| 摘要 |
A method and apparatus for securing a buoyant, surface structure in deepwater, such as those used in offshore oil and gas drilling and producing, is disclosed. The surface structure is water surface piercing or fully submerged. Buoyancy tanks inside the surface structure are used as liquid vibration dampers to enhance the motion performance. All tethers are sufficiently taut and some or all of them are inclined. The attachment points of the tethers on the surface structure are at same or different elevations. An alternative attachment method, named as single tether-multiple attachment leg, is also disclosed. The tether system provides stiffness in both vertical and horizontal direction so that all six degrees-of-freedom motions of the structure, namely, surge, sway, heave, roll, pitch, and yaw are constrained with stiffness. This fully constraint platform (FCP) has minimum motion in winds, currents, swells, and surface and internal waves, and therefore has many practical uses, as outlined herein.
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