Effect of a viscosity reducer in a liquid-liquid flow: II unsteady state annular model in a pipeline

Abstract

The study of extra heavy crude oil flow has increased in recent years, due to the challenges relating to higher viscosity that limits the installed capacity of pipelines and the pumping infrastructure used. This has required the development and implementation of new technologies and chemical formulations to enhance the transport of heavy oil. When flow improvers are injected in a crude stream, it generally does not mix due to its different density and viscosity properties, and the laminar flow regime in the pipe. However, depending on the characteristics of the jet (momentum and turbulence), a mixing might take effect downstream, or a liquid-liquid stratified flow may occur in the fully developed region. Although this behavior can affect the corresponding pressure drop, the transition that occurs from the injection point to the fully developed region has been little studied. Based on conservation of momentum, a mathematical model has been developed to describe the temporal behavior of the velocity profile, where there is no mixing between the oil and the improver, i.e. the fluids are considered immiscible. The model solution shows that the injection into a point very near the tube wall is the best option to reduce pressure drop.