Area of predetermined size in which the drilling rig maintains its intended position (station) in order to not exceed equipment or reaction time limitations. NOTE If the rig moves to the edge of the watch circle, then attention is heightened.
Source: API RP 96, Deepwater Well Design and Construction, First Edition, March 2013. Global Standards
The rig offset perimeter around the well location for which special procedures are to be initiated to prepare to disconnect the drilling riser or actually implement the disconnect to prevent damage due to excessive offset.
Source: API SPEC 16D, Specification for Control Systems for Drilling Well Control Equipment and Control Systems for Diverter Equipment, Upstream Segment, Second Edition, July 2004. Global Standards