Stable Triple-Layer Lubricated Pipeline Flow

Abstract

Recently we have introduced a novel methodology for efficient transport of heavy oil via a triple-layer core-annular flow [1]. Pumping pressures are significantly reduced by concentrating high shear rates to a lubricating layer, while ideas from visco-plastic lubrication were used to eliminate interfacial instabilities. We purposefully position a shaped unyielded skin of a visco-plastic fluid between the transported oil and the lubricating fluid layer. The shaping of the skin layer allows for lubrication forces to develop and balance the density difference between the fluids. Here we show an explicit advantage of the proposed method. Essentially the method can give stable flows for a very wide range of fluid input ratio, although not all will produce the desired reduction in frictional pressure losses. Additionally, we use the extensional flow method derived in [2] to estimate the required yield stress to maintain the skin completely unyielded.