Offshore pipelines installed in the Arctic and other cold regions are often buried to reduce the risk of damage from ice gouging, upheaval buckling, and other loading challenges specific to the region. Pipeline burial is normally achieved through trench excavation and backfill.
Pipelines have been buried using a wide variety of technologies including conventional excavation equipment, hydraulic dredges, ploughs, mechanical trenchers, and jetters. In order to determine a preferred trenching method for a particular route, consideration must be given to a variety of factors. The water depth range and maximum trench depth required along a route are primary considerations when evaluating the various trenching technologies. These are “show stopper” route parameters, which have a direct impact on the ability to complete a particular trench.
If multiple trenching technologies satisfy the primary considerations, a variety of secondary considerations must be used to determine the preferred solution. These include parameters such as seabed geology, backfill method, seabed slopes, and environmental sensitivity. The preferred solution may not always be the only method of excavating the trench, but it may have an advantage compared to other technologies for the route under evaluation.
As developments are proposed for areas that experience relatively deep ice gouging (up to 5m), burial depth requirements will exceed the capabilities of current technologies. New technologies capable of working in deeper water, achieving greater burial depths, achieving reasonable trenching advance rates, operating in harsh environments, and trenching through variable and difficult seabed soils will be required.
