What Does Annular Flow Pattern Mean?
The annular flow pattern refers to the fluid patterns made in a well or pipeline during a multi-phase flow regime. It occurs for wells that have high gas and low liquid velocities with a central core of gas and a liquid film. The lighter fluid or gas flows in the pipe center and the heavier fluid flows as a thin film on the pipe wall.
The annular flow pattern can be observed in vertical as well as horizontal wells. It is not uncommon to observe a simultaneous flow of oil, water and gas mixtures.
Trenchlesspedia Explains Annular Flow Pattern
In the annular flow pattern, the gas moves fast in the center of the pipe while a thin film of liquid slowly moves along the pipe walls. This liquid may be present as a film or as entrained droplets. The film has two parts, a base film and a layer with wavy disturbance, the behavior of which and its interaction with the gas component determines the amount of entrained liquid.
The characteristics of the liquid film and the entrained layers are affected by gravity, shear stresses, and drag forces. In multiphase flow, solid particles are also suspended in the fluid during the production process.
To transport solid entrained multiphase fluids through pipelines, the fluid must be capable of suspending these particles to prevent deposition.