Solan

Location and Geology

• The Solan oil field is situated in the northern part of the North Sea, approximately 129 km west of the main island of Shetland and 165 km north of mainland Scotland, within Block 205/26a of the United Kingdom Continental Shelf.
• The field is located in waters 135 meters deep.

Ownership and Operation

• The Solan oil field is wholly owned and operated by Harbour Energy, through its subsidiary Premier Oil UK.

Discovery and Development

• The Solan field was discovered in the early 1990s. Initially, it was not considered economically viable due to its isolation and harsh environmental conditions.
• The field development plan (FDP) was approved by the UK Government in April 2012. Drilling activities commenced in April 2013, and the first production from the field was achieved in April 2016.

Infrastructure and Facilities

• Platform:
  • The Solan platform is a normally unmanned conventional steel platform, although it was manned during the first year of operation. It has the capacity to accommodate 30 men and is designed to support third-party tie-ins.
  • The platform consists of an integrated topside mounted on a symmetrical 4-legged jacket substructure, anchored to the seabed with 16 piles. The jacket is 158.5 meters high, with dimensions of 20m x 20m at the top and 45m x 45m at the base.
• Subsea Oil Storage Tank (SOST):
  • A specially designed 300,000-barrel subsea oil storage tank was installed to avoid the need for a costly submarine pipeline and to reduce environmental impact. This tank is connected to tanker-loading facilities via a Single Anchor Loading (SAL) system.
• Wells:
  • The field has three production wells (P1, P2, and P3) and two water injection wells (W1 and W2). The wells are tied back to the platform through subsea flowlines and control lines.
  • The wells have 5,000-6,000 feet horizontal sections and require wire-wrap screens for sand control.

Production and Operations

• Production Rate:
  • The field has a production rate of 28,000 barrels of oil per day (bopd).
• Oil Processing and Export:
  • Produced oil is stored in the SOST before being offloaded to a tanker via the SAL system using a displacement method involving seawater.
  • The platform processes up to 28,000 bopd of dry oil and 35,000 bpd of liquids.

Contractors and Service Providers

• Structural Design and Assessment:
  • Atkins Global was responsible for the structural design and assessment of the offshore facilities.
• Offshore Survey:
  • Ocean Installer conducted the offshore survey using the Normand Clipper vessel.
• Drilling Services:
  • Awilco Drilling provided drilling services for the project.
• Fabrication and Installation:
  • Burntisland Fabricators (BiFab) was contracted for the procurement and fabrication of the topsides and jacket of the processing platform. Offshore Design Engineering acted as a subcontractor for the detailed design stage.
  • ADIL constructed the subsea storage tank, and Heerema was responsible for the installation of the platform and subsea tank.
  • Shetland Maritime provided marine support, and FoundOcean handled the structural grouting services.
• Hook-up, Commissioning, and Facility Management:
  • Aker Solutions provided hook-up, commissioning, and facility management services.
• Project Management and Engineering:
  • Emerson Process managed the project, including detailed designing, commissioning, and configuration of electrical and telecommunication equipment.
  • Kent was involved in concept development, Front-End Engineering Design (FEED), and detailed design work, particularly for the SOST.

Decommissioning

• Timeline:
  • Production at the Solan field is expected to become sub-economic by late 2024, leading to the cessation of operations. Decommissioning activities are anticipated to start in 2026 and continue until 2031.
• Environmental Impact Assessment:
  • The environmental impact assessment for the decommissioning process was issued in May 2024.
• Decommissioning Process:
  • The Solan topsides will be entirely removed and transported onshore for recycling and disposal. The jacket will be cut and removed in a single lift, with piles cut internally to a target depth of 3 meters below the seabed level.
  • All subsea installations, including the SOST, SAL system, wellhead protection structures, and trash caps, will be fully removed and transported onshore for recycling or disposal. Pipelines, flowlines, and umbilicals will be disconnected and prepared for decommissioning.

Financial and Economic Aspects

• The field development was undertaken with an estimated investment of $850 million (£646 million).
• The innovative design, particularly the use of the SOST, was crucial in making the project economically viable despite the challenging location and environmental conditions.