The pressure drop in slug flow of heavy oil and gas in a pipe in the laminar regime is studied. A simple mechanistic model with closure laws from the literature is compared against experimental data for two-phase flow of high viscosity refined oil and atmospheric air. It is shown that the agreement between the model and the data is excellent, but the extrapolation to high pressure and large diameter is uncertain. New experiments are recommended for further progress.
There is an increasing interest in offshore heavy oil production. In Norway, oils with viscosities between 100 and about 1000 cP are regarded as heavy, while oils with viscosities between 1000 and 10,000 cP are classified as extra heavy. In the general oil and gas literature, however, "heavy oil" is often used in a much wider sense denoting oils with viscosities from 100 cP to hundreds of thousands of cP. Nuñez et al. (1) give a general overview of heavy oil pipeline transportation methods. However, multiphase wellstream transfer is not covered by this or other reviews. There is a significant amount of high quality experimental data available for multiphase flow with oil viscosity up to about 50 cP. For multiphase flow with oil of higher viscosity, much less data are available. Most of the published data are from small scale facilities with pipe diameter in the order of 2–3 cm and with focus on core-annular flow of extra-heavy oil with and without a gas phase. The few exceptions include studies of gas/oil flow with refined oil with viscosity up to 600 cP, Gokcal (2, 3) and Kora (4), and with 100 cP mineral oil, Smith et al. (5), as well as a study with two-phase flow of air and a high viscosity aqueous model fluid, Nuland (6, 7).