气顶油藏顶部注氮气重力驱数值模拟研究

Study of numerical simulation for gravity drive of crestal nitrogen injection in gas-cap reservoir

针对江苏油田欧北区块的地质条件和开发现状，建立了顶部注氮气重力驱数值模型。从生产井和注入井的控制条件及地质条件出发，分析了影响气顶油藏顶部注氮气重力驱开发效果的各种因素，在此基础上对各种方案的开发指标进行计算对比，并对该区块提高采收率的潜力进行评价，提出了适合同类气顶油藏的开发模式。研究结果表明，气顶油藏顶部注氮气重力驱可以有效地提高采收率，达到降水增油的效果；提高采液速度并不能改善顶部注氮气重力驱的开发效果；注气速度对开发效果以及气顶边缘推进速度有很大的影响，并且存在最佳和临界注气速度。研究区块的最佳注气速度为12500～17500m^3／d，临界注气速度为30000m^3／d。

in view of reservoir properties and development characteristics in Oubei block of Jiangsu Oilfield, a numerical simulation model of gravity drive of crestal nitrogen injection was established. The factors affecting development effect in the model were analyzed according to various controlling and geology conditions of production wells and injection wells. Based on the analysis, the development indexes of various development schemes were calculated, and the potentiality of enhanced oil recovery in the block was estimated. And the development scheme fit to the similar reservoirs was provided. The results show that oil recovery can be enhanced effectively by gravity drive of crestal nitrogen injection for increasing oil production and decreasing water cut. Though the nitrugen injection rate is a factor much more influential than the other parameters on the development effcct and gas-cap advancing, the development effect can not be improved by increasing liquid production rate, and optinmal nitrogen injection rate and critical one are figured out. The optimal injection rate ranges in 12 500-17 500 m^3/d and the critical one of 30000 m^3/d is recommended to the study block.