Retrofit cathodic protection of marine pipelines associated with petroleum production

Description

Monograph, Center for Marine Materials, Florida Atlantic University, 2001, p. 68Marine oil and gas transportation pipelines have been in service in the Gulf of Mexico. These lines are invariably protected from external corrosion by a combination of coatings and cathodic protection. Five research tasks were identified and addressed as:a) Development of a new approach to cathodic protection design for new marine pipelines,b) Development of an inclusive, first principles based attenuation model for marine pipeline cathodic rotection,c) Verification of the proposed cathodic protection design method and attenuation model,d) Definition and examination of critical issues related to pipeline cathodic protection retrofits,e) Recommended protocol for retrofit cathodic protection design of marine pipelines.Structural and high strength steels have historically been the only economically viable material for construction of marine petroleum transport pipelines. However, the inherent lack of corrosion resistance of this material class in sea water and the consequences of pipeline failure require that corrosion control systems be designed, installed, and maintained such that a high degree of reliability is realized. Reliability considerations have become magnified in recent years with the transition from relatively shallow to deepwater installations. While cathodic protection has historically been employed as the sole corrosion control methodology for the submerged portion of petroleum production platforms, both mobile and fixed, the one-dimensional nature of pipelines is such that the combined use of coatings with cathodic protection is required. In the former case (platforms), anode resistance and structure current density demand are the fundamental parameters that are important in cathodic protection design. For pipelines, however, coating quality and metallic path (pipeline) resistance must also be taken into account, at least in the generalized case. Cathodic protection systems, either for pipelines or for other engineering applications, can be of either the impressed current or galvanic anode type. For marine pipelines impressed current cathodic protection systems are invariably limited to1) proximity of landfall where protection can be provided seaward by a shore-based rectifier and anode array to a distance that is defined by the “throwing power” of the system and 2) pipeline runs between two platforms where the distance is sufficiently short that the entire line can be protected by a single rectifier and anode or anode template at one or both ends.CONTENTS:Executive summaryTables of contentsNomenclatureIntroductionProject objectivesDevelopment of new approach to cathodic protection design for new pipelinesDevelopment of an inclusive, first-principles based attenuation model for marine pipeline cathodic protectionVerification of the proposed cathodic protection design method and atenuation modelDefinition and examination of critical issues related to pipeline cathodic protection retrofitsRecommended protocol for retrofit cathodic protection design of marine pipelinesBibliographyApendix A - Derivation of the first-principles pipeline attenuation equationApendix B - Spacing distance between Ccossing pipelines