| 摘要 |
<p>The present invention relates to an improved caisson structure (10) which is adapted to support a production platform (40) above the water (20) and has its base on bottom and has a foot print or base which will pass through the drilling slot of a jackup rig (14). The caisson structure includes a large diameter caisson (26) supported in a base structure (24) including at least three base columns (30) through which piling is placed and bracing (50) extending between the columns and the caisson, a platform (40) supported at the upper end of the caisson with production tubing (36) and its casing (48) extending upward through the caisson, and where desired, filled with concrete (46) surrounding the casing within the caisson. The improved caisson structure can be used to surround and support an existing conductor pipe (44) extending from a subsea wellhead to the surface or to surround a wellhead at the surface and the conductor which extends to such wellhead from a subsea well bore. The improved method of setting the caisson structure includes lifting the structure from a barge (12) and lowering to position its base (24) in engagement with the sea bottom (18) in the desired location, piling (28) is placed in and set through the corner columns (30), the wells (34) are drilled through the caisson (10), the production strings (36) are set and the wellhead production equipment (38) are installed on the productions strings at the platform (40). The piling (28) is steel tubular members which can be cut below the sea bottom to recover the caisson structure after the wells are plugged. The caisson structure after retrieval can be reused in a different location merely by adapting its length to be suitable for the water depth in the new location.</p> |
