Liquid characterization and measurement of fluid properties for reduced uncertainty in multiphase flow area fraction measurements

• Analysis and exemplification of fluid property impact on area fraction measurement.
• Propagation of errors through gamma-ray and permittivity based fraction gauges.
• On-line measurement of fluid density, composition and gamma-ray attenuation.

Meters measuring multiphase flows use one or more physical properties of the fluids to estimate flow area fractions of phases and components. Most common in the oil and gas industry are meters based on measurement of gamma ray attenuation and permittivity. Uncertainty about the actual values of attenuation coefficients and permittivity will lead to systematic errors which we analyze and exemplify. To counter these errors it is desirable to monitor the properties of the fluids on-line with the flow measurement. Subsequently we present measurements of liquid phase properties since these are found to impact flow area fraction measurements more significantly. Dual-modality densitometry, which is based on measurements of gamma attenuation coefficients, is used to characterize liquid components in terms of density and composition. This technique is demonstrated to be well suited for the task, albeit the compositional results are less accurate, and do not allow for precise interferences regarding the permittivity.