Casing string

Oil drilling casing string parts In drilling technology, casing string is a long section of connected oilfield pipes that is lowered into an wellbore and cemented in place. The purpose of the casing pipe is to: Prevent the borehole from collapsing. Prevent formation fluids from entering the borehole in an uncontrolled way (blow out). Prevent fluids in the borehole (such as produced oil or gas, drilling mud, etc.) from entering other formations. Background The pipe segments (called "joints") are typically about 40 feet (12 m) in length, with male threads on each end that connect with short lengths of double-female threaded pipe called couplings. (Some specialty casing is manufactured in one piece with a female thread machined directly into one end.) Specification 5C3 of the American Petroleum Institute standardizes 14 casing sizes from 4.5 inches (11.43 cm) to 20 inches (50.80 cm) outside diameter ("OD"). This and related API documents also set standards for the threaded end finish, the wall thickness (several are available in each size to satisfy various design parameters, and are indirectly specified by standardized nominal weights per linear foot; thicker pipe is obviously heavie