Abstract: In 1990’s, The expandable casing technology was a new drilling technology to save the hole diameter, in the world, but it is now at the stage of theoretic research in our country. The mechanics model of the expand process of the expandable casing with the elastic-plastic finite-element contact question of the ADINA software was established. Through choosing different value of the angle of the expansion cone, the detailed computer simulation analysis of the expand process that expanded the diameter of the N-80 steel tubular from 244.5mm to 298.4mm was done under the same work condition, and under the foundation of qualitative and quantificational comparison of the equivalent stress, the contact pressure, the residual stress, the expansion cone and the axial shrinkage of the tubular, the optimal angle of the cone 12.30 degree was obtained. It provided the supports for the structural design of the expansion cone.

Key words: expandable casing, expansion cone, contact cone angle, computer simulation