Measuring phase distribution in high pressure three-phase flow using gamma densitometry

Abstract

A large campaign of multiphase experiments using formation water, a North Sea crude oil and a blend of gas produced from different North Sea gas fields was performed in the Porsgrunn Multiphase Flow Loop. The tests were performed under realistic field conditions ( p = 100 bar and T = 80 ° C ). Different multiphase flow patterns such as waves and slugs were observed in the experiments. At high pressure conditions it is often difficult to distinguish between these types of flows due to considerable dispersions between the fluid phases. A traversable dual-energy gamma instrument was used to measure phase fractions at different positions at 7 Hz. Careful data analysis was needed to obtain the relevant data from the noisy measurements. Data analysis techniques for three-phase flow were developed and tested against calibration data from single-phase and two-phase flow. In addition it was shown that the averaged density data from the traversable gamma instrument compared favourably to density measurements by a calibrated stationary single-energy gamma instrument. However the traversable densitometer gave much more additional information compared with the single-energy instrument since the transient phase fraction for all three phases could be measured at different positions over the cross section of the pipeline. This information allowed the definite determination of the flow pattern.