Measuring and testing – Volume or rate of flow – Of selected fluid mixture component
Reexamination Certificate
1998-12-22
2002-01-15
Patel, Harshad (Department: 2855)
Measuring and testing
Volume or rate of flow
Of selected fluid mixture component
C073S200000, C073S061730
Reexamination Certificate
active
06338276
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and to a device for determining the value of the flow rate of one or more phases contained in a multiphase effluent, the effluent comprising at least one gas phase and at least one liquid phase.
The invention is used to determine the mass flow rate of the phases of a petroleum effluent comprising a gas phase and a liquid phase (organic and aqueous). The effluent can possibly contain solid particles such as sand, hydrates or paraffins.
The invention is notably applied for enhanced production of a petroleum effluent by injection of gas in the string (gas lift) or by injection of steam in the reservoir. Continuous knowledge of the mass flow rate of the phases produced in each well allows optimum adjustment of the amounts of fluid injected.
2. Description of the Prior Art
Various flow metering methods and devices are known from the prior art.
Patent EP-0 674 249 describes a method and a device allowing mixing of a gas phase and a liquid phase, and to determine the value of the total flow rate of the two phases mixed in a venturi. The method requires a stage of homogenization of the two phases prior to measuring the pressure value at the inlet and at the outlet of the venturi, and a density measuring stage carried out by gammametry, which requires the presence of a radioactive source.
It is well-known to use waves such as microwaves or ultrasonic waves for determining the flow rate of the gas phase and of the liquid phase forming a multiphase effluent. U.S. Pat. Nos. 4,812,739 and 4,820,970 and French Patent 2,722,292 describe methods for determining or measuring, on the one hand, the amount of each of these phases and, on the other hand, an average velocity value or the value of the velocity for each phase, in order to respectively deduce therefrom the average total flow rate or the flow rate of each phase.
The drawback of such devices is that they are expensive and sometimes difficult to install.
SUMMARY OF THE INVENTION
The present invention is a device, flowmeter and a method which overcomes the drawbacks of the prior art.
The present invention relates to a method for determining the value of the flow rate of at least one phase forming a part of a flowing multiphase medium, the multiphase medium comprising at least one liquid phase and at least one gas phase. The invention comprises at least the following steps:
a) feeding the multiphase medium into a chamber comprising at least one delivery line, a sampling device comprising sampling ports and at least one discharge line,
b) determining at least two pressure values P
1
and P
2
at least at two different points A and B of the chamber and/or of the sampling device, and the internal pressure value Po,
c) determining, from the values determined in step b), from the knowledge of the density of the gas phase and of the liquid phase and/or from the average value of the density of the multiphase medium in the slotted tube, from a relation connecting at least the following parameters: GLR or the level of the interface between the liquid phase and the gas phase, from pressures P
1
, P
2
, Po, the value of the total flow rate Qt of the flowing multiphase medium and/or the flow rate of each of phases q
g
and q
l
.
According to the invention, the value of the flow rate of the gas phase and/or of the liquid phase can be determined by means of relations between the flow rates of the phases and the measured pressure differences, and notably the following relations:
q
g
=
S
g
C
g
2
(
P
1
-
P
0
)
g
ρ
0
g
q
l
=
S
l
C
l
2
(
P
2
-
P
0
-
g
ρ
0
l
z
2
2
)
g
ρ
0
l
where
S
g
and S
l
correspond to the sum of the areas of the ports situated in the gas phase and in the liquid phase respectively,
z
2
being the distance between the liquid-gas interface and a point,
&rgr;
og
and &rgr;
ol
being the densities for the gas and the liquid at the pressure Po and for a temperature T
o
,
C
g
and C
l
being the values of the passage coefficients of the ports of the slotted tube, and the pressure values P
1
and P
2
being measured at the level of the sample tube.
Qt=q
l
+q
g
and
GLR=q
g
/q
l
.
The value of the GLR can be determined by measuring the level of the interface between the gas phase and the liquid phase in the chamber, by taking account of the total height H of the slotted tube and of the characteristics of the sampling device such as the value of the bore coefficient of the tube, the characteristic function of the bore of the slotted tube that equips the chamber f(H,h).
The relation between the various parameters of step c) can be established by calibrating the device by varying the values of the GLR, of the differential pressures Po−P
1
and P
2
−Po and of pressure Po, and of densities &rgr;g, &rgr;l.
The liquid phase has, for example, two liquid phases L
1
and L
2
of differentiable densities &rgr;
1
and &rgr;
2
. A third pressure value P
3
is measured in the chamber. The level of the interface between the liquid phase and the gas phase is determined for example by considering the highest liquid level in the chamber, and the value of the fraction of liquid phase L
1
is determined,
W
1
=
1
ρ
1
-
ρ
2
[
ρ
3
-
ρ
2
g
×
h
-
ρ
2
]
W
1
=fraction of the liquid phase of density &rgr;
1
brought back to volume of the mixture of liquid phases. Stating from the value of W
1
, it is determined the value of
x
1
=
W
1
1
+
GLR
corresponding to the fraction of the liquid phase L
1
, and the value of
x
2
=
1
-
W
1
1
+
GLR
corresponding to the fraction of the liquid phase L
2
knowing the value of ql and the values of x
1
and/or x
2
, one determines the value of flowrate q
L1
and/or q
L2
.
The temperature and/or the pressure prevailing in the chamber can be determined and the density and/or GLR values can be corrected.
The average density &rgr;m can be determined by measuring the pressure difference between two points located a distance h apart on the slotted tube; the pressure difference can be measured in a flow element situated between the outlet of the slotted tube and the multiphase medium discharge line.
The invention also relates to a device for determining at least the value of the total flow rate of a flowing multiphase medium, the multiphase medium comprising at least one liquid phase and at least one gas phase, the device comprising a chamber provided with at least one delivery line, at least one discharge line and a sampling device comprising sampling ports for removing the liquid phase and the gas phase. The device comprises at least three pressure measuring devices, one intended to measure the internal pressure of the chamber and the two others, the pressure prevailing at two points of the chamber and/or of the sampling device, these point being located a distance d apart, a device which determines the value of the volume ratio GLR of the gas phase and of the liquid phase of the flowing multiphase medium, a processing unit which stores these measured or determined values and initially determined parameter values such as the values of the density of each phase or the average value of the density of the multiphase medium, a relation connecting at least the following parameters: the level of the interface between the gas phase and the liquid phase and/or the GLR, pressure values (P
1
, P
2
, Po), the processing unit determining at least the value of the total flow rate Qt of the multiphase medium.
The device can comprise at least one flow element situated between the outlet of the sampling device and the discharge line, the pressure measuring device being placed at the level of the flow element.
The device can comprise a device which determines the average density &rgr;m of the multiphase medium at the level of the sampling device.
The device can comprise a mixer which mixes the liquid phase and the gas phase, situated between the outlet of the sampling devi
Castel Yvon
Durando Pierre
Falcimaigne Jean
Ferre Daniel
Vandenbroucke Eric
Institut Francais du Pe'trole
Patel Harshad
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