Completion of a well means preparing and finishing the well for production.

The main types of completion are:

• Open hole completions are rarely used, consists of simply running the casing directly down into the formation, leaving the end of the piping open. Only used in formations that are unlikely to cave in.
• Perforated completions consist of production casing run through the formation and the sides of this casing are perforated to enable inflow of formation fluid or gas.
• Sand completions consist of screening or filtering systems to prevent sand from entering the well. This sort of barriers is used in areas containing loose sand and in conection with open hole completions as well for perforated completions.
• Multizone completion allows production from more than one formations or zone from the same well, with or without commingling the reservoir fluids from each reservoir. The multizone completions are made as single string or as dual string completions. The multizone production strings are equipped with isolation packers and sliding sleeves, operated by “well workover” to controle the production. The dual string completion is normally used when it is desired to produce two zones simultaniously but keeping them isolated from each other.
• Drainhole completions are horizontal completions running out of a vertical well, providing enhanced drainage from the formation.