Offshore apparatus and method for oil operations

摘要

An offshore apparatus and method for oil operations at a deep water well site wherein a lower hull includes a pontoon portion providing a large water plane area and also includes an upwardly facing body opening, an upper hull is fabricated within said body opening in fully telescoped relation therewith, said upper hull and lower hull being vertically relatively movable, and a deck carried by the upper hull. The pontoon portion has suffient displacement to support the apparatus in towing draft mode. The lower hull and upper hull include floodable compartments for selective ballasting and deballasting to raise and lower the hulls relative to each other in order to submerge the apparatus under stable conditions and to change the draft from towing mode to operating mode in which the hulls are in extended nontelescopic relation at a selected draft. Support lines interconnecting the lower hull and deck are selectively tensioned to aid in the transition from towing draft to operating draft. Interengagable stop shoulders are provided between the upper and lower hulls and at operating draft may be secured to assist in maintaining the extended nontelescopic relation thereof. Guides for relative vertical motion of the upper and lower hulls are provided at the outer surface of the upper hull and the stop shoulder of the lower hull. The support lines may later serve as anchor lines.