A hydraulic cylinder enclosing a cavity, the cylinder containing a thru hole, an inner cylinder surface, and a longitudinal axis, and a piston within the cavity and movable relative to the cylinder in parallel to the longitudinal axis between a first and second positions. The piston includes a rod extending through the thru hole, the piston attached to the rod and in sealed engagement with the inner cylinder surface, and dividing the cavity into low and high pressure cavities, and each of the low and high pressure cavities containing a hydraulic fluid. The hydraulic cylinder further including a flexible bladder within the high pressure cavity containing a gas and preventing the gas from mixing with hydraulic fluid in the high pressure cavity. The flexible bladder is attached to an end of the cylinder, and is expandable within the high pressure cavity so that when the piston is in the first position, the flexible bladder and the gas are compressed, and as the piston moves toward the second position, the flexible bladder and the gas fill at least a portion of the high pressure cavity.

The present invention relates to a motion compensation system for an element hanging from a mobile unit, the system comprising two blocks, at least two articulated arms, a compensation cylinder and a cable. According to the invention, at least one characteristic length of the articulated system (for example: the length of a link or the distance between two sheaves of two articulated arms) is adjusted according to the motion to be compensated for.

A method of heave compensation between a floating installation, which has a drilling floor, and at least a riser or a pipe extending down towards, possibly through, a blowout preventer, the method including the steps of—installing an electromechanical actuator with attachment points, in the form of an end cap and an anchoring point, between the floating installation and a suspension device for the riser or the pipe; connecting the electromechanical actuator to a power supply and a control system; and heave-compensating for the relative displacement between the floating installation and the riser or the pipe by letting the control system adjust the length and power output of the electromechanical actuator.

The invention is a system for controlling the relative movement of a load P, comprising at least one main damper having a longitudinal action of stroke C and two ends with one end being connected to a frame and the other being connected to the load. A compensation device is included having at least one secondary damper of longitudinal action with two ends with one end being secured to the frame and the other end is connected to the end of the main damper connected to the load The secondary damper is arranged so that, at one point of stroke C, the secondary damper has an action orthogonal in direction to the direction of the movement.

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 mudline closure device is lowered between tensioners coupled to a deck of a vessel or rig onto a subsea wellhead. A tensioner platform is then attached to the tensioners. The tensioner platform includes a platform opening having an inner diameter through which an emergency disconnect system may pass. The tensioner platform also includes rotation bearings secured in the platform opening. A split support includes outer surfaces disposed along its circumference. The outer surfaces are seated on the rotation bearings. The split support includes a support opening having an inner diameter through which a marine riser may pass. The split support also includes a landing shoulder secured in the support opening to suspend a surface blowout preventer to the deck. As the vessel or rig changes direction, the split support rotates relative to the tensioner platform without imparting excessive torsion on the marine riser.

A method of deploying a jointed tubular string into a subsea wellbore includes lowering the tubular string into the subsea wellbore from an offshore drilling unit. The tubular string has a slip joint. The method further includes, after lowering, anchoring a lower portion of the tubular string below the slip joint to a non-heaving structure. The method further includes, while the lower portion is anchored: supporting an upper portion of the tubular string above the slip joint from a rig floor of the offshore drilling unit; after supporting, adding one or more joints to the tubular string, thereby extending the tubular string; and releasing the upper portion of the extended tubular string from the rig floor. The method further includes: releasing the lower portion of the extended tubular string from the non-heaving structure; and lowering the extended tubular string into the subsea wellbore.

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 hoisting system for a drilling rig, which has a crown block for attaching to a derrick, the crown block comprising a plurality of sheaves; a travelling block suspended from the crown block via a hoisting cable, the travelling block comprising a plurality of sheaves and being connectable with a payload, the travelling block being arranged to move along a workpath; the hoisting system further comprising: a floating block comprising a plurality of sheaves reeved on the hoisting cable; wherein the floating block is configured to move between: a first arrangement in which the floating block is fixed relative to the crown block; and a second arrangement in which the floating block is fixed relative to the travelling block; wherein the hoisting system is arranged such that, when the floating block is in one of the first or second arrangement, the sheaves of the floating block overlap a sheave of the crown block or travelling block in a direction of the workpath.

Well centre assembly for an offshore drilling rig and associated method. There is described a well centre assembly 10 for an offshore drilling rig. The well centre assembly 10 comprises a diverter assembly 16 and a movement control system 18. The movement control system 18 is operable between the diverter assembly 16 and a supporting structure 12 of the rig. In use, the movement control system 18 controls or permits relative movement between the diverter assembly 16 and the supporting structure 12. A connector such as a riser 34 connected to the diverter assembly 16 during deployment, while deployed or during retrieval of the riser 34 may experience external forces such as from tidal, wind and/or wave movement at a water surface 50, which may cause the positioning and/or orientation of the riser 34 to vary. The movement control system 18 may control the movement of the diverter assembly 16 so as to compensate for movement of the riser 34.