Relative permeability curve method and stream-tube method are commonly used to plot theoretical curves of water-cut vs.recovery percent of reserves.When the former method is used to plot the theoretical curves

the relationship between relative permeability and water cut is often analyzed through statistical and regression analyses

resulting in water cut tends to be high in low water saturation stage

and tends to be low in high water saturation stage. This problem can be solved by directly using experimental data to calculate.If a constant value is assigned to volumetric sweep efficiency

a universal conclusion is often obtained

i.e.development effects are relatively poor in medium-low water cut stage

and are relatively good in high water cut stage.This problem can be solved by establishing statistical relational expression through analyzing the relationship between volumetric sweep efficiency

mobility ratio in a pattern system and permeability variation coefficient.