas phase content, oil phase content, oil phase mass flow rate, and water phase mass flow rate of the multiphase fluid based on the incoming flow pressure, the fluid temperature, the differential pressure, the pressure loss, and the water phase content.

[0016] Optionally, the pressure sensor is located at a first predetermined length from the inlet end of the Venturi throttling element; the first predetermined length is equal to the diameter of the measuring pipe; the temperature sensor is located at a second predetermined length from the outlet end of the Venturi throttling element; the second predetermined length is equal to nine times the diameter of the measuring pipe.

[0017] An online method for measuring the flow rate of three phases of oil, gas, and water, wherein the method is applied to the aforementioned measurement system, and the method includes:

[0018] The instrument measures the incoming pressure in the measuring pipe, the fluid temperature in the measuring pipe, the differential pressure between the upstream pressure tap and the throat pressure tap of the Venturi throttling element, the pressure loss between the upstream pressure tap and the downstream pressure tap of the Venturi throttling element, and the water phase content of the multiphase fluid.

[0019] Based on the incoming flow pressure, the fluid temperature, and the composition of the gas and oil phases in the multiphase fluid, determine the oil phase density, gas phase density, and water phase density of the multiphase fluid;

[0020] The pressure drop ratio of the Venturi throttling element is determined based on the differential pressure and the pressure drop.

[0021] The apparent theoretical flow rate of the multiphase fluid in the gas phase is determined based on the differential pressure, the gas phase density, and the structural parameters of the Venturi throttling element; the structural parameters of the Venturi throttling element include: the throat cross-sectional area of ​​the Venturi throttling element, the diameter of the measuring pipe, and the cross-sectional area of ​​the measuring pipe.

[0022] The definitions of liquid phase mixing density, gas-liquid density ratio, gas phase density Froude number, and gas-liquid mass flow rate multiplier of the multiphase fluid are determined based on the relationship between the flow rate, density, and phase content of each phase in the multiphase fluid.

[0023] The fitting correlation between the gas-liquid density ratio, the gas phase density Froude number, the Loma parameter, and the gas-liquid mass flow rate multiplier was determined by experimental calibration and used as the first fitting correlation.

[0024] The fitting correlation between the gas-liquid density ratio, the gas phase density Froude number, the pressure loss ratio, and the Loma parameter was determined by experimental calibration and used as the second fitting correlation.

[0025] Based on the first fitting correlation, the second fitting correlation, the definition of the liquid phase mixing density, the definition of the gas-liquid density ratio, the definition of the gas phase density Froude number, and the definition of the gas-liquid mass flow rate multiplier, a gas phase mass flow rate calculation model is constructed.

[0026] Based on the oil phase density, the gas phase density, the water phase density, the pressure loss ratio, and the apparent theoretical gas phase flow rate, the gas phase mass flow rate calculation model is iteratively solved with the goal of satisfying the set condition for the difference between the gas phase mass flow rates obtained from two adjacent solutions, and the gas phase mass flow rate is determined.

[0027] Based on the gas phase mass flow rate and the second fitting correlation, the gas phase content, oil phase content, oil phase mass flow rate, and water phase mass flow rate are determined.

[0028] Optionally, the gas phase mass flow rate calculation model is as follows:

[0029]

[0030] Where, m g X is the gas phase mass flow rate. LM For Loma parameters, m g,th ρ is the apparent theoretical flow rate of the gas phase, K is the gas-liquid mass flow rate multiplier, and ρ is the apparent theoretical flow rate of the gas phase. l ρ is the liquid phase mixing density. g This represents the gas phase density.

[0031] Optionally, the first fitting correlation is:

[0032]

[0033] Where K is the gas-liquid mass flow rate multiplier, Fr g X is the gas phase density Froude number. LM Here, DR is the gas-liquid density ratio, a1 is the first coefficient, a2 is the first exponent, a3 is the second exponent, and a4 is the third exponent.

[0034] Optionally, the second fitting correlation is:

[0035]

[0036] Among them, X LM Here are the Loma parameters, δ is the pressure drop ratio, and Fr is the pressure drop ratio. g denoted as Froude number for gas phase density, DR as gas-liquid density ratio, b1 as the second coefficient, b2 as the fourth exponent, b3 as the fifth exponent, b4 as the sixth exponent, c1 as the third coefficient, and c2 as the seventh exponent.

[0037] Optionally, the definition of the gas phase density Froude number is:

[0038]

[0039] Among them, Fr g The gas phase density is the Froude number, m g ρ is the gas phase mass flow rate. gLet ρ be the gas phase density, A be the cross-sectional area of ​​the measuring pipe, g be the acceleration due to gravity, D be the diameter of the measuring pipe, and ρ be the gas phase density. l This represents the liquid phase mixing density.

[0040] Optionally, determining the gas phase holdup, oil phase holdup, oil phase mass flow rate, and water phase mass flow rate based on the gas phase mass flow rate and the second fitted correlation specifically includes:

[0041] Based on the gas phase mass flow rate and the second fitting correlation, determine the Loma parameters, gas phase content, and oil phase content;

[0042] The total liquid phase mass flow rate is determined based on the gas phase mass flow rate and the Loma parameters;

[0043] The oil phase mass flow rate and the water phase mass flow rate are determined based on the total liquid phase mass flow rate, the oil phase content, and the water phase content.

[0044] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0045] This invention provides an online measurement system and method for three-phase flow of oil, gas, and water. The measurement system includes a differential pressure flow measurement device and a phase content measurement device. The phase content measurement device obtains the water phase content, while the differential pressure flow measurement device obtains the incoming flow pressure in the measurement pipeline, the fluid temperature in the measurement pipeline, the differential pressure between the upstream pressure tap and the throat pressure tap of the Venturi throttling element, and the pressure loss between the upstream and downstream pressure taps of the Venturi throttling element. Based on the above parameters, the three-phase flow of oil, gas, and water is determined online. This eliminates the need for separation of multiphase flow, avoids the use of radioactive devices, and is unaffected by changes in the dielectric constant of the measurement medium. It has advantages such as simple structure, small size, high accuracy, and low cost. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the structure of the online oil-gas-water three-phase flow measurement system provided in an embodiment of the present invention;

[0048] Figure 2 A data processing flowchart for the online measurement method of three-phase flow of oil, gas and water provided in an embodiment of the present invention.

[0049] Symbol explanation: Venturi throttling element-1, measuring pipe-2, pressure sensor-3, first differential pressure sensor-4, second differential pressure sensor-5, temperature sensor-6, capacitance probe base-7, capacitance probe sensor-8. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] The purpose of this invention is to provide an online method and system for measuring the three-phase flow of oil, gas and water, so as to realize the online measurement of the three-phase flow of oil, gas and water, and simplify the system structure.

[0052] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] Figure 1 This is a schematic diagram of the structure of the online flow measurement system for three phases of oil, gas, and water provided in an embodiment of the present invention. Figure 1 As shown, the measurement system includes a differential pressure flow measurement device and a phase content measurement device. The differential pressure flow measurement device includes a Venturi throttling element 1, a pressure sensor 3, a first differential pressure sensor 4, a second differential pressure sensor 5, and a temperature sensor 6, all installed on the measurement pipe 2.

[0054] The Venturi throttling element 1 is located inside the measuring pipe 2 and is arranged along the flow direction of the multiphase fluid, that is, the multiphase fluid flows from the inlet end of the measuring pipe 2 through the Venturi throttling element 1 to the outlet end of the measuring pipe 2; the side where the inlet end of the measuring pipe 2 is located is upstream; the side where the outlet end of the measuring pipe 2 is located is downstream; specifically, the area in front of the contraction section of the Venturi throttling element 1 is called the upstream of the Venturi throttling element 1, and the area behind the diffusion section of the Venturi throttling element 1 is called the downstream of the Venturi throttling element 1.

[0055] The pressure sensor 3 is located upstream of the Venturi throttling element 1; the temperature sensor 6 is located downstream of the Venturi throttling element 1; the first differential pressure sensor 4 is located between the upstream pressure tap and the throat pressure tap of the Venturi throttling element 1; the second differential pressure sensor 5 is located between the upstream pressure tap and the downstream pressure tap of the Venturi throttling element 1; the phase content measuring device is located upstream of the differential pressure flow measuring device and is connected to the inlet end of the measuring pipe 2. Specifically, the first differential pressure sensor 4 is connected to the upstream pressure tap and the throat pressure tap of the Venturi throttling element 1 respectively through pressure tapping pipes; the second differential pressure sensor 5 is connected to the upstream pressure tap and the downstream pressure tap of the Venturi throttling element 1 respectively through pressure tapping pipes.

[0056] The pressure sensor 3 is used to measure the incoming pressure in the measuring pipe 2; the temperature sensor 6 is used to measure the fluid temperature in the measuring pipe 2; the first differential pressure sensor 4 is used to measure the differential pressure between the upstream pressure tap and the throat pressure tap of the Venturi throttling element 1; the second differential pressure sensor 5 is used to measure the pressure loss between the upstream pressure tap and the downstream pressure tap of the Venturi throttling element 1; the phase content measuring device is used to measure the water phase content of the multiphase fluid. The incoming pressure, the fluid temperature, the differential pressure, the pressure loss, and the water phase content are used to determine the gas phase mass flow rate, gas phase content, oil phase content, oil phase mass flow rate, and water phase mass flow rate of the multiphase fluid.

[0057] In one specific implementation, the pressure sensor 3 is located upstream of the Venturi throttling element 1, at a first predetermined length from the inlet end of the Venturi throttling element 1; the first predetermined length is equal to the diameter of the measuring pipe 2. The temperature sensor 6 is an invasive temperature sensor; the temperature sensor 6 is located downstream of the Venturi throttling element 1, at a second predetermined length from the outlet end of the Venturi throttling element 1; the second predetermined length is equal to nine times the diameter of the measuring pipe 2. By placing the pressure sensor 3 upstream of the Venturi throttling element 1, this invention can accurately measure the pressure of the upstream flow and thus calculate the three-phase fluid density; by placing the temperature sensor 6 downstream of the Venturi throttling element 1, interference with the fluid flow within the measuring pipe 2 can be avoided, resulting in more accurate measurement results.

[0058] Further, the phase content measurement device includes a capacitance probe sensor 8 and a capacitance probe base 7. The capacitance probe base 7 is located upstream of the differential pressure flow measurement device and is connected to the inlet end of the measurement pipe 2; the capacitance probe sensor 8 is located on the capacitance probe base 7. The capacitance probe sensor 8 is used to measure the water phase content of the multiphase fluid. In this embodiment, the phase content measurement device is connected to the inlet end of the measurement pipe 2 via a flange. Specifically, the capacitance probe base 7 is connected to the inlet end of the measurement pipe 2 via a flange.

[0059] Preferably, the measurement system further includes a processor. The processor is connected to the pressure sensor 3, the first differential pressure sensor 4, the second differential pressure sensor 5, the temperature sensor 6, and the phase content measuring device (specifically, the capacitive probe sensor 8 within the phase content measuring device). The processor is used to determine the gas phase mass flow rate, gas phase content, oil phase content, oil phase mass flow rate, and water phase mass flow rate of the multiphase fluid based on the incoming flow pressure, the fluid temperature, the differential pressure, the pressure loss, and the water phase content.

[0060] Furthermore, the processor includes:

[0061] The three-phase density determination unit is used to determine the oil phase density, gas phase density, and water phase density of the multiphase fluid based on the incoming flow pressure, the fluid temperature, and the composition of the gas and oil phases in the multiphase fluid.

[0062] The pressure loss ratio determination unit is used to determine the pressure loss ratio of the Venturi throttling element based on the differential pressure and the pressure loss.

[0063] The apparent theoretical flow rate determination unit is used to determine the apparent theoretical flow rate of the multiphase fluid based on the differential pressure, the gas phase density, and the structural parameters of the Venturi throttling element; the structural parameters of the Venturi throttling element include: the throat cross-sectional area of ​​the Venturi throttling element, the diameter of the measuring pipe, and the cross-sectional area of ​​the measuring pipe.

[0064] The relevant definition determination unit is used to determine the definition of the liquid phase mixing density, the gas-liquid density ratio, the gas phase density Froude number, and the gas-liquid mass flow rate multiplier of the multiphase fluid based on the relationship between the flow rate, density, and phase content of each phase in the multiphase fluid.

[0065] The first fitting correlation determination unit is used to determine the fitting correlation between the gas-liquid density ratio, the gas phase density Froude number, the Loma parameter and the gas-liquid mass flow rate multiplier using an experimental calibration method, and use it as the first fitting correlation.

[0066] The second fitting correlation determination unit is used to determine the fitting correlation between the gas-liquid density ratio, the gas phase density Froude number, the pressure loss ratio and the Loma parameter using an experimental calibration method, and use it as the second fitting correlation.

[0067] The gas phase mass flow rate calculation model construction unit is used to construct a gas phase mass flow rate calculation model based on the first fitting correlation, the second fitting correlation, the definition of the liquid phase mixing density, the definition of the gas-liquid density ratio, the definition of the gas phase density Froude number, and the definition of the gas-liquid mass flow rate multiplier.

[0068] The gas phase mass flow rate calculation unit is used to iteratively solve the gas phase mass flow rate calculation model based on the oil phase density, the gas phase density, the water phase density, the pressure loss ratio, and the apparent theoretical gas phase flow rate, with the objective that the difference between the gas phase mass flow rates obtained from two adjacent calculations meets the set conditions, in order to determine the gas phase mass flow rate.

[0069] Other parameter determination unit is used to determine gas phase content, oil phase content, oil phase mass flow rate and water phase mass flow rate based on the gas phase mass flow rate and the second fitting correlation.

[0070] This invention also provides an online method for measuring the three-phase flow of oil, gas, and water, wherein the method is applied to the aforementioned measurement system, and the method includes:

[0071] Step S1: Obtain the incoming flow pressure in the measuring pipe, the fluid temperature in the measuring pipe, the differential pressure between the upstream pressure tap and the throat pressure tap of the Venturi throttling element, the pressure loss between the upstream pressure tap and the downstream pressure tap of the Venturi throttling element, and the water phase content of the multiphase fluid.

[0072] Step S2: Determine the oil phase density, gas phase density, and water phase density of the multiphase fluid based on the incoming flow pressure, the fluid temperature, and the composition of the gas and oil phases in the multiphase fluid.

[0073] Step S3: Determine the pressure drop ratio of the Venturi throttling element based on the differential pressure and the pressure drop.

[0074] Step S4: Determine the apparent theoretical flow rate of the multiphase fluid in the gas phase based on the differential pressure, the gas phase density, and the structural parameters of the Venturi throttling element; the structural parameters of the Venturi throttling element include: the throat cross-sectional area of ​​the Venturi throttling element, the diameter of the measuring pipe, and the cross-sectional area of ​​the measuring pipe.

[0075] Step S5: Determine the definitions of the liquid phase mixing density, gas-liquid density ratio, gas phase density Froude number, and gas-liquid mass flow rate multiplier of the multiphase fluid based on the relationship between the flow rate, density, and phase content of each phase in the multiphase fluid.

[0076] Step S6: Determine the fitting correlation between the gas-liquid density ratio, the gas phase density Froude number, the Loma parameter, and the gas-liquid mass flow rate multiplier using the experimental calibration method, and use it as the first fitting correlation.

[0077] Step S7: Use experimental calibration to determine the fitting correlation between the gas-liquid density ratio, the gas phase density Froude number, the pressure loss ratio, and the Loma parameter, as the second fitting correlation.

[0078] Step S8: Construct a gas phase mass flow calculation model based on the first fitting correlation, the second fitting correlation, the definition of the liquid phase mixing density, the definition of the gas-liquid density ratio, the definition of the gas phase density Froude number, and the definition of the gas-liquid mass flow multiplier.

[0079] Step S9: Based on the oil phase density, the gas phase density, the water phase density, the pressure loss ratio, and the apparent theoretical gas phase flow rate, with the objective that the difference between the gas phase mass flow rates obtained from two consecutive solutions meets the set conditions, the gas phase mass flow rate is determined by iteratively solving the gas phase mass flow rate calculation model.

[0080] Step S10: Determine the gas phase content, oil phase content, oil phase mass flow rate, and water phase mass flow rate based on the gas phase mass flow rate and the second fitting correlation.

[0081] Further, determining the gas phase fill, oil phase fill, oil phase mass flow rate, and water phase mass flow rate based on the gas phase mass flow rate and the second fitted correlation specifically includes:

[0082] Step S10.1: Determine the Loma parameters, gas phase content, and oil phase content based on the gas phase mass flow rate and the second fitting correlation.

[0083] Step S10.2: Determine the total liquid phase mass flow rate based on the gas phase mass flow rate and the Loma parameters.

[0084] Step S10.3: Determine the oil phase mass flow rate and the water phase mass flow rate based on the total liquid phase mass flow rate, the oil phase content, and the water phase content.

[0085] In practical applications, the data processing flowchart of the online measurement method for three-phase flow of oil, gas, and water provided by this invention can be found here. Figure 2 Specifically, it includes the following steps:

[0086] Step 1: The differential pressure ΔP between the upstream pressure tap and the throat pressure tap of the multiphase fluid passing through the Venturi throttling element is measured by the first differential pressure sensor 4. tp The multiphase flow pressure loss ΔP between the upstream and downstream pressure taps is measured by the second differential pressure sensor 5. m The pressure P and temperature T of the multiphase fluid are measured by pressure sensor 3 and temperature sensor 6.

[0087] Step 2: Based on the pressure P and temperature T of the multiphase fluid, and combined with the known composition of the gas and oil phases in the multiphase fluid, calculate the density ρ of each phase (oil, gas, and water). o ρ g ρ w This leads to the determination of the definition of liquid phase mixing density, i.e. Where α w α represents the water phase content. o This represents the oil phase content.

[0088] Step 3: Establish the relationship between the gas-liquid mass flow rate multiplier K and the Loma parameter X through experimental calibration. LM Gas phase density Froude number Fr g The fitting correlation between the gas-liquid density ratio DR and the gas-liquid density ratio DR is used as the first fitting correlation:

[0089]

[0090] In the formula, a1, a2, a3 and a4 are all constant terms, determined through experimental calibration, where a1 is the first coefficient, a2 is the first exponent, a3 is the second exponent and a4 is the third exponent.

[0091] K is the gas-liquid mass flow rate multiplier, defined as the ratio of the total gas-liquid flow rate to the apparent theoretical gas flow rate, expressed as: Where m g The mass flow rate is m in the gas phase. l The total liquid phase mass flow rate (including the water phase mass flow rate and the oil phase mass flow rate), m g,th This represents the apparent theoretical flow rate in the gas phase.

[0092] X LM For the Loma parameter, its expression is:

[0093] DR is the gas-liquid density ratio, and its expression is:

[0094] Fr g The gas phase density Froude number is expressed as follows: Where m g ρ is the gas phase mass flow rate. gLet A be the gas phase density, A be the cross-sectional area of ​​the measuring pipe, and g be the acceleration due to gravity, which is taken as 10 m / s² in this embodiment. 2 D is the diameter of the measuring pipe, which is taken as 50mm in this embodiment. ρ l This represents the liquid phase mixing density.

[0095] Step 4: Establish the Loma parameter X through experimental calibration. LM Compared with the Venturi pressure drop ratio δ, the gas phase density Froude number Fr g The fitting correlation between the gas-liquid density ratio DR and the gas-liquid density ratio DR is used as the second fitting correlation:

[0096]

[0097] In the formula, b1, b2, b3, b4, c1, and c2 are all constant terms, determined through experimental calibration. b1 is the second coefficient, b2 is the fourth exponent, b3 is the fifth exponent, b4 is the sixth exponent, c1 is the third coefficient, and c2 is the seventh exponent; δ is the voltage drop ratio of the Venturi throttling element, and has... This represents the ratio of upstream-downstream pressure loss to upstream-throat differential pressure, where ΔP tp For differential pressure, ΔP m This is pressure loss.

[0098] Step 5: Establish a gas phase mass flow rate calculation model based on the definition of K and the first fitting correlation equation:

[0099]

[0100] In the formula, m g,th The apparent theoretical flow rate in the gas phase is known. Where A t Let be the throat cross-sectional area of ​​the Venturi throttling element, β be the throttling ratio of the Venturi throttling element, and β be known.

[0101] Step Six: Measure the capacitance of the oil-gas-water multiphase fluid using a capacitance probe sensor. Since the capacitance value is related to the length of the water film covering the probe surface, the water phase content in the multiphase fluid can be further calculated based on the capacitance value. Specifically, after measuring the capacitance value, the built-in circuit board converts the capacitance value into an acquireable voltage signal, and then calculates the water phase content α. w .

[0102] Step 7: Given that the total phase content of the oil-gas-water three-phase mixture is 1, i.e.: α o +α g +α w =1, and there is a correlation between the Loma parameter and the gas phase holdup, X LM =(1-α) g ) / α gBy simultaneously solving the above equations, the gas phase mass flow rate is iteratively calculated. The iteration stops when the difference between two consecutive solutions of the gas phase mass flow rate meets a set condition, thus yielding the gas phase mass flow rate m. g In this embodiment, the set condition is that the difference between the gas phase mass flow rates obtained from two consecutive solutions is less than or equal to a set value; the set value is 0.1%, that is, the set condition is specifically: Δm g ≤0.1%. The obtained gas phase mass flow rate m g Substitute into the second fitting correlation to solve for the Loma parameter X LM Gas phase content α g and oil phase content α o .

[0103] Step 8: Measure the gas phase flow rate (m) g Loma parameter X LM The total mass flow rate of the liquid phase can be calculated, i.e. Combined with the oil phase content α o and liquid phase content α w Further calculations yield the oil phase mass flow rate m. o and aqueous phase mass flow rate m w .

[0104] This invention addresses the aforementioned problems by providing a system and method for online measurement of the three-phase flow rates of oil, gas, and water. The online three-phase flow rate measurement system includes a differential pressure flow measurement device and an online phase holdup measurement device. The water phase holdup is obtained through the online phase holdup measurement device, and the gas-liquid two-phase flow rates and phase holdup are obtained through the flow measurement device, ultimately yielding the three-phase flow rates of oil, gas, and water. This system enables online measurement of the three-phase flow rates of oil, gas, and water, and features a simple, stable, and reliable structure, significantly reducing costs while maintaining accuracy. Compared to existing technologies, the online phase holdup measurement device of this invention is unaffected by changes in the dielectric constant of the measured medium, and possesses advantages such as simple structure, small size, high accuracy, low cost, and ease of operation and maintenance.

[0105] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0106] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for online measurement of three-phase flow rates of oil, gas, and water, characterized in that, The online measurement method for three-phase flow of oil, gas, and water is applied to an online measurement system for three-phase flow of oil, gas, and water. The online measurement system includes a differential pressure flow measurement device and a phase content measurement device. The differential pressure flow measurement device includes a Venturi throttling element, a pressure sensor, a first differential pressure sensor, a second differential pressure sensor, and a temperature sensor. The Venturi throttling element is located inside the measurement pipe and is arranged along the flow direction of the multiphase fluid. The pressure sensor is located upstream of the Venturi throttling element. The temperature sensor is located downstream of the Venturi throttling element. The first differential pressure sensor is located between the upstream pressure tap and the throat pressure tap of the Venturi throttling element. The second differential pressure sensor... The device is located between the upstream and downstream pressure taps of the Venturi throttling element; the phase content measuring device is located upstream of the differential pressure flow measuring device and connected to the inlet end of the measuring pipe; the pressure sensor is used to measure the incoming flow pressure in the measuring pipe; the temperature sensor is used to measure the fluid temperature in the measuring pipe; the first differential pressure sensor is used to measure the differential pressure between the upstream and throat pressure taps of the Venturi throttling element; the second differential pressure sensor is used to measure the pressure loss between the upstream and downstream pressure taps of the Venturi throttling element; the phase content measuring device includes a capacitance probe sensor and a capacitance probe base, used to measure the water phase content of the multiphase fluid; The online measurement method for three-phase flow of oil, gas and water includes: The instrument measures the incoming pressure in the measuring pipe, the fluid temperature in the measuring pipe, the differential pressure between the upstream pressure tap and the throat pressure tap of the Venturi throttling element, the pressure loss between the upstream pressure tap and the downstream pressure tap of the Venturi throttling element, and the water phase content of the multiphase fluid. Based on the incoming flow pressure, the fluid temperature, and the composition of the gas and oil phases in the multiphase fluid, determine the oil phase density, gas phase density, and water phase density of the multiphase fluid; The pressure drop ratio of the Venturi throttling element is determined based on the differential pressure and the pressure drop. The apparent theoretical flow rate of the multiphase fluid in the gas phase is determined based on the differential pressure, the gas phase density, and the structural parameters of the Venturi throttling element; the structural parameters of the Venturi throttling element include: the throat cross-sectional area of ​​the Venturi throttling element, the diameter of the measuring pipe, and the cross-sectional area of ​​the measuring pipe. The definitions of liquid phase mixing density, gas-liquid density ratio, gas phase density Froude number, and gas-liquid mass flow rate multiplier of the multiphase fluid are determined based on the relationship between the flow rate, density, and phase content of each phase in the multiphase fluid. The fitting correlation between the gas-liquid density ratio, the gas phase density Froude number, the Loma parameter, and the gas-liquid mass flow rate multiplier was determined by experimental calibration and used as the first fitting correlation. The fitting correlation between the gas-liquid density ratio, the gas phase density Froude number, the pressure loss ratio, and the Loma parameter was determined by experimental calibration and used as the second fitting correlation. Based on the first fitting correlation, the second fitting correlation, the definition of the liquid phase mixing density, the definition of the gas-liquid density ratio, the definition of the gas phase density Froude number, and the definition of the gas-liquid mass flow rate multiplier, a gas phase mass flow rate calculation model is constructed. Based on the oil phase density, the gas phase density, the water phase density, the pressure loss ratio, and the apparent theoretical gas phase flow rate, the gas phase mass flow rate calculation model is iteratively solved with the goal of satisfying the set condition for the difference between the gas phase mass flow rates obtained from two adjacent solutions, and the gas phase mass flow rate is determined. Based on the gas phase mass flow rate and the second fitting correlation, the gas phase content, oil phase content, oil phase mass flow rate and water phase mass flow rate are determined; The gas phase mass flow rate calculation model is as follows: ； in, m g This refers to the gas phase mass flow rate. X LM For Loma parameters, m g,th This is the apparent theoretical flow rate in the gas phase. K For gas-liquid mass flow rate multiplier, ρ l The density of the liquid phase mixture, ρ g This refers to the gas phase density. The second fitting correlation is: ； in, b 1. b 2. b 3. b 4. c 1. c Both 2 are constant terms, determined through experimental calibration, where b 1 is the second coefficient. b 2 is the fourth index. b 3 is the fifth index. b 4 is the sixth index. c 1 is the third coefficient. c 2 is the seventh index; δ The voltage drop ratio of the Venturi throttling element is given, and there is... Δ represents the ratio of upstream-downstream pressure loss to upstream-throat differential pressure, where Δ P tp For differential pressure, Δ P m For pressure loss; X LM For Loma parameters, Fr g The gas phase density is the Froude number. DR This is the gas-liquid density ratio.

2. The method for online measurement of three-phase flow of oil, gas and water according to claim 1, characterized in that, The capacitive probe base is located upstream of the differential pressure flow measurement device and is connected to the inlet end of the measurement pipeline; the capacitive probe sensor is located on the capacitive probe base; The capacitive probe sensor is used to measure the aqueous phase content of the multiphase fluid.

3. The method for online measurement of three-phase flow of oil, gas, and water according to claim 1, characterized in that, The online three-phase flow measurement system for oil, gas and water also includes: a processor; The processor is connected to the pressure sensor, the first differential pressure sensor, the second differential pressure sensor, the temperature sensor, and the phase content measurement device, respectively. The processor is used to determine the gas phase mass flow rate, gas phase content, oil phase content, oil phase mass flow rate, and water phase mass flow rate of the multiphase fluid based on the incoming flow pressure, the fluid temperature, the differential pressure, the pressure loss, and the water phase content.

4. The method for online measurement of three-phase flow of oil, gas and water according to claim 1, characterized in that, The pressure sensor is located at a first predetermined length from the inlet end of the Venturi throttling element; the first predetermined length is equal to the diameter of the measuring pipe; the temperature sensor is located at a second predetermined length from the outlet end of the Venturi throttling element; the second predetermined length is equal to nine times the diameter of the measuring pipe.

5. The method for online measurement of three-phase flow of oil, gas and water according to claim 1, characterized in that, The first fitting correlation is: ； in, K For gas-liquid mass flow rate multiplier, Fr g The gas phase density is the Froude number. X LM For Loma parameters, DR The gas-liquid density ratio, a 1 is the first coefficient. a 2 is the first index. a 3 is the second index. a 4 is the third index.

6. The method for online measurement of three-phase flow of oil, gas and water according to claim 1, characterized in that, The definition of the gas phase density Froude number is: ； in, Fr g The gas phase density is the Froude number. m g This refers to the gas phase mass flow rate. ρ g The density is the gas phase density. A To measure the cross-sectional area of ​​the pipe, g It is the acceleration due to gravity. D To measure the pipe diameter, ρ l This represents the liquid phase mixing density.

7. The method for online measurement of three-phase flow of oil, gas and water according to claim 1, characterized in that, The step of determining the gas phase content, oil phase content, oil phase mass flow rate, and water phase mass flow rate based on the gas phase mass flow rate and the second fitting correlation specifically includes: Based on the gas phase mass flow rate and the second fitting correlation, determine the Loma parameters, gas phase content, and oil phase content; The total liquid phase mass flow rate is determined based on the gas phase mass flow rate and the Loma parameters; The oil phase mass flow rate and the water phase mass flow rate are determined based on the total liquid phase mass flow rate, the oil phase content, and the water phase content.

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