Study On Hierarchy Optimization And Software Development For Oil Transportation System In Low Throughput Running State

Some oilfields have entered low throughput transportation state in the middle-later developed period.Pumps,pipelines and other equipment are running near the edge of security limit.Meanwhile,most of the crude oil produced in our country belongs to high viscosity and high freezing point,which needs to be transported by heating.High temperature will produce a lot of energy consumption.Conversely,low temperature will affect the operation security of the system.It is important to control the heating temperature when the oil field enters low throughput running state.In addition,the pressure of oil transportation should be controlled in a reasonable range to ensure the security of oil transportation and reduce energy consumption.Therefore,in order to reduce the energy consumption and ensure the security of the system,it is necessary to optimize the system under the low throughput running state.In this paper,the hierarchical optimization model of oil transportation system is established according to different functions of the system in various stages.The model is divided into three levels: internal optimization,inter station optimization and reconstruction optimization.The first level of optimization model is available to calculate and give the pump operation status in different flow intervals by using dynamic programming and similarity theory,based on fully consider the change of pump performance under conditions of pump speed regulation and impeller cutting.The optimization result gives pump adjustment scheme in different flow stages and provides basis for the pump optimization part in the inter station optimization.The second level of optimization model is used to provide optimal hydraulic and thermal transmission scheme for each station under the target throughput.The operation optimization model is established with minimum total operation cost as the objective function,based on careful and profound analysis of the security,energy consumption and law of oil transportation conditions between stations in low throughput state.The model is calculated by the two-level hierarchical optimization method and the depth first search algorithm,with combined the first level result.When the first and second level optimization can't guarantee safety of the oil transportation system,the third level optimization makes a holistic analysis on the system to judge which pipeline reaches the safe running limit and do reconstruction optimization according to the predicted transportation flow in fixed term.The optimal reconstruction scheme is determined by comparing pipeline replacement and station depot degradation based on fully consider pipeline service life and equipment load during system operation period.Practical case's calculation shows that the hierarchical optimization model of oil transportation system can ensure economic and safe running of the system in operation period.Based on the theoretical studied above,the process optimization software of oil transportation system is made with Visual Basic,which is successfully applied to the Y oilfield oil transportation system.And it is of significance for actual operation and reconstruction of the oil field which have entered the low throughput running state.