Prediction and Analysis of Liquid Carrying by Plunger Gas Lift in Wellbore

Abstract

Plunger gas lift is a good method to drain the accumulated water in the wellbore. In this work, a dynamic model is established to predict the liquid carrying process by plunger. A case study is carried out to investigate the applicability of the proposed model, and the law of liquid carrying by plunger is analyzed. Three stages exist during the movement process of plunger, that is, the accelerated ascent stage, decelerated ascent stage and drainage stage. The decelerated ascent stage has the longest duration, and the velocity increases significantly with time as the liquid level reaches the wellhead during the drainage stage. As the well depth increases, the variation magnitude of the plunger velocity during the accelerated ascent stage and decelerated ascent stage decrease, and the duration during the decelerated ascent stage increases. As the initial height of water column increases, the velocity of the plunger decreases at each stage, and the decrease magnitude becomes less obvious. As the inner diameter of the tubing decreases, the speed of the plunger gradually decreases at each stage. Among the three influencing factors, the height of initial water column has the greatest impact on the efficiency of liquid carrying by plunger.