Experimental and numerical study on the pushout shear strength of conventional and expanding cement–casing sections for well integrity

A good bond between the well casing and cement is often considered essential for avoiding generating microannulus leakage paths along the interface between the two materials. A common method for characterizing the casing-to-cement bond is to perform laboratory pushout tests. This study comprehensively investigates pushout tests conducted on conventional class G and well cement samples containing a 3% expanding additive. Firstly, experimental pushout tests were performed on various full-scale diameter cement samples, allowing for an accurate evaluation of their bond strength. Secondly, a finite element (FE) model incorporating cohesive-based surface behavior and a friction formulation is proposed to simulate the behavior of cement sections under pushout loading conditions. The results from the FE model were compared with the experimental responses, demonstrating good agreement in simulating the pushout behavior of conventional class G cement and expanding cement samples. Notably, the significant findings of this article fill a critical gap in the literature. Few experimental tests and elastoplastic numerical models have been carried out in the literature to comprehensively capture the damage evolution and predict the pushout shear strength in cement-casing interactions in P&A scenarios.