Method and apparatus for wet gas flow measurements and measurement of gas properties
A method for determining the flow rates of a fluid comprising a multi-component mixture of a gas and at least one liquid in a pipe, the method comprising the following steps: a. The temperature and pressure of the multi-component mixture is determined, b. the fractions of the multi-component mixture is determined based on at least two measured physical properties of the multi-components mixture and knowledge of the same physical property of the individual components of the multi-component mixture, c. the velocity of the multi component mixture is determined, d. based on the result from step a-c, the flow rate of the individual component of the fluid is determined, characterized by a method for determining the physical properties of at least one of the components of the multi-component mixture where e. an electromagnetic loss or phase measurement is performed, f. a statistical parameter related to the electromagnetic measurement is calculated, g. the said statistical parameter is compared to an empirical derived threshold value corresponding to the value of the statistical parameter when only one of the component of the multi component mixture is present, and h. the said physical properties of said fluid is determined if the statistical parameter exceeds the threshold value for the said component and used in step b-d to provide an improved value of the fractions, velocity and flow rate of the individual components of the multi-component mixture. An apparatus for performing the method is also disclosed.
1. An apparatus for determining the flow rates of a fluid comprising a multi-component mixture of a gas and at least one liquid in a pipe, the apparatus comprising a tubular section and the following elements:
a. means for determining the temperature and pressure of the multi-component mixture,
b. means for measuring at least two physical properties of the multi-component mixture,
c. means for calculating the fractions of the individual components of the multi-component mixture based on knowledge of the said physical properties of the individual components of the multi-component mixture,
d. means for determining the velocity of the multi component mixture,
e. means for calculating the flow rate of the individual fractions of the multi-component mixture,
wherein the measured physical properties of at least one of the components of the multi-component mixture is measured based on:
f. means for performing an electromagnetic loss or phase measurement,
g. means for calculating a statistical parameter based on the electromagnetic measurement, said statistical parameter related to droplet size, number of droplets and amount of water in liquid droplets in a wet gas stream,
h. means for comparing the statistical parameter towards an empirical determined threshold value,
i. means for determining that said statistical parameter is below said threshold value to detect a gas only condition when only gas is naturally present in the fluid, and
j. means for measuring a physical quantity of at least one of the components of the multi-component mixture when the statistical parameter is above said threshold value and using said physical quantity to determine an improved value of the fractions, velocity, and flow rate of the individual components of the multi-component mixture when said statistical parameter is above said threshold value.
2. An apparatus according to claim 1 , comprising means for transmitting electromagnetic energy into the tubular section and recording received electromagnetic energy from the tubular section.
3. An apparatus according to claim 1 , comprising means for providing electromagnetic resonances within the tubular section.
4. An apparatus according to claim 1 , comprising means for transmitting electromagnetic energy into the tubular section and recording reflected electromagnetic energy from the tubular section.
5. An apparatus according to claim 1 , comprising means for measuring said velocity in a narrow passage of the tubular section.
6. An apparatus according to claim 1 , wherein a venturi is used to determine said velocity.
7. An apparatus according to claim 1 , wherein a V-cone is used to determine said velocity.
8. An apparatus according to claim 1 , comprising means for measuring said velocity by cross-correlating measurements performed in two cross-sections of the tubular sections.
9. An apparatus according to claim 1 , comprising a radioactive source and photon detector for measurement of physical quantities of the multi-component mixture.
10. An apparatus according to claim 1 , comprising multiple pressure drop measurements for measurement of physical quantities of the multi-component mixture.
11. An apparatus according to claim 1 , comprising a combination of a pressure drop device and cross correlation velocity device for measurement of physical quantities of the multi-component mixture.