Angola Cameia Development Casing-Settlement Calculations

Abstract

The amount of axial settlement of casings supported by regions of axial elastic foundations is computed. The differential equation of axial equilibrium, including the foundation stiffnesses, is solved by use of cubic axial finite elements. The analysis is applied to 101 m of a vertical 914-mm (36-in.) casing supporting a 559-mm (22-in.) casing running from 3 m above the mudline to near the bottom of the 1201-m hole. The upper casing is supported by a region of layered clay sediments. The lower casing has a long openhole region, followed by a bottom region encased in cement. A series of loading increments is applied, with the connection of the tree/blowout preventer (BOP) as the last. The settlement at the mudline was calculated to be less than 0.1 m. This study shows that for weak upper foundations, a good cement job is needed to support the tree/BOP without large mudline settlements.