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 Formation Fines and Factors Controlling Their Movement in Porous Media
T.W. Muecke, SPE-AIME, Exxon Production Research Co.
This paper defines sub-400 mesh (-37 micron) material as "fines." Even with these extremely small formation fines, migration was shown to be controlled by wettability. The fines would not move in the non-wetting phase, and an adequate saturation of the wetting phase was necessary to achieve a continuous phase before fines migration was initiated. Therefore, water-wet fines may be held in place by the immobile connate water saturation until waterflood breakthrough. Since fine particles have extremely high surface to volume ratios, it is understandable that particle wettability (surface interfacial forces) control fines migration.
Other interesting conclusions: Chemical analyses showed the primary constituent of formation fines was NOT clay! (Found 39% quartz!). This is significant because many chemical treatments to stabilize fines often are designed to stabilize clay only! Injection of mutual solvents or surfactants were shown to mobilize fines that were previously held in place by wetting and interfacial forces.
Comment — This study may corroborate industry reports of fines migration associated with increased condensate or watercut in gas wells, and fines production that begins during cleanup of water-based fracturing fluids or waterflood breakthrough in oil wells. |
