油井转注后，随着注入水将井底附近的油驱走，注水井吸水指数不断增加，然而这一变化规律并 无准确的计算公式。文中以平面径向流等饱和度面移动方程和经典的达西径向流公式为基础，结合含水 率随含水饱和度变化曲线，推导出注水井米吸水指数随米累积注水量的变化规律。最后利用油田实例进 行分析计算来验证公式的正确性，为未来注水井米吸水指数的计算和水井的配注提供理论依据。

When a production well adjusted to an injection well, the water injectivity index of the well will keep increasing with the oil near the well bottom being droved away by the injected water. However, there is no accurate formula to describe the law so far. Based on the Buckley-Leverett equation and the classical Darcy equation, combined with the relationship curve of water cut and water saturation, the relationship formula of the injectivity index per meter and cumulative water injection per meter was deduced. Finally, the field data was used to analyze and verify the validity of the formula. This formula provides a theoretical basis for the future calculation of injectivity index per meter and the well injection allocation.