Erha and Erha North Development: Overview
Authors: Parker T.C. , Sofidiya A. 
Published: October 2008

In March 2006, ExxonMobil affiliate Esso Exploration and Production Nigeria Limited (EEPNL) started production from the world-class Erha deepwater development located in Oil Mining License (OML) 133, approximately 97 km offshore Nigeria in 1,200 m of water. The Erha development also includes Erha North, a satellite development that came onstream in September 2006. Erha North was online within 30 months of discovery, setting a Nigeria deepwater record. The Erha and Erha North development is EEPNL's first operated production from Nigeria's deepwater OML 133, with a total production capacity of more than 200,000 barrels per day (bpd). The Erha and Erha North Project consists of 32 subsea wells tied back to a floating production, storage, and offloading vessel (FPSO). A catenary anchor leg mooring (CALM) buoy, one of the world's largest, is used for crude carrier docking and product transfer.

This paper discusses the Project, from development planning through execution, emphasizing project management aspects and unique accomplishments and challenges.

Introduction

In May 1993, EEPNL and its co-venturer, Shell Nigeria Exploration and Production Company Limited (SNEPCO), acquired the rights to explore offshore Oil Prospecting Lease (OPL) 209, which was converted to OML 133 in March 2006. The Nigerian National Petroleum Corporation (NNPC) is the concessionaire of the block. OML 133 is operated by EEPNL with a 56.25% working interest, and SNEPCO is the only coventurer, with a 43.75% working interest. OML 133 covers 1,100 km2 and has water depths ranging from 800 m to 1,960 m.

By year-end 2005, eight exploration wells had been drilled in OML 133. The first exploration well, Bosi-1 was drilled on the block in 1996. The Erha oil discovery was made with the Erha-1 well in February 1999. The Erha-2 appraisal well was completed in November 1999, and the Erha-3 appraisal well and sidetrack were completed in September 2001. The Bosi-2 well discovered oil in March 2002. After the start of Erha development drilling, an oil discovery was made in March 2004 with the Erha-7 and 7 sidetrack, leading to the addition of a third drill center, Drill Center North (DCN), to the Project scope. Recoverable reserves in OML 133 are estimated to exceed 500 million barrels of oil.

The Erha and Erha North execution plan included sequential start-up of three drill centers, managed simultaneously with a two-rig development drilling program and ongoing production operations. The development consists of subsea wells connected to a new-build, spread-moored FPSO via flowlines and steel catenary risers (SCRs). Processing facilities installed on the FPSO handle 210,000 bpd of oil, as well as provide injection capability for 150,000 bpd of water and 340 million standard cubic feet per day (Mscfd) of gas. Processed crude is stored in the FPSO and periodically offloaded to trading tankers by a CALM offloading buoy.

Development Planning

Development planning activities began shortly after the Erha oil discovery with efforts focused on selection of a development concept for the Erha field N4 resource and including flexibility to accommodate future tiebacks to commercialize additional exploration discoveries on the block.