B S & W measuring means and method

• US 5,249,455 A
• Filed: 12/23/1991
• Issued: 10/05/1993
• Est. Priority Date: 12/23/1991
• Status: Expired due to Fees

• Current Assignee: Texaco Incorporated (Chevron Corp.)
• Original Assignee: Texaco Incorporated (Chevron Corp.)
• Inventors: Cox, Percy T.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): DOMBROSKE, GEORGE M
• Application Number:
  US07/811,633
• Time in Patent Office: 652 Days
• Field of Search: 324/689, 73/61.44, 73/61.61, 73/61.71
• US Class Current: 73/61.44
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: G01N 27/226 Construction of measuring vessels; Electrodes therefor
• CPC Class Codes: G01N 33/2823 Raw oil, drilling fluid or polyphasic mixtures

Abstract

A water cut meter includes a test cell through which a petroleum stream will flow. The test cell includes an outer shell, a sensor probe which cooperates with the outer shell to form a sensor capacitor with the flow of the petroleum stream as the dielectric and a reference probe surrounded with pure oil as the dielectric to form a reference capacitor. Processing apparatus includes a comparator network electrically connected to the sensor capacitor and to reference capacitor which compares the capacitance of the sensor capacitor with the capacitance of the reference capacitor. The comparator network provides a signal corresponding to the capacitance difference between the sensor and reference capacitors. An output circuit connected to the comparator network provides an output corresponding to the water cut of the petroleum stream in accordance with the signal from the comparator network.

Claims

1. A BS&

W meter comprising;

test cell means for having a petroleum stream flowing through it including;

an outer shell of conductive material,

sensor probe means located within the outer shell for cooperating with the outer shell to form a sensor capacitor with the flowing petroleum stream as the dielectric, and

a reference capacitor, located within the outer shell, which has pure oil as the dielectric; and

processing means including;

comparator means electrically connected tot he sensor capacitor and to a reference probe means for comparing the capacitance of the sensor capacitor with the capacitance of the reference capacitor and providing a signal corresponding thereto, and

output means connected to the comparator means for providing an output corresponding to the water cut of the petroleum stream in accordance with the signal from the comparator means, and

in which the comparator means includes;

first oscillator means for providing a signal having a frequency within a desired range of frequencies, and

capacitor means connected to the sensor capacitor and to the reference capacitor so as to form a bridge network for providing an output in accordance with the capacitance difference between the sensor capacitor and the reference capacitor, and

in which the capacitor means includes;

a fixed capacitor connecting one of the capacitor in the test cell means to the first oscillator means,

a variable capacitor connecting the other capacitor in the test cell means to the connection of the fixed capacitor and the first oscillator means,

means connected to both capacitors in the test cell for providing a common ground connection for both capacitors in the test cell means, and

conductive means connected to the connection of the fixed capacitor to a capacitor in the test cell means and to another connection of the variable capacitor to the other capacitor in the test cell means for providing the voltage across those two connections as the signal corresponding to the capacitance difference between the sensor capacitor and the reference capacitor.

2. A meter as described in claim 1 in which the output means include:

second oscillator means for providing a beat frequency signal,

mixer means connected to the conductive means and to the second oscillator means responsive to the beat frequency signal to provide a signal at an intermediate frequency corresponding to the signal from the conductive means,

rectifier means for rectifying the signal from the mixer means to provide a corresponding direct current signal, and

utilizing means for utilizing the direct current signal from the rectifier means to provide the water cut signal.

3. A meter as described in claim 2 in which the utilizing means includes:

first converter means connected to the rectifier means for converting the direct current signal to digital signals, and

memory means connected to the first converter means for using the digital signals to select a water cut value from stored values of water cuts for different combinations of oil and water in a petroleum stream and for providing digital signals, corresponding to the selected water cut, as the water cut output.

4. A meter as described in claim 1 and further comprising:

mounting means attached to the sensor probe means and to the reference probe means for mounting the sensor probe means and the reference probe means within the outer shell; and

in which the reference capacitor includes;

housing means electrically connected to the outer shell for providing one electrode of the reference capacitor,

the reference probe means for providing the other electrode of the reference capacitor,

and wherein the pure oil is located within the housing so as to separate the two electrodes.

5. A meter as described in claim 4 in which the mounting means has a plurality of passageways for the petroleum stream to flow through it and additional passageways for electrical connection of the sensor probe means and the reference probe means to the comparator means.

6. A meter as described in claim 5 in which sensor probe means includes:

a first probe made of conductive material,

a first probe tip made of non-conductive material attached to one end of the probe, and

means made of non-conductive material and having a passageway therein for attaching the sensor probe means to the mounting means; and

in which the outer shell is narrow in an area adjacent to the probe so that first probe and outer shell in that area form a co-axial capacitor.

7. A meter as described in claim 6 in which the reference probe means includes:

a second probe made of conductive material,

a second probe tip made of non-conductive material attached to one end of the second probe, and

means made of non-conductive material and having a passageway therein for attaching the sensor probe means to the mounting means, and

means for encompassing the second probe in oil in a manner so as to cooperate with the second probe to form a capacitor with the oil as the dielectric.

8. A BS&

W meter comprising;

test cell means for having a petroleum stream flowing through it including;

an outer shell of conductive material,

sensor probe means located within the outer shell for cooperating with the outer shell to form a sensor capacitor with the flowing petroleum stream as the dielectric, and

a reference capacitor, located within the outer shell, which has pure oil as the dielectric; and

processing means including;

comparator means electrically connected to the sensor capacitor and to the reference probe means for comparing the capacitance of the sensor capacitor with the capacitance of the reference capacitor and providing a signal corresponding thereto, and

output means connected to the comparator means for providing an output corresponding to the water cut of the petroleum stream in accordance with the signal from the comparator means; and

in which the comparator means includes;

control means for providing a control signal,

signal means for providing a voltage signal V and a current signal I in accordance with the capacitance of a capacitor, and

switch means, responsive to the control signal, for connecting the sensor capacitor to the signal means while in a first state and connecting the reference capacitor to the signal means while in a second state so that the signals V and I are provided in accordance with the capacitance of the sensor capacitor or the reference capacitor.

9. A meter as described in claim 8 in which the signal means include:

oscillator means for providing a driving signal at a preferred frequency within a range of frequencies,

a current resistor connecting the oscillator means to the switching means,

voltage means for utilizing a voltage at the connection of the current resistor had the switching means to provide a voltage output,

signal V means connected to the voltage means for the voltage signal V in accordance with the voltage output,

current means for utilizing the voltage across the current resistor to provide a current output, and

signal I means for providing the current signal I in accordance with the current output.

10. A meter as described in claim 9 further comprising:

means connected to the signal V means and to the signal I means for providing a signal PH corresponding to the phase difference between the voltage signal V and the current signal I.

11. A meter as described in claim 9 in which the output means includes:

microprocessor means for providing the control signal to the switching means, and

means for providing a water cut output in accordance with signals V and I.

12. A meter as described in claim 11 for determining the measured impedance Z_MEA when the switching means is in the one state, and

means for determining the reference impedance Z_REF when the switching means is in the other state,

means for determining the impedance difference Z_DIFF in accordance with signal Z_REF and Z_MEA, and providing a signal corresponding thereto, and

means for determining the water cut in accordance with the following equation:

space="preserve" listing-type="equation">WC=A+B (Z.sub.DIFF),

where A and B are empirically derived constants, and providing the output corresponding thereto.

13. A BS&

W metering method comprising the steps of;

causing a petroleum stream to flow through a test cell,

using an outer shell of conductive material as part of the test cell,

locating a sensor probe within the outer shell so that the sensor probe cooperates with the outer shell to form a sensor capacitor with the flowing petroleum stream as the dielectric, and

locating a reference capacitor within the outer shell which has pure oil as the dielectric; and

comparing the capacitance of the sensor capacitor with the capacitance of the reference capacitor,

providing a comparison signal corresponding to the comparison, and

providing an output corresponding to the watercut of the petroleum stream in accordance with the comparison signal; and

providing a control signal,

using signal means to provide a voltage signal V and a current signal I in accordance with the capacitance of a capacitor, and

using switch means, responsive to the control signal, for connecting the sensor capacitor to the signal means while in a first state and connecting the reference capacitor to the signal means while in a second state so that the signals V and I are provided in accordance with the capacitance of the sensor capacitor or the reference capacitor.

14. A method as described in claim 13 in which the output step include:

providing a beat frequency signal,

mixer means mixing the comparison signal with the beat frequency signal to provide an intermediate frequency signal corresponding to the comparison signal,

rectifying the intermediate frequency signal to provide a corresponding direct current signal, and

utilizing the direct current signal to provide a water cut signal.

15. A as described in claim 14 in which the utilizing step includes:

converting the direct current signal to digital signals,

using the digital signals to select a water cut from memory means having stored values corresponding to water cuts for different combinations of water and oil in a petroleum stream, and

providing digital signals, corresponding to the selected water cut value, as the water cut output.

16. A method as described in claim 13 which using the signal means step includes:

providing a driving signal with an oscillator at a preferred frequency within a range of frequencies,

connecting the oscillator to the switching means with a current resistor,

utilizing a voltage at the connection of the current resistor and the switching means to provide a voltage output,

providing the voltage signal V in accordance with the voltage output,

utilizing the voltage across the current resistor to provide a current output, and

providing the current signal I in accordance with the current output.

17. A method as described in claim 16 further comprising the step:

providing a signal PH corresponding to the phase difference between the voltage signal V and the current signal I.

18. A method as describe in claim 13 in which the comparing step includes:

providing a voltage signal V_MEA functionally related to the capacitance of the sensor capacitor,

providing a current signal I_MEA functionally related to the capacitance of the sensor capacitor,

providing a sensed impedance signal Z_MEA in accordance with the voltage signal V_MEA and the current signal I_MEA,

providing a voltage signal V_REF functionally related to the capacitance of the reference capacitor,

providing a current signal I_REF functionally related to the capacitance of the reference capacitor,

providing a reference impedance signal Z_REF in accordance with the voltage signal V_REF and the current signal I_REF, and

in which the comparison signal step includes;

providing a signal Z_DIFF, corresponding to the difference between the measured impedance Z_MEA and the reference impedance Z_REF, as the comparison signal.

19. A method as described in claim 18 in which the steps of providing the voltage signal V_MEA, the current signal I_MEA, the voltage signal V_REF and the current signal I_REF are repeated 50 times, and further comprising the steps of:

averaging the voltage signals V_MEA, the current signals I_MEA, the voltage signals V_REF and the current I_REF to provide an average value voltage V_MEA, an average current value I_MEA, an average voltage signal V_REF and an average current signal I_REF, respectively,

providing the sensed impedance signal Z_MEA in accordance with the average voltage signal V_MEA, and the average current signal I_MEA, and

providing the signal Z_REF in accordance with the average voltage signal V_REF and the average current signal I_REF.

20. A method as described in claim 19 in which the output providing step includes:

determining the water cut of the petroleum stream in accordance with the following formula;

space="preserve" listing-type="equation">WC=A+B (Z.sub.DIFF)

where A+B are empirically derived constants, and

providing the output corresponding to the water cut as the determined water cut.

21. A method as described in claim 20 in which the water cut determining step is repeated 20 times.