Marnock

Location

The Marnock field is located approximately 240 km east of Aberdeen, UK, in the Central North Sea, within the UK Continental Shelf (UKCS) Block 22/24a. It is about 35 km from the UK/Norway median line.

Geology and Reservoir Characteristics

Marnock is a gas-condensate accumulation characterized by high pressure and high temperature, with conditions of about 9,000 psi and 300°F. The field exhibits variations in gas richness, with liquid yields ranging from 30 billion barrels per million cubic feet (Mft³) in the east to 1.7 Gbbl / Mft³ in the west. The reservoir is developed using natural depletion.

Development and Drilling

The development plan for Marnock involves six near-horizontal wells. The field has been developed through a series of drilling operations, with the focus on optimizing production from the gas-condensate reservoir. The wells are tied back to the central processing facility (CPF) of the ETAP project.

Production Facilities

The ETAP development, centered over the Marnock field, includes two platforms:

• A processing, drilling and riser (PDR) platform, which houses the production risers and Marnock wellheads.
• A quarters and utilities (QU) platform, which provides accommodation and utilities. These platforms are approximately 60 meters apart and linked by two bridges.

Production and Processing

The CPF is designed to handle a significant volume of production, including up to 120,000 barrels per day (bpd) of oil and approximately 440 million standard cubic feet (Mscf) per day of gas. The gas produced is exported, and the facility generates around 1,100 tons of natural gas liquid products each day. The ETAP platform operates with a 100% produced water reinjection system, ensuring zero discharge of produced water into the sea.

Operational History and Future Plans

The ETAP project, including the Marnock field, began production in 1998. The project has undergone several phases of development and is currently undergoing a $1 billion investment program to upgrade operations, which is expected to extend production into the 2030s. The BP-operated fields within ETAP, including Marnock, have produced more than 550 million barrels of oil equivalent (gross) to date.

Integration with Other Fields

The Marnock field is part of a larger complex that includes other fields operated by BP (Mungo, Monan, Machar, Mirren, and Madoes) and Shell (Heron, Egret, and Skua, although Egret and Skua have ceased production). These fields are all geographically located within a 35 km area and are integrated through the ETAP hub.

In summary, the Marnock oil project is a critical part of the ETAP development, characterized by its complex geology, advanced drilling and production techniques, and integration with other nearby fields to maximize economic recovery from the North Sea reservoirs.