Systems, apparatuses, and methods for removing fixed offshore platforms

Abstract

Systems, apparatuses, and methods for removing fixed offshore platforms using a semi-submersible marine vessel are described. The semi-submersible marine vessel may comprise a main body, a mooring system, a lifting system, and a gate disposed at the second end. The main body may have an extended shape sized to house a fixed offshore platform oriented in a prone position. The main body may have a first end opposing a second end and a first side opposing a second side, the first end and the second end having dimensions that exceed dimensions of a footprint of the fixed offshore platform, the first side and the second side having dimensions that exceed dimensions of the fixed offshore platform oriented in a prone position. The lifting system may have a plurality of strand jacks and plurality of strand jack cables.

What is claimed is: 
     
         1 . A semi-submersible marine vessel configured for removing fixed offshore platforms such as steel piled jackets, the semi-submersible marine vessel comprising:
 a main body having an extended shape sized to house a fixed offshore platform oriented in a prone position, the main body having first end opposing a second end and a first side opposing a second side, the first end and the second end having dimensions that exceed dimensions of a footprint of the fixed offshore platform, the first side and the second side having dimensions that exceed dimensions of the fixed offshore platform oriented in a prone position;   a mooring system;   a lifting system having a plurality of strand jacks and a plurality of strand jack cables; and   a gate disposed at the second end.   
     
     
         2 . The semi-submersible marine vessel of  claim 1 , wherein the main body has a lower portion and an upper portion, the lower portion being configured to provide sufficient buoyancy to maintain the upper portion above a waterline, and wherein the lower portion is configured to store air or liquid matter. 
     
     
         3 . The semi-submersible marine vessel of  claim 1 , wherein the main body comprises steel plates. 
     
     
         4 . The semi-submersible marine vessel of  claim 1 , further comprising a plurality of vertically disposed columns extending between the upper and the lower portions of the vessel. 
     
     
         5 . The semi-submersible marine vessel of  claim 1 , further comprising a plurality of horizontally disposed pontoons extending between adjacent columns proximal to the lower portion. 
     
     
         6 . The semi-submersible marine vessel of  claim 1 , wherein the upper portion comprises a plurality of mooring winches. 
     
     
         7 . The semi-submersible marine vessel of  claim 1 , wherein the lower portion comprises two or more compartments such that at least some adjacent compartments are in fluid contact with each other. 
     
     
         8 . The semi-submersible marine vessel of  claim 1 , wherein the lower portion comprises a plurality of swivel fairleaders. 
     
     
         9 . The semi-submersible marine vessel of  claim 1 , wherein the gate is a neutrally buoyant gate. 
     
     
         10 . The semi-submersible marine vessel of  claim 1 , wherein the mooring system comprises:
 a first end operatively connected to the semisubmersible vessel configured to secure the mooring system to the vessel;   a second end configured to secure the mooring system to the seabed; and   a line between the first end and the second end configured to facilitate the mooring of the vessel to the seabed, wherein the line between the first end and the second end is arranged in catenary.   
     
     
         11 . The semi-submersible marine vessel of  claim 1 , wherein the lifting system further comprises:
 a plurality of gantry cranes mounted on rails on the upper portion.   
     
     
         12 . The semi-submersible marine vessel of  claim 2 , wherein the liquid matter stored in the lower portion comprises one or more of sea water, and/or ballast water. 
     
     
         13 . The semi-submersible marine vessel of  claim 9 , wherein the gate is opened via removal and flotation on water. 
     
     
         14 . The semi-submersible marine vessel of  claim 9 , wherein the gate is affixed to the vessel via hinges configured to facilitate opening and closing of the gate. 
     
     
         15 . The semi-submersible marine vessel of  claim 10 , wherein the line is a neutrally buoyant line. 
     
     
         16 . The semi-submersible marine vessel of  claim 10 , wherein the second end of the mooring system further comprises an anchor configured to anchor the mooring system to the seabed. 
     
     
         17 . The semi-submersible marine vessel of  claim 10 , wherein the second end of the mooring system further comprises a deadweight. 
     
     
         18 . The semi-submersible marine vessel of  claim 10 , wherein the line is a neutrally buoyant line. 
     
     
         19 . The semi-submersible marine vessel of  claim 10 , wherein the first line portion is a chain. 
     
     
         20 . The semi-submersible marine vessel of  claim 10 , wherein the first line portion is a cable. 
     
     
         21 . A method for decommissioning fixed offshore platforms such as steel piled jackets, the method comprising:
 maneuvering a semi-submersible marine vessel towards a fixed offshore platform jacket, the semi-submersible marine vessel comprising:
 a main body having an extended shape sized to house a fixed offshore platform oriented in a prone position, the main body having first end opposing a second end and a first side opposing a second side, the first end and the second end having dimensions that exceed dimensions of a footprint of the fixed offshore platform, the first side and the second side having dimensions that exceed dimensions of the fixed offshore platform oriented in a prone position; 
 a mooring system; 
 a lifting system having a plurality of strand jacks and a plurality of strand jack cables; and 
 a gate disposed at the second end; 
   opening the gate   surrounding the fixed offshore platform jacket with the semi-submersible marine vessel main body;   ballasting the main body so that the a lower portion of the main body is submerged in the water;   attaching the fixed offshore platform jacket to the strand jack cables at two or more points on the fixed offshore platform jacket   affecting a buoyancy of the fixed offshore platform jacket to facilitate lifting or rotating the fixed offshore platform jacket;   deballasting the main body in order to free the offshore platform jacket from seabed;   rotating the fixed offshore platform jacket under water from a vertical position to a prone position;   housing the fixed offshore platform jacket oriented in the prone position within the main body to enable transport of the semi-submersible marine vessel towards a dry-dock;   closing the gate; and   guiding the semi-submersible marine vessel towards the dry-dock.   
     
     
         22 . The method of  claim 21 , wherein affecting the buoyancy of the fixed offshore platform jacket includes filling at least a portion of the fixed offshore platform jacket with compressed air. 
     
     
         23 . The method of  claim 21 , wherein the affected buoyancy of the fixed offshore platform jacket is at or near neutrally buoyant in sea water. 
     
     
         24 . A semi-submersible marine vessel configured for removing fixed offshore platforms such as steel piled jackets, the semi-submersible marine vessel comprising:
 a main body sized to surround a portion of a fixed offshore platform oriented in a vertical position, the main body having a first end and a first side opposing a second side, the first end having dimensions that exceed a first lateral dimension of the fixed offshore platform oriented in a vertical position, the first side and the second side having dimensions that exceed a second lateral dimension of the fixed offshore platform oriented in a vertical position, the first lateral dimension being perpendicular to the second lateral dimension;   a mooring system; and   a lifting system having a plurality of strand jacks and a plurality of strand jack cables.   
     
     
         25 . The semi-submersible marine vessel of  claim 1 , wherein the main body has a lower portion and an upper portion, the lower portion being configured to provide sufficient buoyancy to maintain the upper portion above a waterline, and wherein the lower portion is configured to store air or liquid matter. 
     
     
         26 . The semi-submersible marine vessel of  claim 1 , wherein the main body comprises steel plates. 
     
     
         27 . The semi-submersible marine vessel of  claim 1 , further comprising a plurality of vertically disposed columns extending between the upper and the lower portions of the vessel. 
     
     
         28 . The semi-submersible marine vessel of  claim 1 , further comprising a plurality of horizontally disposed pontoons extending between adjacent columns proximal to the lower portion. 
     
     
         29 . The semi-submersible marine vessel of  claim 1 , wherein the lower portion comprises two or more compartments such that at least some adjacent compartments are in fluid contact with each other. 
     
     
         30 . The semi-submersible marine vessel of  claim 1 , further comprising a gate disposed opposite to the first end. 
     
     
         31 . The semi-submersible marine vessel of  claim 1 , wherein the upper portion comprises a plurality of mooring winches. 
     
     
         32 . The semi-submersible marine vessel of  claim 1 , wherein the lower portion comprises a plurality of swivel fairleaders. 
     
     
         33 . The semi-submersible marine vessel of  claim 1 , wherein the mooring system comprises:
 a first end operatively connected to the semisubmersible vessel configured to secure the mooring system to the vessel;   a second end configured to secure the mooring system to the seabed; and   a line between the first end and the second end configured to facilitate the mooring of the vessel to the seabed, wherein the line between the first end and the second end is arranged in catenary.   
     
     
         34 . The semi-submersible marine vessel of  claim 1 , wherein the lifting system further comprises:
 a plurality of gantry cranes mounted on rails on the upper portion.   
     
     
         35 . The semi-submersible marine vessel of  claim 2 , wherein the liquid matter stored in the lower portion comprises one or more of sea water, and/or ballast water. 
     
     
         36 . The semi-submersible marine vessel of  claim 7 , wherein the gate is a neutrally buoyant gate. 
     
     
         37 . The semi-submersible marine vessel of  claim 10 , wherein the line is a neutrally buoyant line. 
     
     
         38 . The semi-submersible marine vessel of  claim 10 , wherein the second end of the mooring system further comprises an anchor configured to anchor the mooring system to the seabed. 
     
     
         39 . The semi-submersible marine vessel of  claim 10 , wherein the second end of the mooring system further comprises a deadweight. 
     
     
         40 . The semi-submersible marine vessel of  claim 10 , wherein the line is a neutrally buoyant line. 
     
     
         41 . The semi-submersible marine vessel of  claim 10 , wherein the first line portion is a chain. 
     
     
         42 . The semi-submersible marine vessel of  claim 10 , wherein the first line portion is a cable. 
     
     
         43 . The semi-submersible marine vessel of  claim 13 , wherein the gate is opened via removal and flotation on water. 
     
     
         44 . The semi-submersible marine vessel of  claim 13 , wherein the gate is affixed to the vessel via hinges configured to facilitate opening and closing of the gate. 
     
     
         45 . A method for decommissioning fixed offshore platforms such as steel piled jackets, the method comprising:
 maneuvering a semi-submersible marine vessel towards a fixed offshore platform jacket, the semi-submersible marine vessel comprising:   a main body sized to surround a portion of a fixed offshore platform oriented in a vertical position, the main body having a first end and a first side opposing a second side, the first end having dimensions that exceed a first lateral dimension of the fixed offshore platform oriented in a vertical position, the first side and the second side having dimensions that exceed a second lateral dimension of the fixed offshore platform oriented in a vertical position, the first lateral dimension being perpendicular to the second lateral dimension;
 a lifting system having a plurality of strand jacks and a plurality of strand jack cables; 
 a mooring system; and 
 a gate; 
   opening the gate   surrounding the fixed offshore platform jacket with the semi-submersible marine vessel main body;   ballasting the main body so that a lower portion of the main body is submerged in the water;   attaching the fixed offshore platform jacket to the strand jack cables at two or more points on the fixed offshore platform jacket   affecting a buoyancy of the fixed offshore platform jacket to facilitate lifting;   deballasting the main body in order to free the offshore platform jacket from a seabed;   housing the fixed offshore platform jacket oriented in the vertical position within the main body to enable transport of the fixed offshore platform jacket above the seabed surface;   closing the gate;   guiding the semi-submersible marine vessel towards a higher elevation along an inclined surface of seabed;   setting the fixed offshore platform jacket down vertically on the inclined surface of seabed;   cutting an exposed top portion of the fixed offshore platform jacket;   loading the cut potion on a barge in order to be shipped to shore for further processing; and   repeating the previous steps as necessary to completely remove the fixed offshore platform jacket from water.   
     
     
         46 . The method of  claim 22 , wherein affecting the buoyancy of the fixed offshore platform jacket includes filling at least a portion of the fixed offshore platform jacket with compressed air. 
     
     
         47 . The method of  claim 22 , wherein the affected buoyancy of the fixed offshore platform jacket is at or near neutrally buoyant in sea water.