Centralizers for highly inclined and horizontal wells have to fulfill several requirements. Their main task is to provide adequate standoff. Additionally, centralizers have to facilitate casing and liner running and should allow pipe rotation. While bow-type centralizers normally are made of steel, various other alloy materials have been introduced for rigid type centralizers, including aluminium and zinc-aluminium alloys. Investigations have shown, however, that steel is a preferred material also for rigid type centralizers. Friction factors under all mud-wetting conditions of steel versus formations and pipe surface as well as the wear rate are low compared to other materials.
This paper describes the details of the investigations and describes two steel centralizers specifically designed for use in highly inclined and horizontal wells.