Design And Fabrication Of The Auger Deck
Authors: Arnold Peter , Kenney J.J. , Knoll D.A. , Stuart C.R. , Gros G.D. 
Published: October 2008

The Auger deck structure, covering an area approximately 300 feet by 300 feet, is an open truss design that provides support for nine major modules and numerous equipment skids that are required for drilling and production operations.

The design of the deck was accomplished in four distinct cycles that increased in sophistication as the design requirements matured. The concept cycle allowed for the efficient evaluation of major system configuration alternatives. The preliminary cycle provided realistic weight estimates of alternative truss configurations in the deck. Once the final configuration was set, the design and analysis cycle was utilized to develop construction drawings. The final cycle was during the early construction phase to adapt the design to the contractors capabilities and fabrication plans.

The deck was fabricated and assembled by McDermott Inc. at their facilities in Amelia, Louisiana. The primary trusses, assembled from prefabricated nodes and girders, along with other prefabricated subcomponents, were constructed in buildings, transported to the erection site and assembled to form the complete deck. Major modules and other equipment skids that were provided by Shell Offshore Inc. were integrated into the structure as the structural components were erected.

The deck contract specified that the contractor establish and maintain a Quality System documented in a formalized Quality Manual and Quality Plan. The Quality System was patterned after the requirements of International Organization for Standardization (ISO) 9002. This was the first time Shell Offshore Inc. entered into a major fabrication contract with the contractor performing the primary quality control and assurance functions.

The Auger deck was a very complex structure to design and fabricate due to its wide range of functional requirements, the novel systems and strict weight budget requirements. Designers, field staff and the contractor worked continuously to improve the design and construction methods to improve productivity and schedule without sacrificing quality.

STRUCTURAL DESIGN

The Auger deck structure, as shown In Fig. 1 without modules, is an open truss design that provides support for the equipment required for drilling and production operations. A 70 ft. by 190 ft. wellbay for drilling operations and the production risers was provided In the center of the structure. Two main deck levels support major prefabricated modules, skids and small equipment packages. Elastomeric bearing pads at the lower deck level are provided for support of the major modules as shown in Fig. 2. These pads Isolated the modules from the fatigue damaging cyclic wave loads present In the lower deck framing.

All major vertical and horizontal truss members were fabricated from rectangular cross section tubulars (boxes). Supports for top-tensioned production risers are Integrated into the truss members of the central wellbay, with an Intermediate deck level for access to the wellheads. A horizontal truss system at the lower chord level reacts the squeeze-pry loads due to wave forces on the superstructure consisting of the hull and deck. A fixed drilling rig substructure was installed above the center of the wellbay for drilling and completion operations.