Water quality is an important consideration in the design of a cost-effective reservoir maintenance or secondary oil recovery project. Proper filtration equipment selection often is not based on scientific facts since knowledge of the formation may be unavailable. Rules-of-thumb that relate size of particulate in injection water to potential permeability reduction have been developed and are used for selection of proper filtration equipment. However, laboratory procedures have not been rigorously applied to the 1/3 and 1/7 rules-of-thumb currently being used to specify water filtration equipment design.

This evaluation of the 1/3 and 1/7 rules-of-thumb used three different core types: Berea sandstone, Cottage Grove sandstone, and a synthetic core. The results showed that rules-of-thumb based on permeability and contaminant particle size are useful in selecting filtration equipment. Results indicated that loss of permeability (core damage) during coreflooding was more severe than expected when the 1/3 rule-of-thumb was used, but not severe enough to consider application of the more stringent 1/7 rule-of-thumb. These two competing rules appear to bracket a reasonable range for water quality.

A model used to relate the amount of oil production to loss of injectivity confirmed these results by indicating reasonable oil production using the 1/3 rule-of-thumb with slightly improved production using the 1/7 rule-of-thumb.

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