Method of and apparatus for the anchoring of drilling and production platforms on a structure sunk on a sea bottom

#The present invention relates to the anchoring of a drilling or production platform (hereinafter referred to in short as a "platform") upon the columns of a support structure previously affixed in the sea bottom or an artificial island, and, more particularly, to an arrangement for fixing the platform to such a structure whereby the kinetic energy of the platform, resulting from sea movements, is cushioned during the anchoring operation.

#Drilling and production platforms, e.g. for the recovery of fossil-fuel material, for example, petroleum and natural gas, are frequently anchored to a support structure previously affixed in the sea bottom. Such platforms may be formed as semi-submersible sea-going vessels which can carry the drilling rig or production equipment and are adapted to be partially submerged in the sea and securely affixed to the substructure or support.

#The support generally comprises a plurality (usually three) columns or posts which have previously been anchored in the sea bed and which are adapted to be affixed to the platform at their upper end.

#The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

#FIG. 1 is a vertical cross-sectional view through an assembly, in accordance with the invention, shown in diagrammatic form and comprising a column previously anchored in the sea floor or on a portion of an off-shore drilling island adapted to support a platform;

#FIG. 2 is a view of the assembly in another position, i.e. after positioning of the platform;

#Referring first to FIG. 3, it can be seen that a platform 1 of the semi-submersible type can be anchored to a plurality of posts or columns 2 in the sea 21, the posts having previously been anchored on the sea bottom 19 or an off-shore island formed on the sea bottom. The platform 1 can carry a drilling derekly and various housing structures 15 and 16 for pumps or the like for drilling or production of a fossil-fuel substance such as crude oil or natural gas. Winches 14 can be carried by the platform 1 and can have hawsers 13 which can be attached to eyes 12 on the columns 2 to align the plungers 7 with the sockets formed in the upper ends of the columns 2. The platform may have a hole 18 through which the drilling string can pass between the columns 2.

#In FIGS. 1 and 2, more specifically, I have shown the drilling and production platform 1 as a semi-submersible vessel which can be floated into position with the plungers 7 above the respective sockets formed at the upper ends of the posts.

#The deck load of the platform may range up to 40,000 Mp (Mp = 1,000 Kp where Kp = Kg-f, i.e. kilograms-force). To carry this load it is preferred to provide the posts 2 as part of an off-shore drilling island.