Effects of High Oil Viscosity on Oil/Gas Flow Behavior in Horizontal Pipes

Summary Oil/gas pipe flows are expected to exhibit significantly different behavior at high oil viscosities. Effects of high-viscosity oil on flow pattern, pressure gradient, and liquid holdup are experimentally observed, and differences in flow behavior of high- and low-viscosity oils are identified. The experiments are performed on a flow loop with a test section of 50.8-mm ID and 18.9-m-long horizontal pipe. Superficial liquid and gas velocities vary from 0.01 to 1.75 m/s and from 0.1 to 20 m/s, respectively. Oil viscosities from 0.181 to 0.587 Pa·s are investigated. The experimental results are used to evaluate the performances of existing models for flow pattern and hydrodynamics predictions. Comparisons of the data with the existing models show significant discrepancies at high oil viscosities. Possible reasons for these discrepancies are carefully examined. Some modifications are identified and implemented to the closure relationships employed in the Zhang et al. (2003) model. After these modifications, the model predictions provide better agreement with experimental results for flow pattern transition, pressure gradient, and liquid holdup.