Optimizing Technology Research Of Gas Lift Production During The Later Stage Of Water Flooding In L Oilfield In Indonesia

Gas lift is one of artificial lift methods used wildly in China and overseas,which plays a very important role and next to the sucker-rod pump in oil production.At present,gas lift technology is popularized in Tuha,Zhongyuan,Sichuan oil field and so on,whose optimization design and operation level of the technology are all mature.Gas lift has many advantages,such as adapting high productivity and deep well,easy operation,convenient maintaining etc.,which has strong adaptability on some complicated conditions,such as high GOR(gas oil ratio),corrosion gas,deviated well and so on.Nowadays,many overseas oilfields are in the stage of the middle or later period of high water cut and gas lift technology begins to develop into two directions: the one is the well with high water cut and high productivity but producing less;the other is the well with low productivity,high injected GLR(Gas liquid ratio)and serious waste of injected gas.In addition,some bad field working conditions,such as high corrosion,high scale,high formation temperature etc.,are limiting the available range of gas lift technology development and present hard challenges on gas lift.To solve these limited issues of gas lift application is very important and significant meaning to development those oilfields economically,efficiently and reasonably.Based on the practical conditions of L field production and scientific analysis methods,analyzing the factors of limiting the efficiency of gas lift well,exploring the optimization method of the individual gas lift well design and optimized gas distribution method of gas lift well group.For individual well optimization,base on the precise modeling,quantitative analysis and the practical conditions of field,the effect of parameters on the optimization result are confirmed.For the system optimization,base on the practical conditions of field and each part of reservoir,production and surface facilities engineering,the essence is confirmed by the analysis of limited factors and the key and methods of the system optimization are found by statistic analysis and optimized sorting.In this thesis,the main achievements and recognitions are as follows:(1)Lifting method optimizationEven if it has been proved by theory research and filed practice that gas lift oil production is less economic when the water cut of the field goes beyond 70%,but the practical conditions of L field in Indonesia decide that gas lift technology is the best adaptation on the site: firstly,the whole gas lift plant is available in the field;secondly,stable gas source is available;thirdly,gas lift technology is more easy to manage and maintain.Therefore,base on the lifting method optimization,it is found that gas lift technology is the most suitable lifting method in L field.(2)The efficiency of gas lift systemGas lift oil production system consists of gas lift pumping plant,gas distribution network,gas lift wells,pipeline between gas lift wells and metering station.Those parts effect each other and connect each other.So,analyzing the whole system,finding the essence and key of optimization issue and confirming the important links of gas optimization and design are needed to explore the optimization issue of gas lift system.It is improved by theory analysis and filed practice that the most part of energy is consumed during the course of vertical lifting stage in the whole system.Therefore,the key to improve the system efficiency lies in the optimization of lifting parameters of individual well in the stage of vertical flowing in the wellbore and the optimization of well group system's parameters.Gas injection rate and gas injection pressure are the common parameters of the individual well and well group system's optimization.The optimization of individual gas lift well lies in the reasonable design of the relative formation parameters and production parameters;The system optimization of gas lift well group lies in the reasonable gas injection rate's distribution of every well.By analyzing,the characteristic curves of earch gas lift individual well can be matched into a quadratic polynomial.Combining all the characteristic curves of gas lift wells,the characteristic curve of well group can be got and it also fits the rules of the quadratic polynomial.Therefore,by mathematic method,the optimization issue of gas injectin rate and the maximum oil production rate of well group can be converted into the extreme value issue of the quadratic polynomial,which can make the problem simplified and easy to solve.(3)Individual well parameters design of nodal analysisIndividual well optimization highlights precise modeling and quantitive analysis of parameters' sensitivity.Base on the result of analysis,the different importance of influential factors can be decided.Among the formation parameters,formation pressure is the most sensitivie,and water cut is slightly sensitivie,and gas oil ratio isn't sensitivie.Among the production parameters,gas injection rate is the most sensitivie,and tubing inside diameter and well head pressure are slightly sensitivie,and gsa injection pressure isn't sensitive after it reaches the some value.Therefore,the optimization of individual well should focus on the adjusting gas injection rate and optimizing the production rate to improve the lifting efficiency,and meanwhile,cooperate with the measure treatment of the recovery of formation pressure by water injection,water shut-off and injection profile adjustment.Based on the result of nodal analysis and the production practice of individual well,11 gas lift wells totally get the additional liquid by 755 bbl/d,the additional oil by 31.9bbl/d and less gas lift valves by 16 than the present production,which indicates that the optimization result is remarkable.(4)Optimization of gas lift well groupBase on optimization model of gas lift well group,considering the practical conditions of oil field development and production maintaining requirements,relative production rates with the change of gas injection rate of all gas lift wells are carried out statistic and analysis,which simplifies the optimization issue to the sequencing problem of individual well oil increase with equivalent incremental gas injection rate.By the result analysis,the optimization plan of gas injection is decided.The prediction method of the gas injection and gas production balance analysis under the condition of limited gas resource is provided by the balance analysis of technology.