Auger TLP Topsides Facilities: Design And Construction Overview
Authors: Bacon M.L. , Bailliet R.M. , Brooks A.M. , Forster L.D. , Harris K.H. , Lindsay M.S. , Schafer D.R. 
Published: October 2008

The topsides facilities for the Garden Banks 426A, "Auger" Tension Leg Platform (TLP) include full production and drilling rig facilities plus shared facilities such as accommodations, utilities and power generation. From 1988 through 1993, a diverse engineering and construction team utilized multiple consultants and fabrication contractors to design and construct numerous modules and skids for subsequent integration into the TLP deck structure (see schedule overview - Figure 1).

The project team developed design and construction strategies, consultant and contractor selection strategies, and coordinated the actual design and construction process. The team took the initial design basis for various TLP systems (e.g., production, drilling, utilities, power generation, etc.) and by combining existing technology with new, unique ideas, developed a state-of-the art facility which will ultimately drill, complete and produce oil and gas wells in 2860 ft of water at Garden Banks 426A.

The TLP deck, complete with modules, was mated to the hull in October 1993. Commissioning activities were performed simultaneously as associated interconnecting piping and electrical work was completed. The entire TLP was ultimately towed to its Gulf of Mexico site for tendon installation in December 1993 with final start-up scheduled for 1st Quarter 1994.

DESIGN DEVELOPMENT

A. Consultant Usage

Multiple design consultants provided the wide variety of skills required and fulfilled the substantial engineering and drafting manpower requirements. Following requests for quotations, the consulting firms were selected based on engineering/drafting expertise, cost, and manpower availability.

The contracts were generally distributed as follows:Production Process and Utilities SystemsDrilling Rig SystemsPower Generation/Distribution SystemsControl SystemsAccommodationsRegulatory Submittals

Detailed engineering contracts were awarded in the 2nd Quarter of 1988. The primary engineering/drafting effort was concluded in mid-1991.

B. Design Influences

Although many different factors influenced the final design basis, several major factors are as follows:Design ParametersNumerous design parameters such as production flow rates, drilling depths, drilling loads and environmental effects influenced the design of various topsides systems. These parameters are discussed in the "Design Basis" section.Weight BudgetA critical consideration for TLP design is payload weight. Not only is weight costly, but a change in payload weight during the design cycle can have significant cost and schedule impact. Therefore, a topsides weight budget was established during the conceptual design phase and an estimated weight (plus contingency for error and unidentified items) and center of gravity was provided for each module, building, skid, etc.

This weight budget was then utilized by the TLP deck and hull structural designers. As topsides design progressed and additional items were identified, weight estimates were refined and the weight budget updated. The weight budget was ultimately "frozen" in December 1989 so that deck and hull structural analysis could be finalized.

After fabrication, all items greater than 100 tons were weighed with load cells for final verification.