Abstract: Stresses in Cement Sheaths

FLECKENSTEIN, WILLIAM

This paper presents the results of a finite element study of the stresses in cement sheaths under a variety of environmental conditions. These conditions include varying the internal casing pressures, cement material properties, and insitu formation stresses.

In 1990, Goodwin and Crook performed experiments on cement sheaths to determine the conditions for failures (SPE #20453). The authors in this paper expand on their work by mathematically modeling their experimental apparatus. The Von Mises, tangential, and radial stresses within cement sheaths are determined using the finite element method. The stresses within the cement sheaths are determined for various internal casing pressures and are compared to the original experimental results. This data is used to determine the failure stress conditions in the cement. In addition, relationships are developed between the cement material properties and resulting stress profiles for various cement slurries. Finally the effects of insitu formation stresses are examined to show the relationship between higher insitu formation stresses and the lower tangential stresses in the cement sheath.

AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California