Formation damage due to clay migration may be observed when the injected brine replaces the connate water during operations such as waterflooding, chemical flooding including alkaline, surfactant and polymer processes.

This work deals with the effects of physico-chemical changes induced by brine replacement on the permeability behavior of consolidated argillaceous sandstones.

The experimental investigation is made up of:

  • core flow experiments in clayey sandstones. Effluent pH and ionic concentration are measured at the outlet of the porous medium and permeability variations are simultaneously monitored when the injected salinity is abruptly decreased.

  • batch coagulation tests giving both critical salt concentration and pH in a salinity-pH diagram.

Brines are prepared with sodium and potassium salts.

A physico-chemical flow model is also developped based on cationic exchange with the proton when the salinity decreases. The model allows:

  • the interpretation of the experimental observations (pH and concentration)

  • the knowledge of the transition compositions

  • the effect of the major parameters like the clay content through the cation exchange capacity.

The model gives pH and salinity profiles. The comparison of these values with the salinity-pH diagram critical ones leads to the prediction of the effect of the fluid composition on the damage process.

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