A method for mitigating the effects of cable wear in an active heave compensated hoisting system of an offshore vessel in a locked to bottom mode of operation is disclosed. The method comprises supporting an upper end of a string which is connected to a subsea well from a travelling block of the hoisting system, wherein the travelling block is suspended from a crown block via a cable. The method further comprises operating an active heave compensation system to control a drawworks of the hoisting system to pay in and out the cable to compensate for motion of the offshore vessel and maintain a target overpull in the string. The method further comprises adjusting a ballast system of the offshore vessel to vary the draft of the vessel, and controlling the drawworks in accordance with the variation in the draft of the vessel to cause a length of cable to slip through the hoisting system and maintain the target overpull in the string.

A method for mitigating the effects of cable wear in an active heave compensated hoisting system of an offshore vessel in a locked to bottom mode of operation is disclosed. The method comprises supporting an upper end of a string which is connected to a subsea well from a travelling block of the hoisting system, wherein the travelling block is suspended from a crown block via a cable. The method further comprises operating an active heave compensation system to control a drawworks of the hoisting system to pay in and out the cable to compensate for motion of the offshore vessel and maintain a target overpull in the string. The method further comprises adjusting a ballast system of the offshore vessel to vary the draft of the vessel, and controlling the drawworks in accordance with the variation in the draft of the vessel to cause a length of cable to slip through the hoisting system and maintain the target overpull in the string.

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.

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.

The invention is a land drilling rig (10) having a drilling mast (12), a top drive (14) movable in the drilling mast (12) along the vertical axis of the drilling mast (12), and a crown bearing (18) at an upper end (16) of the drilling mast (12), the crown bearing (18) being movable by means of a positioning device (24), and a method of operating such a drilling rig (10) and a method of operating a top drive (14) in the drilling mast (12) of such a drilling rig (10).

The invention is a land drilling rig (10) having a drilling mast (12), a top drive (14) movable in the drilling mast (12) along the vertical axis of the drilling mast (12), and a crown bearing (18) at an upper end (16) of the drilling mast (12), the crown bearing (18) being movable by means of a positioning device (24), and a method of operating such a drilling rig (10) and a method of operating a top drive (14) in the drilling mast (12) of such a drilling rig (10).

A compensated elevator link is disclosed. In at least one aspect, the compensated elevator link comprises a plurality of cylinder housings and a rod having a plurality of ends, each end comprising a piston head adapted to be slideably received within one of the cylinder housings for defining first and second hydraulic cylinders. Each hydraulic cylinder has at least one annulus for receiving a non-compressible fluid. The rod comprises a passage for receiving a compressible fluid, wherein each piston head comprises at least one passage to allow selective displacement of the non-compressible fluid between the annulus of the cylinder housing and the passage within the rod during selective displacement of the hydraulic cylinders between a contracted condition to an extended condition for either compression or expansion of the compressible fluid by the non-compressible fluid.

A compensated elevator link is disclosed. In at least one aspect, the compensated elevator link comprises a plurality of cylinder housings and a rod having a plurality of ends, each end comprising a piston head adapted to be slideably received within one of the cylinder housings for defining first and second hydraulic cylinders. Each hydraulic cylinder has at least one annulus for receiving a non-compressible fluid. The rod comprises a passage for receiving a compressible fluid, wherein each piston head comprises at least one passage to allow selective displacement of the non-compressible fluid between the annulus of the cylinder housing and the passage within the rod during selective displacement of the hydraulic cylinders between a contracted condition to an extended condition for either compression or expansion of the compressible fluid by the non-compressible fluid.

A motion compensating system is usable on a vessel during well intervention operations through a riser. The system includes a first floor; a second floor; a plurality of hydraulic cylinders connecting the first floor to the second floor; a bearing retainer attachable to the second floor; a spherical bearing provided between the second floor and the bearing retainer, wherein the spherical bearing includes a central opening therethrough for the riser to allow angular movement of the riser relative to the first and second floors; an insert bearing sleeve at least partially located inside the central opening of the spherical bearing; and a slip bowl attachable to the insert bearing sleeve. Each of the first floor, the second floor, the bearing retainer, the insert bearing sleeve and the slip bowl have an opening therethrough for the riser, and each opening is aligned with the central opening of the spherical bearing.

Disclosed is a drilling system for rock drilling with a drill string, wherein the drill string includes at least one bendable drill pipe. The drilling system further includes at least two block and tackle systems for driving an end of the drill string in a first direction; and at least two conveyor devices adapted to guide and bend the drill string between the first direction and a second direction, so as to convert a motion of the drill string between the first direction and the second direction.