Mariner

Mariner Oil Field Profile

Location and Geology

The Mariner oil field is located on the East Shetland Platform in the UK North Sea, specifically in block 9/11a, approximately 150 km (93 mi) east of the Shetland Isles and 320 km (200 mi) northeast of Aberdeen.

The field consists of two shallow reservoir sections:

• The Maureen Formation, situated at a depth of around 1,492 meters (4,895 feet), containing oil with an API gravity of about 14.2°.
• The Heimdal Formation, at a depth of approximately 1,227 meters (4,026 feet), containing oil with an API gravity of about 12.1°.

Discovery and Development History

The Mariner field was first discovered by the Union Oil Company of California (Unocal) in 1981. The field was later appraised by Texaco through a multi-well program in 1996-1997. Due to the complexity of the reservoirs, the field remained undeveloped until Equinor acquired the operatorship from Chevron in 2007.

Development Concept and Infrastructure

The Mariner field development involves a production, drilling, and quarters (PDQ) platform, known as Mariner A, based on a steel jacket. This platform is accompanied by a floating storage and offloading unit (FSU), Mariner B, which has an 850,000-barrel capacity. Mariner B was built by Samsung Heavy Industries in South Korea and is operated by OSM Offshore. The FSU is located 2.5 km (1.6 mi) from the Mariner A platform and is responsible for receiving, storing, and offloading the oil produced from the field, as well as providing diluent to ensure flow assurance.

Production and Reserves

The Mariner field began production in mid-August 2019 and is expected to produce more than 300 million barrels of oil over the next 30 years. The annual average plateau production rate is estimated to be around 55,000 barrels of crude oil per day, with peak production reaching up to 70,000 barrels per day. The combined oil and diluent flow is expected to be around 80,000 barrels per day.

The field is estimated to hold up to 3 billion barrels of oil in place, with recoverable reserves initially estimated at 300 million barrels, though this has undergone revisions.

Drilling and Operations

The development includes the drilling of over 100 wells over the first 12-14 years, with 50 wells and 92 side tracks planned for the Mariner field. Additional wells are planned for the nearby Mariner East field. Drilling operations are conducted from the Mariner A PDQ platform, assisted by a jack-up rig during the initial phase, and a semi-submersible drilling rig for the Mariner East wells.

Investment and Economic Impact

The Mariner project involved a gross investment of more than $7.7 billion, making it one of the largest capital commitments to the UK Continental Shelf (UKCS) in recent years. The project has generated significant economic benefits, including contracts worth over $1.3 billion awarded to UK suppliers. It supports more than 700 long-term jobs and will continue to generate revenue in the supply chain for decades.

Technology and Innovation

The Mariner field is notable for its use of advanced technology and digital solutions. Equinor has emphasized the application of new technology to optimize production, ensure safe operations, and increase oil recovery. The field is considered one of the most digitally advanced in the UK North Sea.

Environmental and Regulatory Aspects

The development of the Mariner field involved the submission of an environmental statement to the UK Department of Energy and Climate Change (DECC) in May 2012. The final investment decision (FID) was announced in December 2012, and approval for the development was granted in February 2013.

Partners and Ownership

Equinor operates the Mariner Area with a 65.11% stake. The other partners include JX Nippon (20%), Siccar Point (8.89%), and ONE-Dyas (6%).

Long-term Contribution

The Mariner field is expected to contribute significantly to the UK's energy security over the next 30 years, aligning with the industry's Vision 2035 to meet as much of the UK's oil and gas needs from home-produced resources as possible.