TOTAL-Compagnie Francaise des Petroles (C.F.P.) has developed, in association with Institut Francais du Petrole (I.F.P.) and ELF-Aquitaine, a dynamic and some static calculation programs for studying the behavior of part, or the totality, of a drilling riser.
This paper:
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gives the conclusions of the theoretical studies about the relative influence of every parameter necessary for full determination of a riser,
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gives some qualitative test results about different equipment proposed by manufacturers and liable to solve one of the most important problems that are
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lastly, presents three systems that have not yet been realized and that could represent solutions for some problems examined in this study.
Let it immediately be pointed out that the value 4,000 feet in the title only refers to the magnitude of the water depth now aimed at, not only by TOTAL, but also by all the major oil companies.
At the present time, many wells have been drilled over a water depth between 500 and 1,000 feet, the present record is held by SHELL at 2,000 feet, and about twenty drill ships or semi-submersibles have been ordered and should be equipped for depths between 2,000 and 4,000 feet.
This paper focuses on the risers for this latter category of drilling supports.
It is understandable that the riser is one of the most important problems to be solved for deep sea drilling, and that the solution, if any, is to satisfy every condition of security, on pain of seeing the whole project fall into jeopardy.
That is why all the French companies joined together to spend several tens of thousands of dollars for creating very sophisticated static and dynamic calculation programs, for testing equipment such as buoyancy materials or riser connectors, and for developing new technology where existing techniques could not be extended.
This program is bi-dimensional and calculates, statically or dynamically, the forces exerted and the stresses inside the riser, whether connected to the well head or disconnected.
Appendix A describes:
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the external actions that are considered by the program,
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the simulation of the connections at the top and at the bottom of the riser,
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the hypotheses and the principle of the calculation.
The riser is defined as the assembly of several stumps of which it is necessary to specify:
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the length of each one,
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the O.D. and thickness of the resistant section, that is, the section considered for calculating the stresses,
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the mass per meter of length, the hydrodynamic diameter D that is considered for calculating the drag forces,
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the diameter D considered for calculating the buoyancy,
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the modulus of elasticity.
