دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a floating offshore drilling unit that has pontoons and columns that, when flooded. cause the unit to submerge to a predetermined depth. Living quarters, storage space, and so forth are assembled on the deck. Semisutxnersible rigs are self-propelled or towed to a drilling site and anchored or dynamically positioned over the site, or both. In shallow water, some semi-submersibles can be ballasted to rest on the seabed. Semi-submersibles ale more stable than drill ships and ship-shaped barges and are used extensively to drill wildcat wells in rough waters such as the North Sea. Two types of semi-submersible rigs ale the bottle- type and the column-stabilized. See floating offshore drilling rig.