OFFSHORE DRILLING VESSEL AND INSTALLATION FOR PERFORMING SUBSEA WELLBORE RELATED ACTIVITIES.

摘要

An offshore drilling vessel comprises a floating hull, a moonpool, and a drilling tower. A main hoisting device comprises a travelling top drive carrier, a top sheave assembly with carrier suspension cable sheaves, and vertically oriented hydraulic piston-and-cylinder type lift devices. Carrier suspension cables have one end secured to the carrier and extend over a respective sheave to another end connected to one of an anchor or to a winch fixed in relation to the hull. A vertically mobile working deck is provided with a slip device that is configured to suspend a tubulars string in the firing line. The working deck is suspended from a working deck suspension cable which is reeved independent from the lift devices. An integrated heave compensation system is provided that is configured to establish, in operation thereof, a heave compensated motion of the working deck and a synchronous heave compensated motion of the carrier in order to obtain synchronous heave compensated motions of the working deck and the carrier. The system comprises a common heave compensation device that acts on both the carrier suspension cables and the working deck suspension cables so that when a load formed by a tubulars string initially suspended from the carrier is transferred to the slip device or vice versa, the load on the common heave compensation device remains substantially the same.