Remaining Useful Life, Structural reliability methods, Failure rate , Mean Time to Failure, Casing design
Resumo
This work proposes a reliability-based framework to estimate the Remaining Useful Life (RUL) of well tubulars throughout the lifecycle of oil and gas wells. The RUL estimation is supported by a probabilistic analysis that accounts for uncertainties in geometrical and material properties, based on failure modes defined in the API/TR 5C3 standard. The framework is applicable to both design and monitoring phases, incorporating degradation mechanisms such as corrosion. The methodology integrates a mechanical model to calculate safety factors and failure probabilities associated with internal and external pressures and axial forces, as defined by API/TR 5C3. Structural reliability methods combined with Monte Carlo simulation are used to propagate uncertainties and to update failure probabilities over time. The framework enables the estimation of key integrity indicators, such as the failure rate and Mean Time to Failure (MTTF), essential for RUL assessment. A case study is presented, utilizing statistical data on mechanical properties, and degradation effects. The proposed methodology allows for integrity assessment under both serviceability and survival load conditions, incorporating advanced features such as the effect of corrosion in several loading scenarios. By capturing the variability of mechanical and geometrical parameters over time, the approach provides a robust basis for evaluating the mechanical condition and failure probability of casing and tubing strings. These results support more informed decision-making in RUL analysis and contribute to the improvement of well design and monitoring strategies
