The intent of this paper is to demonstrate the important role that the functionality and weight of a topsides has on the design and selection of a deepwater floating production platform. The discussion will focus on topsides of Tension Leg Platform, (TLP), Spar and Semisubmersible floating platforms in the deepwater Gulf of Mexico (GoM), but the principles apply to other deepwater regions as well. Early field development planning decisions that impact key topsides functions are addressed. These include whether or not to include a drilling or workover rig and choosing between developing the field with subsea (wet) or surface (dry) trees. Selecting a topsides installation method is a critical design consideration and must be firmed up early in the design cycle. Topsides installation options are presented as a function of topsides weight and platform type. The strong symbiosis between topsides weight and hull design is demonstrated. The need to prioritize topsides weight management is emphasized and some topsides weight reduction strategies are offered. Finally, topsides weight and water depth domains of applicability for various platform types are presented. These will allow development planning teams to rapidly converge on practical platform options during the screening process.

Reservoir Characteristics and Topsides Functions

When designing a floating platform topsides the first order of business is to establish its functional requirements (process, export, drilling, power, utilities, quarters etc.) and a design basis. These are primarily driven by the characteristics and fluid properties of the reservoir to be developed by the floating platform. Figure 1 is a schematic that shows how reservoir characteristics and its fluid properties influence decisions on topside functions.

The subsurface drilling and completions teams are responsible for specifying well count, top-hole locations, well production profiles, recovery mechanisms (natural drive, water injection, gas lift etc.) and fluid characteristics. These in turn determine the two most important topsides functional requirements: whether or not to have surface or subsea trees and whether to incorporate drilling or workover capability on the platform. These functional requirements fundamentally influence size and weight of topsides and platform selection.

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