Systems and Methods for Tethering a Subsea Structure

Abstract

A system for tethering a subsea structure includes an anchor embedded in the sea bed, a mud mat disposed partially above the seafloor, a link attached to the anchor and to the mud mat, and a flexible tension member. One end of the flexible tension member is coupled to a tensioning system configured to pay in and pay out the flexible tension member. The tensioning system is mounted on one of the subsea structure or on the mud mat. The other end of the flexible tension member is coupled to the other of the subsea structure or on the mud mat. The anchor may optionally be buried below the seafloor.

1 . A system for tethering a subsea structure, the system comprising:
 an anchor embedded in the sea bed;   a mud mat disposed partially above the seafloor;   a link attached to a point of the anchor located below the seafloor and to the mud mat;   a flexible tension member, wherein the flexible tension member extends horizontally and vertically from a first end to a second end to impart a lateral preload and a vertical preload to the subsea structure; and   a tensioning system mounted on the mud mat, wherein the tensioning system is configured to pay in and pay out the flexible tension member,   wherein the first end of the flexible tension member is coupled to the tensioning system, and   wherein the second end of the flexible tension member is coupled to the subsea structure.   
     
     
         2 . A system for tethering a subsea structure, the system comprising:
 an anchor embedded in sea bed;   a mud mat disposed partially above the seafloor;   a link attached to a point of the anchor located below the seafloor and to the mud mad;   a flexible tension member, wherein the flexible tension member extends horizontally and vertically from a first end to a second end to impart a lateral preload and a vertical preload to the subsea structure; and   a tensioning system mounted on the subsea structure, wherein the tensioning system is configured to pay in and pay out the flexible tension member,   wherein the first end of the flexible tension member is coupled to the tensioning system, and   wherein the second end of the flexible tension member is coupled to the mud mat.   
     
     
         3 . The system of  claim 1 , wherein the anchor is buried below the seafloor. 
     
     
         4 . The system of  claim 3 , wherein the anchor includes one of a torpedo anchor and suction embedded plate anchor (SEPLA). 
     
     
         5 . The system of  claim 1 , wherein the anchor has an upper end disposed above the seafloor and a lower end disposed in the seabed below the seafloor. 
     
     
         6 . The system of  claim 5 , wherein the anchor includes a suction pile. 
     
     
         7 . The system of  claim 1 , wherein the subsea structure includes a subsea blow-out preventer (BOP). 
     
     
         8 . The system of  claim 1 , further comprising another tensioning system mounted on the subsea structure, wherein the second end of the flexible tension member is coupled to the subsea structure by attaching the second end of flexible tension member to the other tensioning system. 
     
     
         9 . The system of  claim 2 , further comprising another tensioning system mounted on the mud mat, wherein the second end of the flexible tension member is coupled to the mud mat by attaching the second end of flexible tension member to the other tensioning system. 
     
     
         10 . A method for tethering a subsea blow-out preventer (BOP) coupled to a subsea wellhead, the method comprising:
 embedding an anchor to in the sea bed;   disposing a mud mat partially above the seafloor;   attaching a link to a point of the anchor located below the seafloor and to the mud mat;   mounting a tensioning system on the mud mat; and   applying tension to a flexible tension member to impart a lateral preload and a vertical preload to the subsea BOP,   wherein the flexible tension member extends horizontally and vertically from a first end coupled to the tensioning system to a second end coupled to the subsea BOP, and   wherein the tensioning system is configured to pay in and pay out the flexible tension member.   
     
     
         11 . A method for tethering a subsea blow-out preventer (BOP) coupled to a subsea wellhead, the method comprising:
 embedding an anchor to in the sea bed;   disposing a mud mat partially above the seafloor;   attaching a link to a point of the anchor located below the seafloor and to the mud mat;   mounting a tensioning system on the subsea BOP; and   applying tension to a flexible tension member to impart a lateral preload and a vertical preload to the subsea BOP,   wherein the flexible tension member extends horizontally and vertically from a first end coupled to the tensioning system to a second end coupled to the mud mat, and   wherein the tensioning system is configured to pay in and pay out the flexible tension member.   
     
     
         12 . The method of  claim 10 , wherein the anchor is buried below the seafloor. 
     
     
         13 . The method of  claim 10 , wherein the anchor has an upper end disposed above the seafloor and a lower end disposed in the seabed below the seafloor. 
     
     
         14 . The system of  claim 2 , wherein the anchor is buried below the seafloor. 
     
     
         15 . The system of  claim 14 , wherein the anchor includes one of a torpedo anchor and suction embedded plate anchor (SEPLA). 
     
     
         16 . The system of  claim 2 , wherein the anchor has an upper end disposed above the seafloor and a lower end disposed in the seabed below the seafloor. 
     
     
         17 . The system of  claim 16 , wherein the anchor includes a suction pile. 
     
     
         18 . The system of  claim 2 , wherein the subsea structure includes a subsea blow-out preventer (BOP). 
     
     
         19 . The method of  claim 11 , wherein the anchor is buried below the seafloor. 
     
     
         20 . The method of  claim 11 , wherein the anchor has an upper end disposed above the seafloor and a lower end disposed in the seabed below the seafloor.