Perpustakaan Digital ITB

This study investigates the mechanical integrity of the cement sheath in a vertical well using a finite element method (FEM)–based numerical approach, focusing on fracture behavior under increasing bottom hole pressure (BHP). Simulations were conducted at three different depths to evaluate the influence of in-situ stress variations on fracture initiation and propagation. The model incorporates multiaxial stress from geologic stress regimes combined with internal hydraulic loading, with failure criteria based on stress, strain, and crack width evolution. Results indicate that compressive failure dominates over tensile failure, with crack development concentrated around the perforation zone. Greater well depth correlates with a higher critical BHP required to initiate mechanical failure, reflecting the beneficial effect of lateral confinement leading to enhanced structural integrity. Tensor field visualization confirms that fractures primarily propagate axially and radially around perforations, in agreement with localized stress distribution theory. The findings emphasize the importance of site-specific geomechanical evaluation prior to injection operations and suggest that integrating stress–strain and crack width indicators can enhance the predictive accuracy of cement failure modeling.