Patent ID: 7819182

Claim:
An offshore well system, comprising: a subsea wellhead; a surface wellhead for location on a platform above water, the surface wellhead having a longitudinal axis and a sidewall containing a viewing port; a casing hanger assembly landed within the surface wellhead; a string of casing having a lower end latched into the subsea wellhead and an upper end secured to the casing hanger assembly, the casing hanger assembly being axially adjustable within the surface wellhead for retaining a selected amount of tension to the string of casing; at least one pattern on an outer surface of the casing hanger assembly, the pattern being a geometric series of lines providing a visible change in dimension in response to a change in tension in the portion of the casing hanger assembly on which the pattern is located, the pattern being located inward from the viewing port; an optical reader positioned within the viewing port in sight of the pattern to monitor any change in the dimensions in the pattern and provide a signal in response; and a controller operably coupled to the optical reader for determining the tension in the string of casing in response to the signal provided by the optical reader.