Prediction of Gas–Liquid Two‐Phase Flow Pressure Wave in the Wellbore During the Re‐Production of Deep Gas Wells

The pressure of the tube at the wellhead is abruptly released during the opening of a high‐production gas well, causing pressure fluctuation and subjecting the tubing to extra stress. In extreme circumstances, shock load may shatter tubing, compromising the integrity of the well and safe production. Thus, the dynamic boundary conditions of the wellhead valve opening procedure and the complex operating circumstances of the gas well must be fully taken into account. To determine the changes in wellhead pressure and velocity following valve opening, a nonlinear mathematical model of transient flow during valve opening is developed, and a method of characteristics is used for numerical solution. Next, examine how wellhead pressure and velocity are affected by well opening time T op , valve opening coefficient m , production Q g , and holdup H L . According to the study, wellhead pressure steadily drops from shut‐in static pressure and approaches steady flow pressure during fluctuation following valve opening. Wellhead pressure and flow rate variations essentially occur at the same time. The wellhead pressure is discharged and the pressure fluctuation decays more quickly with a shorter well opening period. The pressure variation lasts longer the longer the well is opened. The wellhead opening decreases as the valve opening coefficient decreases. The pressure drops off more quickly as the flow rate rises. The fluctuation pressure first rises and then falls as output rises. The larger the production, the quicker the fluid steady flow rate, provided that the tubing's cross section stays constant. Wellhead pressure rises and the wellhead flow rate falls as the liquid holdup increases. This study is of practical significance for determining how to reduce wellbore fluctuation pressure and improve wellbore integrity.