Casing Centralizer ia a mechanical device that keeps casing from contacting the wellbore wall. A continuous 360-degree annular space around casing allows cement to completely seal the casing to the borehole wall. There are two distinct classes of centralizers. The older and more common is a simple, low-cost bow-spring design which can provide complete centralization in vertical or slightly deviated wells as the bow springs are slightly larger than the wellbore.. The second type is a rigid blade design. This type is rugged and works well in deviated wellbores.