Cayley

Cayley Oil and Gas Field Profile

Location

The Cayley Oil and Gas Field is located offshore in the United Kingdom, specifically in the Central North Sea. It is situated approximately 10 km west of the Montrose field, at coordinates 57.4205, 1.2258 (WGS 84).

Discovery and Development

• The Cayley field was discovered in 2007 by the well 22/17-3, which was drilled by Talisman (now part of Repsol Sinopec Resources UK) about 10 km west of Montrose at a water depth of 91 meters.

Operator and Ownership

• The field is operated by Repsol Sinopec Resources UK Limited, which holds a working interest of 58.97%. Marubeni Oil & Gas (U.K.) Limited is the sole partner in the project.

Production

• Production from the Cayley field began in 2017 as part of the Montrose Area Redevelopment (MAR) project.
• The field produces both gas and oil. As of 2019, the production figures were 364.63 million m³ of gas and 0.52 million barrels of oil per year. By 2022, these figures had adjusted to 225.84 million m³ of gas and 0.22 million barrels of oil per year.
• The field is expected to contribute to a gross incremental production peak of 40,000 barrels of oil equivalent per day (boepd) when combined with the Godwin and Shaw fields.

Field Characteristics

• The Cayley field is a relatively high-pressure gas-condensate reservoir with high-salinity fluids, posing an associated risk of corrosion. It is on the margin of high-pressure/high-temperature (HP/HT) conditions but does not have significant step-out design features in the wells.
• The field is developed through two subsea production wells that are deviated to minimize late-life sand ingress. The wells are equipped with water wash facilities and can receive lift-gas from the new bridge-linked platform (BLP) if needed.

Infrastructure and Connectivity

• The Cayley field is developed as a subsea tie-back to the BLP, which is connected to the Montrose Alpha platform. The production wells are tied back to the BLP via an 8½-in. pipe-in-pipe production line, a 3-in. lift-gas line, and a 4-in. utility line, all combined within a 32.5-in. pipeline bundle.
• Gas from the field is transported through a new riser into the existing WAGE (Wood And Gas Export) module at the Montrose Platform, which is tied into BP’s Central Area Transmission System (CATS) that runs to Teesside. Oil is exported using an existing flowline into BP’s Forties Pipeline system and further to the Cruden Bay Pipeline.

Project Context

• The Cayley field is part of the larger Montrose Area Redevelopment (MAR) project, which aims to extend the life expectancy of the existing Montrose, Arbroath, Brechin, Arkwright, Carnoustie, and Wood fields to beyond 2030. The project is expected to unlock up to 100 million barrels of oil equivalent of additional production.

Economic and Employment Impact

• The MAR project, which includes the development of the Cayley field, was sanctioned with a brownfield allowance (BFA) of £1.6 billion and is expected to create up to 2,000 jobs.

Technical and Operational Challenges

• The project faced significant technical and legacy challenges, particularly due to the decline in oil prices starting in 2014. The partners had to revise the project plan and accept additional investments while also deciding to cancel or postpone certain costly activities to save costs.

Long-term Outlook

• The successful delivery of the Cayley field, along with the Godwin and Shaw fields, is expected to extend the life of the Montrose facilities to beyond 2030. The fields are anticipated to remain in production for 15-20 years.