1. n. [Well Completions]

The process of placing a cement sheath around a casing or liner string. The main objectives of primary cementing operations include zonal isolation to prevent migration of fluids in the annulus, support for the casing or liner string, and protection of the casing string from corrosive formation fluids.

See: casing string,  formation fluid

2. n. [Drilling Fluids]

The first cementing operation performed to place a cement sheath around a casing or liner. The main objectives of primary cementing include zonal isolation to prevent fluid migration in the annulus, support for the casing or liner, and protection of the casing from corrosive fluids.