The first deepwater production operated by ExxonMobil affiliate Esso Exploration and Production Nigeria Limited (EEPNL) began in March 2006 with the Erha and Erha North development, comprising three drill centers producing to a spread-moored floating production, storage, and offloading vessel (FPSO) in 1,200 m of water, 97 km offshore Nigeria. The new-build Erha FPSO is one of the largest in the world, at 285 m long by 63 m wide, with a 2.2 million barrel capacity hull and capacity for 210,000 barrels per day (bpd) oil processing, 340 million standard cubic feet per day (Mscfd) gas injection, and 150,000 bpd water injection. This paper discusses the development of the FPSO, including design and operational features incorporated to meet fieldspecific requirements. This paper also addresses the project management challenges associated with each phase of the job, with emphasis on the safe and timely execution of a sequential drill center start-up while managing simultaneous production operations and in-field development drilling.
The Erha and Erha North development, located in 1,200 m of water approximately 97 km offshore Nigeria, consists of three subsea drill centers tied back to the FPSO via steel catenary risers (SCRs). Injection fluids are transferred from the FPSO via the SCRs and flowlines for subsea injection at the drill centers. Figure 1 shows the full Erha and Erha North field layout.
The FPSO is a new-build, spread-moored vessel consisting of two trains of three-stage oil separation. Processed crude is stored in the hull and regularly offloaded to tankers via offloading lines and a catenary anchor leg mooring (CALM) buoy. Associated gas is compressed and dehydrated to provide fuel gas, with the remainder reinjected back into the producing reservoir. Water injection facilities inject treated seawater into the reservoir for pressure maintenance to enhance oil production. Seawater treatment includes filtration and deaeration.
The design, fabrication, integration, and start-up of the Erha FPSO was a global undertaking, with engineering performed primarily in France, India, and Nigeria; hull fabrication in Korea; and topsides fabrication in Singapore, Malaysia, and Nigeria. The hull and topsides were integrated in Singapore, and the FPSO was towed to offshore Nigeria for installation. This work was carried out under a single prime contractor, Saipem SA, and its in-country affiliate, Saipem Contracting Nigeria Limited (SCNL), and included key design and execution interfaces with the Erha tiebacks and subsea system prime contractors.
Figure 1. Erha and Erha North Field Layout (available in full paper)
Figure 2. FPSO Key Fabrication Sites (available in full paper)
The large number of geographically dispersed fabrication sites (Figure 2) increased interfaces and tended to complicate the work. To mitigate this issue, construction site teams were established at key locations. Interface coordinators within each subproject team assisted with resolution of interface issues.
During the front-end engineering and design (FEED) phase, the Project definition was matured, and three engineering, procurement, and construction (EPC) lump sum bid packages were prepared. The work packages covered engineering, procurement, construction, integration, transportation, installation, hook-up, and commissioning. A two-step, sequential, competitive bid process was used: technical followed by commercial.