In most marine guidance there is a distinction made between different lengths of move. Often they are described as a field move, an inter-field move, and an ocean tow. The DNV Rules for MOU stability describe a field move as one which can be carried out in favourable weather in less than 12 hours. The approach reflects the greater degree of preparation required for ocean tows.
Today there is always the option of using a heavy lift vessel to move either a semi-submersible or a jack-up. However it should be remembered that considerable water depth in sheltered conditions is required at both ends. In all cases timing and costing is of the essence, and while a dry tow is generally preferable for all long distance jack-up moves, under some circumstances it can be financially and operationally viable to engage a substantial towing vessel to move semi-submersibles over distance.
Marex can provide consultants to advise on all aspects of ocean tows. Whether it would be appropriate to contract a heavy lift vessel, and to investigate loading and unloading locations anywhere in the world. Should a wet tow be selected, then Marex can manage all aspects of the operation on behalf of their clients. The tasks required are to ensure the suitability and the integrity of the unit, and its ability in terms of the towing connections and the bridle to withstand the towing forces during all weather conditions. In addition the towing vessel, or vessels, need to be assessed for suitability and their ability to provide the service for the duration of the operation.
There are other aspects of long distance tows, such things as crew changes and refueling opportunities have to be considered, and unless properly managed all can involve risks for the rig. Marex can provide towmasters for the operation and offer the necessary management to ensure that the operation can be completed as rapidly and safely as possible.