Abstract
Liquid loading is one of the main challenges in the later life of natural gas wells. Several methods have been tested to remedy this issue and unload gas wells, with various efficiencies. Preliminary studies on the impact of partial restrictions reveals that they improve liquid lifting by generating droplets and preventing the liquid film from falling back. These restrictions are commonly in shape of orifice rings or inserts. This study evaluates liquid unloading by employing such restrictions to improve liquid lifting. The restrictions can be incorporated into the tubing joint design, making them cheaper and easier to install compared to other techniques. Comprehensive experiments are conducted to understand the effect of inserts and liquid properties on two-phase flow behavior. The tests are performed in a 0.0508-m (2-inches) inner diameter vertical flow loop, using water or oil as the liquid phase and air as the gas phase. The tests are conducted with insert opening inner diameters of 0.0381 and 0.0445 m (1.5 and 1.75 inches.)The inserts cause significant mixing and generate high amplitude waves, which facilitate droplet generation. In churn flow with inserts, a thin liquid film is observed traveling downward, while liquid droplets travel upward. The results show that the inserts have the most positive effect at lower gas rates of churn flow and at lower liquid rates. Moreover, inserts provide the largest reduction in the liquid holdup for oil-air flow, due to lower density and surface tension compared to water. The results show that the inserts may enhance the liquid lifting by lowering the liquid holdup, while also increase the pressure drop by increasing the frictional losses. This indicates the need to choose the optimum insert diameter to minimize frictional losses and enhance liquid lifting.
Published Version
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