5,000 KM ROW CP SURVEY ANALYSIS AND THE POTENTIAL ADVANTAGES OF THE - 100 MV POLARIZATION CRITERION FOR THE CP OF AGED COATING OIL AND GAS PIPELINES IN GULF AND NORTH OF MEXICO

摘要

A survey of over 5,000 Km of pipelines was developed in 2006 to assess the CP performance of the pipelines located in the main ROWs of the Mexican States of Veracruz, Tamaulipas, Nuevo Leon, Coahuila, Durango, y Chihuahua. Historically the CP surveying in the region has been done measuring the ON potentials and applying the -850 mV criterion to these measurements. By employing a set of several satellite synchronized by GPS instrumentation, the instant OFF potentials presently reported resulted considerably more electropositive, and the compliance to the -850 mV criterion was found under 50%, in a set of over 5,000 measurements in this important region of Mexico. Besides the needs of new CP infrastructure, we report the main causes that impair the compliance of the CP to the -850 mV criterion of the NACE RP 0169 - 2002. Among these are the problems of isolation of the pipelines to main processing units such as refineries, pumping or metering stations. Findings of irregular, non instrumented or even controlled electrical interconnections between the pipelines in production or abandoned, were also pointed out as major causes for the insufficient CP. Old and damaged coatings of pipelines with many years in service contribute tu limit the CP compliance to codes. Out of service and poorly coated pipelines were found sharing the CP systems in the ROWs, with very deleterious effect on the overall CP performance due to the elevated current demand of abandoned pipelines lacking coating maintenance. In the present scenario a remarkable effort is to be made to pursue the electrical isolation of the pipelines, the needed coating reparations, as well as the use of the 100 mV potential criterion was concluded to be a sound approach to maximize the pipeline operational compliance to the integrity management programs in the Gulf and North of Mexico.