东河1石炭系具稠油垫油藏注气开发数值模拟

Numerical Simulation of Gas Injection Development in Donghe-1 Carboniferous Reservoir With A Heavy Oil Cushion

针对东河1石炭系油藏泡点压力低、油藏底部带稠油垫、构造幅度大、夹层发育等特点,建立等效数值模型模拟该油藏注水开发后转注气开发调整机理,分析不同时间点转换为组分模型误差,确定合理转换时间点,提高模型运算效率和精度。通过对比顺层网格和混合网格划分法处理稠油垫的差异,合理描述稠油垫形态,分析其对生产动态的影响,提高历史拟合精度。利用等效模型快速模拟油藏注水开发后转注气开发的过程,对比不同注入介质和不同注入方式的差异,为油藏实际模型的建立和注气开发机理研究提供依据。研究结果表明,建立等效模型可大幅提高研究效率;混合网格划分法在描述稠油垫形态和垂向属性方面更准确;在注水开发历史拟合结束由油水两相或三相黑油模型转为组分模型,可节省约90%的拟合时间,误差在可控范围,主要指标相对误差小于1%.机理研究表明,油藏注水转注气开发,夹层对气窜起到一定的抑制作用,受重力影响,随着气油水三相垂向动态平衡,可能在次生气顶底部形成新的油环层;气油比超过200 m3/m3时,需要通过控制产气量增加注气受效。

Aiming at the characteristics of low bubble point pressure,high structure amplitude,having a heavy oil cushion at the bottom of the reservoir and developed interlayers in Donghe-1 Carboniferous reservoir,equivalent numerical models are established to simulate the gas injection reservoir development mechanism after waterflooding,to analyze the errors of component models converted at different time,to determine the reasonable conversion timing and improve the efficiency and accuracy of the models.By comparing the differences between conventional grid and hybrid grid methods to deal with the heavy oil cushion,the paper describes the shape of the heavy oil cushion,analyzes the influences of the cushion on production performance and improves the history matching accuracy.The equivalent models are used to rapid simulate the gas injection process after waterflooding and to compare the differences between different injection media and different injection modes,providing basis for the establishment of actual reservoir model and study of gas injection mechanism.The study results show that the equivalent models can significantly improve the research efficiency;the hybrid grid method is more accurate in describing the shape and vertical properties of the heavy oil cushion;at the end of waterflooding,about 90%of the fitting time can be saved and the error can be controlled with the relative errors of main indicators less than 1%by changing the oil-water two-phase or three-phase black oil model into the component model.The mechanism study indicates that during reservoir development converted from waterflooding to gas injection,interlayers could inhibit gas channeling to some extent.Influenced by gravity and with the vertical dynamic balancing of gas-oil-water three phases,a new oil ring may occur at the bottom of secondary gas cap.When gas-oil ratio exceeds 200 m3/m3,gas yield should be controlled to increase gas injection efficiency.