Rochelle

Location and Geology

The East Rochelle oil and gas field is situated in the UK section of the North Sea, specifically in Block 15/27 of the Greater Rochelle area. This area is approximately 72 miles away from the UK coastline in the central North Sea and about 115 miles north-east of Aberdeen, Scotland. The field is located in a water depth of roughly 450 feet (approximately 138 meters).

Field Composition and Production

The Greater Rochelle area includes two main oil and gas fields: West Rochelle (located in blocks 15/26b and 15/26c) and East Rochelle (located in Block 15/27).

• East Rochelle Field: This field was developed as a subsea tie-back to the Scott platform, which is operated by Nexen. The field started production in February 2014 and has an average production rate of 65 million cubic feet of gas per day and approximately 3,000 barrels of oil per day (bopd).

• West Rochelle Field: The first production from the West Rochelle (W1) well began in October 2013, with an average production capacity of 44 million cubic feet of gas per day and 2,500 bopd.

Ownership and Operation

The Greater Rochelle area is jointly owned by:

• Endeavour Energy: A subsidiary of Endeavour International Corporation, holding a 44% working interest.
• Nexen Petroleum UK: A subsidiary of Nexen, holding a 41% working interest and operating the field.
• Premier Oil: An independent upstream oil and gas company, holding a 15% working interest.

Discovery and Development

• Discovery: The original Rochelle field was discovered by Hess Corporation (formerly Amerada Hess) in April 2000. The field was later renamed East Rochelle after the discovery of the West Rochelle accumulation in 2010.
• Development: Endeavour acquired the field’s licence in 2006 and drilled an appraisal well in late 2008. The development included the construction of two production wells and the installation of a new production pipeline tied back to the Scott platform. Technip was awarded the engineering, procurement, construction, and installation (EPCI) contract for the East Rochelle development in June 2011.

Hydrocarbon Reserves

• Gas Reserves: Estimated gas in place for the East Rochelle field ranges from 119 billion cubic feet (bcf) for the low case to 195 bcf for the high case. The planned recovery of gas is estimated to be between 68 bcf for the low case and 137 bcf for the high case.
• Condensate Reserves: Condensate recovery rates are estimated to be approximately 2.3 million barrels (mmbbl) for the low case, 4.4 mmbbl for the base case, and 4.9 mmbbl for the high case.

Infrastructure

• Subsea Tie-back: The East Rochelle field is developed as a subsea tie-back to the Scott platform located in Block 15/22. This includes a 19-mile control umbilical for hydraulic, electrical control, chemicals, and pipeline treatments.
• Production Pipeline: A 10”/14” pipe-in-pipe (PiP) production pipeline connects the West and East Rochelle wells to the Scott platform, installed in 2012 and commissioned in 2013.

Decommissioning

• Ceased Production: The Rochelle field ceased production on May 30, 2020, due to continued production not being economically viable.
• Decommissioning Plan: The decommissioning programme involves flushing and disconnecting the production pipelines and umbilicals, removing jumpers and spools from the seabed, plugging and abandoning the wells, and final wellhead severance and recovery. These activities are scheduled to take place from the first half of 2024 to the end of 2025.

Environmental and Regulatory Compliance

The decommissioning programmes are submitted in compliance with national and international regulations and guidelines from the Offshore Petroleum Regulator for Environment and Decommissioning (OPRED). The process includes public, stakeholder, and regulatory consultation to ensure environmental impacts are minimized.