A Reliability-Informed FMECA Approach to Integrity Risk in Well Systems

Failure Modes, Effects, and Criticality Analysis (FMECA) provides a rigorous and transparent framework for identifying potential failure modes in well systems, evaluating their consequences, and prioritizing controls throughout the life cycle, from design to decommissioning. This work formalizes a five-step implementation consisting of preparation, structural analysis, functional analysis, failure analysis, and action or optimization. Risk priority is established using three scored factors: a consequence-based Severity scale, a Reliability measure derived from component reliability modeling that maps failure rates to a mission-time probability of failure, and a Detection scale that reflects demonstrated surveillance and testing performance, including monitoring cadence, function-test intervals, and diagnostic latency. The outcome is a living risk register that links each high-priority failure mode to explicit prevention and detection measures, accountable ownership, deadlines, and verification criteria. The FMECA is embedded within a comprehensive well-integrity analysis, ensuring that its outputs are consistent with barrier reliability models, leak-path assessments, consequence evaluations, and aggregate well risk profiles. In practice, the register consumes reliability values from the modeling workflow, aligns failure modes with barrier and leakpath structures, and presents color-coded priorities that support surveillance planning, maintenance selection, and work-over justification. This integrated configuration ensures traceability from component-level assessments to fieldlevel decision-making, allowing for consistent comparison across wells and various operating contexts. Recognized limitations of conventional prioritization schemes, including non-uniqueness, scale compression, and sensitivity to subjective ratings, are addressed through transparent rating guidance, reliability-backed occurrence mapping, and periodic recalibration as operational evidence accumulates. The formulation provides a defensible basis for ranking integrity risks and directing resources toward the most consequential threats while maintaining auditable links to the wider well-integrity workflow.

Keywords: FMECA, well integrity, failure modes, risk prioritization..