The Derrick

The derrick provides the necessary height and support to lift loads in and out of the well, and must be strong enough to support the hook load, deadline and fast-line loads, pipe setback and wind loads, The drill string, when retrieved from the wellbore, if not laid down, will be stood back in stands vertically in the set back area,  a specially designed  section of the drillfloor  that  will support the dry load , On an offshore rig  the derrick  is seldom  shorter that 142 feet from the water table to the rig floor  (no TDS installed)  however they can be as tall as  221 feet if it is intended to drill with doubles and special down hole drilling tools   The modern design of the Derrick allows for simultaneous drilling and stand building. The V-door opening simplifies handling of large equipment and tubular's onto and off of the drill floor.   Derrick and pipe handling systems are designed for triple average 93.5 ft or doubles 121 ft  length stands of tubular (range II in trebles and range III in doubles).   Forces and loads from the following equipment are transmitted to the Derrick:   Load in traveling block, crown block   Top drive system with retractable dolly   Man rider and utility winches   Stabbing basket/ board   Setback including vertical pipe handling system