An offshore drilling system includes a drilling tower, a tubular string hoisting device with a crown block and a travelling block suspended from the crown block in a multiple fall arrangement. A heave compensation system is adapted to provide heave compensation of the travelling block. The heave compensation system includes a hydraulic sheave compensator. The system further includes a mobile working deck which is movable with respect to the drilling tower within a motion range including a heave compensation motion range. The heave compensation system is further adapted to provide heave compensation of the mobile working deck by a hydraulic deck compensator, which is hydraulically connected via a hydraulic conduit to the hydraulic sheave compensator, such that in operation the deck compensator moves synchronously with the sheave compensator of the heave compensation system.

Aspects of the present disclosure relates to disruptive coupling systems and methods, and apparatus thereof, for subsea systems. The subsea systems may be subsea oil and gas systems. In one implementation, a subsea system includes a subsea component disposed in seawater, and a disruptive coupling device coupled to the subsea structure and/or surrounding fluid.

A system for monitoring a condition of a component of a well system located proximate to a seabed includes a first sensor assembly to couple to a telescopic joint coupled to an upper end of a riser, wherein the first sensor assembly is configured to measure at least one of a vibration, an inclination, and a strain in the riser, and a data processing system in signal communication with the first sensor assembly, wherein the data processing system is configured to estimate the condition of a subsea stack system based on measurements provided by the first sensor assembly.

A motion compensation system disposed on a structure of a drilling vessel. A stabilization assembly for use with the motion compensation system includes a first arm connectable to the structure, a first sheave connectable to the structure, a second arm connectable to the first arm, and a second sheave connectable to the second arm. At least one of the first arm and the first sheave are connectable to the structure at different locations and the first arm and the second sheave are connectable to the second arm at different locations.

In accordance with embodiments of the present disclosure, a ram-style riser tensioner cylinder assembly includes an outer cylinder barrel and an inner rod barrel disposed within and extending in a first direction from the outer cylinder barrel. The cylinder assembly also includes a high pressure seal disposed along a sliding interface between an end of the inner rod barrel and an inner wall of the outer cylinder barrel. In addition, the cylinder assembly includes a cap coupled to an end of the inner rod barrel extending from the outer cylinder barrel, and a fluid reservoir disposed in the cap. The fluid reservoir may be used to store and communicate fluid from the fluid reservoir to the high pressure seal for lubricating the seal.

A platform assembly (10) for providing a work area around a well riser (16) is disclosed. The platform assembly (10) comprises a platform (26) configured to be attached to the well riser (16). The platform assembly (10) further comprises a plurality of tensioning means (28) for supporting the platform (26) relative to a vessel (14) and for supporting the riser (16). At least part of tensioning means (28) is configured to change in length relative to another part of tensioning means (28) responsive to angular motion of the riser (16) and the vessel (14).

A retainer system, device and method are provided for retaining a severed pipe string such as a landing string suspended from a rig of a floating vessel or platform during a failure of a primary or secondary heave compensation system and prevent the severed pipe string from flying over the rig floor. The retainer system includes a retainer device including a housing mounted to a platform or vessel, the housing defining a through bore for receiving a pipe string suspended from the platform or vessel. A safety sleeve extends through the housing. A stop arrangement is mountable on the pipe string, to permit engagement between the safety sleeve and the stop arrangement in order to limit relative movement between the housing and the pipe string in order to retain a severed pipe string in an emergency situation.

The first aspect of the present invention relates to an offshore drilling system and a method for performing subsea wellbore related activities involving a riser extending between the vessel and a subsea wellbore. The offshore drilling system comprising a drilling vessel with a floating hull, a drilling tower and a tubular string main hoisting device. A vertically mobile working deck with a rig floor slip device is positioned above the moonpool. A telescopic joint and a diverter are provided, wherein the inner barrel of the telescopic joint is secured to the diverter via a flexible joint. Furthermore an integrated heave compensation system is provided such that said travelling block and the mobile working deck move synchronously in heave compensation.

A packer assembly for dynamically sealing against an inner tubular of a telescoping joint including axially activated packers. The assembly includes an inner housing positionable about the inner tubular of the telescoping joint, the inner housing assembly comprising a packer configured to dynamically seal against the inner tubular of the telescoping joint, and an outer housing assembly positionable about the inner tubular of the telescoping joint and axially below the inner tubular housing, the outer housing comprising a packer configured to dynamically seal against the inner tubular of the telescoping joint.

A passive heave compensator comprising: a main hydraulic cylinder, including a moveable piston having a piston rod extendible through the main hydraulic cylinder and a piston head, a gas phase above the piston head, and at least one oil phase below the piston head separated by a boundary; an upper connection point associated with the main hydraulic cylinder and a lower connection point associated with the piston rod; and at least one accumulator, the or each accumulator having a moveable separator to divide the accumulator between a gas phase above the separator, and an oil phase below the separator, and the or each oil phase being in communication with an oil phase in the main hydraulic cylinder; characterized in that the main hydraulic cylinder further comprises a cylinder sleeve co-axial with the piston head to provide, in co-ordination with the piston head, the boundary between the gas phase and the at least one oil phase in the main hydraulic cylinder. In this way, the variation in the coordination between the shape, longitudinal position, or both of the piston head, which naturally must be smaller in cross-section than the cross-section of the main hydraulic cylinder, and the transverse extent of the cylinder sleeve, provides variation in the cross-sectional area of oil volume in the main hydraulic cylinder, and thus different damping effects along the length of the main hydraulic cylinder, which are available to the user.