Chapter 6 an introduction to corrosion and protection of casing

Abstract

This chapter provides an introduction to the corrosion and protection of casing. Corrosion attacks casing during drilling and producing operations through electrochemical processes in the presence of electrolytes and corrosive agents in drilling, completion, packer, and production fluids. The components present in the fluids that promote the corrosion of casing in drilling and producing operations are oxygen, carbon dioxide, hydrogen sulfide, salts, and organic acids. Destruction of metals is influenced by various physical and chemical factors that localize and increase corrosion damage. Corrosion of metals continues provided electrically conductive metal and solution circuits are available to bring corrodants to the anodic and cathodic sites. In most corrosion problems, the important differences in reaction potentials are those that exist between separate areas interspersed over all the surface of a single metal. The casing can be protected by one or a combination of the following: using wellhead insulator, cementation, placing completion fluids around casing that has not been cemented, cathodic protection, and steel grades. © 1995 Elsevier B.V.