The standard evaluation methods for MFL-A inspections are based on simple calibration approaches that lead to stable results as long as the corrosion tends to be isolated and shallow. This paper presents a method suitable for complex and deep corrosion that utilizes FEM simulations on ultra-high resolution MFL-A data.
It follows two main aspects: The first aspect is to learn from dig verifications by using laser scans of corrosion anomalies as a finite-element model to simulate the corresponding magnetic flux to confirm the magnetic flux measurement of the ILI tool. This way the simulation model is validated.
The other aspect is to apply the achieved insights as a new depth sizing concept: the complete corrosion geometry as indicated by the ILI measurement is put into the validated FEM model to simulate the magnetic flux that should correspond to the one measured by the ILI tool.
In this new sizing method the influence of complex corrosion is considered, as all surrounding features are part of the model. Several models are calculated in order to minimize the impact of ambiguity of depth results. This increases the accuracy and, ultimately, stabilize pipeline operators’ integrity assessments.
In the big picture, novel approaches to MFL-A data interpretation, such as FEM, empower operators to make more informed decisions specific to their asset integrity management programs while reducing the costs, uncertainty and conservatism associated with these decisions.