The analysis of indirect inspection data is a critical factor in conducting a successful External Corrosion Direct Assessment (ECDA) process. Any “out of range” data must be validated prior to being considered an ECDA indication. Furthermore, standard methods of validating the accuracy of the field data must be reviewed when special conditions are present.
This paper covers a number of lessons learned by dealing with less well-known sources of measurement error, during nine years of ECDA application on more than 100 projects.
Topics like “clipped” gradients during the DC Voltage Gradient (DCVG) Survey, AC current drain by well casings during influence testing, and sharp drops in potential indicating the presence of an underground isolating flange are discussed in detail in this paper.
