Devices for determining the flow characteristics of a multi-phase fluid

• US 6,345,537 B1
• Filed: 06/17/1999
• Issued: 02/12/2002
• Est. Priority Date: 06/25/1998
• Status: Expired due to Term

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Salamitou, Philippe F.
• Primary Examiner(s): Fuller, Benjamin R.
• Application Number:
  US09/335,069
• Time in Patent Office: 971 Days
• Field of Search: 738/610.4, 738/610.2, 738/610.6, 738/611.2, 738/611.4, 738/611.5
• US Class Current: 73/861.04
• CPC Class Codes: G01F 1/64 by measuring electrical currents passing through the fluid flow; measuring electrical potential generated by the fluid flow, e.g. by electrochemical, contact or friction effects G01F1/58 takes precedence
• CPC Class Codes: G01F 1/712 using auto-correlation or cross-correlation detection means
• CPC Class Codes: G01F 1/74 Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid

Abstract

A capacitive device for measuring the dielectric constant of a two-phase fluid flowing along a pipe, this device comprising two electrodes and power supply system for applying an AC voltage across the two electrodes. A first one of these electrodes forms an excitation electrode disposed at the periphery of a measurement electrode, and the device further comprises apparatus for maintaining the electrodes at the same potential and for measuring the current (i) flowing between the excitation electrode and the measurement electrode, and apparatus for deducing the dielectric constant from the measured current. Application to measuring flow rates of water in hydrocarbon wells, in particular in hydrocarbon wells that slope.

Claims

1. A device for capacitively measuring the dielectric constant of a two-phase fluid flowing along a pipe, comprising:

at least one capacitive sensor comprising at least one excitation electrode which part of the surface defines a cutout to allow free space in which at least one measurement electrode is disposed, said electrodes being arranged to be applied against said pipe;

power supply means connected to the excitation electrode of said capacitive sensor in order to apply an AC voltage to said excitation electrode;

amplification means connected to both the excitation electrode and the measurement electrode in order to maintain said electrodes at the same potential and capacitively measure the current (i) output by said measurement electrode; and

deducing means connected to said amplification means in order to deduce said dielectric constant from said current (i).

2. A device according to claim 1, in which said excitation electrode is connected to the general ground of said power supply means.

3. A device according to claim 1, in which an electrode is connected to the general ground of said power supply means, a floating ground being provided for said amplifying means for measuring the current.

4. A device according to claim 3, in which said amplifying means for measuring the current comprise a first amplification stage referenced relative to the potential of the excitation electrode, and a second amplification stage organized to bring the reference of the output signal to the general ground.

5. A device according to claim 4, including shielding electrically connected to the excitation electrode, around the measurement electrode and around said first amplification stage.

6. A device according to claim 1, in which said excitation electrode covers the measurement electrode.

7. A device for capacitively measuring the volume fraction of a first fluid in a two-phase fluid flowing along a pipe, comprising:

at least one device for capacitively measuring the dielectric constant of said fluid, said device comprising;

at least one capacitive sensor comprising at least one excitation electrode which part of the surface defines a cutout to allow free space in which at least one measurement electrode is disposed, said electrodes being arranged to be applied against said pipe;

power supply means connected to the excitation electrode of said capacitive sensor in order to apply an AC voltage to said excitation electrode;

amplification means connected to both the excitation electrode and the measurement electrode in order to maintain said electrodes at the same potential and capacitively measure the current (i) output by said measurement electrode;

calculating means connected to said amplification means in order to deduce said dielectric constant from said current (i) and calculate said volume fraction from said dielectric constant.

8. A device according to claim 7, comprising a plurality of devices for capacitively measuring the dielectric constant of said fluid, said plurality of devices being distributed over the periphery of a cross-section of said pipe.

9. A capacitive device for measuring the speed of a two-phase fluid flowing along a pipe, comprising:

at least two devices that are disposed in different cross-sections of said pipe, said devices comprising;

at least one capacitive sensor comprising at least one excitation electrode which part of the surface defines a cutout to allow free space in which at least one measurement electrode is disposed, said electrodes being arranged to be applied against said pipe;

power supply means connected to the excitation electrode of said capacitive sensor in order to apply an AC voltage to said excitation electrode;

amplification means connected to both the excitation electrode and the measurement electrode in order to maintain said electrodes at the same potential and capacitively measure the current (i) output by said measurement electrode; and

deducing means connected to said amplification means in order to deduce said dielectric constant from said current (i); and

correlating means connected to both of said two devices in order to establish a cross-correlation between the measurements delivered by said two devices and for deducing said speed therefrom.

10. A device according to claim 9, in which said at least two devices are disposed substantially along the same generator line of said pipe, and have a common excitation electrode.

11. A device for capacitively measuring the flow rate of a fluid in a two-phase fluid flowing along a pipe, comprising

at least one device for capacitively measuring the volume fraction of a said fluid, comprising:

at least one device for capacitively measuring the dielectric constant of said fluid, said device including at least one capacitive sensor comprising at least one excitation electrode which part of the surface defines a cutout to allow free space in which at least one measurement electrode is disposed, said electrodes being arranged to be applied against said pipe;

power supply means connected to the excitation electrode of said capacitive sensor in order to apply an AC voltage to said excitation electrode;

amplification means connected to both the excitation electrode and the measurement electrode in order to maintain said electrodes at the same potential and capacitively measure the current (i) output by said measurement electrode; and

calculating means connected to said amplification means in order to deduce said dielectric constant from said current (i) and calculate said volume fraction from said dielectric constant;

at least one capacitive device for measuring the speed of a two-phase fluid flowing along a pipe, comprising;

at least two devices that are disposed in different cross-sections of said pipe, said two devices including at least one capacitive sensor comprising at least one excitation electrode which part of the surface defines a cutout to allow free space in which at least one measurement electrode is disposed, said electrodes being arranged to be applied against said pipe;

power supply means connected to the excitation electrode of said capacitive sensor in order to apply an AC voltage to said excitation electrode;

amplification means connected to both the excitation electrode and the measurement electrode in order to maintain said electrodes at the same potential and capacitively measure the current (i) output by said measurement electrode;

deducing means connected to said amplification means in order to deduce said dielectric constant from said current (i);

and correlating means connected to said capacitive device for measuring the speed, in order to establish a cross-correlation between the measurements delivered by capacitive device and to deduce said speed and thus said flow rate therefrom.

12. A method of measuring the dielectric constant of a two-phase fluid flowing along a pipe, said method comprising the steps of placing two electrodes on either side of a portion of said fluid, and applying an AC voltage across the two electrodes, wherein at least one excitation electrode has part of its surface that defines a cutout to allow free space in which at least one measurement electrode is disposed, and further comprising the steps of maintaining said excitation electrode and said measurement electrode at the same potential, measuring the current flowing between said electrodes, and deducing said dielectric constant from said current.