Experimental and modeling studies on the prediction of liquid loading onset in gas wells

Liquid loading is a major problem that limits production of gas wells. When liquid loading occurs, the gas well will suffer a rapid decrease in gas flow rate and eventually cease. An accurate prediction of liquid-loading onset is vital for operators to optimize production or take other measures in time. Through a careful review of previous studies, it's more reasonable to relate liquid-loading onset to liquid-film reversal rather than liquid-droplet reversal. However, few mechanistic approaches based on liquid-film reversal are available to predict the critical gas velocity. Furthermore, these models have complicated calculation and conservative results. This paper develops a more comprehensive and simpler analytical model for prediction of liquid-loading onset on the basis of liquid-film-reversal criterion. To reach this goal, experimental investigation has been conducted to analyze the effect of inclined angle and liquid velocity on the critical gas velocity. The Belfroid et al. (2008) angle-correction term has been adopted in the new model to predict critical gas velocity in inclined pipes. After validation against laboratory and field data from the published literature, this model has better performance compared with other models. Considering its simple form and high accuracy, the new model can provide a convenient approach for gas production engineers to predict critical gas flow rate.