This paper reports the main results of an experimental study of the process of permeability impairment by particles suspended in injection water.

The experiments were carried out under well defined conditions both realistic and sufficiently well-known to yield clear and useful conclusions concerning actual retention mechanisms and their consequences for formation damage. Injection of waters containing particles of different sizes into sandstones of different permeabilities resulted in drastic permeability reductions, even for particles smaller than pore throats, with a very high flow rate sensitivity. The different possible steps in formation damage process have been characterized and related to phenomena at pore scale level. The results are analysed according to a new theory capable of predicting retention by two mechanisms for particles smaller than pore throats that do not absorb on pore walls without flow. This theory takes into account the competition between surface forces and hydrodynamic forces which can either induce or prevent retention depending on force balance at the location of capture.

All experimental observations agree with this theory which, therefore, provides a reliable basis for quantitative predictions of formation damage.

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