一种新型水驱特征曲线关系式的理论推导

On the theoretical basis of the linear relationship between relative permeability ratio and water saturation on the semi-log coordinate in the stage of middle water-cut and the frontal-drive equation proposed by Buckley-Leverett, combining with material balance equation, a new water flooding characteristic curve was derived which is constituted by the water cut and cumulative fluid production. By dissecting the feature of the characteristics of curves, elaborating the multiple values of water cut to water saturation leading to the monotonicity of the new water flooding characteristic curve,which is reducing before increasing. And the water flooding characteristic curve line segment should begin after water cut greater than 50%,which is consistent with the traditional experience, proposing how to improve the accuracy by choosing the reasonable starting point to make linear regression. The calculation results indicate that the new water flooding characteristic curve is a practical tool in the prediction of production indexes in the late development stage of oilfields.