Michael Y.H. Luo

Improvements in Heavy Topside Installation Onto Spar Hull by Catamaran Floatover Method

The Murphy Kikeh Spar in Malaysia was the first Spar to employ a catamaran floatover method to install the topsides onto the Spar hull at the platform offshore location. The single column hull of the Spar dictates that the most practical way to float a topsides onto the Spar hull is by use of a catamaran system where the topsides structure forms a connection between the twin barges. For the Kikeh Spar the topside was first loaded out onto a single barge before being transferred to the catamaran system. The transfer operation was performed in sheltered waters. After the transfer and installation of the seafastening, the topside was towed to the installation site. The transfer of the topside weight was accomplished by deballasting the Spar and no quick release mechanism was used in the separation of the topside from the catamaran barges.While the operations described were successfully implemented for the 4,000 MT Kikeh topside in a relative mild environment, improvements are recommended to perform this operation for heaver topsides in harsher environments such as the Gulf of Mexico.This paper summarizes an internal study by Technip to extend and improve the floatover installation of Spar topsides to the Gulf of Mexico. This paper presents a step-by-step overview of an improved process for the installation of topsides having transportation weights of up to 25,000 ST. Similarities and improvements compared with Kikeh floatover installation will be discussed with particular focus on the following areas:1. A new method of loading out of the topsides from the fabrication yard directly to the catamaran barges, requiring only one operation and eliminating the need for a transfer barge.2. Specific Catamaran Ocean tow design and analysis considerations for the Gulf of Mexico. This addresses the effects of the harsher environment on the barges, grillage and topsides structure. A novel method of preloading the catamaran system is presented that reduces or, in some instances, eliminates the requirement for additional topside steel weight to accommodate additional motion-induced dynamic loads on the catamaran system during the ocean tow. The preloading also eliminates the risk associated with the operation of cutting tied-down braces.3. A quick load release system is described which enables the rapid separation of the barges from the topside following the appropriate level of topside load transfer to the Spar hull.Copyright