Techniques and systems to reduce deflection of a riser extending from offshore platform. The riser may be coupled to a seafloor and may experience movements due to, for example, currents. A riser restraint device may be utilized to reduce these movements of the riser. This riser restraint device may be coupled to the seafloor. This coupling of the riser restraint device may aid in allowing the riser restraint device to reduce movement of the riser and, thus, reduce deflection of the riser.

A method of removing a flexible line deployed between an offshore platform and a subsea structure, where the platform has a landing deck on which the flexible line is installed, the landing deck facing away from the platform towards an installation side. The method comprises: decoupling a topside end of the flexible line from the landing deck; lowering the topside end from the landing deck to the sea bed using a platform mounted winch, and detaching the winch from the topside end; moving the platform in a direction away from the installation side and positioning an installation vessel on the installation side; lowering a recovery line from the installation vessel and attaching an end of the recovery line to the topside or subsea end of the riser; raising the attached topside or subsea end onto the installation vessel from the seabed using the recovery line; and recovering the flexible line onto the installation vessel, whereupon the platform can be moved back to an operating position.

An apparatus including an external surface portion shaped so as to mate with a docking device, and two half-shells having internal surfaces of semi-circular cross section. The apparatus further includes a plurality of segments arranged inside the two half-shells and including teeth for gripping onto a shaft, and an installation tool operable to cause the two half-shells to close around the shaft, thereby securing the apparatus to the shaft.

Techniques and systems to reduce deflection of a riser extending from an offshore platform. A device may include a main tube disposed along a length of the device. The device may also include a support member that may be coupled to the main tube, wherein the support member may surround the main tube. The device may include a buoyancy assembly that may at least partially surround the main tube, wherein the buoyancy assembly may have an elongated non-circular and non-cylindrical shape. The buoyancy assembly may also include buoyancy foam.

Embodiments disclosed herein describe cylindrical structures with indents configured to reduce vortex induced vibrations (VIV). For example, the cylindrical structures may be configured to reduce VIV for drilling risers subject to ocean currents. In embodiments, the indents may be positioned on an outer surface of the cylindrical structures, wherein the indents may be parallel pairs. The pairs may be mirrored between a first end and a second end of the cylindrical structure, and be positioned in a helical pattern, which may be continuous or staggered.

Current profile of water (e.g., ocean) around a riser connected to a wellhead may be measured and used to determine integrated current load on the riser at any given moment in time. The integrated current load may be used to estimate the wellhead fatigue damage rate at that moment in time. The estimated wellhead fatigue damage rate may be used to make operational decisions for the well.

A clamping arrangement 10 of a buoyancy clamp assembly. The arrangement 10 includes three identical arcuate members 12 engageable together to define a ring. Each of the arcuate members 12 has three discrete resilient members 14 engageable on for instance a pipe 68. Engagement members 42 are provided extendable between adjacent pair of arcuate members 12 to prevent relative twisting of adjacent arcuate members 12.

A riser system with a primary conduit extends between a surface vessel and a subsea location and an auxiliary conduit that extends adjacent the primary conduit. In one example a composite jumper conduit extends from the surface vessel and is fluidly connected to the auxiliary conduit. The jumper conduit includes a composite material formed of at least a matrix and one or more reinforcing elements embedded within the matrix. In one example a subsea composite jumper conduit extends from subsea infrastructure and is fluidly connected to the auxiliary conduit. The subsea jumper conduit includes a composite material formed of at least a matrix and one or more reinforcing elements embedded within the matrix.

A flexible dynamic riser comprising: a riser; a coil tubing disposed within the riser, wherein the riser and the coil tubing define an annulus; and a packing material disposed within the annulus.

A mineral lifting system, S includes a seabed working machine 13, having an excavator 131, excavating minerals at a seabed, and a slurry pump 132, sucking in and pumping a solid-liquid mixture of the minerals and seawater, a generator, supplying electric power to the seabed working machine 13 by an electric power cable 12, a main float 20, a mineral lifting pipe 21, conveying the solid-liquid mixture to the main float 20 side, auxiliary floats 22, mounted Co the mineral lifting pipe 21 at predetermined intervals and imparting a buoyancy, and a sorting unit 3, sorting and collecting the minerals from the solid-liquid mixture conveyed to the main float 20 side.