A weighted nonlinear regression-based inverse model for interpretation of pipeline survey data

An inverse model, useful for interpreting pipeline survey data in terms of the physical condition of pipe coating, was developed by coupling a boundary-element forward model with a nonlinear regression algorithm. The forward model accounted for the passage of current through a three-dimensional homogeneous medium and yielded soil surface potentials for given pipe/anode configurations and pipe coating properties. The number of regressed parameters was reduced by using a function for coating resistivity that allowed specification of coating defects. A weighted simulated-annealing nonlinear regression algorithm facilitated analysis of noisy data. A method was developed to determine the appropriate number of fitted parameters. The procedure is demonstrated by simulation of a coated underground pipe segment protected by a sacrificial anode. © 2004 Elsevier Ltd. All rights reserved.