JACKABLE OIL RIGS AND CORNER COLUMNS FOR PRODUCING LEGS IN AN OIL RIG

摘要

2063380 9101411 PCTABS00003 The invention relates to a jackable oil rig designed for large ocean depths and which comprises at least one leg and a deck having a jack system. The rig's leg comprises a number of corner columns together with transverse bracing stays and each corner column comprises a substantially annular outer pipe (26) in which a substantially annular inner pipe (28) is arranged. The annular space (27) between the inner wall of the outer pipe and the outer wall of the inner pipe is filled with a hardenable material such as concrete, capable of transferring forces between the pipes, the outer diameter of the outer pipe (26) being approximately constant over the whole length of the column (24), and the oil rig is characterised in that the outer diameter of the inner pipe (28) is approximately constant while its wall thickness ti increases from upper section (I) of the corner column to the lowermost section (VI) of the corner column. According to a preferred construction the wall thickness ti of the inner pipe (28) increases step by step from about 30 mm in the upper section of the rig leg to about 150 mm in the lower section of the leg. This corner column construction makes it possible to produce jackable oil rigs which can operate at ocean depths completely down to 200 metres.