Liquid loading in low production gas wells is a nuisance for production engineers in the natural gas industry. It is essential to maintain gas wells free of liquid; otherwise, the production will be severely reduced by backpressure of the accumulated liquids, and by reduced gas relative permeability in the surrounding formation.

The most fundamental solution for the liquid loading problem is to select tubing diameter for the well such that the natural energy in the reservoir will give a gas velocity sufficient to lift liquids from the sand face of the reservoir to the surface. Unfortunately, the optimum diameter varies for different periods in the life of a well.

Here, a new approach to the liquid loading problem is reported. By introducing restrictions, such as orifices, inside the tubing to alter flow mechanisms, liquid may be lifted by gas flow rates below the conventionally accepted critical rate. Extensive laboratory experiments with a 40-foot-tall flow loop with 1.5-inch-inside-diameter tubing were conducted to test the effect of five different designs of restrictions. In these experiments, the effects of gas flow rate, of restriction design, of flow loop inclination, and of design of the outlet at the top of the loop were considered. The experiments proved that the restrictions alter two-phase flow behavior and improve liquid lifting rate in the flow loop.

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