Floatover arrangement and method

Abstract

An arrangement and method for restraining surge and sway of the barge during floatover of a topside onto a substructure. Roller bumpers provided on the substructure guide the barge during slot entry and exit without the use of secondary mooring lines and restrain sway at the floatover position. Dedicated vertical bearing surfaces are provided on the substructure at the entry to the slot. Resilient bumpers are provided on the barge. The resilient bumpers engage the dedicated vertical bearing surfaces on the substructure and position the barge in the floatover position in the longitudinal direction. A tug boat tows the barge into the slot until the resilient bumpers engage the dedicated vertical bearing surfaces. The tug continues to pull throughout the floatover operation to hold the barge in the floatover position.

1 . An arrangement for a floatover operation offshore wherein a topside structure supported by a floating structure is floated over a substructure and the topside is then installed onto the substructure, comprising:
 a. a plurality of roller bumpers attached to the substructure and extending from the substructure so as to contact the floating structure during the floatover operation;   b. a vertical bearing surface attached to the substructure; and   c. at least two resilient bumpers attached to the floating structure and positioned so as to contact the vertical bearing surface on the substructure during the floatover operation.   
     
     
         2 . The arrangement of  claim 1 , wherein the resilient bumpers are positioned on the floating structure so as to act as a longitudinal stop to position the floating structure and topside in the proper alignment for installation on the substructure. 
     
     
         3 . A floatover method for installing a topside supported on a floating structure onto a substructure offshore, comprising the steps:
 a. providing a plurality of roller bumpers on the substructure such that the roller bumpers extend from the substructure and contact and guide the floating structure during the floatover operation;   b. providing at least two vertical bearing surfaces on the substructure;   c. providing at least two resilient bumpers on the floating structure supporting the topside such that the resilient bumpers contact the vertical bearing surfaces on the substructure during the floatover operation;   d. moving the floating structure supporting the topside into position adjacent the substructure and into contact with the roller bumpers such that the roller bumpers aid in proper positioning of the floating structure;   e. continuing movement of the floating structure into position such that the resilient bumpers contact the vertical bearing surfaces, which position aligns the topside and substructure for installation of the topside onto the substructure;   f. ballasting the floating structure down and installing the topside onto the substructure; and   g. removing the floating structure.