RU2386931C2 - Method for detection of multiphase medium flow parametres and ultrasonic flow metre for its realisation - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: flow metre of multiphase medium flow components comprises two vertically and serially installed sections of pipe 1, 2, cross section areas of which are same, N and M of gas and liquid phases motion speeds conversion into Doppler shift frequency 3 and 5 and n and m converters of gas content 4 and 6, installed in each section of pipe, unit of memory 10, in which calibration values of converters and constants are contained: speed of sound in oil and water and its dependence on temperature, memory unit 12 to store current values of converter signals, control panel 13, memory unit 14 for storage of calculated flow parametres, indicator 15, real time clock 16. Final parametres of multiphase flow are calculated after preliminary detection of integral characteristics of speed and gas content conversion, which are calculated by controller 11 according to given formulas with account of individual weight coefficients of converters, detected experimentally depending on position of converter relative to the centre and along pipe length.

EFFECT: invention increases accuracy of multiphase multicomponent medium composition detection and simplifies processing of signals.

2 cl, 5 dwg

Description

The invention relates to measuring equipment and can be used in information-measuring systems of oil refining, oil production, chemical and other industries.

A known method for determining the components of a multiphase medium according to patent RU No. 2138023, G01F 1/74, G01F 1/708, G01F 1/66, 1999. Inside the pipeline in a controlled flow volume set the source and receiver of acoustic pulses. The time spent by the pulses through the controlled volume is recorded. The number of pulses not recorded during a fixed period of time and their proportion with respect to the total number of pulses are determined. Measure the flow velocity and calculate the flow rate of the components according to the given formulas. Velocity measurement is carried out by the correlation method, using an additional controlled volume located with displacement along the flow direction, or by the Doppler method.

This method for the case of multiphase multicomponent media has a large error in measuring the velocity and concentration of the stream when determining their real value.

Known ultrasonic flow meter in accordance with the patent of the Russian Federation 2062995, class. G01F 1/66, 1996. It is equipped with a vertically mounted measuring chamber with inlet and outlet nozzles, a control unit and a density measuring unit and a second counting and recording device connected in series. In this case, the piezoelectric transducers are located on the upper and lower walls of the measuring chamber, the inputs of the control unit are connected respectively to the inputs of the flow measuring unit and the density measuring unit, and the output of the control unit is connected to the input of the switching device and the first input of the density measuring unit, to the second input of which the piezoelectric transducer is connected located on the bottom wall of the measuring chamber.

The technical result of this solution is that the direct and inverse piezoelectric effects are used on the same transducers, and the flow and density are measured in one zone. And this allows us to eliminate errors in the calibration of the device and changes caused by fluctuations in the properties and parameters of the controlled medium along the flow.

The disadvantages of the device are that it is a batch device that controls the flow of a multiphase medium outside the pipeline and, accordingly, does not take into account the time-varying ratio of components in the flow. This implies the inaccuracy of the resulting information on the real phase relationships, which in some cases, for example, when analyzing the state of produced oil wells, can lead to inadequate decision making.

The closest in technical essence to the proposed invention are patent No. WO01 / 067051 A1, G01F 1/74, 1/712, 1/708, 1/66, G01N 29/02, 2000 and the dissertation of V. Drobkov “Development and research of ultrasonic methods and an information-measuring system for measuring the flow of oil and gas flow. Abstract of dissertation for the degree of Doctor of Technical Sciences. M., signed on April 20, 2007. ”(hereinafter referred to as the prototype), in which the method and design of the device for determining the flow rate of the liquid phase Q _g , gas phase Q _g and water concentration W in the liquid phase of the multiphase flow are stipulated.

The hydraulic channel in the prototype consists of two consecutive vertical pipe sections, the cross-sectional areas of which differ by 2 times. The definition of multiphase flow parameters is as follows:

- at various radial locations and in each cross section of the first and second pipe sections, local Doppler frequencies f are measured by flow rate sensors, which are then averaged for subsequent calculations;

- at various radial locations and in each cross section of the first and second pipe sections, gas sensors measure the local gas contents α equal to the ratio of the number of probe pulses that have not passed to their total number, which are then averaged for subsequent calculations;

- at various radial locations, water concentration sensors measure local sound velocities V in the medium, which are then averaged for subsequent calculations;

- in a pipe of larger diameter, the temperature T and the pressure P of the flow are measured.

To calculate the flow parameters Q _W , Q _g and W, the following sensor readings are preliminarily found by the formulas:

where f _yk, f _Yn, f _ShTs, f _lim, α _yk, α _y, α _ShTs, α _wp - local Doppler frequency and the local void fraction in the narrow (y) and broad (br) sections for the central (i) and peripheral ( n) sensors.

From formula (1) it follows that when calculating the reduced Doppler frequency, only the difference in the area of the pipe segments by 2 times is taken into account, which is reflected in formula (1) by the presence of a coefficient 2 for the readings of flow rate sensors installed in a wide section, where the flow rate is 2 times less. In other words, it is understood that their readings are 2 times less than that of sensors installed in a narrow section, as theoretically follows from the formula for determining the Doppler frequency:

where f ₀ is the frequency of the probe ultrasound beam;

υ is the flow velocity;

α is the angle between the axis of the waveguide of the emitter (receiver) and the direction of the average flow vector;

C is the speed of sound in the medium.

In practice, it is experimentally confirmed that the readings of flow rate sensors in a wide section differ from the readings of sensors in a narrow section not by 2 times, but by a value lying in the range 1.5 ... 2.5. Also differ are the readings of flow rate sensors 0.8 ... 1.2 times installed in the center and on the periphery of the pipe. These differences are determined by many factors, for example, the position of the sensors relative to the axis of the pipe, relative to the confuser, the diameter of the cross section, etc.

Due to the presence of different pipe diameters, the pressure and flow rate in these sections are different, therefore, gas bubbles in different sections of the hydrochannel have different diameters, the number and sizes of water and oil globules change, and the flow structure changes. The presence of a confuser between pipes of different diameters leads to the appearance of a radial component of the fluid motion, which leads to additional turbulence in the field of narrow section sensors, as well as to the expansion of the spectrum width of the Doppler frequencies. As a result of this, the local readings of the flow rate sensors installed in pipes of different diameters will always differ from each other not inversely proportional to the ratio of the cross-sectional areas of the pipes, which will lead to an additional error in calculating the flow rates of liquid and gas in the prototype, since the readings from the sensors calculated by formulas (1) and (2) will be influenced to a greater extent by sensors with the greatest deviation of their readings from the average value of the readings of all sensors.

Due to the significant dispersion of the piezoelectric characteristics of the piezoelectric elements used to generate and receive ultrasound, as well as the technological dispersion of the geometric dimensions of ultrasonic resonator waveguides, which affect their sensitivity, the flow rate and gas sensors are not interchangeable, that is, when the sensor is replaced with another sensor of the same type, its readings may differ by a value reaching in some cases 20%, which is confirmed in practice.

Given the above facts, in order to increase the accuracy of determining the parameters of a multiphase medium, it becomes necessary to multiply the readings of the transducers of the flow parameters by a dynamically changing individual weight coefficient determined by known hydrodynamic formulas or experimentally. Also, in addition to the signal processing formula, which is opposed to the prototype, it is necessary to make the diameters of the flowmeter pipes the same, eliminating one of the factors that increase the measurement error of multiphase flow parameters.

The task of the invention is to increase the accuracy of determining the parameters of a multiphase flow - the composition and flow rate of a multiphase multicomponent medium and simplifying the design of the pipeline.

This is achieved by the fact that in the method for determining the flow parameters of a multiphase medium using an ultrasonic flow meter, a flow velocity transducer is placed in a Doppler displacement frequency and gas content transducers in a pipeline containing two pipe sections and the flow parameters are calculated after preliminary finding the integral characteristics of the flow parameter transducers calculated according to the formulas:

integral characteristic of flow velocity converters reduced to the first (a) or second (b) pipe section:

where F _1k , F _2l are local Doppler frequencies measured by the flow velocity transducers in the first and second pipe segments, respectively, taking into account individual weight coefficients, experimentally determined depending on the position of the transducer with respect to the center and along the length of the pipe;

S ₁ , S ₂ - the cross-sectional area of the first and second pipe sections;

N, M - the number of converters of the flow velocity in the first and second pipe sections;

integral characteristic of gas content converters φ _int :

where φ _1k , φ _2l are the local values of the gas content equal to the ratio of the number of not transmitted probe pulses to their total number, determined by the gas content converters in the first and second pipe sections, respectively, taking into account individual weight coefficients experimentally determined depending on the position of the converter with respect to center and length of the pipe;

n and m are the number of gas content converters installed respectively in the first and second pipe sections;

Diagnostics of the device’s performance is carried out according to the deviation of the local readings of the converters from the integral value.

An ultrasonic flowmeter for components of a multiphase medium flow in a pipeline, comprising: two pipe sections mounted vertically in series, N and M local converters of the flow velocity to the Doppler frequency and n and m local gas converters installed in each pipe section, a controller configured to calculating the values of the flow parameters, characterized in that the flow meter additionally contains the first memory block in which the calibration values are located ia flowmeter transducers and additional constants of the flow components, such as the speed of sound in oil, in water and its dependence on temperature, a second memory block for storing current transducer signals, a control panel, a third memory block for storing the calculated flow parameters, an indicator of the values requested from the console information control, real-time clock, while the cross-sectional areas of the pipe segments are equal, and the controller is configured to calculate the integral characteristics of the converter taking into account individual weight coefficients for local converters of speed and gas content.

The invention is illustrated by drawings. Figure 1 shows a structural diagram of an ultrasonic flow meter. Figure 2 shows a diagram showing the effectiveness of the proposed method for determining the flow parameters of a multiphase medium. Figure 3, 4 shows the diagrams corresponding to the matrices of data taken during calibration of the flowmeter on a certified installation. Figure 5 shows the optimal location of the installation of the transducers of the flow parameters, taking into account the partial separation of the flow into its phases - oil, water, gas.

A diagram of an ultrasonic flow meter in accordance with the claimed invention is presented in figure 1. Here 1 and 2 are pipe sections, 3 and 5 are flow velocity converters, 4 and 6 are gas content converters, 7 is a water concentration converter in the liquid phase, 8 is a communication line, 9 is an electronic processing, storage, indication, received, processed and calculated signals, comprising: 10 - the first memory block, which contains the calibration values of the flowmeter transducers and additional constants of the flow components, for example, the speed of sound in oil and water and its dependence on temperature, 11 - the controller, 12 - the second memory block for storing the current converted values of the flow parameters, 13 — the control panel, 14 — the third memory block for storing the calculated flow parameters, 15 — the indicator of the values of the information requested from the control panel, 16 — the real-time clock.

The method is carried out through the integral (averaged) primary parameters of the flow parameter converters, namely: the integral (taking into account individual weight coefficients) Doppler frequency offset value and integral gas content, expressed in relation to the number of not transmitted probe pulses to the total number of probe pulses that went into the stream by formulas:

integral characteristic of flow velocity converters reduced to the first (a) or second (b) pipe section:

where F _1k , F _2l are local Doppler frequencies measured by the flow velocity transducers in the first and second pipe segments, respectively, taking into account individual weight coefficients, experimentally determined depending on the position of the transducer with respect to the center and along the length of the pipe;

S ₁ , S ₂ - the cross-sectional area of the first and second pipe sections;

N, M - the number of converters of the flow velocity, respectively, in the first and second pipe sections;

integral characteristic of gas converters φ _int :

where φ _1k , φ _2l are the local values of the gas content equal to the ratio of the number of not transmitted probe pulses to their total number, determined by the gas content converters in the first and second pipe sections, respectively, taking into account individual weight coefficients experimentally determined depending on the position of the converter with respect to center and length of the pipe;

n and m are the number of gas content converters installed respectively in the first and second pipe sections.

The device (figure 1) works as follows. When a multiphase flow, consisting of oil, water and gas, flows along the first and second pipe sections of the device, the flow is probed by ultrasonic transducers. In the converters of the flow velocity 3 and 5, it is converted to the frequency of the Doppler shift F. In the gas converters 4 and 6, the ratio φ of the number of transmitted probe pulses to their total number during the measurement period is calculated. In the transducer 7 of the concentration of water in the liquid phase, the propagation time of ultrasonic pulses from the emitter to the receiver is measured through a measuring volume filled with the liquid phase of the mixture. Each transducer must have at least two pairs of emitter-receiver located along the radius of the pipe segments. The transducers must be spaced apart from each other along the length of the pipe sections to avoid mutual influence.

The encoded signals from the converters in digital form are transmitted via communication line 8 to the electronic unit 9 for storing, processing, indicating received and processed signals (Fig. 1). There, 8 signals from pressure and temperature sensors, for simplicity not shown in the diagram, come through the communication line. The primary signals from the transducers and sensors enter the communication line 8 at the request of the controller 11 at regular intervals and are stored in the memory unit 12 to save the current converted values of the flow parameters with reference to the real-time clock 16. Then, the controller 11 extracts information from the memory block 12 for the last time interval and calculates the integral characteristics for a given period of time, finds the dependences F _int = f (Q _w , Q _g , t, P), φ _int = φ ( Q _g , Q _g , t, P) for known values of temperature and pressure, solves the system of equations and finds the concentration and flow rates of the liquid Q _g and gas Q _g . Further, according to the testimony of the converter 7, the concentration of the components of the liquid phase (water with oil) according to the known dependencies, the controller 11 determines the oil flow and writes the found flow rates to the third memory unit 14 for storing the calculated flow parameters.

From the control panel 13, the controller is given a command to perform certain actions, for example, calculating the components of gas, oil, water for the last day or week, etc. In this case, the controller refers to block 14, extracts from it the values of expenses for individual time intervals in a given time interval, sums them up and displays the calculated values on an indicator, bus or printer, etc.

As can be seen from the description of the operation of the device, for the flowmeter to work, it is necessary that the first memory block 10, which contains the calibration values of the flowmeter transducers and additional constants of the flow components, for example, the speed of sound in oil and water and its dependence on temperature, be filled. To do this, on a special stand, the flowmeter must be calibrated with the exact flow rates set in the calibrated points of the flow rate through the flowmeter, lying in the measuring range of the flow rate of the working mixture, consisting of different ratios of the volumetric flow rates of the components - hydrocarbon liquid, water, gas in the range of measured concentrations, in the range of measured pressure and temperature. According to the calibration results, the integral characteristics are calculated according to the previously given formulas. Calibration results for intermediate flow points must be approximated using splines or other types of approximation, based on the obtained minimum approximation error between two adjacent approximated points, obtaining a tangent to both curves at the calibration point for all coordinates of temperature, pressure, etc.

In the converters and the electronic unit, imported microcircuits are used, characterized by compactness, versatility and low cost:

microcontrollers MSP430F149;

programmable logic matrix XCR3128XL-XTQ144;

variable gain operational amplifiers

AD602AR;

low resistance logic keys ADG702BRM;

high-speed comparators LT1715IMS;

interface microcircuit "RS485" MAX1480BEPI.

We present the experimental data obtained during the calibration of the flow meter (figure 2, 3, 4).

Figure 2 shows the dependence on the liquid flow rate of local gas contents given by formula (2) of the gas content prototype (dashed line) and integral gas content (dash-dot line) calculated according to formula (5) of the present application. It can be seen from the diagram that, with an increase in the liquid flow rate of more than ~ 200 m ³ / day, the readings of the sensors installed in a narrow section of the hydrochannel begin to increase, especially in the center, distorting the given characteristic φ_pr so that ambiguity regions are formed on it, in which one value reduced gas content correspond to two values of fluid flow. The integrated characteristic φ_int has a monotonically decreasing form, which does not allow duality in determining the flow rate of a liquid in a multiphase flow.

The calibration results of the flow velocity transducers and gas content transducers are stored in the memory of the calculator-indicator in the form of a set of two-dimensional matrices, graphical interpretations of which are shown in FIGS. 3 and 4, respectively.

Based on the test results, the following conclusions are made:

- the selected technical solutions made it possible to more reliably calculate the flow parameters of the received signals and carry out their effective processing at all well operation modes;

- the numerical values of the flow parameters obtained during the measurements are close to measurements using standard measuring systems and the values obtained in laboratory tests. The difference in results from each other during repeated measurements in individual areas does not exceed 2.5% for liquid and 5% for gas.

Claims (2)

1. The method of determining the flow parameters of a multiphase medium using an ultrasonic flow meter of flow components, which consists in the fact that in the pipeline containing the first and second pipe section, in each of the sections are placed respectively local speed converters of the flow velocity to the frequency of the Doppler shift and gas content converters and calculate flow parameters, characterized in that the final multiphase flow parameters are calculated after preliminary finding the integral characteristics of the conversion Callers calculated by the formulas:
the integral characteristic of the converters of the flow velocity to the frequency of the Doppler shift, reduced to the first (a) or second (b) pipe sections:

where F _1k , F _2l are Doppler frequencies measured by local converters of the flow velocity in the first and second pipe sections, respectively, taking into account individual weight coefficients, experimentally determined depending on the position of the converter with respect to the center and along the length of the pipe;
S ₁ , S ₂ - the cross-sectional area of the first and second pipe sections;
N, M - the number of converters of the flow velocity in the first and second pipe sections;
integral characteristic of gas converters:

,
where φ _1k , φ _2l are the values of gas content equal to the ratio of the number of transmitted probe pulses to their total number, determined by local gas content transducers in the first and second pipe sections, respectively, taking into account individual weight coefficients experimentally determined depending on the position of the converter with respect to the center and along the length of the pipe;
n and m are the number of gas content converters in the first and second pipe sections;
the health of an ultrasonic flow meter is diagnosed by the deviation of the readings of the local transducers from the integral value. 2. An ultrasonic flowmeter of the components of a multiphase medium flow in a pipeline, comprising: two pipe sections installed vertically in series, N and M local converters of the flow velocity to the Doppler frequency and n and m local gas-content converters installed in each pipe segment, a controller made with the possibility of calculating the value of the flow parameters, characterized in that the flow meter additionally contains the first memory block in which calibration values are located the flowmeter transducers and additional constants of the flow components, such as the speed of sound in oil and water and its dependence on temperature, a second memory unit for storing current transducer signals, a control panel, a third memory unit for storing the calculated flow parameters, an indicator of the values requested from the control panel information, real-time clock, while the cross-sectional areas of the pipe segments are equal, and the controller is configured to calculate the integral characteristics of the converter lei taking into account the individual weights of the local converters of speed and gas content.

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