Wellhead Insulation
Use of electrical insulation stops current flow down the casing from the surface and reduces both internal and external casing corrosion. Dielectric insulation materials for both screw and flange joints are commonly used to insulate casing from flowlines. Insulation of wells by connecting them to a single battery is often recommended. It should be noted that when the flowline is at high potential due to cathodic protection, it may induce interference corrosion. In this case, the insulating joints may be partially shunted or wellhead potential is elevated by attaching a sacrificial anode (see Fig. 6.2). Heat resistant material should be selected for hot, high-pressure wells to prevent failure of insulation materials.