Liuhua 11-1 Development-Design and Fabrication Considerations for the FPS
Authors: Frase John R. , Liang Xiao Qi , Clark Lindsay E. 
Published: October 2008

The Nanhai Tiao Zhan is a major component of the Liuhua 11-1 Development System. It is a modified drilling semi-submersible Specially converted to maintain station in a severe typhoon environment, drill and complete horizontal subsea wells, supply power for downhole electrical submersible pumps, and support installation and maintenance of the unique Liuhua 11-1 subsea production system. Final design and conversion of the Nanhai Tiao Zhan was accomplished in approximately two years In the first year, a major engineering effort produced plans and specifications for converting a Sedco 700 series mobile offshore drilling unit into the floating production system Nanhai Tiao Zhan. The second year of the project entailed procurement and construction activities associated with the unit's conversion and refurbishment. The project as accomplished on schedule within its original budget.

Introduction

The Nanhai Tiao Zhan is a one-of-a-kind semi-submersible floating production system (FPS). It is part of a specialized field development system designed to meet the unique technical and commercial challenges of the Liuhua 11-1 Field. OTC 8172 (Ref. 1) presents an overview of the Liuhua 11-1 Field Development, its history and the challenges presented to partners, Amoco Orient Petroleum Company, China Offshore Oil Nanhai East Corporation, and Kerr-McGee China Petroleum Ltd. The Nanhai Tiao Zhan's installation in July 1995 marked the end of an engineering and construction effort that began with conceptual studies in 1988. By 1991, the early conceptual studies of 1988 evolved into a comprehensive field development preliminary engineering program. A fully integrated, multidiscipline field development project team performed this preliminary front-end engineering program. By March of 1993, the project team identified the system concept that was the best economic solution for field development, and the Liuhua 11-1 partners approved processing with the project.

The development system concept approved in 1993 is a working system today. It includes the Nanhai Tiao Zhan permanently moored over a subsea production system teamed with a floating production, storage and offloading (FPSO) system permanently moored nearby. Fig. 1 depicts the total Liuhua Development System. The engineering and construction project under-taken to create the FPS Nanhai Tiao Zhan via conversion of an existing semi-submersible mobile offshore drilling unit is the focus of this paper.

In June 1993, the Liuhua partners chose Reading & Bates Development Company (R&B) as General Contractor for the Liuhua Ff'S conversion project. The scope of this project included final vessel selection, engineering, procurement, and the conversion work, R&B subcontracted the conversion work to Far East Livingston Shipbuilding Ltd. (FELS) in Singapore. The Sedco 700 series drilling semi-submersible West Stadrill (Fig. 2) entered FELS Pioneer Yard in June of 1994. In June of 1995, the converted semi-submersible FPS, Nanhai Tiao Zhan (Fig. 3), was delivered for tow to the Liuhua Field slightly ahead of schedule and within its original budget.