![]() Since the individual piles forming the rings are inclined upon entry into the substratum, wells drilled from these piles may be directionally inclined into more distant formations than those accessible if purely vertical conduits were used to direct a drill string into the substratum.Īdditionally, the concentric ring concept provides an ideal pattern for drilling wells due to the minimum interference of each well with the adjacent wells as each well leaves the rather congested area at the base of the structure. The flexure joint also compliantly resists rotational movement of the structure about the structure's longitudinal axis due to the opposite inclination of the members of each separate ring. The close spacing of the piles at the base of the column minimizes stress due to oscillatory sway movements of the tower, while the orientation or "batter" of the piles aids in resisting lateral movement and large horizontal forces at the base of the column. The resultant flexure joint formed by the orientation of these concentric rings at the ocean floor eliminates the need for cumbersome ball joints. ![]() ![]() The apparatus of the present invention comprises piles oriented at the ocean floor so as to form at least two concentric rings, the orientation of the batter or inclination of the piles of one ring being opposite the orientation of the batter or inclination of the piles of the other ring. The same apparatus should also not limit the drilling of wells to formations disposed vertically beneath the structure. 4, 1972, ball joints may be incorporated into the piles adjacent the ocean floor, or a ball joint may be used in the column, above the piles.īut use of these ball joints necessarily increases the cost and complexity of assembly of the underwater structure and leaves the integrity of the structure dependent upon the ball joints' continued operation.Īn apparatus needs to be developed therefore that is not dependent upon the proper operation of mechanical stress compensation devices. 3,648,638, entitled "Vertically Moored Platforms", filed Mar. Wells may also be drilled vertically downward through these piles, though it is well recognized that use of a curved or inclined pile to direct the well into the substratum would allow the well to be drilled into more distant hydrocarbon bearing formations.ĭue to lateral and rotational movement of the buoyant structure means must also be used at the ocean floor to reduce the resultant shear and bending stresses encountered in the piles. 13, 1970, a circular arrangement of vertical piles can also be used to form the column structure of the buoyant tower. 3,488,967, entitled "Combination Deep Water Storage Tank and Drilling and Production Platform", filed Mar. In any event, the piles must also resist the lateral movement of the buoyant column and supplementary "shear piles" may be added for this purpose.Īs described in U.S. To offset the tower's buoyancy ballast may also be used near the base of the tower. Anchoring can assume a number of forms presently known and including primarily the use of vertical piling which is normally embedded downward into the substratum a sufficient distance to be held in position by the subsoil. To achieve such a purpose, the lower or base end must be so firmly embedded or weighted to the ocean floor that, in effect, it will tether the buoyant tower structure to the ocean floor. In the instance of a self-supporting or buoyant tower structure for use in deeper water, however, with a single upstanding column-like member that is controllably buoyant in the water, the lower portion of such a buoyant tower member must be firmly anchored to the ocean floor such that the column will, under the influence of wind, waves and other elements, be permitted only a limited degree of oscillatory movement about a fixed lower end. In the positioning of a floatable or semi-submersible marine structure in an offshore body of water, the method normally followed is to anchor the structure by use of anchors and lines which radiate downwardly from the structure. The invention relates to an apparatus used to secure an offshore buoyant tower structure to the ocean floor.
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