| 摘要 |
<p>Semi-submersible legs are embodied as close-ended cylinders or other similar shapes or combination of shapes having the capability to be ballasted or made buoyant. The semi-submersible legs are connected to a jack-up drilling vessel so that they slide vertically through the vessel deck into the underlying body of water and are lockable at any position along their vertical path. The method of their use requires lowering the extendible main supporting legs of a jack-up drilling vessel above the ocean floor, lowering the semi-submersible legs into the water, making them buoyant so as to cause the vessel to raise out of the water to a distance above probable wave action at which time the extendible main support legs are lowered to a supporting position onto or into the ocean floor. With the extendible supporting legs in a supporting position, the semi-submersible legs are retracted; if the extendible legs penetrate a soft bottom, the semi-submersible legs are first ballasted to serve as an additional jacking down source for the supporting legs and then retracted and deballasted. The foregoing steps are reversed when the drilling vessel is to be relocated with or without the supplemental steps of making the semi-submersible legs additionally buoyant and or lowering the vessel hull to the water surface thus providing an extra lift force on the support legs. The vessel hull is jacked up on the buoyant support of the semi-submersible legs prior to completely removing the extendible main legs from the ocean floor penetration or surace contact.</p> |
