CIDS
CIDS is an acronym for "Concrete Inland Drilling System". It's a bottom supported MODU that is used for drilling wells in arctic conditions and is also known as "Arctic Submersible". CIDS or Arctic submersible rig is used for drilling arctic wells in shallow waters. In winter, ice blocks tend to flow with the ocean current and apply enough force to damage the jack up legs or barge hulls. Hence reinforced hulls called "Caisson" are used with arctic submersible rigs. CIDS is towed to location when the sea is ice free and Caissons are submerged into sea bottom to allow uninterrupted operations even with ice flow.