Semi-submersible production platform

A semi-submersible production platform (10) intended for oil production, water injection and oil and gas export includes a hull (11) of basic rectilinear shape consisting of floats (17) with rectangular cross-section forming a closed square ring (12). Four columns (13) of square section are located, one in each vertex, of the closed square ring (12). A risers receipt system (14) consists of lateral supports (15) and connectors of square section (16). A passive anchoring system (19) is provided along with a truss-shaped deck structure (23), an equipment arrangement (24) with full seggregation of process equipment, utilities and quarters. A water intake (25) system at large depths has an intake pipe (26) connected at the top to the float (17) through a flexible coupling (27).

FIELD OF THE INVENTION 
This invention refers to a semi-submersible platform for oil production, 
water injection and oil and gas export. 
STATE OF THE ART 
The semi-submersible production platforms include various systems, such as 
water intake, fire fighting, ventilation, air conditioning, power 
generation, anchoring, risers, etc. . . . The platforms of this type, as 
known so far, integrate some of these systems, but fail to do so in 
relation to others of equal importance. 
PURPOSES OF THE INVENTION 
The purpose of this invention is a semi-submersible production platform 
which integrates all the systems required for her operation. 
More specifically, the purpose of this invention is a semi-submersible 
production platform which lodges better the process equipment, allowing 
also for the natural ventilation of said equipment, as well as integrates 
all production facilities, the naval utilities, the plant utilities, the 
platform architecture and the hull structure. 
It is also the object of this invention a semi-submersible platform which 
utilized a model of closed-ring floats, making the floats responsible for 
the structural stiffness, with a deck relieved and less rigid. 
DESCRIPTION OF THE INVENTION 
The semi-submersible production platform, object of this invention, 
includes: 
a--a hull of rectilinear shape, formed by standardized parts, which makes 
easy to assemble is in medium- and small-size shipyards; 
b--a risers receipt system where the supporting of the risers connectors is 
achieved at float level, which minimizes the dynamic loads applied to the 
platform and the problems of interference with the structure, thus 
eliminating the requirement of deck space to support the connectors, and 
also increasing the operational safety, since an area of risk is moved 
away from the crew; 
c--a passive anchoring system which eliminates the traditional windlasses, 
which makes it possible to reduce the weight on the deck, increase the 
space availability, utilize gravity piles and thus reduce the anchoring 
radius and clear the marine ground; 
d--a truss-shaped deck structure which allows for the natural ventilation 
of the process areas and of the large thermal dissipation equipment; 
e--a system of water intake at large depths which eliminates the need for 
the usual systems of water cooling; 
f--a fire-fighting system integrated with the utilities of intake, 
injection, cooling and ballast water; 
g--an equipment arrangement with full seggregation of the process 
equipment, utilities and quarters, thus increasing the operational safety 
of the platform.

DETAILED DESCRIPTION OF THE INVENTION 
As it can be inferred from the Figures, the semi-submersible production 
platform, referred to in general by number 10 on FIG. 1, intended for oil 
production, water injection and oil and gas export in water depths in 
excess of 400 m, includes a hull 11 of basic rectilinear and standardized 
shape, so as to permit assembly in medium- and small-size shipyards. The 
platform consists of a float of rectangular cross-section forming a closed 
square ring 12, FIG. 2, and four columns 13 of square section, located one 
in each vertex of the closed square ring 12, this configuration withstands 
the stresses induced by the waves at the level of the float, and which 
being a closed ring, presents higher stiffness than a configuration with 
two pontoons, thus making possible to eliminate bracings and rendering the 
structure more compact and easier to build. A risers receipt system 14, 
FIG. 1, provides a lateral support 15 of connectors 16 of square section 
to be achieved at the level of the float 17. The result is minimizing the 
dynamic loads applied to the platform 10 and the problems of interference 
with the structure, while eliminating the need for deck space to support 
the connectors and increasing the operational safety, and moving away from 
the crew an area of risk. As shown also in FIG. 6, a set of seven risers 
are positioned on the pontoon 18. FIG. 8 illustrates the catenary formed 
by each riser 14. A passive anchoring system 19 where the arrangement of 
the anchoring lines and the composition may be seen in FIGS. 9 and 10. A 
pre-laid anchoring consisting of chain 20, line or cable 21, and chain 22 
reduces the anchoring loads on the platform 10. A truss-shaped deck 
structure 23, FIG. 11, allows for the natural ventilation of the process 
areas and of the large thermal dissipation equipment. An equipment 
arrangement 24 with full seggregation of the process equipment, utilities 
and quarters, increases the operational safety of the platform. A 
water-intake system 25 at large depths, FIG. 12, has an intake pipe 26 
connected to the float 17 through a flexible coupling 27 and receives cold 
water through a bell mouth 28 at the platform, eliminating systems of 
water cooling; and a fire-fighting system integrated with the units of 
water intake, injection, cooling and ballast. 
It must be pointed out that the rectilinear shape and the configuration of 
the hull 11 maximize the utilization of fillet welding, which can be 
automatically done with high efficiency and small similar blocks optimize 
the prefabrication of the structure in workshops, reducing thus the costs. 
The small dimensions of the hull make it possible for a larger number of 
shipyards to have technical conditions to build the unit. The shape of the 
hull also allows the hull and the deck to be built in different sites, 
with both parts being connected through a mating operation which, due to 
the reduced dimensions, could be achieved in a region with nearly only 28 
m. The shape of the hull allows it to be built with alternative materials, 
such as concrete, for instance. 
The main characteristic of the platform 10 is, therefore, the integration 
among the various systems, resulting from such integration the open deck, 
allowing for the natural ventilation of the equipment, intake of cold 
water at large depths, risers sustained by the floats, passive anchoring, 
etc.