The Effect of Water Index on Water Cut Increasing Rate

Water cut is an important evaluation index which can comprehensively reflects the development effect of a water flooding reservoir. Study the variation law of water cut is very important for reservoir development evaluation. A mathematical model for estimate water cut and water cut increasing rate was established based on Corey expression of relative permeability curve and fraction flow equation. Three parameters were proposed to quantitatively describe the character of water cut increasing rate. The three parameters have specific meanings and can describe the shape character of the relation curve between water cut increasing rate and water cut and the relation curve between water cut increasing rate and recovery percent. The effect of water index on water cut increasing rate was discussed. The relationship curve between three parameters and water index under the condition of different water oil mobility ratio was established. The result shows that when water-oil mobile ratio is greater than 10, water index has great effect on water cut increasing rate. With the increase of water index, the maximum value of water cut increasing rate gradually increase, the recovery degree when water cut increasing rate reaches the maximum value gradually increase and the water cut when water cut increasing rate reaches the maximum value also gradually increase. When water-oil mobile ratio is less than 10, water index has little effect on water cut increasing rate.