Introduction to Offshore Structures - Offshore Structures: Design, Construction and Maintenance - page 3

schemes. After that, the various alternative schemes are compared and the most
beneficial one is identified.
During this phase, due to the absence of detailed information about reservoir
characteristics, future market conditions and field-development alternatives,
experts make judgments based on their past experience and on cost and
schedule estimates based on data available from previous history. The success
of oil and gas companies depends on this expertise, so most companies keep
experts on hand and compete with each other to recruit them. Sometimes, the
experiential data are not enough, so decisions are made as a result of brain-
storming sessions attended by experts and management, and these are greatly
affected by a company s culture and past experiences.

The reservoir management plan is affected by the characteristics of the fluid
the reservoir produces, the reservoir

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s size and topography, regional politics,
company and partner culture and the economics of the entire field-development
scheme. Well system and completion design are affected by the same factors
that affect the reservoir management plan, except perhaps the political factors.
Platforms, facilities for processing and production, storage systems and export
systems are affected by all these factors as well.
The field-development scheme has to take into account:

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Reservoir characteristics

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Production composition (e.g., oil, gas, water, H 2 S)

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Reservoir uncertainty ●

Environment (e.g., water depth) ●

Regional development status

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Technologies available locally

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Politics

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Partners

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Company culture

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Schedule

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Equipment ●

Construction facilities ●

Market

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Economics

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If the preliminary economic indicators in the feasibility study phase are
positive, seismic data generation and evaluation, done by geophysicists, follow.
These data comprise reasonable information about the reservoir s characteristics,

such as its depth, spread, faults, domes and other factors, and an approximate
estimate of the recoverable reserves of hydrocarbons.
If the seismic indications are positive and the decision is to explore further,
exploratory drilling commences. Depending on water depth, the environment
and what

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s available, an appropriate exploration scheme is selected.
A jack-up exploratory unit is suitable for shallow water depths. In water depths
exceeding 120 m (400 ft), ships or semisubmersible drilling units are utilized.

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