Editing Oil platform (section)

===Semi-submersible platform===
{{Main|Semi-submersible platform}}
These platforms have hulls (columns and pontoons) of sufficient [[buoyancy]] to cause the structure to float, but of weight sufficient to keep the structure upright. Semi-submersible platforms can be moved from place to place and can be ballasted up or down by altering the amount of flooding in buoyancy tanks. They are generally anchored by combinations of chain, wire rope or polyester rope, or both, during drilling and/or production operations, though they can also be kept in place by the use of [[dynamic positioning]]. Semi-submersibles can be used in water depths from {{convert|60|to|6000|m|sigfig=1}}.