Month: July 2009

The advent of more and more deepwater discoveries brings with them significant challenges. Deeper waters mean higher pressures from not only the wells, but also from the subsea environment. A well at 1,500 meters causes an environmental pressure on the valve of 150 bar or 2,175 psi. At these depths, it is necessary not only to keep the process stream in, but also to keep the environment out. Since in addition it is necessary to ensure the equipment meets a design life of over 25 years, the technology used on the pressure boundaries and on dynamic stem sealing applications, must work first time, every time. the majority of subsea equipment is required to conform to API 6A / API 17D PR2. This type of test requires the valve to undergo 160 ambient gas cycles at the maximum operating differential pressure prior to 20 cycles each at the maximum and minimum operating temperatures also on gas

A submersible rig is a mobile drilling platform that is towed to the well site where it is submerged by flooding its lower hull tanks until it rests on the sea floor, with the upper hull above the water surface. After completion of the drilling operation, the rig is refloated by pumping the water out of the lower hull, so that it can be towed to another location. Submersible rigs typically operate in water depths of 12 to 85 feet.

A particular type of floating vessel, usually used as a mobile offshore drilling unit (MODU) that is supported primarily on large pontoon-like structures submerged below the sea-surface. The operating decks are elevated 100 or more feet [30 m] above the pontoons on large steel columns. Once on the desired location, this type of structure is slowly flooded until it rests on the seafloor. After the well is completed, the water is pumped out of the buoyancy tanks the vessel refloated and towed to the next location. Submersibles, as they are known informally, operate in relatively shallow water, since they must actually rest on the seafloor