The re-injection of produced waters for pressure maintenance becomes more and more attractive in the industry since the environmental regulations for rejection (sea, rivers, deep aquifers) are more constraining associated with increasing surface treatment costs. One important difficulty in this re-injection process is the ability to predict the impact of water qualities on well injectivities. This is mainly due to the poor knowledge in the mechanisms of porous media damage by mixtures of micronic solid particles and oil droplets which are the main components of produced waters. In a first attempt this paper does not deal with the matrix internal filter cake formation. It focuses on the external filter cake build-up and flow properties which are believed to have the larger impact on well injectivity over most of the well life. It is shown that the injection of micronic dispersed oil leads to compressible filter cakes with very low permeabilities in the micro-darcies range. The retention on the filter is amplified by oil agglomeration while oil passing through the filter is dispersed in particles smaller than the filter pore throats. They become finer and finer as the pressure increases and are able to migrate deeply within the reservoir without adverse internal injectivity effects. These results on synthetic oil emulsions are compared to a real produced water behavior.

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