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Shale gas wells in the Changning block of Weiyuan, Sichuan, China, experience water production problems throughout their life cycles. In actual field production, plunger lift is typically used to discharge liquid from a shale gas well. However, it is difficult to test the formation inflow performance relationship curve (IPR) of a plunger lift well. Hence, data on the formulation and optimization of plunger lift well systems are lacking. Based on actual measured data related to casing pressure changes at the wellhead and the gas-liquid distribution characteristics in a wellbore during the shut-in phase, this paper establishes a method for calculating the formation IPR curve of a shale gas plunger lift well by calculating changes in wellbore gas volume continuously. This method has a fast calculation speed. The gas-water interface distribution can be obtained in 3–5 iterations, and the inflow dynamic curve can be calculated in less than 5 seconds. This method tested the IPR curves of gas wells in the Changning block. The IPR curves of plunger lift wells showed concave characteristics contrary to the conventional upward convex curves. This is because the bottom hole flowing pressure changes caused variations in the water saturation of the near-wellbore zone. Consequently, the productivity equation of the plunger lift well is established by introducing the variation coefficient of water saturation expressed by bottom hole flow pressure. This equation fits with the measured IPR curve with an average R2 of approximately 0.9989. [ABSTRACT FROM AUTHOR]

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. • Mechanism of liquid film delamination slippage in inclined pipe is proposed. • The critical liquid carrying state is that the cross-section liquid flow is 0. • The elliptic distribution equation of liquid film in inclined pipe is established. • A new calculation model of critical liquid carrying velocity and flow rate of inclined pipe is established. [ABSTRACT FROM AUTHOR]