A suction anchor for a subsea well is provided. The suction anchor includes a wellhead support structure. The wellhead support structure is at least in part external of the internal volume of the suction anchor.

A suction anchor for a subsea well is provided. The suction anchor includes a wellhead support structure. The wellhead support structure is at least in part external of the internal volume of the suction anchor.

A multi-impeller passive-rotating-stirring-type rotary drilling rig for open caissons includes a hollow main drill pipe, a drill bit, four cutting edges, four impeller shafts, four passive impellers and a rotation bracket. Through being uniformly distributed at a peripheral of the drilling rig, four passive impellers contact with a hole wall of a borehole during the drilling process for passively generating relative rotation opposite to the rotation direction of the drill bit, so as to accelerate sufficient mixing of silt and water for forming mud during the drilling process.

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

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

A multi-impeller passive-rotating-stirring-type rotary drilling rig for open caissons includes a hollow main drill pipe, a drill bit, four cutting edges, four impeller shafts, four passive impellers and a rotation bracket. Through being uniformly distributed at a peripheral of the drilling rig, four passive impellers contact with a hole wall of a borehole during the drilling process for passively generating relative rotation opposite to the rotation direction of the drill bit, so as to accelerate sufficient mixing of silt and water for forming mud during the drilling process, thus enhancing the stirring effect of the drill bit on the mud. The present invention is able to improve the mud discharge efficiency without adding additional power, thus avoiding the blockage of the mud suction pipe and blockage or even breakage of the drill bit due to poor mud discharge during the drilling process.

A method of connecting a lower pipe portion to a subsea foundation is provided. The method comprises: providing the subsea foundation, wherein the subsea foundation comprises an upper pipe portion connected to the subsea foundation, deploying the subsea foundation subsea; and connecting the lower pipe portion to the upper pipe portion. A subsea foundation system is also provided. The subsea foundation system comprises: a subsea foundation; an upper pipe portion connected to the subsea foundation, and a lower pipe portion, wherein the subsea foundation system is arranged such that subsea the lower pipe portion can be connected to the upper pipe portion. The lower pipe portion may be connected to the subsea foundation in a stowed position before deployment subsea. The lower pipe portion may be connected to a pull-in arrangement before deployment subsea. The subsea foundation may comprise a pipe overlap section that is arranged to overlap a portion of the upper pipe portion and/or the lower pipe portion when the lower pipe portion is connected to the upper pipe portion.

A caisson for maritime works, consisting of a base (1) and at least one lateral wall (2) attached to the same and formed by a plurality of voussoirs (3). Within the same a main space (4) is defined, intended to receive granular material as ballast. The voussoirs (3) feature an upper side (5), a lower side (6) and lateral sides (7) and are arranged with the lateral sides (7) of adjacent voussoirs (3) attached to each other, forming horizontal segments (8). Said horizontal segments (8) are attached to other identical horizontal segments (8) to define the lateral wall (2) by means of the union of the lower sides (6) and upper sides (5) of the voussoirs (3) forming the same. The base (1) has a geometric shape which coincides with the geometric shape of the horizontal segments (8). A procedure for the assembly of said caisson for maritime works is also described.

A method for the offshore installation of a construction laid by gravity on the seabed, comprising: the provision of a concrete base (1) delimited by a lower slab (8), a roof (2) and a perimeter wall (5), the interior whereof comprises vertical walls (6, 6′) forming cells (7, 12, 22); connecting at the periphery of the roof (2) a plurality of hollow metal floats (3) formed by a column with a circular or polygonal base; towing the assembly to the offshore location where the construction is to operate; allowing seawater to enter the cells (12) located below the roof (2), maintaining the cells (22) located below the metal floats (3) empty, in such a way that when the cells (12) located below the roof (2) are totally full, both the base and the metal floats (3) are submerged; once the cells located below the roof (2), but not those located below the metal floats (3) are full of water, allowing water to enter the cells (22) located below the metal floats (3) in such a way that the immersion of the assembly is completed, the base thereof resting on the seabed; and removing the metal floats. A gravity-based structure comprising a concrete base (1) and a plurality of hollow metal floats (3) connectable thereto.

A method for the offshore installation of a construction laid by gravity on the seabed, comprising: the provision of a concrete base (1) delimited by a lower slab (8), a roof (2) and a perimeter wall (5), the interior whereof comprises vertical walls (6, 6′) forming cells (7, 12, 22); connecting at the periphery of the roof (2) a plurality of hollow metal floats (3) formed by a column with a circular or polygonal base; towing the assembly to the offshore location where the construction is to operate; allowing seawater to enter the cells (12) located below the roof (2), maintaining the cells (22) located below the metal floats (3) empty, in such a way that when the cells (12) located below the roof (2) are totally full, both the base and the metal floats (3) are submerged; once the cells located below the roof (2), but not those located below the metal floats (3) are full of water, allowing water to enter the cells (22) located below the metal floats (3) in such a way that the immersion of the assembly is completed, the base thereof resting on the seabed; and removing the metal floats. A gravity-based structure comprising a concrete base (1) and a plurality of hollow metal floats (3) connectable thereto.