1. . 
The location, or depth, at which drilling an interval of a particular diameter hole ceases, so that casing of a given size can be run and cemented. Establishing correct casing points is important in the design of the drilling fluid program. The casing point may be a predetermined depth, or it may be selected onsite by a pressure hunt team, selected onsite according to geological observations, or dictated by problems in the openhole section. In many cases, weak or underpressure zones must be protected by casing to enable mud weight adjustments that control unstable formations or overpressure zones deeper in the wellbore.