This paper presents simple models to describe casing loading and wellhead movement during the completion (mechanical) phase and the production (thermal) phase. A wellhead-drop incident is investigated. The theory is simple, and the formulations are suitable for hand-calculation or spreadsheet. The presented models are suitable both for conventional and HP/HT (high-pressure/high-temperature) wells.

This paper also investigates an abrupt wellhead drop of several feet for an offshore well. The incident took place during wellhead cooling following a routine shutdown. The expected wellhead cooling contraction did not occur. After a cooling period the wellhead suddenly released. A corroded segment of the surface casing collapsed and the wellhead dropped.

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