Offshore Platform Integration and Floatover Technology

Offshore platforms are designed to perform exploration, production at offshore oil fields. An offshore platform structurally can be divided into two parts: the topsides and the substructure. The topsides is a steel structure providing spaces to hold various kinds of facilities for exploration/production and human activities. Substructures are necessary to support the topsides “sitting” at an elevation safely above the ocean free surface. In general, the topsides and the substructure of a platform are designed and fabricated separately. The completed topsides and the substructure are then integrated at inshore or offshore site. Integration methodology depends on the topsides and substructure design, at the same time, the selected integration method has strong impacts on the platform design, especially the design of the topsides. Discussion in this chapter starts from platform topsides and covers the various kind of topsides design philosophies. Through examples, it is shown that platform design is strongly related to the platform integration methodology, changing integration method at the later stage of platform design will impact the project in the negative way in general.

There are many kinds of platforms designed to be suitable for the specific working environment. For each platform design, there is a best corresponding platform integration method to make the operation safe and cost effective. Discussions in this chapter present various kinds of platforms and the corresponding integration method options. Through discussions with examples, the history of platform concept development and the corresponding platform installation technology are presented with information in certain depth. For fixed platform and floaters, the most used platform integration method is still by heavy lifting for both modularized topsides and integrated topsides. However, the design and fabrication of massive and heavy integrated topsides make the floatover method a better choice. The conclusion can be drawn from the installation activities of real projects carried out at different time along the offshore industry history.

Floatover technology appeared in 1970s together with the invention of the “integrated topsides”. This technology was initially aimed for the heavy topsides installation of the fixed platforms, but the first application of the floatover technology was on the steel GBS Maureen. The floatover operation can be performed at inshore sites as well as the offshore sties. Discussions in this chapter cover the floatover concept, the history of the technology development and the advantages of the floatover method comparing to the heavy lifting method. Development and evolution of floatover technology have never been stopped. Brief introduction of several main floatover techniques such as HIDECK, UNIDECK, catamaran floatover, etc. is made in this chapter and leave the detailed discussion in the following chapters.

Floatover technology starts from HIDECK floatover. It is the most successful floatover method for inshore and offshore platform integration. HIDECK floatover was invented for installing heavy integrated topsides on the jackets of the fixed platforms without heavy lifting equipment. A single barge is used to transport the topsides to the installation site. The mating of the topsides and the jacket is accomplished by de-ballasting the barge. The method can also be applied to floaters such as TLP, semi-submersibles. HIDECK floatover method has been widely used for offshore open water topsides installation. It becomes the favored method for integration of platforms with heavy integrated topsides. In this chapter, the concept and the development of HIDECK are discussed in depth with the application examples. The successful accomplished projects presented convincingly show the advantages HIDECK floatover method in safety and cost effectiveness.

One of the operation challenges to single barge floatover is to handle the heave motion of the installation vessel induced by the environment during the floatover operation. The natural period values of the vessel carrying the topsides fall in the period range of long waves such as ocean swell. In the region like West Africa, swell is often the dominant environment factor, HIDECK method is not suitable for the direct application. Two single vessel floatover methods are capable of handling the swell induced motion by specially designed equipment and operation procedures. They are the UNIDECK method and the Smartleg method. The UNIDECK method is an “active” floatover method. The UNIDECK transportation/floatover vessel is equipped with a specially designed jacking system which makes possible for the mating process to be reversible during the operation. The same vessel/barge can do both HIDECK floatover and UNIDECK floatover depending on what installation equipment put onboard. A vessel with UNIDECK equipment can carry out the floatover operation by only using the ballasting system as the HIDECK method. The UNIDECK method has been quite successful in offshore open water platform integration. The SMARTLEG technology is also capable of handling the swell environment. Different from UNIDECK, SMARTLEG system is designed to avoid the taking place of the impact during the mating process, hence it was also called “shockless floatation method”. However, this technology has not gone very far with only one offshore application. Discussion in this chapter covers the technical details of these two methodology through the presentation of real projects.

When the platform substructures do not have openings wide enough for installation vessels to move in, catamaran floatover method is the choice of platform integration. Two floatover vessels and the topsides form a catamaran. The mating operation procedure are the same as the HIDECK, except the involvement with two vessels. Catamaran floatover methodology has been successfully applied in both inshore and offshore platform integration. In general, the catamaran is formed at the location near the mating site, therefore the topsides will be transported from the yard to the selected location by a third vessel and then the topsides is transferred to the floatover vessels. This extra step operation need to be well prepared through intensive engineering efforts. Discussion in this chapter covers the operation details with the examples of CGBS inshore integration and the spar offshore integration. For these operations, floatover vessels do not need specially designed equipment besides grillages and sea-fastenings. Two other catamaran floatover methods using special equipment: the Versatruss and TML methods are also presented in this chapter.

Commonly, an engineer is more interested in the technical details and the development journey of a new technology. However, if he/she has the opportunities to be assigned to a real project for the floatover operation, his/her knowledge in the project management will be a very important factor for him/her to effectively fit in the project team. Project management plays the vital role in the success of the project. If the reader is only interested in the technique aspect of the floatover technology, he/she can skip this chapter. The discussions in this chapter touch several important issues for offshore installation project management. Through the materials presented, it is emphasized how the integrated efforts can be realized through well-established management systems. Details of project team framework, project QMS, PEP, communication network, document control system, etc. are also covered in the discussion.

Although floatover operations are performed by the crew at the installation site, engineers play important supporting roles in PEP development, operation procedure development through intensive engineering efforts. Besides engineering analysis/simulation of motion and loading calculation, the work scope also cover the structural/mechanical design, technical specification for equipment fabrication, QA/QC and on site supporting, etc. Discussion in this chapter covers a wide range of the engineering work with multiple engineering disciplines. Successfully accomplished projects are referred for some technical details. Through the discussion it is very clear that the engineering work is not the isolated efforts. Communication under the project QMS system is vital for the success. The importance of the early engineering involvement for the project success is also addressed.

As the offshore installation projects in general, floatover operation is a campaign involving vessels, equipment, crew, engineers and management team at the offshore site. Every step for each task must follow the instructions specified in the operation manual strictly. The discussion in this chapter focuses on the one vessel floatover operation. Operation activities of loadout, topsides floatover installation and post-installation are presented with details form preparation to actions at each stage. Contingency procedure and its importance are also addressed through the discussion of a real project.

This chapter goes through the history of the floatover concept development and briefly summarizes the process of technology evolution. The success of the execution of floatover projects since its early invention is accompanied with continuous technology improvement. The HIDECK floatover started by using selected barges towed by tugs/OCVs. To handle the floatover installation of the ever enlarged platforms in open sea with long transportation journey, self-propelled HLVs and DP technology have been introduced to make the project execution more cost-effective. Catamaran floatover technology has also been seriously considered for the platform decommissioning. New vessel concepts stemmed from floatover technology such as the Pioneering Spirit, DISV, etc. show the efforts of making the floatover operations safer, faster, less hindered by environmental conditions and cost-effective have never been spared.