柱塞气举动力学模拟研究

【作者】 张凤东；

【导师】 李洪建；

【作者基本信息】 西南石油学院 ， 油气田开发工程， 2005， 硕士

【摘要】 柱塞气举是通过在油管柱内上下循环运动的柱塞把地层产液举出地面的人工举升方法。它在举升气体和被举升液体之间形成一种固体密封界面,使举升过程中的气体滑脱和液体回落大大减少,从而改善了常规气举的不稳定性,使气体的举升效率得以有效提高。柱塞气举是间歇气举中最有效的举升方式之一,在经济成本、气体的利用效率及清除结蜡结垢等方面,优于其它的人工举升方式。它是连续气举采油最有效的接替技术,技术的关键是对柱塞运动的控制。 一个完整的柱塞举升周期由柱塞上行、液段产出、气体放喷及液段再生四个阶段组成。本文通过对四个阶段过程的分析,分别建立了相应的动力学模型,应用四阶龙格—库塔法进行求解,并以实例井对模型进行了检验,模型预测结果与实例井数据得到较好的吻合。 通过对柱塞气举系统中各敏感性参数的计算和分析,得出各参数之间的内在关系及对举升效率的影响,提出了各关键参数优化设计的思路,为优化气举系统设计提供了理论依据,以达到提高气举效率、降低开采成本、提高采收率的目的。 本文在柱塞气举的理论方面主要完成了以下研究工作: 1.考虑柱塞举升过程中不同时刻和位移的井筒温度、流体粘度、气体偏差系数、液体回落量、采液指数等参数的变化及地层产液与举升液量的协调关系,对举升过程进行了详细的动力学模拟; 2.在动态模拟的基础上,应用四阶Runge—Kutta法及Visual Basic语言,编制计算程序对柱塞气举参数进行求解,用于柱塞气举的特性分析及举升效果预测; 3.对柱塞气举参数进行了敏感性分析,并重点分析了举升效率的影响因素,如注气量、举升液量、气液比、采液指数、周期压力的变化及其对柱塞速度、举升周期及液体回落量等因素的影响。在此基础上,得出了各举升参数之间的关系及其对举升特性的影响; 4.推导出了柱塞举升中最佳注气压力的动态关系方程式,建立了举升中其它关键参数的优化方法。从而优化出达到最佳举升效果的参数。柱塞举升的优化研究有助于提高效率、增加产量和采收率。更多还原

【Abstract】 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.更多还原