Collapse Analysis of the Casing in a High Temperature Geothermal Well

Abstract

Casing failures such as collapse is the suspected result of combined loads and impurities in the casing and/or the surrounding concrete. In this paper a simple case of collapse caused by a geometric defect in the casing is analyzed using the finite-element method (FEM). The collapse of an impaired casing and its resulting shape is investigated with respect to the external supporting concrete. A specific load history for the production casing is used in the analysis. The first load consists of the external pressure of the cement slurry during well cementing, followed by subsequent cyclic thermal loads. The load history represents the fundamental loads which occur during the lifetime of a typical well. The magnitude of the external pressure and its stimulus for later collapse is also analyzed. The collapse shape obtained in the FEM analysis is similar to collapse shapes that have been observed in geothermal wells.