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 riser assembly and method of installing a riser assembly are disclosed. The riser assembly includes a first attachment element connected to a first portion of flexible pipe and a second attachment element connected to a second portion of flexible pipe. The first attachment element and second attachment element are connected by at least one tether element, via a fixed structure in a configuration such that, in use, in response to movement of the first and second portions of flexible pipe, the tension load at any moment in time, at each attachment element, remains substantially equal.

A method for riser string handling on an offshore drilling vessel, the offshore drilling vessel including a multiple firing line hoist system, a riser tensioner system arranged in the second firing line, and a suspended riser transfer device. The method including 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 clamp for a flexible pipe is provided that provide a load bearing flange on the flexible pipe permitting buoyancy jackets to be joined thereto. The clamp has a longitudinal axis arranged to extend along the length of the flexible pipe and a radial axis being perpendicular to the longitudinal axis. The clamp includes: a plurality of separate clamp elements being supported together in a radial array extending at least partially around the longitudinal axis; engagement means located between neighboring clamp elements to movably interconnect the clamp elements; and a strap being adapted to surround the clamp elements, in use for exerting a compressive force thereon. Also provided is a clamp element for use in the aforementioned clamp.

A riser assembly for transporting fluids from a sub-sea location is disclosed. The riser assembly includes a riser having at least one segment of flexible pipe and a plurality of buoyancy compensating elements connected to the riser and connected together in an in-line configuration to form a mid-line buoyancy section. The riser assembly also includes at least one buoyancy aid connected to the riser at a position above and spaced apart from the mid-line buoyancy section. The at least one buoyancy aid forms a first distributed buoyancy section and is sufficiently buoyant to maintain a tension load on the riser between the first distributed buoyancy section and the mid-line line buoyancy section. The riser assembly further includes at least one further buoyancy compensating element connected to the riser at a position above and spaced apart from the first distributed buoyancy section to form a second distributed buoyancy section. The second distributed buoyancy section is configured to support a portion of the riser in a wave configuration.

A device and method for anchoring a raceway mounting of a seabed-to-surface facility. The apparatus having a rigid structure immersed in a subsurface by floats and anchored to the sea bottom by tension legs, the device suitable for supporting troughs in a bottom-to-surface connection installation, having a plurality of flexible lines extending to the sea bottom, the flexible lines being supported by the troughs, the trough support structured is connected to a base resting on and/or anchored to the bottom of the sea by a plurality of n tension legs tensioned in parallel, by the float, n being not less than six, each of a plurality of p tension legs from the n tension legs, where p is not less than (n2) being connected at one of its ends to a distance-varying device secured to the base or to the support structure, the distance-varying device suitable for varying the distance between the support structure and the base.

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.

Disclosed are riser assemblies for connecting a topside structure and a subsea production facility. The assembly includes an upper riser having an upper end terminating at the topside structure, a flow diverting structure having an upper interface configured to connect to the upper riser and a lower interface configured to connect to at least two lower risers such that the upper riser is in communication with the at least two lower risers. Methods of deployment of the riser assemblies are also disclosed. The method includes connecting an upper riser to the topside structure, and connecting a first lower riser to a lower bore of the flow diverting structure such that the upper riser, the flow diverting structure and the first lower riser are connected, and the upper riser is in fluid communication with the first lower riser. Additional lower risers can be installed at a later time if desired.

The disclosure relates to a method for detecting water in a tensioning buoy of a riser column of an installation located in an aquatic environment, the method including, in succession, steps of: defining a representative standard echo; emitting the ultrasonic signal on a wall of the buoy; measuring a representative response echo due to the reflection of the ultrasonic signal in the buoy; comparing the representative response echo to the representative standard echo; and determining whether water is present in or absent from the buoy from the comparison.

A drilling riser configured to convey drilling materials between a drilling vessel and a subsea wellhead. The drilling riser has an upper section, and a lower section coupled via a connector to the upper section. The lower section has a buoyant material for distributed passive buoyancy of the lower section. The overall drilling riser is neutrally or negatively buoyant, whereas the lower section is positively buoyant when decoupled from the upper section and coupled to the subsea wellhead.