Platforms gravity based

Tension leg and floating platforms can easily be released and towed away for service elsewhere, which is cheap and attractive. In the case of the fixed platforms, the topside modules are removed by lift barge and taken to shore for disposal. Gravity based structures can in theory be deballasted and floated away to be re-employed or sunk in the deep ocean, and steel jackets cut and removed at an agreed depth below sea level. In some areas jackets are cleaned and placed as artificial reefs on the seabed. The... 

Ahydrate blockage in the export line from Shell s Bullwinkle platform in the Green Canyon Block 65 to the Boxe platform was reported in DeepStar Report A208-1 (Mentor Subsea, 1996, p. 52). The 12 in., 39,000 ft line was not insulated. The seawater temperature was 50°F at the base of the platform in 1,400 ft of water. Gas gravity was 0.7 and the flow rate was 140 MMscf/d at an inlet pressure of 800 psi. 

Schematic of base of gravity platform showing dowel, concrete skirt, and steel skirt.

There are two primary purposes of the dowels (1) to help position the platform during touchdown, and (2) to prevent lateral platform motion during penetration of the foundation skirts. Cross sections through the caisson base for a number of North Sea gravity structures are shown in Figure 10.35. 

After the base of the gravity structure has been seated, the gap between the seafloor and the base is grouted. The primary purposes for grouting are (1) to avoid further penetration and maintain verticality, (2) to develop uniform stresses on the platform and prevent localized stress concentrations, and (3) to avoid piping from water pockets below the base during environmental loading. 

Gravity is such a pervasive force that its ramifications on erq)eriments are often not considered since the influence of gravity is perceived to be unavoidable. As a result, laboratory platforms that achieve an effective reduction of acceleration on e q)eriments are often under appreciated. Based on the above arguments it is apparent that the reduction in the effects of acceleration on e q)eriments can be used fi>r studies of diffusive processes, sur ce-tension driven convection, containerless processing of materials, research on the scaling properti of phase transitions, etc. Space Shuttle experiments have been conducted involving each of the above topics. 

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