Drag reduction performance in transportation of thermally produced heavy oil by self-generating foam injection

Abstract

This work proposes a novel approach utilizing an oil-resistant, thermally stable self-generating foam system to achieve boundary lubrication drag reduction in thermal heavy oil transportation, focusing on the drag reduction characteristics of non-Newtonian self-generating foam and Newtonian oil phases under horizontal pipe co-flow conditions. Experiments were conducted in a 12-m-long, 25-mm-inner-diameter horizontal borosilicate glass pipe with roughened walls, measuring pressure gradients for co-flowing high-viscosity oil and foam at superficial velocities of 0.12–0.65 m/s (oil) and 0.06–0.63 m/s (foam). High-speed imaging identified stratified flow (ST) and eccentric core annular flow (ECAF) as dominant regimes across tested conditions. A three-zone two-phase model was developed for horizontal foam-oil flows, integrating the Carreau-Yasuda rheology of self-generated foam at 60°C. The model demonstrates strong agreement with experimental data over broad operational ranges, confirming that full oil core encapsulation by foam determines the critical foam injection volume fraction for maximum drag reduction. Additionally, optimal oil transport efficiency was linked to specific oil core-to-pipe diameter ratios.