Modular Relocatable Offshore Support Tower

Abstract

An offshore support tower assembly comprises a base disposed at the sea floor. In addition, the support tower assembly comprises a plurality of anchors securing the base to the sea floor. Further, the support tower assembly comprises a support frame coupled to the base. The support frame comprises plurality of modular tower sections in a stacked arrangement. The support tower assembly also comprises a deck supported by the support frame.

What is claimed is: 
     
         1 . An offshore support tower assembly, comprising:
 a base disposed at the sea floor;   a plurality of anchors securing the base to the sea floor;   a support frame coupled to the base, wherein the support frame comprises plurality of modular tower sections in a stacked arrangement; and   a deck supported by the support frame.   
     
     
         2 . The support tower assembly of  claim 1 , wherein the base is ballast adjustable. 
     
     
         3 . The support tower assembly of  claim 2 , wherein the base comprises a plurality of tubular members, wherein each tubular member is independently ballast adjustable. 
     
     
         4 . The support tower assembly of  claim 2 , wherein the base comprises an upper deck and a lower deck coupled to the upper deck with a plurality of support members. 
     
     
         5 . The support tower assembly of  claim 1 , wherein the anchors are moveably coupled to the base. 
     
     
         6 . The support tower assembly of  claim 1 , wherein each anchor is a driven pile, a gravity pile, or a suction pile. 
     
     
         7 . The support tower assembly of  claim 1 , wherein the modular tower sections are releasably coupled to the base and to each other with a plurality of mechanical connections. 
     
     
         8 . The support tower assembly of  claim 1 , wherein the deck is part of a jack-up rig having a plurality of legs moveably coupled to the deck; and
 wherein the plurality of legs are coupled to an upper end of the support frame.   
     
     
         9 . The support tower assembly of  claim 1 , wherein the deck is supported by the support frame at a position above the surface of the water. 
     
     
         10 . A method for deploying an offshore support tower assembly, the method comprising:
 (a) lowering a base subsea to the sea floor;   (b) lowering a plurality of anchors subsea;   (c) securing the base to the sea floor with a plurality of anchors after (a) and (b);   (d) installing a modular support frame onto the base; and   (e) coupling a deck to an upper end of the support frame.   
     
     
         11 . The method of  claim 10 , further comprising ballasting the base after (a). 
     
     
         12 . The method of  claim 11 , further comprising de-ballasting the base before (a). 
     
     
         13 . The method of  claim 10 , wherein (d) comprises:
 (d1) lowering a plurality of modular tower sections subsea;   (d2) stacking the modular tower sections one on top of the other; and   (d3) releasably and mechanically coupling the modular tower sections to each other and to the base.   
     
     
         14 . The method of  claim 13 , wherein each modular tower section is ballast adjustable. 
     
     
         15 . The method of  claim 14 , further comprising:
 de-ballasting each modular tower section before it is lowered subsea;   ballasting each modular tower section after it is coupled to the base.   
     
     
         16 . The method of  claim 13 , wherein at least one of the modular tower sections is transported offshore in a horizontal orientation and transitioned to a vertical orientation before being lowered subsea. 
     
     
         17 . The method of  claim 10 , wherein the anchors are suction piles, and wherein (c) comprises:
 pumping fluid from an interior of each anchor to penetrate the sea floor with each anchor.   
     
     
         18 . The method of  claim 10 , further comprising:
 (f) removing the deck from the support frame after (e);   (g) uninstalling the modular support tower from the base after (f);   (h) removing the base from the sea floor after (g);   (i) moving the base and the modular support tower to another offshore installation location; and   (j) repeating (c)-(e) after (i).   
     
     
         19 . The method of  claim 10 , further comprising coupling a plurality of mooring lines to the modular support tower. 
     
     
         20 . The method of  claim 10 , wherein the deck is supported by the support frame at a position above the surface of the water. 
     
     
         21 . The method of  claim 10 , further comprising supporting a jack-up rig including the deck with the support tower. 
     
     
         22 . A method for deploying an offshore tension leg platform (TLP), the method comprising:
 (a) floating the TLP offshore to an installation site;   (b) transporting a base to the offshore installation site;   (c) lowering the base to the sea floor;   (d) lowering a plurality of anchors subsea, wherein each anchor has a lower end and an upper end comprising a tendon termination coupling;   (e) securing the base to the sea floor with the plurality of anchors after (d); and   (f) coupling the TLP to the base after (e) with a plurality of tendons, wherein each tendon has a lower end releasably coupled to one of the tendon termination couplings and an upper end secured to the TLP.   
     
     
         23 . The method of  claim 22 , further comprising de-ballasting the base during (c) and ballasting the base after (c). 
     
     
         24 . The method of  claim 22 , wherein the base is ballast adjustable. 
     
     
         25 . The method of  claim 22 , wherein each of the anchors is a suction pile and (e) comprises:
 pumping fluid from an interior of each anchor to penetrate the sea floor with each anchor.   
     
     
         26 . The method of  claim 22 , further comprising:
 (g) disconnecting the plurality of tendons from the anchors after (f);   (h) removing the base from the sea floor after (h);   moving the base and the TLP to another offshore installation location; and   (j) repeating (e) and (f) after (i).