Induction effects of 2D structures on buried pipelines

OSELLA, A.,; MARTINELLI, PATRICIA; FAVETTO, A.; LÓPEZ, ERNESTO

IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Lugar: New York; Año: 2001 vol. 40 p. 197 - 205

0196-2892

The implementation of cathodic protection systems is very complicated since many factors can contribute for current flowing off the pipe. The design requires the characterization of the parameters impacting the corrosion process, such as soil resistivity, size of the pipe and quality of the coating. In the present paper we study the effect of geomagnetic fields on the pipe-induced currents considering it as an additional cause of corrosion. A theoretical method previously implemented to model the currents induced on pipes embedded in homogeneous soils, indicated a dependence between the intensity of the currents and the electrical resistivity of the soil and predicted that a drainage of current through the pipe would occur at zones of shallow electrical discontinuities. Here, we present another method for the calculation of the induced currents that lets to consider also multilayered structures and lateral discontinuities in the earth resistivity. Applying this method, we quantify the currents induced in pipelines embedded in different bidimensional structures, in order to obtain an estimation of the effects produced by the presence of such kind of terrains.Then, we applied this method to model measured data. Field work was performed along a 200 km-route of a pipeline-system. In this zone, the pipe-to-soil potential was measured at different sites and a geophysical study was made to determine the discontinuities in soil resistivities . We obtained a correlation of the measured currents and soil resistivity that is consistent with the theoretical predictions. This fact strongly suggests that in zones of deep high resistive contrast, the current circulating in the pipes increases, being the consequent risk for the coating and the cathodic protection adjusting, not only dependent on the resistivity of the ground-bed but also on this deep structure.