Semi-submersible floating structure with dynamic positioning

Claim 2

Semisubmersible mobile marine structure including three submersible caissons located at the respective apices of a substantially equilateral triangle, said caissons being interconnected by cross-bracing members, an aerial part supported by columns integral with said caissons, the assembly of said cross-bracing members and of said columns constituting a substantially regular tetrahedron, each of said caissons having a streamlined shape and being elongated in a common horizontal direction parallel to an axis of symmetry of said equilateral triangle, each of said caissons having a length in said horizontal direction at most equal to 5 times its greatest vertical width, longitudinal and transverse propulsion means adapted to said submersible caissons for dynamically positioning said structure.

Claim 3

Semisubmersible mobile marine structure including three submersible caissons located at the respective apices of a substantially equilateral triangle, said caissons being interconnected by cross-bracing members, an aerial part supported by columns integral with said caissons, the assembly of said cross-bracing members and of said columns constituting a substantially regular tetrahedron, each of said caissons having a streamlined shape and being elongated in a common horizontal direction parallel to an axis of symmetry of said equilateral triangle, each of said caissons having a length in said horizontal direction at most equal to 5 times its greatest width, propulsion means adapted to said submersible caissons, said propulsion means forming a system for dynamically positioning said structure and said aerial part being a substantially closed hollow structure having an aerodynamic flattened shape, substantially of revolution around a vertical axis.

Claim 4

Semisubmersible mobile marine structure including three submersible caissons located at the respective apices of a substantially equilateral triangle, said caissons being interconnected by cross-bracing members, an aerial part supported by columns integral with said caissons, the assembly of said cross-bracing members and of said columns constituting a substantially regular tetrahedron, each of said caissons having a streamlined shape and being elongated in a common horizontal direction parallel to an axis of symmetry of said equilateral triangle, each of said caissons having a length in said horizontal direction at most equal to 5 times its greatest width, propulsion means adapted to said submersible caissons, said propulsion means forming a system for dynamically positioning said structure and said aerial part being a substantially closed hollow structure having an aerodynamic flattened shape, substantially of revolution around a vertical axis.

Claim 5

Semisubmersible mobile marine structure according to claim 1, wherein said aerial part includes a circular working platform rotatable with respect To the remainder of the structure around a vertical axis and which further includes means for rotating said working platform about said axis, and means for maintaining a fixed orientation of said rotatable working platform with respect to the water bottom, irrespective of the variations in the heading of the structure.

Claim 6

Semisubmersible mobile marine structure according to claim 1, wherein the center of said aerial part and the center of said equilateral triangle are located substantially on one and the same vertical axis.

Claim 7

Semisubmersible mobile marine structure according to claim 4, wherein a derrick is provided on said aerial part, said derrick being substantially located on said vertical axis.

Claim 8

Semisubmersible mobile structure according to claim 4, wherein each of said three caissons is provided with means for propulsion in the direction of its axis and with separate transverse propulsion means housed in a tunnel traversing said caisson at right angles to the axis thereof, the tunnels of two of said caissons being aligned along a common axis located in one and the same plane as said vertical axis.

Claim 9

Semisubmersible mobile marine structure including three profiled submersible caissons located at the respective apices of a triangle having an axis of symmetry, said caissons being interconnected by cross-bracing members, and an aerial part supported by columns integral with said caissons, the assembly of said cross-bracing members and of said columns constituting a tetrahedron, said caissons having a streamline shape and being elongated in a common horizontal direction parallel to said axis of symmetry and having in said horizontal direction a length limited to at most 5 times the greatest width of said caissons and a system of longitudinal and transverse propulsion means adapted to said submersible caissons for dynamically positioning said structure.

Claim 10

Semisubmersible mobile marine structure including three profiled submersible caissons located at the respective apices of a triangle having an axis of symmetry, said caissons being interconnected by cross-bracing members, and an aerial part supported by columns integral with said caissons, the assembly of said cross-bracing members and of said columns constituting a tetrahedron, said caissons having a streamline shape and being elongated in a common horizontal direction parallel to said axis of symmetry and having in said horizontal direction a length limited to at most 5 times the greatest width of said caissons and a system of longitudinal and transverse propulsion means adapted to said submersible caissons for dynamically positioning said structure.

Claim 11

Semisubmersible structure according to claim 1, adapted for offshore drilling operation, wherein the caissons of said structure include a power station, reserves of fuel, ballast tanks for submersion and an equipment for the circulation of drilling mud connected with said aerial part of the structure through the interior of the columns and wherein said aerial part includes a centralizing station for remotely controlling said propulsion means of the caissons.

Claim 12

Semisubmersible structure according to claim 1, wherein at least one of the said columns is used for stacking parallely to said column the elements of a drill string and wherein said aerial part is provided with a derrick, the top of which is substantially located in the extension of said column used for stacking the elements of the drill string.

Claim 13

Semisubmersible mobile marine structure including three profiled submersible caissons located at the respective apices of a triangle having an axis of symmetry, said caissons being interconnected by cross-bracing members, an aerial part supported by columns integral with said caissons, the assembly of said cross-bracing members and of said columns constituting a tetrahedron, said aerial part being substantially a closed hollow structure having an aerodynamic flattened shape, substantially of revolution around a vertical axis, said caissons being elongated in a common horizontal direction parallel to said axis of symmetry and having a length limited to at most 5 times the greatest width of said caissons and a system of propulsion means adapted to said submersible caissons for dynamically positioning said structure.

Claim 14

Semisubmersible mobile marine structure including three profiled submersible caissons located at the respective apices of a triangle having an axis of symmetry, said caissons being interconnected by cross-bracing members, an aerial part supported by columns integral with said caissons, the assembly of said cross-bracing members and of said columns constituting a tetrahedron, said aerial part being substantially a closed hollow structure having an aerodynamic flattened shape, substantially of revolution around a vertical axis, said caissons being elongated in a common horizontal direction parallel to said axis of symmetry and having a length limited to at most 5 times the greatest width of said caissons and a system of propulsion means adapted to said submersible caissons for dynamically positioning said structure.