井网加密可以改善油田的开发效果，提高油田采收率。井网密度越大，油田的开发效果越好。目前计算井网密度的方法很多，但针对水驱油田加密井合理井数和经济极限井数的计算方法却较少。该文以谢尔卡乔夫公式为基础，根据将来净现值公式推导出水驱油田加密井合理井数和经济极限井数的理论计算公式，并进行了实例分析。实际应用表明，计算结果合理，可为油田井网加密提供理论支持。

Well pattern infill can improve the effect of oilfield development and enhance oil recovery. The denser the well spacing density is, the better the effect of oilfield development will be. There are manymethods for calculatingwell spacing density at present, but only a few methods are suitable for calculating the reasonable well numbers of well pattern infill and economic limit well number in water drive field. Based on В. Н. шелкачев formula, the net present value formula is applied to deduced the theoretical calculation formula for reasonable well numbers ofwell pattern infill and economic limit well number in water drive field. The application result shows that the calculation result is reasonable, and this method can provide theoretical support for well pattern infill in oilfield.