One of the major causes of formation damage is the movement and trapping of fine particles in pores. These fines may be generated in-situ by the interaction of injected fluids with the formation or they may be injected along with the fluids.

A model is presented that simulates the permeability impairment caused by fines migration or injection in a radial geometry. The physical basis for the equations are the same as for a linear model that has been presented earlier 1,2 . The equations are quite general and can be used to model the permeability reduction for any given pore or particle size distribution.

The fines migration phenomenon is a moving boundary type problem. The position of the boundary is determined by assuming that it propagates as an ideal sharp front. The set of coupled, non-linear partial differential equations for the model are solved by an implicit finite-differencing technique.

The validity of the simulator is tested against analytical equations that have been developed for some special cases. The agreement between the simulator and the analytical solutions is found to be excellent. The simulator is also used to investigate the importance of various parameters. For example it is found that the pore and particle size distributions, as well as their concentrations have a significant effect on the permeability reduction. Other factors of importance are the rate of release of attached particles and the geometry of the pores. Methods of estimating these parameters are suggested. The use of the simulator to calculate the extent and depth of damage of damage, when fluids are injected into the formation, is demonstrated. It is expected that the simulator will prove useful in the design of such operations.

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