David Edelson

Kikeh Development: Spar Topside Floatover Installation

Deck installation is always a major challenge for floating structures, particularly deep draft floaters like the Spar which must be installed in relatively deep water. Derrick barges have been used for Spar deck installations until now. Murphy’s Kikeh Spar, the 1st outside of the Gulf of Mexico, is the 1st Spar to use topside floatover installation technology and represents the 1st catamaran floatover installation of a topside onto a floating platform in open water. The successful execution of the Kikeh 4000Te topside floatover installation has established this method as a viable and cost effective alternative to lift installation. This paper presents an overview of the topside floatover installation for the Murphy Kikeh Spar. The paper describes all aspects of the floatover installation including topside loadout and transportation using a single barge, transfer from the transportation barge to the catamaran barge configuration, catamaran open water tow and floatover to the Spar at the Kikeh location. This paper focuses on the naval architectural, structural and operational tasks that were performed in support of these operations. INTRODUCTION New offshore developments may include several Spar type platforms with varying deck sizes ranging from 16,000 mt to 35,000 mt dry weights. Topsides for all previous Spar platforms were installed by deck lifts ranging from about 3,000 mt (Oryx single lift) to over 10,000 mt multiple lifts. The largest deck installed this way on a Spar was the Diana Deck with a dry weight of about 20,000 mt. This deck installation required five separate lifts [1]. There are potentially large advantages, particularly for the large decks, if an integrated deck could be installed using floatover methods. Some advantages include: • Schedule and cost advantages for the integration and commissioning of modules on land rather than at sea, • Uncoupling the deck fabrication schedules from the availability of heavy lift vessels There is a long history of successful floatover deck operations for floating Gravity Based Structures (GBS) and other floaters in protected waters ranging from the Beryl A Mobil facility in the UK North Sea, 1975, 14000mt deck weight to the Hibernia HMDC facility offshore Newfoundland Canada, 1997, 46000mt deck weight. Until recently, however, only one (1) floatover has been performed on a floating structure in open waters which was the 24,000 ton Auger TLP Deck in 1993 [3]. In 2006, the first floatover deck was installed on a Spar platform: the Kikeh Spar. This installation was performed in 1320 m water depths in the South China Sea, offshore East Malaysia. The deck weight was 4000 mt and the swell at the time of installation was Hs of 0.7m at periods of 7 8 seconds. This was also the first catamaran type floatover performed in open waters. The 46,000 mt Hibernia deck was set using a catamaran configuration in protected waters of Bull Arm in Newfoundland. There are some significant differences between installing decks on a fixed platform versus a floating platform, and of course between sheltered and open water installations. Some of these differences are listed below. The most important difference is the length of time to perform the load transfer between the transportation barges and the floating structure. For a fixed platform installation, jacks may be used to transfer the majority of the deck load within a matter

Floatover Deck Installation on Spars

Deck installation is always a major installation challenge for floating structures, particularly deep draft floaters like the spar which must be installed in relatively deep water. Derrick barges have been used for spar deck installations until now. The 4000 mt deck for the Kikeh Spar was successfully installed using the floatover method in November 2006, off the coast of Sabah in the South China Sea. This demonstrates the feasibility of this concept and opens the door for more floatover decks on spars in the future. This paper will review the technical challenges associated with this type of installation. In particular, the authors will review past studies, which included analysis and model testing of similar deck floatovers for decks up to 30,000 t, and the analysis methods use to validate the procedures and equipment which was successfully used on the Kikeh project. The requirements for application of this technology in the Gulf of Mexico will be highlighted.Copyright

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

Design and Installation Aspects of the Kikeh TAD/SPAR Lashing System

The Kikeh field, owned by Murphy and Petronas Carigali was the first time to use a Spar platform outside of the Gulf of Mexico and also the first time to use a semi-submersible Tender Assist Drilling Unit (TADU) for drilling along a Spar. This paper presents the design and installation aspects of the lashing system of the TADU and the Dry Tree Unit (DTU) Spar for the Kikeh project. The utilization of the TADU in the Kikeh field significantly reduces the weight and cost of the topsides of the Spar and increases the drilling efficiency. In the mean time it has posed a challenging job for the engineers to design the lashing system for the two floaters. This paper will discuss the TADU/DTU concept and benefits along with TADU lashing system design philosophy, design criteria and environment. Different phases of the design process will be discussed in detail, including concept selection, numerical analysis and model test. Several design concepts including the selected design and other alternatives will be explored with pros and cons of each concept explained. Characteristics of the two body motions and lashing tensions will be demonstrated. The selection of the nylon rope and hardware for the lashing system will be discussed. Analysis methodology and modeling of the TADU/DTU lashing system will be discussed. Model test results will be compared with the analytical predictions. Due to the complex nature of the systems and limitation of the analytical tools, model test served as an important tool in the design process. We will show how the results influenced the design of the gangway between the TADU and the DTU. The installation procedures of the TADU mooring and lashing systems will also be presented.Copyright