Offshore apparatus and method for oil operations

An apparatus for offshore oil operations, comprising in combination:

• means for supporting and stabilizing said apparatus including pontoon means having selected displacement and having a water plane area whereby said apparatus may be towed at a selected draft;
• means carried by said support means providing an upwardly facing body opening;
• means receivable within said means providing said body opening in telescopic relation therewith for relative movement and a deck means carried by said receivable means;
• means connecting said deck means and said pontoon means for assisting in control of said relative movement;
• means for selectively ballasting said support means and said means received within said body opening;
• and shoulder means on said support means and shoulder means on said means receivable within said opening for abutting engagement when said receivable means is raised upwardly of said opening to maintain said apparatus in operating mode.

In a method of fabricating, transporting, installing, and operating a floating offshore apparatus for drilling, production, and storage of oil, the apparatus including telescopic arranged upper and lower hulls, said lower hull having a body opening in which the upper hull is received and includes a pontoon having a selected water plane area, said upper and lower hulls having selectively floodable variable ballast tanks, and a deck on top of the upper hull;

• the steps of:
• fabricating the apparatus with the upper hull within the body opening of the lower hull and in telescopic relation;
• supporting the upper and lower hulls in such relation during transport at towing draft;
• flooding selected tanks to provide a slightly positively buoyant lower hull,
• providing sufficient water plane area above said pontoon to assure stability during towing;
• flooding selected ballast tanks in the upper hull to lower the center of gravity of the upper hull in the body opening;
• flooding selected tanks in the pontoon so that the buoyancy of the pontoon is slightly negative;
• connecting the deck to the lower hull by support lines;
• further flooding tanks in the pontoon while maintaining selected tension of the support lines until the lower hull is completely submerged;
• continuing flooding of pontoon tanks and lower hull tanks until the upper hull is displaced upwardly in the body opening and is in non-telescopic relation to the lower hull;
• holding the non-telescopic relation of the upper and lower hulls by abutting stop means thereon;
• deballasting the upper hull to raise the upper and lower hulls to operating draft;
• and holding the position of the apparatus relative to a well site.