Definition - What does Casing String mean?
A casing string is a length of steel pipe assembled together for the purpose of securing the cut sides of a well bore. The individual pipe sections are connected and lowered into the borehole and the resulting space between the casing and the borehole wall is cemented using cement slurry.
The pipe joints are 12 meters in length with each end male threaded and connected using double-female threaded pipes of short lengths called couplings. Casing is very important in a wellbore to isolate the formations that exist adjacent to it. Casing pipes are supported at regular intervals using centralizers that help maintain the spacing between the casing and well bore wall.
Trenchlesspedia explains Casing String
A casing string is an important structural component of a borehole. It maintains the borehole stability, prevents contamination of water sand, protects freshwater aquifers, seals off faults in the formation, and helps control well pressure during drilling, production and workover operations. Casing strings are of six types - conductor casing, surface casing, production casing, intermediate casing, liner tieback casing and liner casing. Casing also provides location for equipment such as the installation of blowout preventers, wellhead equipment and production tubing.