特高含水期相渗关系表征新理论与实践

特高含水阶段油水相对渗透率比与含水饱和度半对数关系曲线发生转折，针对传统相渗线性理论难以适用于特高含水期水驱油田开发问题，开展了特高含水期相渗非线性理论研究。采用数学建模方法建立了相渗有理函数，基于局部加权回归理论对参数进行识别，通过构建F-统计量开展拟合优度检验，率先将有理拟合理论应用到特高含水期相渗关系表征。利用贝尔油田、榆树林油田、西峰油田及羊二庄油田实际数据，对比分析传统线性拟合方法、二次多项式拟合方法、指数拟合方法、基于数据变形的线性拟合法，新方法预测精度更高、相关性更强，且能准确反映特高含水期相渗曲线半对数坐标轴弯曲特性；基于新方法的水驱特征曲线预测精度更高、相关性更强。新方法对于改进特高含水期水驱评价方法及开发指标预测具有极强的实用性。

New Theory and Practice of Characterizing Phase Infiltration Relationships in Ultra-high Water-cut Period

In the (extra) high water-cut stage, the semi-logarithmic curve showing the relationship between the oil/water relative permeability ratio and water saturation tends to reach a turning point. Thus, applying the traditional linear theory of the relative permeability curve to the development of oil/water displacement in the (extra) high water-cut stage is difficult. In this study, nonlinear theoretical study of relative permeability in the high water-cut stage was conducted using a rational function for relative permeability established through a mathematical modeling method. Its parameters were identified based on the local weighted regression theory, and the appropriateness of the fitting was tested by constructing F-statistics. This is the first study in which the rational fitting theory has been applied to the characterization of relative permeability relationships in the (extra) high watercut stage. Through the use of actual data from the Beier, Yushulin, Xifeng, and Yangerzhuang oilfields, the traditional linear fitting, quadratic polynomial fitting, exponential fitting, and linear fitting methods based on data deformation were compared and analyzed. The new method and the oil/water displacement characteristic curve on which the new method is based showed higher prediction precision and stronger correlation. The new method can be used to reflect accurately the semi-logarithmic axis bending characteristics of the relative permeability curve of the (extra) high water-cut stage.