Shell Expro ("Shell U.K. Exploration & Production", operators in the U.K. North Sea on behalf of Shell and Esso) have recently reviewed well vertical movement on platform wells. In this paper the different types of well vertical movement are described and well compression effects are considered in detail. It has been found that short term well compression and thermal effects are of greater significance than any long term well settlement effects. Well compression effects can be estimated by regarding the casingstrings of the well as a set of parallel springs. Total compression during drilling and completion of a well is mainly influenced by the top of cement level supporting the 20″ or 18.5/8″ casing. Measurement of well compression effects can allow estimation of the top of cement level of this casing.