North Sea CCS Characterisation Study

Objective

Veri Energy, a wholly owned subsidiary of EnQuest plc., is evaluating the feasibility of carbon dioxide (CO₂) storage within depleted oil fields in the East of Shetland Basin, Northern North Sea, specifically the Magnus, Thistle (both operated by Veri’s parent Enquest), Eider and Tern fields (both operated by Taqa). This study aims to define technical requirements, identify infrastructure reuse opportunities and establish a reference concept for CO₂ transport, injection and storage. The study also includes a Class 5 cost estimate and initial safety and risk assessments.

Project Scope

The project is phased to scale CO₂ injection capacity in three phases over time. Veri is developing up to 10 million tonnes per annum of storage, and in excess of 300 million tonnes of total capacity at our four licensed storage sites, ramping up from as early as 2028/2029.

The study assessed onshore facilities at Sullom Voe Terminal (SVT), offshore infrastructure, subsea design, flow assurance, safety considerations, and cost estimates. The existing East of Shetland Pipeline System (EOSPS) was reviewed for CO₂ transport feasibility.

Findings & Recommendations

Findings

• Pipeline Feasibility: EOSPS can be repurposed for dense-phase CO₂ transport with a maximum allowable operating pressure (MAOP) of 185 barg, but flow assurance modelling highlights pressure constraints in later phases, requiring offshore boosting.
• Storage Viability: Depleted reservoirs can provide effective storage, but reservoir pressurisation over time will necessitate pressure boosting from Phase 3 onwards.
• Onshore Infrastructure: Existing SVT infrastructure can be modified for CO₂ import and processing, but additional buffer storage and seawater heating systems are required.
• Produced Water Handling: Phase 3 introduces produced water management, requiring offshore treatment and desalination. Further work is needed to confirm water quality and treatment specifications.
• Safety & Risk: CO₂ dispersion modelling indicates that a major loss of containment (LOC) event could impact SVT facilities, requiring further mitigation planning.

Recommendations

1. Validate Reservoir Pressures: Further subsurface analysis is needed to confirm pressure profiles and injection feasibility, particularly for Phases 2 and 3.
2. Refine CO₂ Heating Strategy: Current design assumes seawater heating with electric trim heaters, but alternative solutions (e.g. direct air heating, heat pumps) should be explored to improve efficiency.
3. Assess Magnus Platform Reuse Risks: Magnus is assumed to host subsea control systems for Phases 1 and 2, but its condition and lifespan must be verified.
4. Optimise Offshore Facility Design: The Phase 3 platform requires a semi-submersible or Sevan-style installation due to water depth and CO₂ containment. Further work should confirm feasibility and cost.
5. Develop CO₂ Safety Mitigation Measures: Implement detection systems, barriers, and emergency response plans for SVT and offshore facilities to manage CO₂ release risks.