The Plunger Moves Mechanics Simulation Studies

Plunger lift is a method of artificial lift which uses a free plunger traveling up and down the tubing in a cyclic manner to lift the fluids from the reservoir to the surface. The use of the plunger as a solid sealing interface between the expanding gas and the liquid slug extremely helps to prevent gas breaking through the slug and decreases the fallback of liquids, which serves to improve the instability of conventional gas lift and efficiently increase the efficiency of lifting liquids. Plunger lift is one of most efficient lift manner in intermittent lift. It is predominant in economic cost and the efficiency of using lifting gas and removal of paraffin and scale from wells. Plunger lift is a most efficient substituted technique to successive gas lift production. The key of the technique is control to the motion of plunger.A complete operating cycle is composed of four different stages: plunger rise, slug production, gas blowdown, slug regeneration(gas pressure buildup). Presented here is a establishment of dynamic model equations of plunger lift operations by analysing the different process in different stages. The model is solved by utilizing fourth order Runge-Kutta scheme and is verified by a real data of a case history well. The result of the simulation is in accordance with the case history well.From the calculation and the analysis of every sensible parameter in plunger lift system, we can conclude the intrinsic relation among parameters and the effect to lift efficiency, and bring forth the thinking of key parameters optimization design, presented a theoretical base for the optimization design of plunger lift. The purpose of the calculation of sensible parameter is to enhance the efficiency of gas lift, cost-cutting and enhanced oil recovery.In this paper, the main achievements in the aspect of theory of plunger lift are as follows:1. Considered the variety of temperature of well bore, fluid viscosity, gas deviation factor, liquid fallback, fluid productivity index etc. in different time and the different displacement in the lifting process and the coordinated relation between the reservoir inflow and the lifting liquid, a detailed dynamic simulation for plunger lift process is given.2.Based on the dynamic analysis, employed Runge-Kutta scheme and Visual Basic language, above simulation was programmed to solve all parameters in plunger lift, so as to analyze the performance and predict the effect to plunger lift.3.The sensitive analysis of parameters of plunger lift is made, and put emphasis on analyzing the influence factors to lift efficiency .such as the injected gas volume, lifting liquid, gas-liquid ratio, fluid productivity index, the variety of pressure in a circulation period, and the effect of all these factors lead to the velocity of plunger, circulation period and liquid fallback etc. Based on these, here developed the mutual relation of parameter and the effect which result in the lifting performance.4. The dynamic equation of gas injection pressure was derived and the method to optimize other key parameters in plunger lift is established. So to optimize the parameter for optimum efficiency. The optimizing research to plunger lift can lead to improved efficiency, increased production and recovery.