same function as a complete string of production casing. A typical casing arrangement in a well is shown in the diagram below. In this case, the surface casing is set to a depth of about 3000 ft. Two intermediate strings are set in this well — a 13 ⅜" string and a 9 ⅞" string. A 7 ⅝" production casing is set at a depth of about 15,000 ft and a 5" production liner set to TD. Probably, this well required a high mud weight at the bottom of the hole and cementing the 7 ⅝" casing at TD would have resulted in too much pressure and lost circulation. If lost circulation occurs during a primary cement job, there is little guarantee that cement will fill the designated volume behind the casing. This will require the casing be perforated and cement squeezed into the casing/well bore annulus. See also Oil well Casing Completion References petroleum production. Encyclopædia Britannica. 2005. Encyclopædia Britannica Premium Service. 17 Nov. 2005. External links Schlumberger Oilfield Glossary: production tubing Oil wells Petroleum production Tubing (material)