Abstract

The idea explored is that gas lift may be stabilized by imposed oscillations. This has been experimentally investigated in a scaled-down facility where water is lifted by air. An air-tank provides compressibility emulating a gas filled annulus. Depending on pipe dimension, injection rate and tank volume, the flow may be stable, or oscillate similarily to casing heading in full-size wells.

To control natural oscillations, their dominating frequency was firstly determined. Destructive interference was then imposed by cyclic variation of either the downhole injection valve, or the tubing outlet valve. By injection valve regulation, the flow was stabilized and 40% higher liquid rate obtained. Outlet choke regulation also stabilized the flow, but rate improvement less, up to 13%.

Scaled-down facilities should be viewed with sobriety. However, the facility appears to exhibits static and dynamic behavior similar to real wells, so the experimental results may be lent some credibility. This may provide a new and simpler approach to control of gas lift instability.

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