Safe and cost-effective single-lift removal technology for decommissioned fixed offshore steel platform substructures (“jackets”)
The Patented DeltaLifter Principle
The DeltaLifter is a single-lift tool specifically developed for safe & low-cost removal and transportation to shore of large decommissioned offshore platform jackets, without use of heavy-lift crane vessels or flat-top barges. The DeltaLifter enters the decommissioning process after the platform deck has been lifted off and piles and other subsea connections have been cut. The sole purpose of the DeltaLifter is the safe removal of the jacket, which normally is the largest and heaviest part of an offshore fixed steel platform.
The DeltaLifter being manoeuvred into position (by 4 tugs), no anchors are used. The DeltaLifter is unmanned and power and signals are transmitted through cables from containerised power and control units on the deck of an adjacent supply boat. All systems are fail safe and have full redundancy.
The DeltaLifter is ballasted down and carefully positioned alongside one side of the jacket. In a shallow-water mode the DeltaLifter may rest and rotate on the seabed if appropriate; in a deep water mode it will connect higher up. Pre-positioned cradles on the DeltaLifter deck will serve as guide structures for mating with the jacket.
The DeltaLifter being connected to the top of the jacket. No underwater work is required. All necessary structures for connecting the jacket to the DeltaLifter will have been installed prior to arrival of the DeltaLifter. Most (or all) seabed connections will have been cut off prior to the arrival of the DeltaLifter using proven methods
Tilt-up operation is achieved by controllled de-ballasting of the DeltaLifter
The DeltaLifter in its tow-to-shore condition. The tow-to-shore is carried out in a semi-submerged condition. This enhances the superior motion characteristics of the DeltaLifter.
The DeltaLifter is ballasted on an even keel and the jacket is skidded onto a recycle yard using conventional hydraulic skidding technology. The maximum draft of 8 meters allows access to a number of alternative recycle sites.
Animation Video of the DeltaLifter Removal Cycle
The DeltaLifter Features
DeltaLifter units can be built in different sizes, each designed to remove a range of jackets within each unit’s dimensioning limitations.
Each DeltaLifter unit will provide:
- A safe solution, minimizing subsea and offshore work. No divers, and no operators onboard the Jacket or the DeltaLifter during operations.
- A flat deck area to accommodate support cradles – as part of the removal preparation the robust cradles are welded on deck of the DeltaLifter in a pattern to match the geometry of each jacket, serving the dual purpose of guides during mating and sea-fastening during towing.
- Low wave loads and reduced chance of impact damage on the jacket during connection, lifting and towing.
- A shallow draft allowing access to a range of recycling sites. The flat deck can accommodate various skidding or wheeled transport system configurations for jacket transfer to shore.
- A robust box structure that is easy to fabricate, operate and maintain
- Benign motion characteristics due to limited water surface area during positioning and tie-up – towing to shore can be done in partially submerged position
- Low capital and operational costs – the unmanned DeltaLifter is moved by means of leased tugs. Power and controls to operate pumps and valves are supplied through an umbilical cable from a containerised power unit on deck of an adjacent OPV.
- Ample weather tolerance, permitting a wide operating window and reduced risk of down-time.
- Short operation time offshore, maximizing the number of removal operations per season
- The DeltaLifter design and operating principle is covered by several international patents.
The DL-8000 – approximate dimensions in metres.
The DL-8000 is designed to remove jackets of a wide range of configurations weighting up to 8,200 tonnes in water depths ranging from 60 to 120 m. Other DeltaLifter versions can be designed to handle different size ranges of jackets.All figures are subject to change.
|Overall length||115 m|
|Maximum width||100 m|
|Width between columns||76 m|
|Column height from pontoon top||37 m|
|Column and pontoon width||12 m|
|Steel weight & equipment||9,600 t|
|Max jacket weight||8,200 t|
|Fixed ballast||5,000 t|
|Maximum loaded||22,800 t|
The DeltaLifter Advantages
Elimination of almost all underwater work (other than pre-mobilisation cutting of seabed connections). The fixed temporary connection between the jacket and the DeltaLifter is made above seawater level, before the turning and lifting operation starts. There will be no persons onboard the DeltaLifter or on the jacket during the lifting operation or towing. The time offshore is shortened.
The DeltaLifter is an environment friendly method of jacket removal. It minimises offshore work and allows removal in one piece thus maximising onshore recycling. It uses existing tugs for transportation and only needs power during operations to operate its pumps and valves.
The base version of DeltaLifter targets a range of jackets with a weight up to 8200 t. For larger and heavier jackets, the design can be scaled to the required size.
Highly Competitive costs
Through its simplicity, the DeltaLifter delivers significant financial savings in both capital outlay and operating costs in comparison to other jacket removal technologies. Reduced operating costs are achieved thought simplicity of operations, low maintenance, reduced need for extensive underwater dive operations, and lower levels of manpower required throughout the removal and transportation phases. The robust DeltaLifter is designed for a long economic life.
Reduced operating time
Due to its shape, the DeltaLifter has benign motion characteristics, allowing operations to continue even during adverse weather conditions. The possibility of impact damage during the mating operation is low. In comparison with alternative methods, jacket removal time is significantly shorter due to simplified field operations and less chance of weather-induced downtime. A shorter turnaround cycle means more operations in a season.
The DeltaLifter Development
The DeltaLifter concept is a result of extensive hydrodynamic know-how combined with offshore operations experience. The principal inventor, Dr Birger Natvig, has advised oil companies, naval architects, offshore contractors, terminal operators and shipowners on a range of hydrodynamic, offshore operation and floater design issues. He served as president of the International Society of Offshore and Polar Engineers (“ISOPE”), has authored a number of scientific publications and has served as a speaker and moderator at several professional seminars. He holds a BSc degree in naval architecture from the University of Strathclyde and earned an MSc in ocean engineering and a PhD degree from the University of London on non-linear motion behaviour of floating structures.
His partner, Professor Tor Vinje, earned degrees in applied mathematics and a doctorate in ship structure, and taught at the University of Trondheim and the University of Oslo in Norway as well as the University of Michigan in the US. A recognised authority in hydrodynamics, response statistics, system mechanics and structural engineering, he has held senior technical positions in Det Norske Veritas, Aker Marine Contractors, Norwegian Contractors and Seaconsult AS; in addition, he has authored number of scientific papers and served as expert witness in international arbitrations.
Other team members include naval architects and professionals with extensive experience in the offshore energy industry, in particular in wave response analyses, mooring system analyses and calculations related to a variety of fixed and floating offshore installations.
DeltaLifter Technologies AS, the owner of DeltaLifter patents, has entrusted the further DeltaLifter commercial and technical development to International Contract Engineering (“ICE”). This would include optional development of design packages for Class approval and construction of prototype units. As Europe’s largest independent marine design bureau, ICE has a 50-year history and clients world-wide, including in the offshore energy industry. ICE will also supervise construction and commissioning of prototype DeltaLifter units, and will provide engineering services to builders, owners and operators of DeltaLifter units.