1 WELLBORE INTEGRITY AND CEMENT FAILURE AT HPHT CONDITIONS

This paper presents the development and optimization process of a new high-pressure, high temperature experimental concept for testing wellbore cements on their behavior in cyclic loading situations. The new specimens developed within this paper allow testing cement under wellbore conditions and geometry. For this, a ring like cement sample was designed. After a confining pressure is applied, the cement can be exposed to inner pressure cycles that simulate variable internal pressure. The failure behavior of the cement materials can be evaluated. The failure mechanism and reasons for failure itself are also described and further ways for stress analysis are presented. An analytical and a finite element model were used to calculate the stresses in the cement sheath and to allow failure prediction and transfer of the results to theoretical models. The integrity of wells is essential for their life time. This paper provides an overview of reasons for cement failure and additional methods and techniques to avoid the mentioned problems