Perpustakaan Digital ITB

The long-term integrity of cement sheaths in CO? sequestration wells is essential for the safety and effectiveness of carbon storage. During CO? injection, cement is subjected to both tensile and compressive stresses, which over time can lead to degradation and cracking. This study quantitatively models the mechanical degradation of API Class G cement under the pressure conditions experienced in the Snøhvit Field, using the Finite Element Simulator. A 3D radial model of the Tubåen Formation and a time-dependent pressure ramp of approximately 3 years are used to replicate real-world injection conditions. The transient nonlinear analysis reveals that tensile failure initiates on day 154, when the tensile stress of 486 psi exceeds the cement’s tensile strength of 438 psi, causing a sudden crack of approximately 53 ????m. This crack rapidly propagates to 470 ????m by day 176. After this, cyclic confinement leads to oscillating crack widths, stabilizing above 400 ????m, indicating the cement permanent damage. Meanwhile, compressive stresses remain below the cement’s compressive strength throughout the simulation. These results highlight tensile strength as the critical parameter governing cement sheath performance in CO? sequestration wells, offering important insights into the mechanisms of cement degradation under increasing pressures.