As a natural gas well ages, liquid loading is frequently encountered, accompanied by the tubing scaling and corrosion, leading to the decrease of gas production rate and many other side effects, which may in turn cease the gas production. Thus, to accurately predict liquid loading onset is of significant importance in gas wells for the sake of stable production. With years’ research and development in natural gas industry, the liquid loading onset prediction models prevail in the existing literature. Mainly based on the droplet falling back, liquid film adverse flow or energy mechanisms, the critical gas velocity or flow rate at the transition boundaries of flow regimes in gas wells can be calculated. However, a universally validated model, whether empirical or none-empirical, that is applicable to predict the onset of liquid loading in versatile gas wells conditions, e.g. horizontal, vertical and inclined, is still unavailable yet.
In this paper, a complete literature review and investigation of these existing liquid loading onset prediction models were conducted. The detailed information of more than 600 gas wells, including well geometries, gas properties, operation conditions etc., from different gas fields was obtained. Then, the validity of various liquid loading onset prediction models can be evaluated by a novel model ranking approach. To fully account for the effects of gas well properties (including but not limited to production, wellhead pressure, pipe diameter) to the model prediction accuracy, the proposed method in this paper employs data clustering and normalization techniques, as well as the statistical relative error analysis, to rank and select the best suitable model for each specific gas well. An extensive comparison and verification of the ranking approach indicates that the proposed method provides a good reference for the rational production allocation and stable production of gas wells.