Casing scrapers are used before running other downhole tools to prevent damage to those tools or a loss in efficiency due to foreign materials in the casing. They have a series of hardened steel blades that scrape the inner walls as it is run in and out of the well. These blades are designed to wax, remove mud, cement, rust, scale, perforation burrs and other foreign materials from inside the casing walls.

It is a common practice to run a casing scraper in abandonment operations prior to setting plugs or retainers to ensure a clean and secure seal against the casing.