Improved Prediction of Liquid Loading In Gas Wells

After gas wells are drilled and start producing, early production rates are high enough to carry any liquid produced to the surface. However, as the reservoir pressure declines, the gas-production rate also declines. Eventually, the gas well starts experiencing liquid loading. Liquid loading starts when the current gas rate is incapable of lifting the liquid up to the surface. The liquid can be either water produced from the formation or the condensate. Several correlations in the literature predict the onset of liquid loading. The most famous equation, the Turner et al. (1969) equation, has many limitations, including the inability to account for effects such as diameter of the pipe and inclination angle of well, and incorrect physical assumptions regarding the onset of liquid loading. Belfroid et al. (2008) modified the Turner et al. (1969) equation for inclined wells; however, their expression is also dependent on incorrect physical assumptions and does not account for the diameter of the pipe. Another method, proposed by Shu et al. (2014), uses the correct physical assumption of liquid loading, but is overly conservative. This paper discusses a new modification to the original method proposed by Barnea (1986), which overcomes many limitations of the previous models. The new method is dependent on an assumption that liquid loading initiates when the liquid film starts falling backward. The proposed method accounts for the effect of diameter and inclination angle of the gas well. The method predicts the onset of liquid loading for a wide range of inclination angles, from vertical well to nearly horizontal well. The application of the method has been verified by comparing the results with both laboratory and field data. The method is observed to be better at predicting the onset of liquid loading compared with the other existing models in the literature.