一种通过数值模拟手段划分CO2驱替相带的新方法 ——以高89块油藏为例

 CO₂驱油提高采收率是今后发展的方向.驱油方式存在混相驱、近混相驱、非混相驱3种.CO₂驱油可以膨胀原油体积、降低黏度、降低界面张力,增加注入量,实现大幅度提高采收率.高89块属于低孔特低渗储层,原油黏度低.通过对高89块地层油进行原油复配,划分了8个拟组分.利用PVTi模块进行相态拟合,拟合体积系数、密度、黏度等参数随压力变化的试验数据.该块地层油进行CO₂驱,原油最小混相压力为28.94MPa.利用软件计算的最小混相压力,与细管试验得到的最小混相压力一致.本文通过数值模拟手段调整生产指数、描述地下裂缝展布,进行了精确历史拟合.预测测试井的井底静压与实测的压力一致,证明了拟合的可靠性.基于高89油藏模型的数值模拟研究,建立了不同驱替方式的生产气油比与压力关系的图版和识别标准.不同的驱替模式在气体饱和度、界面张力、黏度场上存在很大的差异.参考该图版评价了重点见气井的驱替模式.该方法对现场实践具有较高的指导意义.

Numerical Simulation for Division of Phase Zone Displacement: With Gao89 as an example

Using the CO₂ flooding to enhance the oil recovery is a development trend. The three displacement modes are the miscible, the near-miscible, and the non-miscible flooding modes. By means of expanding the oil volume, reducing the viscosity, decreasing the interfacial tension, and increasing the injection volume, the CO₂ flooding can substantially enhance the oil recovery. The reservoir in the block Gao89 is of low porosity and ultra-low permeability. The oil in the block Gao89 is divided into eight pseudo components by the crude oil compound. The phase matching is done, including the volumetric factor, the oil density, and the oil viscosity. The MMP of the oil in this area is 28.94MPa. The simulation result agrees with that of the slime-tube test. With the numerical simulation, the production index is adjusted and the fracture distribution is obtained to accurately match the production performance. The static bottom hole pressure of the prediction agrees with that of the test, which verifies the simulation. Based on the numerical simulation for the block Gao 89 reservoir model, different displacement modes are established for the production gas oil ratio, the pressure relationship correlation diagram and the identification standards, with different gas saturations, interfacial tensions, and oil viscosities in different displacement patterns. Accordingly, the displacement pattern for the key well is identified. The method can serve as a guideline for the field application.