After the first oil crisis in 1973 the gas/oil industry shifted its focus on producing oil and gas outside the Middle East. This triggered offshore activities with the need to transport oil and gas simultaneously in pipelines over great distances to shore. At that moment a lot had been achieved on multiphase flow in production tubing, triggered by the pioneering work in 1963 by Duns and Ros with their flow-pattern dependent model. However, the multiphase transport in near-horizontal pipelines was very much more complex, since gravity was now working perpendicular to the flow. The Beggs-Brill (1973) paper with multiphase flow measurements and a widely used method for horizontal and inclined pipes offered interesting starting points. Also their course on a broad range of correlations and their validation with extensive sets of field data was most welcome for new comers in the field like me.
The development of the methods with considerable improvements in the physics, is very nicely summarized by Shippen and Bailey (2012) in the figure shown above. In my opinion the modelling period started already in 1963 with the publication of the first flow-pattern dependent model accounting for slip between the phases. Field data collected during his stay at Shell Oil in the USA enabled Nico Ros to adapt his closure relations based on atmospheric laboratory data at Shell Rijswijk. This led to an important improvement of the accuracy of his model.