Introduction to Offshore Structures - Offshore Structures: Design, Construction and Maintenance - page 8

available from other operations, and some tax hedging is desired, an early high
cash investment option may be preferred. However, if the company is cash
starved or a higher corporate cash discount rate must be imposed due to
many other competing investment options or interest rates, a lower upfront
cash investment option may be preferred.
Of course, this is a somewhat simplistic presentation of the economic factors
affecting the platform concept selection. Many other economic factors other
than the cash flow, including the tax and discount rates, inflation and the
time value of money, also need to be considered, resulting in complex net-
present-value calculations. It is worth mentioning that investment analysis
specialists generally perform these calculations.

1.3.2 Multicriteria Concept Selection
At the FEED stage, external factors, such as country requirements and charac-
teristics, technology transfer and environmental pollution potential, as well as
the culture, politics, economics and infrastructure of the host nation and the
operating oil company and its partners, may have major influences on the con-
cept selection. Not easily comparable criteria, such as the economics, design
completeness and maturity and external factors, have to be weighed against
each other and used for concept ranking and selection. In a multicriteria process,
first the goal of the exercise is defined. Then the viable field-development
options are identified. This is followed by the identification of a multitude of
selection criteria that are grouped and ordered in a hierarchy, after which
experts determine the importance of each criterion by comparing it to the others
in a pairwise manner. The comparisons are then passed through an analytical
process to obtain rankings for each comparison and the alternatives. Currently,
there are several such processes in use.
The basic design defines the platform, production facility and structural con-
figurations and dimensions in enough detail to allow the detailed design to start.
Basic design results enable reliable cost and schedule estimates and the ordering
of long-lead major equipment and structural components. This also allows the
contractor to provide a reliable lump-sum price bid for a detailed EPC contract
for the platform.
The basic design phase includes the following tasks:

A well-defined field-development plan.

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A conceptual design based on field characteristics, operational and environ-
mental parameters, foundation conditions, platform configurations, global
materials selection and other information and assumptions used for concept
development.

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Conceptual drawings showing major component configurations for plat-
forms, topside facilities layouts, well locations and well systems, reservoir
maps and production profiles, storage (if needed) and offloading systems,
pipelines to shore and preliminary sizes.

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