Chapter 7 - Scale Inhibitors

Abstract

This chapter focuses on Scale Inhibitors. Scale deposition occurs in many operations in the petroleum industry, particularly in production, stimulation, and transport. Scaling can occur when a solution becomes supersaturated, which occurs mostly if the temperature changes in the course of injection operations. Also, if two chemicals that will form a precipitate are brought together, a scale is formed. The scale may consist of calcium carbonate, barium sulfate, gypsum, strontium sulfate, iron carbonate, iron oxides, iron sulfides, and magnesium salts. Scale inhibition can be achieved either by adding substances that react with the potential scale-forming substances from a thermodynamics standpoint and reach a stable region, or by adding substances that suppress crystal growth. Conventional scale inhibitors are hydrophilic—that is, they dissolve in water. In down-hole squeezing, it is desirable that the scale inhibitor is adsorbed on the rock to avoid washing out the chemical before it acts as desired. Often, scale inhibitors are applied in combination with corrosion inhibitors.