A MODEL FOR PREDICTING INJECTIVITY DECLINE IN WELTER-INJECTION WELLS

We propose a new method to predict the injectivity decline for water-i njection wells. Both internal and external filtration are considered i n this method. A transition time from internal to external filtration is calculated by use of the trapping efficiency obtained from Stokesia n dynamics simulations. The radius and the permeability of the damage zone are calculated by use of a deep-bed filtration model. Equations a re derived that allow us to combine the flow resistance in the externa l and internal filter cakes to obtain the overall decline in injectivi ty.