Dual energy gamma tomography system for high pressure multiphase flow

For physical understanding and detailed modelling of multiphase flow in pipelines, the distributions of the individual phases are of significant importance. For this reason a dual energy gamma tomography system has been designed, constructed and commissioned at the Norsk Hydro multiphase flow laboratory in Porsgrunn. The system is designed for implementation in a high pressure-high temperature crude oil facility for measurements of the gas-oil-water distribution in a 3″ test pipe. Data from the dual energy system will serve as a basis for further mechanistic modelling of multiphase flow. The set-up uses a 133Ba source along with a CdZnTe detector and a digital spectrum analyser to acquire gamma attenuation data for different chordal positions of the pipe cross section. Special attention has been paid to the transparency of the test pipe, to the choice of isotope and to the spectrum analysis for maximizing the signal to noise ratio. Raw data from the dual energy set-up is used as input to an image reconstruction computer program, and this paper presents three stationary commissioning experiments of the system using different fluid configurations in the pipe cross section. The results from these experiments are encouraging with respect to the overall performance of the system, and prove the ability of the system to resolve different flow configurations in the form of reconstructed tomograms of the pipe cross section.