An improved model for predicting liquid loading onset in inclined pipes with non-uniform liquid wall films

Liquid loading is a phenomenon in which liquid accumulates in the wellbore of mature gas wells, causing a significant reduction in production and sometimes permanent well abandonment. This paper introduces a new model for predicting liquid loading onset, based on the reversal of a non-uniform liquid film. The momentum balance equation for annular flow is, in the proposed model, expressed as a function of liquid holdup instead of liquid thickness. The model employs auxiliary correlations to obtain liquid holdup and an interfacial friction factor, developed from literature data. The accuracy of the proposed model is quantified by comparing laboratory data from this work and field datasets from previous studies, with the predictions of existing models. The proposed model successfully reproduces the experimental data and field data, and gives the highest prediction accuracy and the lowest average error when compared with existing models. The proposed model therefore represents a significant improvement on existing models. The applicability of auxiliary correlations means that this model should be restricted to upward pipe inclinations of 30 degrees-90 degrees; from the horizontal, liquid viscosities of 1.1 cP and 0.018 cP, and superficial velocities of gas of 3-60 m/s and of liquid of 0.01-0.2 m/s. Results show that the model exhibits poor performance when applied to pipe inclinations lower than 3 degrees from the horizontal.

Automated summary

This paper introduces a new model for predicting liquid loading onset in mature gas wells, which successfully reproduces experimental and field data with high prediction accuracy and low average error. The model represents a significant improvement on existing models in predicting liquid loading in gas wells, with restricted applicability to specific conditions.