Casing-cement interaction is considered to be the critical element in maintaining the correct well integrity for life of the well. The literature reveal not a large amount of studies focused on casing-cement interaction, but one of the most focused parameter is the cement interfacial bonding shear strength. The importance of this cement mechanical properties lies in the fact that it is considered to be one of the main parameter that affects the micro annulus forming and thus the well integrity. Many researchers have implied that this mechanical property should be a function of the interface and thus depends on the casing outer surface roughness and chemistry as well as the cement composition and curing conditions. Although several testing methods have been considered in the past, the results in this paper are using a novel, yet simple method, that can help in focusing on the casing-cement interaction in a statistical way. This method was proposed by Teodoriu et al (2019).
Our research have focused in understanding how the temperature will affect the above property, and our results have shown that elevated temperatures will strongly affect the casing-cement interaction. Figure 1 shows the evolution of the cement interfacial bonding strength with temperature, highlighting that elevated temperatures are decreasing the bonding between cement and casing.
Our presentation will first present a short review and detailed discussion of current experimental methods for interfacial bonding shear strength. The second part will show our laboratory experiments and the results, being followed by a discussion about the implications to wellbore integrity and ways to improve it.
Figure 1: Correlation showing the relationship between unconfined cement strength (UCS) and interfacial bonding shear strength of class H cement.