Introduction

British Petroleum has tong had a different approach to the underwater protection of fixed structures from that of other oil companies. The major point of divergence is the use of paint coatings in conjunction with sacrificial cathodic protection. The technique has proved remarkably successful, especially for deep water structures. This paper reviews the history and development of the technique and it discusses in greater depth its application to the deep water Forties field structures. The author has insufficient knowledge of the particular applications of competitive techniques to make safe comparisons. Those with more intimate knowledge must judge.

HISTORY AND DEVELOPMENT

BP formed its ideas through the 1960s. which was a period when it was developing offshore oilfields for Abu period when it was developing offshore oilfields for Abu Dhabi Marine Areas (ADMA) and a gas field at the West Sole in the southern North Sea. Both had water depths in the order of 30 m. and were developed with a lumber of small structures. Some know-how was available in the late 1950s from mainly US sources but it was some of BP's own work on the protection of salt water fed cooling equipment that was found to be the most convincing. Particularly the work had shown the value of coatings for the improvement of the spread of protection and for the extension of anode life. If coal tar/epoxy paints had not been developed around the same time then the technique would probably not have been a success. The pure epoxies used for the cooling water work were too expensive and too difficult to apply for use on structures. The bituminous paints used for a few early ADMA structures suffered badly from attack by marine growth. Coal tar/epoxy has been proved to be cheap enough and sufficiently tolerant in application. Recent inspections on the West Sole have shown no coating degradation after ten years service. Minor mechanical damage has occurred due to abrasion by for instance, wire rope debris and during marine growth removal.

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