Optimization And Decision Of The Late Development Of Oilfield

Oil as the backbone of the national economic development, it plays an important role in the national economic structure and direction. Our country petroleum resource is very scarce, the rapid development of national economy leads to China’s oil demand gap widening and increasing oil import dependency. At present, our country has become the second largest oil demand after the U.S, an annual increase of oil demand accounted for about a third of the world’s new oil demand. Since our country become a net importer of oil for the first time in 1993, oil climbed external dependency. In 2012 China imported 285 million tons of crude oil; oil import dependency reached 58.7%. In China’s energy research published in the China’s energy development report 2012, China’s oil import dependence will be greater than 60% by 2015; the energy security situation is grim.At present, Daqing, Shengli oilfield as the representative of most domestic oilfields have entered the middle and late development stage, the oil field oil production is falling and production costs are rising, economic benefit is gradually becomes poor, this makes oilfield production and operation in our country is facing very serious test. To solve the problem of energy security, on the one hand, we should expand cooperation with foreign oil; on the other hand we should make the internal tapping of old oil fields. We use the effective allocation of resources to optimize the oilfield of oil field development planning. On the basis of reducing the cost of oilfield production and operation, we can ensure that the crude oil production is stable and realize the rational use of oil resources.Oil resource allocation system is complex, during oilfield development decisions we need to consider a range of factors, such as economy and policy. In this paper, we determined the oilfields in the middle and later development stage based on the current situation of oilfield development effect evaluation. In order to ensure the stable production of oil field, according to the distribution rule of remaining oil, this article adopts the method of multi-objective optimization decision-making to optimize the late oilfield development planning and realize reasonable allocation of resources. The main research contents are as follows:(1) The evaluation of the effect of oilfield development. At present, the vast majority of oilfields take water injection as the preferred way of development. For Daqing oilfield water flood development way is still the main measures of the middle and later. So before making oilfield development planning, the first thing we need to know is the present situation of oilfield development, It Includes oil field production, the utilization rate of moisture content, water injection and so on. We evaluate the effect of oilfield development timely and effective on the basis of that. The tasks include determining oil field’s stage of development, assessing the potential of development, improving oilfield development effect and increasing oil field recovery efficiency and economic benefits. This article is mainly to evaluate fields between the north and the south b block rule of water cut, the utilization efficiency of water injection and so on.(2) Forcast of remaining oil distribution and countermeasures. In the late development of oil fields, our main task is studying the saturation of remaining oil, the reservoir would be descripted in a quantitative, precise, dynamic way. This study was based on the historical data of Xingxi oilfield, which found that the number and size of plane of remaining oil distribution is too fragmented according to the numerical simulation of remaining oil distribution. Thus, according to the main reservoir and non-mining major reservoirs of different characteristics, different countermeasures need to be taken in order to ensure stable oil field production.(3) Multi stage goal programming model to optimize production of oil field.The oilfield production model of optimal composition (addressing the problem of optimal composition of natural production, measures-taking production, production of new well in old field and production of new well in new area) and the oilfield production model of optimal allocation (addressing the problem of rational allocation of oilfield total output to the lower mining unit) were included in this part. The periodic effect of output optimization would be taken into consideration, and the decision-making of next stage was based on the development planning and investment decisions of last stage. The development indexes of different levels were optimized to realize the benefits.(4) Multi objective programming model of oilfield stimulation of different priority.The stimulation measures for remaining oil were regarded as decision variables, the production objectives and cost objectives were determined, and the influence of policy makers’preference in optimization of stimulation would be studied by changing the decision-making priorities. Policy makers need to make investments in the appropriate measures according to priority of targets and actual situation, in order to ensure stable oil field production.(5) The bi-level multi-objective programming of oilfield development.The oilfield were regarded as a bi-level structure, the upper level is oilfield corporation and the lower level is oil production plants. The upper level planned the optimal strategy, and the lower level aim to maximize profits according to the task which was assigned by corporation. The total profit of the oilfield system would be maximized through the coordination between two levels.(6) Multi-objective evolutionary algorithm NSGA-II.Because the upper decisions will affect the underlying decisions, the bi-level multi-objective programming’s constraints varies with time, the decision-making environment changes all the time, which requires the algorithm not only can search Pareto solution as much as possible in the fixed evolutionary environment, but also can detect any small change in the evolutionary environment and react appropriately to the change, determine the evolutionary parameters of the new environment. Based on these considerations, the evolutionary algorithms were designed to solve the bi-level multi-objective programming model, and the performance (convergence and uniformity) of the algorithm is analyzed.Based on the multi-objective programming and screen method of satisfactory solution, the late-stage development plan of Xingxi oilfield was analyzed. The ways to achieve the goal of adjusting the energy structure and maintaining steady growth in production would be studied, such as how to arrange production tasks for corporation and oil production plants, how to make targeted investments etc. All this measures would improve the economic efficiency, energy efficiency and social benefit. The main conclusions are obtained as follows:(1) Through the assessment of water injection development effect such as production rule, water cut rule and utilization rate of water injection, it turns out that many problem such as ever-increasing water content and low degree of water flooding control exist in the late stage of Xingxi oilfield. In order to ensure stable oil field production, the effective development planning, the targeted investment, the measures of fracturing, fill holes, water plugging and overhaul, are all in need.(2) A multi-stage programming model of the production optimization is established to meet the needs of the development decision of oil fields in the late, decision makers can formulate development programs according to priorities and decision-making preferences goals. The model uses a rational allocation phased ideas, which considers multiple constraints of resources, effort and funding, The purpose is to better describe the process of oilfield production optimization decisions, and solve the optimal form of oil production and oil extraction plant production each task issue.(3) A goal programming model of the stimulation measures is established, considering the different stimulation of effort,cost and other constraints, by comparing the impact of different priorities goal, The purpose is to better describe the process of investment and decision making in measure stimulation. Which solves the problem that the oilfiled or oil plant in order to ensure stable oil production, how to choose the stimulation measures, and how to change the measures according to the variation of decision-making environment.(4) A multi-objective and bi-level programming model of the Oilfield optimization is established, considering the relationship between the leadership and production of oil layer,which better describe the process of decision making in Oilfield optimization,and solve the problem that due to the oil field organization structure being more complex, oilfield senior policymakers ignore the interests of junior mining unit.(5) Multi-objective evolutionary algorithm NSGA-Ⅱ is applyed to solve the problem with a dynamic decision stage. Compared to the NSGA algorithm, NSGA-Ⅱ has better convergence, coverage and uniformity; this paper take full advantage of NSGA-Ⅱ algorithm in a global perspective to guide the search direction, and detect any small changes occur with the passage of time, the purpose is to make the right response to environment change and determine the evolutionary parameters of the new environment.(6) According to the actual situation of Xingxi oilfield,the best decisions are as follows:First, the constitutes structure of oilfield output becomes more reasonable, the proportion of natural production decline, the proportion of measures production and Arai yields of oldplant rise, so in the late development of oilfield, improving measures production is an effective way to ensure the stable production of oilfield.Second, the reasonable distribution of measures is achieved,to xingxi oilfield, acidification is the less effective measures and should be replaced by investment in new wells, fracturing, fill holes, plugging and overhaul.Third, The formulation of oilfield development planning is more reasonable. For oil companies, oil production is subdivided into various oil production plant, which is conducive to the rational development of production tasks; for oil production plant, the production of new oil production plant improved, while production of old oil production plant declined, which will motivate the production enthusiasm of new factory, and help the old oil production plant for technological innovation,to improve their management level and technical efficiency.Innovation of this paper is mainly reflected in the following aspects:(1) A multi-stage objective programming mode was established to optimize production in mid-later period of oil field.The periodic idea was applied to field development optimization decisions,the periodic effect of output optimization would be taken into consideration, and the decision-making of next stage was based on the development planning and investment decisions of last stage. The development indexes of different levels were optimized to realize the benefits. This model well coordinate optimal production constitution in mid and late period of oil field development planning and the reasonable distribution of each production plant production tasks.(2) The multi objective programming model of oilfield stimulation of different priority was established.The influence of policy makers’ preference in optimization of stimulation would be studied by changing the decision-making priorities. The model describes the stimulation measures decision-making needs in mid-later period of oil field fields, namely:which stimulation measures should oil or oil plant investment for achieveing planning objectives? Which effect of stimulation is better? How to prioritize the objectives of proper stimulation of investment when decision-making environmental changes.(3) The bi-level and multi-objective programming of oilfield development,with the evolutionary algorithm NSGA-Ⅱ. The oilfield were regarded as a bi-level structure, and the total profit of the oilfield system would be maximized through the coordination between two levels. The model meets decision-making need for development planning in mid-later period of oil field,that is to distinguish the leadership and production layer of the oilfield development planning and to study how to develop an effective plan to achieve mutual benefit and win-win development of oil and lower oil production plant. The results show that the NSGA-Ⅱ algorithm is a good solution to the problem with a dynamic decision stage.