Abstract: The key of the expandable tubular technology is dependent on the selection of material, connection and mandrel; expansion force is a base to design and check the strength of expanding tool. Considering the effect of the mechanical properties of steel, the spatial configure of the casing, expandable technology, the cone angle of the mandrel, the friction and lubrication between the mandrel and the inner wall of casing on the expansion force, the expansion force equation is put forward according to the plastic property of casing and plastic deformation theory, the equation calculating expansion force is established by using main stress method, then the expandable experimentation of casing is done, and the calculation results of the analytic model are coincident with the experiment data, which indicates the calculation model is reliable. It can be used in practical operation.

Key words: expandable tabular, expansion force, equation, expansion test, well structure