Protecting Offshore Pipelines from External Interference: Dropped and Dragged Anchors.

Abstract

In congested districts of offshore Oil & Gas Industry, merchant ship traffic, offshore operations or fishing activity may interfere with pipelines in service, which rest exposed on the seabed. Despite the shortcomings of existing technology and knowledge, operators' concerns still emerge after yearly surveys that show new pipe damages from external mechanical interference, not to mention a few ruptures occurred in the last decade due to anchor hooking! Therefore, a question arises: do we know enough about the potential threats to offshore pipelines from external, particularly anchor, interference? The scope of this paper is to outline the rationale of pipeline protection works, both at design stage and in service, with focus on open issues influencing decisions on how and due time to intervene across busy offshore districts. In shallow waters and brown fields, e.g. in the Arabian Gulf and Gulf of Mexico, the consequences, not only economic but also safety wise, of a severe interference, might be relevant. The shallower the water depth and busier the area, the more stringent the safety targets. Sometimes, even having met acceptance criteria, backed by competent engineering modelling and use of state-of-the-art tools, field evidences from early operation may lead to rethink of purpose protection works, to be implemented with minimum impact on field operations. Marine pipeline damage prevention and awareness, from both vessel and field operators, is often a unique way to limit risks and unplanned interruptions.