The invention relates to a method for building concrete foundations for lattice-type offshore structures and to foundations built using this method, which has the main aim of replacing the piles used to anchor lattice structures to the seabed (7) with blocks of on-site reinforced concrete (1) which grant the necessary stability to the lattice structure (2), doing away with all pile-driving works but without performing any structural modification of said structure. Said elements (1) are positioned using templates (12). The advantages of this novel invention lie in the possibility of installation on any type of terrain, providing a perfect connection between the seabed and the foundations thanks to on-site concreting, as well as its ease of construction, reduction of noise emissions and of auxiliary means.

An offshore structure includes an adjustably buoyant hull including a plurality of vertical columns and a plurality of horizontal pontoons. Each pontoon extends between a pair of the columns. The adjustably buoyant hull is configured to receive a topside. Each column has a central axis, an upper end, and a lower end. Each pontoon has a longitudinal axis, a first end coupled to one of the columns, and a second end coupled to another one of the columns. The offshore structure also includes a foundation assembly attached to a lower end of the hull. The foundation assembly includes a column skirt extending downward from the lower end of each column and a pontoon skirt extending downward from a bottom surface of each pontoon.

Provided is a foundation building system for an offshore wind turbine, whereby a monopile is configured to be placed on the seabed, having an upper portion with a first attachment interface for attaching a foundation platform unit, at least one internal, second attachment interface in an interior cavity of the monopile for attaching at least one electrical platform unit, and a third attachment interface for attaching a tower of the offshore wind turbine atop the at least one electrical platform unit, wherein the upper portion is to be placed at least partly above sea level, the foundation platform unit providing at least one foundation platform extending around the tower when installed, and the at least one electrical platform unit comprising at least one platform for electrical equipment for guiding and/or connecting of an connection cable for connecting the offshore wind turbine.

A method includes mounting a lower platform block (300) to a plurality of piles (215) positioned on a surface. The lower platform block includes a first frame (315), a plurality of docking assemblies (305) connected to the first frame and engaging the piles, and a plurality of conductor tubes (310) connected to the first frame to a plurality of piles. The docking assemblies are released from the piles to separate the lower platform block from the piles.

A subsea assembly including; a foundation, a support device; and a subsea equipment adapter frame is provided. The foundation, support device and subsea equipment adapter frame are separate modular components that can be installed separately. The foundation may be a suction anchor. A method of installing and uninstalling the subsea assembly is also provided.

Seal arrangement for a joint of two joint elements, in particular realized as a monopile and a transition piece, of an offshore structure, preferably an offshore wind energy installation, in particular a substructure thereof, in which, for the purpose of producing a stable joint, an upper joint element and a lower joint element are inserted into each other in a clamping manner by means of at least one seal unit, comprising one of the joint elements and the at least one seal unit fixed to the joint element, in such a manner that the seal unit, in a joining position, is arranged between an inner joint surface of one joint element and an outer joint surface of the other joint element, at least one seal unit having at least one elastic sealing element, which extends in the circumferential direction around the entire circumference and the thickness (D) of which is greater than the thickness (D) of an adjoining seal unit region and method for producing a seal arrangement.

A foundation for a subsea assembly is provided. The foundation comprises connection points. The connection points permit other components to be connected to the suction anchor and permit loads to transfer from the component connected to the connection points into the foundation. The foundation may be a suction anchor. A method of converting an exploration well using such a foundation to a production well is provided.

A coupling system to be temporarily coupled to at least one of a jacket pile and a foundation pile comprises an upper fixation member, a lower fixation member and a lifting device for moving the upper and lower fixation members with respect to each other. The coupling system is provided with at least one of a grout transfer line for guiding grout from a grout supply to a space between a jacket pile and a foundation pile upon installing the jacket pile to the foundation pile, and a cleaning device for cleaning the inner and/or outer side of a foundation pile, and a separating device for separating a jacket pile from a foundation pile upon de-installing the jacket pile with respect to the foundation pile, and a measurement device for determining parameters of a jacket pile and/or a foundation pile.

The invention relates to an offshore installation, comprising an underwater foundation structure, a construction placed onto the foundation structure, a docking device for a boat, and a device for cathodic corrosion protection for the underwater foundation structure, said device having at least two anodes (2), which are arranged at a distance from each other and are each fastened to a beam (4) or a support of the foundation structure, the extension arms or the supports being connected directly to the foundation structure below the waterline.

A hoisting system for the installation of a wind turbine wherein said hoisting system comprises measures to achieve a load bearing connection to the tower of the wind turbine and comprises measures to move the hoisting system up and down along the tower wherein the hoisting system, when it is fixed to an already installed part of the wind turbine tower with said load bearing connection, is arranged to install or remove any of a tower segment, a nacelle, a generator, a hub, and a blade in one or more combined hoists or in a single hoist.