Drilling vessel and method for operating a drilling vessel adapted to run large diameter casing strings

A method for running surface casing from a drilling vessel adapted to handle large diameter surface casing joints each having a diameter of over 20 inch (51 cm) and a length of 30-50 feet (9-15 meters), and build a surface casing string from said joints, comprising the step of using the drilling vessel which is provided with:

• a deck with a surface casing stand storage;
• a casing stand handling system comprising a crane and a catwalk machine;
• a surface casing string handling capacity hoisting device having a surface casing string lifting tool connectable to a surface casing stand;
• and
• a surface casing string hanger,
• wherein the method comprises the steps of:
• a) interconnecting, on said vessel, three or more surface casing joints each having a diameter of over 20 inch (51 cm) and a length of 30-50 feet (9-15 meters) into pre-assembled surface casing stands each having a length of over 100 feet (30 meters);
• b) storing the pre-assembled surface casing stands in the surface casing stand storage in a substantially horizontal position;
• c) operating the casing stand handling system to transfer a first pre-assembled surface casing stand of the pre-assembled surface casing stands from the surface casing stand storage to the surface casing string handling capacity hoisting device;
• d) connecting the casing lifting tool to said first surface casing stand;
• e) lifting said first surface casing stand such that the first surface casing stand is suspended in a substantially vertical position from said surface casing string handling capacity hoisting device in a firing line;
• f) operating the surface casing string handling capacity hoisting device to lower the first surface casing stand in said firing line;
• g) temporarily holding the lowered first surface casing stand in the firing line by the surface casing string hanger and disconnecting the first surface casing stand from the casing lifting tool;
• h) repeating steps d)-f) for a second pre-assembled surface casing stand of the pre-assembled surface casing stands;
• i) aligning the second surface casing stand above the first surface casing stand;
• j) interconnecting the second surface casing stand and the first surface casing stand to form a surface casing string;
• k) releasing the surface casing string from the casing string hanger;
• l) lowering the surface casing string over the length of the second surface casing stand by the casing lifting tool;
• m) temporarily holding the surface casing string in the firing line by the surface casing string hanger and disconnecting the surface casing string from the casing lifting tool;
• n) repeating steps d)-f) and i)-l) for a third pre-assembled surface casing stand of the pre-assembled surface casing stands.