Offshore drilling rig and a method of operating the same

An offshore drilling rig comprising:

• a drill deck;
• a first work center arranged in the drill deck;
• a diverter system operatively connectable to a riser extending towards the seafloor;
• a first hoisting system adapted for raising or lowering tubular equipment through the first work center;
• a second work center arranged in the drill deck horizontally spaced apart from the first work center;
• a second hoisting system adapted for raising or lowering tubular equipment through at least the second work center;
• a first positioning system configured for positioning at least the diverter system selectively at a first horizontal position and a second horizontal position, different from the first horizontal position;
• and
• a riser tensioning system operable to provide tension to said riser;
• wherein the first positioning system is further configured to position the riser tensioning system selectively at the first horizontal position and the second horizontal position;
• wherein the first hoisting system is operable to raise or lower tubular equipment through the first work center and through said diverter system at least when said diverter system is positioned at said first horizontal position and the drilling rig is operable to raise or lower tubular equipment through the diverter system by means of at least the second hoisting system when the diverter system is positioned at said second horizontal position.

A method of performing drilling operations by using an offshore drilling rig, the drilling rig comprising:

• a drill deck;
• at least two work centers arranged in the drill deck horizontally spaced apart from each other, at least one of the work centers being operable as a primary well center and at least one of the work centers being displaceable;
• a first hoisting system adapted for raising or lowering tubular equipment through at least one of the work centers;
• a second hoisting system adapted for raising or lowering tubular equipment through at least one of the work centers;
• and wherein the method comprises:
• positioning a displaceable one of the work centers at a first horizontal position;
• performing drilling operations through the displaceable work center by means of at least the first hoisting system;
• moving the displaceable work center from the first to a second horizontal position, different from the first horizontal position;
• continuing drilling operations through the displaceable work center by means of at least the second hoisting system.

An offshore drilling rig comprising:

• a drill deck;
• a first work center arranged in the drill deck;
• a diverter system operatively connectable to a riser extending towards the seafloor;
• a first hoisting system adapted for raising or lowering tubular equipment through the first work center;
• a second work center arranged in the drill deck horizontally spaced apart from the first work center;
• a second hoisting system adapted for raising or lowering tubular equipment through at least the second work center;
• a first positioning system configured for positioning at least the diverter system selectively at a first horizontal position and a second horizontal position, different from the first horizontal position;
• and
• wherein the first hoisting system is operable to raise or lower tubular equipment through the first work center and through said diverter system at least when said diverter system is positioned at said first horizontal position and the drilling rig is operable to raise or lower tubular equipment through the diverter system by means of at least the second hoisting system when the diverter system is positioned at said second horizontal position;
• and
• wherein the diverter system and the first positioning system are configured so that the diverter system can be moved from the first horizontal position to the second horizontal position, while the diverter system is connected to the riser extending towards the seafloor.