Method and apparatus for monitoring multiphase fluid flow

1. A method of monitoring multiphase fluid flow passing within a pipe, which multiphase fluid flow includes a gas phase and a liquid phase, the method comprising the steps of:

providing a flow pressure value and a flow temperature value for the multiphase fluid flow within the pipe;

providing a fluid flowmeter operable to be attached to an exterior of the pipe, the flowmeter including a spatial array of at least two sensors disposed at different axial positions along the pipe, which flowmeter is adapted to produce flow velocity signals indicative of a velocity of the fluid flow traveling within the pipe;

providing a processor adapted to include an equation of state model for pressure, volume, and temperature properties for the multiphase fluid flow, and further adapted to receive composition data values for the multiphase fluid flow, the flow pressure value, and the flow temperature value, and the flow velocity signals from the flowmeter;

determining a volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow;

wherein each of the composition data values includes at least one value representative of a hydrocarbon constituent of the multiphase fluid flow.

2. The method of claim 1 , wherein the sensors of the fluid flowmeter each include an ultrasonic transmitter operable to transmit an ultrasonic signal, and an ultrasonic receiver operable to receive the transmitted ultrasonic signal, wherein the flowmeter is operable to sense the fluid flow within the pipe for coherent properties convecting within the fluid flow.

3. The method of claim 1 , further comprising the step of determining a volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow at standard pressure and temperature values.

4. The method of claim 1 , wherein the fluid flow meter is a first fluid flowmeter that is adapted to produce first flow velocity values, and wherein the method further includes the steps of:

providing a second fluid flowmeter that is adapted to produce second flow velocity values;

determining a measured value for a fluid flow parameter using the first flow velocity values and the second flow velocity values;

determining a calculated value for the fluid flow parameter using the flow pressure value and the flow temperature value and the equation of state model;

comparing the measured and calculated values of the fluid flow parameter to determine an error value;

determining modified composition data values using the current composition data values if the error value exceeds a predetermined value, and iteratively repeating the steps of determining the calculated value, comparing the measured and calculated values, and determining modified composition data values until the error value is less than the predetermined value or other condition is met; and

determining the volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow using the modified composition data values.

5. The method of claim 4 , wherein the first fluid flowmeter is a SONAR type fluid flowmeter and the second fluid flowmeter is a DP flowmeter.

6. The method of claim 4 , further comprising the steps of:

providing a watercut value for the multiphase fluid flow within the pipe;

determining a measured speed of sound value for the liquid phase of the multiphase fluid flow;

determining a calculated speed of sound value for the liquid phase of the multiphase fluid flow using the flow pressure value and the flow temperature value and the equation of state model;

comparing the measured and calculated values of the speed of sound value for the liquid phase of the multiphase fluid flow to determine a SOS error value;

determining a modified watercut value using the current watercut value if the SOS error value exceeds a predetermined value, and iteratively repeating the steps of determining the calculated SOS value, comparing the measured and calculated SOS values, and determining a modified watercut value until the SOS error value is less than the predetermined value or other condition is met; and

determining the volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow using the modified watercut value.

7. A method of monitoring multiphase fluid flow passing within a pipe, which multiphase fluid flow includes a gas phase and a liquid phase, the method comprising the steps of:

providing a flow pressure value and a flow temperature value for the multiphase fluid flow within the pipe;

providing a fluid flowmeter operable to be attached to an exterior of the pipe, the flowmeter including a spatial array of at least two sensors disposed at different axial positions along the pipe, which flowmeter is adapted to produce flow velocity signals indicative of a velocity of the fluid flow traveling within the pipe;

providing a processor adapted to include an equation of state model for pressure, volume, and temperature properties for the multiphase fluid flow, and further adapted to receive composition data values for the multiphase fluid flow, the flow pressure value, and the flow temperature value, and the flow velocity signals from the flowmeter;

determining a volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow;

wherein the fluid flow meter is a first fluid flowmeter, and wherein the method further includes the step of providing a second fluid flowmeter, which second fluid flow meter is sensitive to wetness within the multiphase fluid flow and will over-report a gas flow rate of the multiphase fluid flow when the multiphase fluid flow contains liquid, and wherein the first fluid flowmeter is insensitive to wetness within the multiphase fluid flow relative to the second fluid flowmeter.

8. The method of claim 7 , wherein the processor is adapted to receive first flow velocity signals from the first fluid flowmeter, and second flow velocity signals from the second fluid flowmeter.

9. An apparatus for monitoring multiphase fluid flow passing within a pipe, which multiphase fluid flow includes a gas phase and a liquid phase, the apparatus comprising:

a fluid flowmeter operable to be attached to an exterior of the pipe, the flowmeter including a spatial array of at least two sensors disposed at different axial positions along the pipe, which flowmeter is adapted to produce flow velocity signals indicative of a velocity of the fluid flow traveling within the pipe;

a processor adapted to include an equation of state model for pressure, volume, and temperature properties for the multiphase fluid flow, and further adapted with or to receive composition data values for the multiphase fluid flow, a flow pressure value, a flow temperature value, and the flow velocity signals from the flowmeter, and to determine a volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow using the equation of state model the composition data values, the flow pressure value, the flow temperature value, and the flow velocity signals;

wherein each of the composition data values includes at least one value representative of a hydrocarbon constituent of the multiphase fluid flow.

10. The apparatus of claim 9 , wherein the sensors of the fluid flowmeter each include an ultrasonic transmitter operable to transmit an ultrasonic signal, and an ultrasonic receiver operable to receive the transmitted ultrasonic signal, wherein the flowmeter is operable to sense the fluid flow within the pipe for coherent properties convecting within the fluid flow.

11. The apparatus of claim 9 , wherein the processor is further adapted to determine a volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow at standard pressure and temperature values.

12. The apparatus of claim 9 , wherein the fluid flow meter is a first fluid flowmeter that is adapted to produce first flow velocity values, and wherein the apparatus further comprises a second fluid flowmeter that is adapted to produce second flow velocity values; and

wherein the processor is further adapted to determine a measured value for a fluid flow parameter using the first flow velocity values and the second flow velocity values, and to determine a calculated value for the fluid flow parameter using the flow pressure value and the flow temperature value and the equation of state model, and to compare the measured and calculated values of the fluid flow parameter to determine an error value, and to determine modified composition data values using the current composition data values if the error value exceeds a predetermined value, and iteratively determine the calculated value, compare the measured and calculated values, and determine the modified composition data values until the error value is less than the predetermined value or other condition is met, and to determine the volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow using the modified composition data values.

13. The apparatus of claim 12 , wherein the first fluid flowmeter is a SONAR type fluid flowmeter and the second fluid flowmeter is a DP flowmeter.

14. The apparatus of claim 12 , wherein the processor is further adapted to determine a watercut value for the multiphase fluid flow within the pipe, and to determine a measured speed of sound value for the liquid phase of the multiphase fluid flow, and to determine a calculated speed of sound value for the liquid phase of the multiphase fluid flow using the flow pressure value and the flow temperature value and the equation of state model, and to compare the measured and calculated values of the speed of sound value for the liquid phase of the multiphase fluid flow to determine a SOS error value, and to determine a modified watercut value using the current watercut value if the SOS error value exceeds a predetermined value, and to iteratively determine the calculated SOS value, compare the measured and calculated SOS values, and to determine a modified watercut value until the SOS error value is less than the predetermined value or other condition is met, and to determine a volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow using the modified watercut value.

15. An apparatus for monitoring multiphase fluid flow passing within a pipe, which multiphase fluid flow includes a gas phase and a liquid phase, the apparatus comprising:

a fluid flowmeter operable to be attached to an exterior of the pipe, the flowmeter including a spatial array of at least two sensors disposed at different axial positions along the pipe, which flowmeter is adapted to produce flow velocity signals indicative of a velocity of the fluid flow traveling within the pipe;

a processor adapted to include an equation of state model for pressure, volume, and temperature properties for the multiphase fluid flow, and further adapted with or to receive composition data values for the multiphase fluid flow, a flow pressure value, a flow temperature value, and the flow velocity signals from the flowmeter, and to determine a volumetric flow rate of one or both the gas phase and liquid phase of the fluid flow using the equation of state model the composition data values, the flow pressure value, the flow temperature value, and the flow velocity signals;

wherein the fluid flow meter is a first fluid flowmeter, and the apparatus further includes a second fluid flowmeter, which second fluid flow meter is sensitive to wetness within the multiphase fluid flow and will over-report a gas flow rate of the multiphase fluid flow when the multiphase fluid flow contains liquid, and wherein the first fluid flowmeter is insensitive to wetness within the multiphase fluid flow relative to the second fluid flowmeter.

16. The apparatus of claim 15 , wherein the processor is adapted to receive first flow velocity signals from the first fluid flowmeter, and second flow velocity signals from the second fluid flowmeter.