Numerical study on two-phase flow characteristics of heavy oil-water ring transport boundary layer

Abstract

Studying the characteristics of two-phase flow of heavy oil-water ring transportation is of great significance for determining the structure of heavy oil flow in the bottom layer and the core area of the boundary layer, and establishing an optimal drag reduction model. Based on experimental research, the effects of key factors such as density difference, viscosity difference, velocity difference, and interfacial tension difference between oil and water on the stability and pressure drop of water ring are numerically analyzed. The result shows that there is basically no velocity gradient in the core area of heavy oil during heavy oil-water ring transportation, which can be approximated as the elastic solid, and the water phase friction has a greater impact on the pipe pressure drop. Only the difference in oil-water density will affect the formation of an eccentric water ring, and when only considering the effect of density, the eccentric water ring pressure drop is reduced to the concentric water ring pressure drop. When analyzing the effect of heavy oil viscosity, it is concluded that the oil-water viscosity difference is kept within a certain range, which can maintain stable flow, and the pressure drop of the pipe decreases slightly with the decrease of the viscosity of the heavy oil. By studying the oil-water two-phase velocity difference, it is found that no matter whether oil and water are at the same velocity, or the oil is faster or slower than water, there must be an optimal flow rate to make the heavy oil-water ring transportation stable and efficient. And the velocity is the most critical factor affecting eccentricity. In addition, appropriately increasing the oil-water interfacial tension can reduce the eccentricity and improve water ring stability.