Objective
The object of this project was to prove the feasibility of steel structures supporting hydrocarbon production and drilling equipment and presenting the same display as structures presently installed in water depths ranging from 100 to 300 m, but which could be installed at much more important depths.
The following ROSEAU platforms have been studied:
- in various water depths ranging from 450 to 600 m for the oceanometeorological conditions of the Gulf of Mexico;
- for North Sea conditions (water depth of 600 m);
- for the Gaspian Sea conditions (300 m);
- for the Californian Coast conditions (600 m);
- for the Mediterranean Sea (825 m);
- for the West African Coast (400 m);
The following aspects were covered for each platform:
- definition of the database, particularly the oil exploitation conditions (topload, number of conductor pipes, etc..) and the oceanometeorological data;
- platform dimensioning by means of an analysis method used on a single-wine model;
- a parametric study which allowed to determine optimal values and critical applications for this project;
- a study of the main installation methods;
- a study on specific subjects : fatigue, seismic, torsion, foundation effect, low frequency phenomena;
- a study on the main architectural options possible.
In viewof a detailed inspection concerning the solidity of the platform, program has been developed to analyse the behaviour of the ROSEAU structure. This "step by step" calculation program operates within a temporal domain, that is to stay it simulates the response of the structure versus the excitation of a random surge. The validity of this program has been basin tested on a model in June and July 1984. A comparison of the recordings of certain motion parameters of the model with the results of a simulation calculated with the same surge as that in the test basin has proved that the program makes a good analysis of the phenomena at low and high frequency and takes into account the mean value of forces applied. The program also determines the extreme values and the fatigue damages according to several distinct methods corresponding to different mathematical theories.
Futhermore, basin tests were also run on the behaviour of the stabilizer, so to provide a more accurate definition of its hydrodynamic properties.
Last of all, problems concerning the launching of long and flexible structure from a barge have also been the object of basin tests which allowed to specify the behaviour of the structure during its launching, particularly concerning the efforts on the stabilizer.
To conclude, these studies showed that the ROSEAU concept allowed the extension this jacket concept into deeper waters, without increasing the manufacture, installation and exploration costs.
This ROSEAU concept has been particularly well received and is now in a good position within the list of options chosen by oil companies concerned by deep offshore oil production. This has been proven by the success obtained by the "ticket" proposed for the detailed study of a platform in a 600 m water depth in the Gulf of Mexico to 10 different oil companies: Chevron, Elf, Marathon, Occidental, Petrobras, Philips, Shell, Sohio, Texaco, Union.
The ROSEAU column is designed to support drilling and production equipment in deep waters. Contrary to the very rigid structures of the jacket type, the functioning of the ROSEAU is based on the flexibility of the structure and the resulting dynamic effect due to a first natural period very much superior to the wave periods. This allows a relatively light structure. Compared to other flexibles structures, ROSEAU presents numerous advantages, the main being is its resemblance with conventional jackets and the fact that it requires neither buoyancy tanks, guylines nor articulation.
Studies relative to the ROSEAU platform concerned mainly its feasibility. The purpose was to provide a better understanding of the phenomena determining the behaviour of the structure, in order to define the analysis methods, find the possible architectural designs and the appropriate installation methods.
Programme(s)
Topic(s)
Call for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
92754 Nanterre
France