Drilling system and method

Abstract

A system for drilling a subterranean bore at a subsea location is provided, the system comprising a drilling unit for location on the seabed and remotely operable from the water surface to drill a bore using a drill string; a transport assembly moveable between the water surface and the drilling unit when at the location on the seabed, wherein the transport assembly comprises a receptacle for receiving a downhole tool; first transfer means for transferring a first downhole tool from the drill string to the transport assembly; and second transfer means for transferring a second downhole from the transport assembly to the drill string; whereby the first and second transfer means are operable to recover from the drill string a first downhole tool and deliver to the drill string a second downhole tool in a single deployment of the transport assembly from the water surface to the drilling unit. A method for drilling a subterranean bore at a seabed location comprises providing a drilling unit on the seabed; conducting a drilling operation using a drill string by remote operation of the drilling unit from a surface location, the drill string having therein a first downhole tool; transporting a second downhole tool from the surface to the drilling unit by means of a transport assembly; recovering the first downhole from the drill string to the transport assembly; transferring the second downhole tool from the transport assembly to the drill string; transporting the first downhole tool to the surface by means of the transport assembly; and continuing the drilling operation using the second downhole tool. The system and method are especially useful in the recovery, transport and deployment of an inner tube for holding a core sample.

Dependencies are inferred from the claim text.