ABSTRACT

The search for oil has demanded that platforms be built in deeper water and to resist revised criteria forheav1er storm loading. To meet the demands for these larger structures the construction industry has developed the new 500 ton capacity derrick barges. In addition to their increased crane capacity, this equipment has demonstrated its ability to reduce the amount of time lost because of weather.

The ability of a semi-submersible to further decrease this weather loss has been noted and some think that this may be a more logical solution than the present trend of conventional barges. The advantages and disadvantages of a semi-submersible are discussed, the chief disadvantage and the major deterrent to its use being its cost. All data is based on conditions found in the Gulf of Mexico.

INTRODUCTION

Before a discussion of the new larger construction equipment can begin, it would be well to look back and trace the development of this equipment. In the early beginnings of the search for oil in the offshore areas, the equipment used in the marshes and shallow bays was the only thing available for use offshore. This equipment was mounted on small barges with no provisions for quarters and usually consisted of a set of fixed leads for driving piling with a drop hammer. One of the first platforms offshore was installed in Bay Marchand and was constructed of timber pile, similar to most of the inshore platforms. Fig. 1 shows a view of this platform under construction. The platform was very successful until it was demolished by the first winter storm. But it did stand long enough to prove that oil existed under the waters of the Gulf of Mexico, and men of vision had the information they required to launch a new industry.

With this new discovery, oil companies and the contractors that supplied them were hard pressed to develop new methods of platform construction. Two problems presented themselves construction equipment was needed immediately and the prospects of its continued use in the future were vague. Because of these factors construction people were reluctant to build any new equipment. Oil companies were willing to risk capital for further investigation of the oil potential but they wanted this search to begin with deliberate speed. So contractor s had to innovate and use some rather make-shift solutions to provide time needed to search for a better solution.

As the search for better equipment continued, a number of large cranes that has been used on rivers and in ports were pressed into service. Some were full revolving cranes, but most were stiff-legs, with such large capacities to astound the imaginations - 50, 75 and even some 100tons. Only a very few are still in service today, but they served well during these early beginnings of the industry.

About 1949, the first of the derrick barges designed for offshore use was introduced.

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