South East Asia has long been an active marine oil field. In fact, some of the early marine structures were built off the Coast of Brunei. However, offshore activity did not continue, and the ares remained relatively quiet and approximately five years ago when platform construction resumed. During the time that South East Asia was inactive, offshore construction was carried on in many other parts of the world. This allowed the construction industry to radically improve, making particularly significant advances in platform design and construction technology. Today, the offshore construction industry has the ability to determine the conditions at the site, to perform the necessary design engineering, and to construct an adequate platform designed to meet almost any environmental conditions.
Is this technology being properly applied in South East Asia? South East Asia is an extremely large area, with quite varied climate and geology. Storms offshore include such extremes as typhoons and monsoons. Fortunately, at locations of construction activity to date, the weather condition have been relatively mid.
These less severe conditions and the resulting capability of more frequent resupply have allowed the use of lighter and less complicated structures in this area. Even for South East Asia, however, the platform designs should be tailored specifically for the requirements of the particular site.
This is not meant to infer that each platform should be completely custom-designed, but that each structure should be designed with a rational balance between the constraints imposed by standard construction practices, material availability, economics, and owner requirements.
In simplest terms, a fixed offshore platform is a steel or concrete island providing above-water working space where oil field operations can be performed in an air environment. A platform has four basic requirements. The size and arrangement must be adequate for the intended operations. The structure must be adequate to support the operational loadings and to resist the intended environmental conditions. The method of construction must be practical. The cost must be reasonable so the platform, as part of an overall economic system, can produce a satisfactory return on the investment.
It is the designer's job to produce a platform which is operationally and structurally adequate, practical to construct, and economically feasible. However, before a platform design can be started, considerable planning should be given to insure that the platform will provide adequate area, suitably arranged for both initial and future operational requirements, Unfortunately, in an effort to speed up the delivery of the structure, this type of planning has frequently been inadequate. All too often, the need for additional space is discovered while construction is in progress. Minor modifications, which could have been added at negligible cost during the planning stages, can become very costly late in fabrication.
Before design can begin, it is also necessary to determine the conditions at the site and to establish the level of environmental conditions to be used as the basis of design. Generally, it is not practical to design for the absolute maximum possible occurrence, but rather for some less severe condition more likely to occur during the life of the structure. Obviously, one of the major factors involved in this selection is economics. In addition, careful consideration must be given to the safety of personnel on the platform, the possibility of pollution, the intended use, and the planned life of the structure.
Establishing an environmental "risk criteria" as a basis of design is not unique to the offshore industry; similar evaluations are done in all types of construction. In earthquake prone areas, a most "probable" criteria is used instead of prone areas, a most "probable" criteria is used instead of one based on "maximum" possible occurrences. As another example, most buildings are designed for extreme wind forces. However, few, if any, are designed for tornadoes. Similar consideration must be given to other types of risks which occur in marine or oil field operations such as blowouts. fires, and collisions with vessels.
More conventional structures, such as buildings or bridges, are usually designed in accordance with local building codes which set forth not only the design environmental loadings, but also the allowable stresses. In many areas of offshore operations, no such "building codes" have been established. Many features of structural design practice which had previously been developed for other applications cannot be previously been developed for other applications cannot be applied directly to platform design. To fill this need and to provide the designer with the best information available, the provide the designer with the best information available, the American Petroleum Institute has formulated API R2 2A. "Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms". Following the methods set forth in this publication, adequate design techniques and stress levels can generally be assured.
As far as offshore operations are concerned, the area generally considered as South East Asia reaches from India on the west, Australia on the south, Mainland China on the north. and the Pacific Ocean on the east. As illustrated in Fig. 1, it is a large geographical area covering more territory than the entire Continental United States of America.