Offshore drilling system, vessel and method

An offshore drilling vessel for performing subsea wellbore related activities, wherein the drilling vessel comprises:

• a floating hull comprising a moonpool;
• a drilling tower positioned on said hull at or near said moonpool;
• a tubular string main hoisting device comprising:
• a main hoisting winch and main cable connected to said main hoisting winch;
• a crown block mounted on said drilling tower;
• and
• a travelling block suspended from said crown block in a multiple fall arrangement of said main cable, which travelling block is adapted to suspend a tubular string therefrom along a firing line through said moonpool;
• a drill pipe storage rack for storage of drill pipe sections therein, wherein the drill pipe storage rack is mounted on said hull;
• a vertically mobile working deck positioned above the moonpool and vertically movable with respect to said drilling tower and to said hull along said firing line within a motion range including a heave compensation motion range;
• a heave motion compensating pipe racker system comprising at least one pipe racker device that is adapted to move a drill pipe section between said drill pipe storage rack and a position wherein the drill pipe section is in said firing line and between the vertically mobile working deck and the travelling block, wherein said pipe racker device comprises multiple racker assemblies, each of said racker assemblies having a motion arm and a gripper member at an end of said motion arm, said gripper member being adapted to grip a drill pipe section, wherein said racker assemblies of said pipe racker device are arranged on a common vertical rails,
• wherein said common vertical rails with said racker assemblies arranged thereon is mobile in a heave compensation mode with respect to the drilling tower,
• wherein said pipe racker system further comprises a heave motion synchronization system, and
• wherein the mobile working deck is provided with an opening therein that is aligned with said firing line, and wherein the mobile working deck is provided with a drill string slip device that is configured to suspend a drill string in said firing line;
• and
• an integrated heave compensation system configured to provide, in operation thereof, a heave compensated motion of the vertically mobile working deck relative to the hull within said heave compensation motion range and a synchronous heave compensated motion of the travelling block in order to obtain synchronous heave compensated motions of the working deck and the travelling block,
• wherein said heave motion synchronization system of the pipe racker system is configured to, in operation thereof, bring said common vertical rails with said racker assemblies arranged thereon in said heave compensation mode with respect to the drilling tower so that a drill pipe section that has been retrieved from the drill pipe storage rack by means of said racker assemblies of said racker device is brought into a vertical motion that is synchronous with the heave motion of the mobile working deck and of the drill string slip device provided on said mobile working deck.