Analysis And Optimization Technology Of Lifting System In Offshore Oil Field

With the development of offshore fields gradually entering late stage,to ensure the efficient development of oil fields,a series of infill wells,comprehensive adjustment and potential technical measures were conducted.The problems of the oil field development were gradually exposed.The lifting system in wellbore is the core of offshore oil production system.With the implementation of infill wells and stratification measures,oil production,pressure,water cut will change accordingly,resulting in problems between wells and reservoir formation.Meanwhile,the wellbore lift system is affected by gathering system.Therefore,the lifting system needs to be optimized to achieve the coordination between lifting system and reservoir formation.To ensure the target of production,the lowest operating cost of production is crucial to improve the efficiency of offshore oil development.This paper is to solve the problems in the lifting system of the offshore oilfield development.Through key technology research,the multi-objective models were established for the wellbore lifting system by considering the factors such as economic,oil production and system efficiency.The ESP working parameters monitoring system and injection-production system simulator were developed.Moreover,the integration and intelligent optimization methods for wellbore lifting system of offshore oilfield were established.This model and methods were verified with the actual implement of an oilfield in Bohai.Firstly,the wellbore lifting system including the well inflow performance,wellbore multiphase flow,wellbore temperature field,wellbore fluid emulsion law,and flow through choke were studied.Meanwhile,the intelligent integrated optimization model and genetic algorithm optimization based on mathematical models ANN were systematically studied.A multi-objective optimization model was established to efficiently conduct the research of wellbore lifting performance and optimization.For the difficulty of achieving the downhole equipment operation parameters,this paper established the models to obtain the parameters such as motor speed and torque.The monitoring system for working parameters of ESP was studied.The verification with actual data shows that it can meet the oil production and management needs.Furthermore,it can truly reflect the actual working conditions of the wells.Therefore,this model can be used to analyze the monitoring data of wellbore lifting system and its performance.To solve the limitations of the theoretical model,the offshore platform dynamic simulation device was designed and made,which can correct the models such as productivity model,wellbore flow model,ESP characteristic model,chock model by using the actual data like the liquid,downhole pressure,in-and-out flowing pressure of ESP,wellhead pressure.Meanwhile,the optimization methods and plan were verified,showing that the models in this paper can be used to optimize the offshore oilfield wellbore lifting system.On the basis of theoretical and experimental studies,this paper used the established analytical method to analyze their production conditions.Considering the problems such as the non-critical nozzle flow of wells and the serious well interference problems,an integrated optimization technology and multi-objective genetic algorithm(NSGA-2)at two levels(adjusting the nozzle,pump optimization re-election)were optimized.A better optimization result was achieved which verified the reliability of the theoretical model and optimization method.Through the study of this paper,a systematical method for wellbore lifting system of offshore oilfield,performance analysis and optimization was developed to achieve the optimization of offshore oilfield.The best combination of the entire system and energy efficiency was achieved.This method is capable of taking advantages of offshore oil and gas production systems under the existing resources and limited production facilities.With the optimized method and the lowest energy consumption,the maximum economic returns were obtained.