This work deals with the impairment of rocks subjected to the injection of water with solid particles in suspension. The effect of the permeability reduction and consequent loss in rock injectivity is analyzed by the interpretation of core flow tests, previously reported, and simulated by using a computational program developed for this research. The program is based on the Pang and Sharmas model (1994) for the prediction of injectivity decline, chosen amongst a set of existing models, and contemplates the process of impairment due the formation of an external and/or an internal filter cake, where the concept of transition time is introduced. The formulation also uses two important parameters: lambda, defined as filtration coefficient, and beta, damage factor, which can be determined by test data or empirical correlations. A new theory of Bredrikovetsky (2001) that suggests the calculation of both parameters for pressure data is used. With the objective to validate the model and the program, a parametric study is presented whose information can be used in the prediction of the behavior of the injection wells.