18 - Cathodic Protection of Well Casings

Abstract

The chapter discusses the various electromagnetic and mechanical measuring methods for the protection and stabilization of wells, which determines if there is an external or an internal corrosion. In oil and natural gas fields and reservoirs, the boreholes are cased to stabilize the wells. The usual practice in old wells of only partially cementing the outer pipe can lead to cell formation in the transition regions to the uncoated sections. The most important parameters in the cathodic protection of a well casing are the depth of penetration of the protection current and its magnitude. These depend on the geological formations and the specific electrical resistance of the individual layers. Insulating layers are a disadvantage because they limit the extent of the protected region. Depending on the type of field or reservoir, it is recommended that measurements are carried out on the casing. In planning the cathodic protection of oil and gas fields or reservoirs, depending on the subsoil of the pipelines, the required technical data on the casing include diameter, wall thickness, depth, cement filling, and the geological situation in its vicinity. Other factors that must be considered are operational data such as temperature of the deposits, well head temperature, electrical heating of oil in oilfields and the conductivity of the transported media.