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

Abstract

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. Introduction Gas/liquid two-phase flow in pipes is a common occurrence in the petroleum, chemical, nuclear, and geothermal industries. In the petroleum industry, it is encountered in the production and transportation of oil and gas. Accurate prediction of the flow pattern, pressure drop, and liquid holdup is imperative for the design of production and transport systems. High-viscosity oils are discovered and produced all around the world. High-viscosity or "heavy oil" has become one of the most important future hydrocarbon resources, with ever-increasing world energy demand and depletion of conventional oils. Almost all flow models have viscosity as an intrinsic variable. Two-phase flows are expected to exhibit significantly different behavior for higher viscosity oils. Many flow behaviors will be affected by the liquid viscosity, including droplet formation, surface waves, bubble entrainment, slug mixing zones, and even three-phase stratified flow. Furthermore, the impact of low-Reynolds-number oil flows in combination with high-Reynolds-number gas and water flows may yield new flow patterns and concomitant pressure-drop behaviors. The literature is awash with two-phase studies addressing mainly the flow behavior for low-viscosity liquids and gases. However, very few studies in the literature have addressed high-viscosity multiphase flow behavior. In this literature review, the state-of-the-art of two-phase flow is first summarized. Then, the studies addressing the effects of liquid viscosity on two-phase oil/gas flow behavior are reviewed.

Multiphase Flow Modeling for Gas Hydrates in Flow Assurance

“…Figure 4 shows the results for our model flow regime predictions for air-medium viscosity oil ( ϭ 36 cP) and air-high viscosity oil ( ϭ 587 cP) systems. The results have been compared with the experimental data from Brito et al (2013) for the medium viscosity oil system and Gokcal et al (2005) for the high viscosity oil system. The results were also compared with other theoretical models as shown in the figure.…”

“…Tulsa (Meng, 1999) 153 Manabe 2001 Natural gas-crude oil 2 Univ. Tulsa (Manabe, 2001) 247 Mata et al 2002 Air-oil (ϭ 0.480 cP) 2 Intevep, Venezuela (Mata et al, 2002) 8 0 Abduvayt et al 2003 Nitrogen-water 2, 4 Waseda Univ., Japan (Abduvayt et al, 2003) 443 Gokcal et al 2005 Air-oil (ϭ 0.181-0.587 cP) 2 Univ. Tulsa (Gokcal, 2005) 183 Brito et al 2012 Air-oil (ϭ39-166 cP) 2 Univ.…”

Effects of High Oil Viscosity on Slug Liquid Holdup in Horizontal Pipes

“…The first experimental study at Tulsa University Fluid Flow Projects (TUFFP) on high viscosity oil was completed by Gokcal (2005). The effects of high oil viscosity on oil-gas two-phase flow behavior were investigated and significant changes in flow behavior were observed.…”

Characteristics of Gas/Water/Viscous Oil in Stratified-Annular Horizontal Pipe Flows

“…One explanation may be the reduction on the surface tension of the liquid phase (Water has almost three times the oil surface tension). According to previous studies the effect of the liquid viscosity was found to be negligible over the stratified to annular flow transition (See Gokcal et al (2008); Weisman et al (1979)). According to previous studies the effect of the liquid viscosity was found to be negligible over the stratified to annular flow transition (See Gokcal et al (2008); Weisman et al (1979)).…”