Modular offshore drilling unit and method for construction of same

A mobile offshore drilling unit including:

• at least one hull member have an opening of predetermined size for receiving a separately fabricated non-buoyant interchangeable rig block;
• and
• a separately fabricated non-buoyant interchangeable rig block sized to be received in said opening, said block including:
• a main deck including:
• the draw works,
• the drilling floor, and
• a plurality of pipe racks;
• a machinery deck including:
• the diesel/electric power system,
• at least one mud pump, and
• at least one mud tank;
• and
• a tank deck including:
• at least one fuel tank, and
• at least one drilling water tank.

A method of constructing a mobile offshore drilling unit including:

• constructing at a marine shipyard a hull member having an opening of predetermined size for receiving a separately fabricated a non-buoyant interchangeable rig block;
• separately assembling a non-buoyant interchangeable rig block sized to be received in said opening of the hull member, said step of assembling including:
• constructing a main deck having a drilling floor, and mounting a draw works thereon, and
• constructing a machinery deck and installing at least one diesel driver, an electric generator, and at least one mud pump thereon;
• and
• installing the non-buoyant interchangeable rig block in the opening of the hull member and fixably connecting the rig block to the hull member.

A method of constructing a mobile offshore drilling unit including:

• removing a first non-buoyant interchangeable rig block received in an opening of a separately assembled hull member;
• replacing the first non-buoyant interchangeable rig block with a second non-buoyant interchangeable rig block including:
• a main deck having a drilling floor, and a draw works thereon, and
• a machinery deck having at least one diesel driver, an electric generator, and at least one mud pump thereon;
• and
• installing the second non-buoyant rig block in the opening of the hull member and fixably connecting the second non-buoyant rig block to the hull member.