US Patent 10161200 Heave compensation system

A drilling system comprises a drilling vessel comprising a rig floor, a derrick extending from the rig floor of the drilling vessel along a longitudinal axis. The derrick comprises a first end disposed at the rig floor and a second end longitudinally spaced from the first end, and a heave compensation system disposed at the second end of the derrick. The heave compensation system comprises a support structure comprising a first laterally extending frame coupled to the second end of the derrick, and a second laterally extending frame spaced from the first frame, a crown block coupled to the support structure and a transport assembly coupled to the second frame of the support structure. The transport assembly comprises a first lifting lug and a cylinder assembly supported by the first frame, wherein the cylinder assembly is releasably coupled with the crown block and configured to longitudinally displace the crown block relative to the support structure in response to a heave movement of the vessel. The transport assembly is configured to releasably couple with the cylinder assembly via a cable extending through the first lifting lug, and to support the weight of the cylinder assembly in response to the cylinder assembly being lowered from the first lifting lug to the rig floor through an internal volume of the derrick.