Measuring and testing – Volume or rate of flow – Of selected fluid mixture component
Reexamination Certificate
2002-06-21
2003-12-09
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Volume or rate of flow
Of selected fluid mixture component
Reexamination Certificate
active
06658944
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and a device for determination volume flow rates and volume concentrations of liquid phase components and gas in multiphase liquid/gas mixtures such as oil well fluids, composed of oil, water and gas. In particular the invention relates to such a method and such a device according to the preambles of claims 1 and 15 respectively.
BACKGROUND OF THE INVENTION
An effluent flowing along a pipeline from an oil well is a multiphase mixture of oil, water and gas. Accurate and simultaneous measurement of flow rates and volume concentrations of mixture components is important for control of the well operation.
Methods and devices for measuring these flow characteristics accepted up to the present demand preliminary separation of gas in special separators which are installed in measuring devices on the territory of oil fields. This fact leads to considerable capital expenses by execution of such measurements.
Techniques for measuring of the said multiphase flow characteristics without a prior separation of gas phase are also known. These methods and devices are based on various physical principles: difference of density and electromagnetic characteristics of the components, interaction with gamma-rays and ultrasonic waves, and others.
RU-C-2138023 discloses a method and device according to the preamble of claim 1 and to the preamble of claim 15 respectively. With the prior art method at one location along a pipeline, which passes a multiphase mixture with constant flow velocity, the acoustic conductivity of the mixture is measured by transmitting acoustic pulses through a controlled volume of the mixture by a transmitter and counting these pulses if received by a receiver, and with a ratio of transmitted and received pulses representing the amount of a phase of the mixture. In addition, at each of two locations the time it takes for a pulse to transit through a controlled volume is measured, said time is cross correlated with that obtained from the other location and then used in combination with a value of the distance between said locations to calculate the velocity. During equipment calibration using clean oil and clean water, times of impulse transit through a controlled volume is measured and used in combination with an actual (in situ) measured transit time, said phase amount ratio, said velocity and a value of the cross section of the pipeline to calculate the actual flow rates of gas, oil and water.
EP-A-0684458 discloses a multiphase flow meter in which a pipeline comprises two restrictions, which each provide a change of velocity of the flow with respect to the flow velocity in locations just before and in each restriction respectively. For each restriction a pressure difference between said locations is measured. A value for the volume V between the restrictions must be determined in advance. By using pressure difference signals and the volume value V the total volume flow rate q can be determined. By measuring a static pressure difference a first approximation of the density p of the mixture can be determined. A further device is used to provide one or more indications about the composition of the multiphase mixture. Given the densities &rgr;
o
, &rgr;
w
, &rgr;
g
of the components of the multiphase mixture, the flow rates of the phases are determined. With this prior art flow meter, at locations where the velocity of the mixture has been changed, that is at each restriction, the velocity is not measured itself. Neither is the velocity measured at a distance from the restriction. Instead, a pressure difference at each restriction must be measured to therefrom determine a time wich the mixture takes to travel from the one restriction to the other restriction. From said time and the known distance between the restrictions the velocity is calculated.
U.S. Pat. No. 5,287,752 describes a device for determination flow rates of multiphase fluids by means of a set of capacitors placed on two parallel plates which are arranged inside a horizontal or inclined pipeline parallel to a flow direction. In order to determine a water/oil volume proportion and a part of pipeline cross-section occupied by liquid phase impedances of a medium located at the moment in measuring cells of all elementary capacitors are measured. A velocity of the liquid phase is determined by measuring and cross-correlation impedances of elementary capacitors located in a matrix row situated in a part of cross-section occupied by the liquid phase. A velocity of gas is determined by measuring passage time of structural deformations of the flow in the upper part of the pipeline. Volume flow rates of the phases are determined taking into account the parts of the pipeline cross-section occupied by the liquid and gas phases of the flow.
The proposed method has limited sphere of application since it can be effectively used only by an intermittent flow regime. Besides a type of emulsion and dispersion of components aren't taken into account in this method.
U.S. Pat. No. 5,367,911 describes an apparatus for sensing fluid behaviour in a conduit that can be used as a flow meter. The measuring device includes at least two sensors arranged within a pipeline, one downstream the other. The sensors may include acoustic transducers or electrical conductivity (or resistivity) sensors. Each sensor provides an output data signal, indicative of the measured physical property of a medium flowing in respective sampling volumes. Output signals are processed in a circuit and are cross-correlated. Since a distance between the sensors is known a calculation of the flow speed is made.
However the authors of the patent don't take into account that a gas phase moves relative to a liquid phase in multiphase flows.
European patent A 0684458 relates to a method and a device for measuring flow rate of multiphase fluids. The device comprises two sections situated at a distance one from the other along a duct. The sections are implemented in the form of venturis. Each section includes a passage with different cross-section areas provided with means for inducing a change of speed therein and a variation of dynamic pressure correspondingly. Besides the device includes appropriate means for measuring the resulting pressure differences. Two pressure difference signals obtained in the said respective sections are suitable for cross-correlation to produce a third signal representative of a total volume flow rate. In order to determine the flow rates of phases another pressure difference is measured in a venturi type flow section and the signal that is a function of the total mass flow rate Q and density &rgr; of a mixture is obtained. One more pressure difference is measured in the section of a “gradiomanometer” type. This section is disposed in a portion of a vertical duct that has constant cross-section area. In a conventional manner the latter pressure difference represents a static pressure difference that is proportional, to a first approximation, to the density p of the mixture. In addition, the device includes a module situated in the duct, that provides one or more indications of composition of the multiphase fluid, in other words, determines volume or mass concentrations of components constituting the fluid. A processor calculates the mass flow rate Q via parallel paths depending on gas content. When the gas content is moderate (<65%) a first processing way is used on the basis of a signal proportional to the expression Q
2
/&rgr; and a signal representative of the density &rgr; of the mixture. A second processing way based on a signal representative of the total volume flow rate and a signal representative of the density p of the mixture is used when the gas content is high (>65%).
It is necessary to note that devices with venturi type sections have a small dynamic range and hence may be used in a limited range of flow rate measurements. Besides, a flow rate factor of such devices significantly depends on gas content that influences on the measurement accuracy. In the desc
Drobkov Vladimir
Melnikov Vladimir
Shustov Andrey
Lefkowitz Edward
Nest International N.V.
Schneider, Esq. Ryan A.
Thompson Jewel V.
Troutman Sanders LLP
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