A generally cylindrical element adapted for immersion in a fluid medium, the cylindrical element comprising an elongate body having a length and a generally circular cross-section, and a plurality of raised body portions disposed about and extending along the length of the elongate body, the raised body portions being arranged generally parallel to a longitudinal axis of the body and having a height between 2% and 10% of a diameter of the body. The plurality of raised body portions are adapted to reduce vortex-induced vibration and/or drag on the cylindrical element when the cylindrical element is immersed in the fluid medium and there is relative movement between the cylindrical element and the fluid medium.

A drilling riser system includes a plurality of interchangeable dockable modules having sealable hydraulic connections configured to connect to a module docking structure disposed in at least one specific segment of a drilling riser and to seal the hydraulic connections. Each of the interchangeable dockable modules includes at least one of an hydraulic termination or connection to an hydraulic device for each of a fluid conduit in fluid communication with the and at least one auxiliary line associated with the riser.

A flow modification device connectable to a generally cylindrical element adapted for immersion in a fluid medium, the device comprising an elongate body having a length and a generally circular cross-section; a plurality of raised body portions disposed about and extending along the length of the elongate body, the raised body portions being arranged generally parallel to a longitudinal axis of the body and having a height between 2% and 10% of a diameter of the body; and an aperture extending through the length of the elongate body, the aperture being adapted to receive the generally cylindrical element such that the flow modification device is arranged about the cylindrical element. The plurality of raised body portions are adapted to reduce vortex-induced vibration and/or drag on the cylindrical element when the device is connected to the cylindrical element and the connected device and cylindrical element are immersed in the fluid medium and there is relative movement between the connected device and cylindrical element and the fluid medium.

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.

Buoyancy modules (200) are made from a foam composition that includes a combination of a thermally fusable powder and glass microspheres heated in a manner that provides a hardened syntactic foam having both low density and a high degree of compressive strength. An outer barrier (220) may enclose the buoyancy module.

The present invention relates to a method for riser string handling on an offshore drilling vessel (1), the offshore drilling vessel comprising a multiple firing line hoist system, a riser tensioner system (50) arranged in the second firing line, and a suspended riser transfer device (60). The method comprising the steps of lowering a riser string in the first firing line, and simultaneously assembling and preparing a riser tensioner system in the second firing line, wherein the riser hang-off assembly displaces the riser string, leaving the top end of the riser string exposed, from the first firing line to the second firing line to be connected to the riser tensioner system.

A system with an underwater vehicle for installation and de-installation of buoys (9) under sea level (6). The vehicle (10) comprises a buoyancy adjustment system (19) for continuously adjusting the buoyancy of the vehicle (10) during underwater operation. A gripper (24) is connected to the vehicle frame (10) by an orientation adjustment mechanism (29, 30, 31) for adjusting the gripper (24) orientation when installing a buoy (9) onto a flexible underwater line or for deinstalling the buoy (9) therefrom. The vehicle (10) further comprises a controller for manoeuvring and operation.

A method of installing a flexible line between an offshore platform and a subsea structure and a method of removing a flexible line deployed between an offshore platform and a subsea structure. The method of installing includes at least partially deploying the line in the water using an installation vessel located outside of an exclusion zone in the vicinity of the platform, including lowering a topside end of the line either to the seabed or to an intermediate location between the seabed and the platform. The method further includes pulling the topside end to a position within the exclusion zone and winching the topside end up to the platform, and coupling the topside end to the platform. The method of removing includes decoupling a topside end of the riser from the platform, lowering the topside end from the platform and pulling the topside end to a position outside of an exclusion zone in the vicinity of the platform, and at least partially removing the line from the water using an installation vessel located outside of the exclusion zone, including raising the topside end of the line onto the installation vessel either from the seabed or from an intermediate location between the seabed and the platform.

A buoy accomplishes a fluid connection between a vessel on a water surface and a subsea template located on a seabed via at least one riser. A fluid is transported by the fluid connection from the vessel to the subsea template, and the fluid is injected from the subsea template (120) into a subterranean void via a drill hole. At least one valve in the buoy is controllable from an external site in response to commands so as to shut off the fluid connection from the vessel to the at least one riser.

Fastening devices are described. In one example, the fastening devices can be used for a landing string buoyancy solution. The landing string hardware includes a stop collar to be fitted and secured around a drill pipe and stop collar hardware to secure the stop collar together around the drill pipe. The stop collar can be secured at one end of a number of buoyancy modules placed along a longitudinal length of the drill pipe to hold them into place along the drill pipe. The stop collar can be formed from long fiber thermoplastic using extrusion-compression molding. The stop collar hardware includes a bolt having an external thread formed from long fiber thermoplastic and a nut having an internal thread formed from long fiber thermoplastic. Both the stop collar and the stop collar hardware are tested for suitability for the application of holding the buoyancy modules in place under operating conditions.