Numerical Investigations of Tensile Induced Debonding Due Temperature Variation in Geothermal Wells

Abstract

Geothermal wells are often exposed to temperature variations during their lifetime. In a previous study we have shown that shear bonding strength is limited and decrease with curing temperature of the cement. In a new study we have investigated the tensile debonding of cement-casing system as a function of casing size and temperature variation. While most of the past studies focused mainly on debonding or not debonding situation, our detailed finite element study focused on the size of the debonding gap, the so called micro annulus. We found that tensile debonding can occur at relatively low temperature variation and this failure will result in a micro annulus that will affect the geothermal well integrity. Furthermore, our study found that the surrounding formation properties could play a positive role towards casing-cement debonding.