Experimental investigation on liquid–liquid–gas flow: Flow patterns and pressure-gradient

The use of core-annular flow pattern, where a thin fluid surrounds a viscous one, may be attractive to heavy oil transportation and as an artificial lifting method in heavy oil wells, a situation that can become frequent in the Brazilian offshore scenario. However, in petroleum production operations gas is frequently present. Therefore, the study of three-phase flow of heavy oil, water and gas is in order. This paper reports pressure drop measurements and three-phase flow patterns observed in horizontal and vertical 2.84-cm i.d. glass pipes. The focus was a mixture of heavy crude oil (3400 mPa s, 970 kg/m3 at 20 °C), water an air at several combinations of the individual flow rates. Three-phase pressure drop data were compared with single-phase oil and two-phase oil-gas flows to assess the gains due to water injection. In addition, three-phase flow patterns formed inside vertical and slightly inclined 1.0 cm i.d. pipes are also presented. Thus, scale-up and inclination effects could be qualitatively analyzed. Full-scale onshore-field experiments were conducted in order to investigate the applicability of using water to transport heavy oil in actual lines in the presence of gas. A big steel pipeline (7.7 cm i.d. and 274 m) conveying a very viscous crude oil (36950 mPa s, 972.1 kg/m3 at 20 °C), natural gas (GOR 15 m3/m3) and water was used. Onshore-field three-phase flow tests were carried out and pressure gradient data are reported. The observed improvements in oil production rates and the pressure drop reductions obtained are remarkable.