Liquid loading is the inability of a riser or gas well to produce liquids, resulting in reduction of gas production in mature gas fields. Mechanisms describing liquid loading initiation are not well understood for inclined pipes or deviated wells. Knowing the effect of pipe inclination over the liquid-loading initiation will help for the development of a predictive tool for flow assurance, well production forecast as well as remediation techniques enhancing gas production.

An experimental study of low liquid loading has been conducted for 90°, 75°, 60° and 45° inclined pipes. Air/water flow in a 3-in ID pipe has been investigated. Pressure gradient and average liquid holdup were measured. Visual observations with high and low speed cameras have been recorded to identify flow patterns and liquid film behavior for each test point. Pipe inclination effects on critical gas velocity for flow pattern transition have been investigated.

The critical gas velocity represents the maximum gas flow rate where the liquid loading is observed. This critical velocity increases as pipe inclination deviates from vertical. Pressure gradient fluctuations and liquid film flow behavior are closely related with liquid loading initiation. As the pipe deviates from vertical and owing to the increasing liquid film thickness at the bottom of the pipe, slug and churn flow patterns are promoted. Therefore, the existing critical velocity prediction models, which ignore the circumferential variation of film thickness, produce significantly different values of critical velocities when compared with the experimental data.

Liquid loading is one of the main problems that the industry faces during the production of natural gas wells and transportation of low liquid loading gas-liquid flow through a riser. This study serves as a foundation for future model developments to avoid and remedy liquid loading related problems in risers and gas wells.

You can access this article if you purchase or spend a download.