Erha Floating Production, Storage, and Offloading Vessel

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper OTC 18659, "Erha and Erha North Development: Erha Floating Production, Storage, and Offloading Vessel," by S.M. Day and G.J. Parker, ExxonMobil, and P. Barclay and H. Boulais, Saipem, prepared for the 2007 Offshore Technology Conference, Houston, 30 April-3 May. The new-build Erha floating production, storage, and offloading vessel (FPSO) is one of the largest in the world, at 285 m long by 63 m wide, with a 2.2-million-bbl-capacity hull and capacity for 210,000 B/D oil processing, 340 MMscf/D gas injection, and 150,000 B/D water injection. The full-length paper discusses the development of the FPSO, including design and operational features incorporated to meet field-specific requirements. The 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 startup while managing simultaneous production operations and in-field development drilling. Introduction The Erha and Erha North development, in 1200 m of water approximately 97 km offshore Nigeria, consists of three subsea drill centers tied back to the FPSO by steel catenary risers (SCRs). Injection fluids are transferred from the FPSO by the SCRs and flowlines for subsea injection at the drill centers. 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 offloaded regularly to tankers through offloading lines and a catenary anchor leg mooring (CALM) buoy. Associated gas is compressed and dehydrated to provide fuel gas, with the remainder reinjected into the producing reservoir. Water injection facilities inject treated seawater into the reservoir for pressure maintenance to enhance oil production. The design, fabrication, integration, and startup of the Erha FPSO was a global undertaking, with engineering performed primarily in France, India, and Nigeria; hull fabrication in Korea; and topside fabrication in Singapore, Malaysia, and Nigeria. The hull and topside 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 S.A., and its in-country affiliate, Saipem Contracting Nigeria Ltd. (SCNL) and included key design and execution interfaces with the Erha tiebacks and subsea-system prime contractors. Facilities Description The Erha FPSO (Fig. 1) is a barge-shaped, new-build monohull with all of the processing equipment on its top deck. It has a 2.2-million-bbl oil-storage capacity. Processed oil is offloaded to export tankers by the CALM buoy offloading system. The FPSO also has the capability to offload crude to tandem moored export tankers in a "bow-to-bow" configuration in the event that the offshore loading system is not available.