A Mathematical Model for Accessing Liquid Accumulation in Production Tubing: Effect of Tubing Height

Abstract

Liquid-loading is challenging in mature gas-fields globally. It causes increasing reverse-pressure from increasing liquid-column, thereby significantly affecting production overtime. In this study, a new critical-velocity model was developed for predicting onset of liquid-loading in gas-wells. This was done following the reverse film concept, while incorporating separate pressure drops for both liquid and gaseous phases. Also, influence of production tubing length and liquid-film thickness was equally considered. A comparative analysis of prediction-accuracy of developed-model was also conducted alongside other critical velocity models like Turner et al. (1969), Coleman et al. (1991), Nossier et al. (2000), Li et al. (2001), and Pagou and Wu (2020) models using data from literature. The obtained field data was from 18 vertical gas-wells from Xinjiang North-West gas field in China. The prediction accuracies of critical-velocity models followed the order, Nossier et al. (2000), Turner et al. (1969), Coleman et al. (1991), Li et al. (2001), Pagou and Wu (2020), and developed-model. To increase the prediction accuracy of developed-model, model coefficient adjustments were done by percentage-reduction of developed model coefficient. In the end, the prediction-accuracy of developed-model was tremendously increased by reducing model coefficient.