The Global Optimization Theory And Method Of OilField Production System

Oil fields are confronted with a lot of difficult after they entered into the high water-cut stage, such as the sharp aggrandizement of liquid-oil ratio, the great rising of liquid production, the unaccommodated ground projects, the obviously augmentation of treatment workload and cost that in order to maintain the steady production of oil field, and so on. For the sustainable development of oil field, we must optimize every stimulation treatment, and arrange the development work more reasonablely. Based on the theory and method of oilgas preservation and transportation, petroleum reservoir engineering, and petroleum engineering, the paper analyzes the current programming optimization models of oil field development, combines the system character of oilfield development and the localizations when using current methods to deal with the multiobjective multi-stage and multi-subsystem problem, utilizes systems engineering method, optimization theory and node analysis to establish the multiobjective decision-making model under water drive and polymer displacement. The economic benefit, cost, production and final recovery ratio are considered comprehensively. By solving this largescale optimization model, we can make the idea, underground submit to ground and underground consider the ground, modeling and quantification. So, the global optimization project can be achieved. According to the optimization project, by reconstructing reservoir system whose water cut is very high and remaining oil distribution is asymmetry and the corresponding oil well system and injection well system, and by optimization design the new put into production well net to reduce the cost greatly and enhance the economic benefit and the development level of oil field. Because of the complexity of oilfield production system, if the optimization model is established directly, the mathematical model will be very large and including a mass of mathematical equations, data, pipe line and oil layer constraint conditions. Solving this optimization model in current calculation condition will wastes large amount of computer time, and it is difficulty to popularize in production. Based on the decompose-harmony principal of large scale system, the oilfield production system can be disassembled as five subsystems. They are ground injection system, injection well bore system, reservoir system, oil well lift system, and ground gathering and transport system of oil, gas and water. The flowage of liquid is restricted by many factors. The result is that the system will in a dynamic harmony condition. There is a interface of in-out that exists between two adjacent systems. They are interactional and interinhibitive by the interface. Introducing into the node analysis method, the five subsystems of oilfield production system can be connected by four nodes. And every node divides the adjacent system into upper system and lower system. The node is the export of the upper system and the entrance of the lower system. The liquid is transferred between the two systems at the point of node. The corresponding dynamic indexes are flux and pressure. Based on the node analysis, utilizing systems engineering process and optimization theory, the objective function and constraint condition of the system can be confirmed, and the optimization model can be established. Based on the analysis of the ground injection system, feathers of the flow and every part of it are ascertained. Utilizing corresponding parameters, formulas, figures, the ground injection system optimization model is established, which takes the law of liquid pressure, velocity of flow and temperature etc. in injection water processing stations, pipelines into account. The changing of pressure, velocity of flow, temperature gradient, flow resistance in well bore is analyzed. Based on the well bore structure of injection well and production well and the characteristics of every part, the well bore optimization model of injection well and production well is established. Based on the numerical simulation of double-dimension and double-phase, the reservoir optimization model is established. Integrating with dynamic detaching method, the forecast model of sedimentation unit remaining oil distribution and delamination dynamic indexes is founded. And the corresponding software is programmed. Utilizing fuzzy mathematics technique, the optimization model of delamination treatment projects, which considers the dynamic characters of injection system and production well bore system, is established. According to the established optimization model, and considering the practical value, the result of subsystem can be resolved. In the view of the connected relation of subsystems, the global optimization model that aims at economic benefit can be established, and the global optimization of whole production system can be realized. Finally, the ground and underground general optimization project of one plot in oil field is proposed.