Adsorption is considered the primary mechanism of scale inhibitor retention during squeeze treatments of sandstone formations. Steps are often taken to avoid inhibitor precipitation for fear of formation damage. In limestone and dolomite formations, phosphonic acid inhibitors are deliberately allowed to react with the formation and precipitate as the slightly soluble calcium salt. This can result in longer scale protection times. Even neutralized inhibitors react with limestone to form precipitates.

This paper investigates the factors that affect the inhibitor precipitation and retention in carbonate formations. Core tests show an absence of damage during inhibitor injection but good retention. A slow rate of inhibitor return is observed during brine backflow. In formation brines containing Ca++, inhibitor dissolution is slowed by the common ion effect.

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