A new calculation model of critical liquid-carrying velocity in inclined wells based on the principle of liquid film delamination slippage

Abstract

Liquid loading has always been a production problem in the middle and late production of gas wells. Severe loading will even lead to the shutdown of gas wells. In actual production, critical liquid-carrying velocity is often used to judge the loading of gas wells. Most conventional calculation models are modified vertical pipe models for the critical liquid-carrying gas velocity of an inclined pipe. They are established based on liquid film inversion without considering the characteristics of liquid film delamination slippage. In this study, the elliptical distribution model of the liquid film of the inclined pipe is first established. Then the cross-sectional velocity distribution model is coupled to solve the cross-sectional flow rate integrally. When the cross-sectional liquid flow rate is 0, the gas velocity is the critical liquid carrying velocity. Model calculations reveal that the critical liquid-carrying velocity is the largest when the inclination angle is 50°, consistent with experimental data. Using the data of production wells in the Changning block, Sichuan, China, to analyze well loading, the accuracy between the prediction results of loading in this study and field production judgment reached 93.75%, which is 25% higher than that of the Belfroid model. The model in this study accounts for the delamination slippage of the liquid film for the first time, and the calculated critical liquid carrying velocity can better reflect the flow state of gas-liquid two-phase flow in inclined pipe, which is beneficial for researchers to accurately evaluate and understand the production status of gas wells.