Stella Maris

Background and project purpose?
The Stella Maris Feasibility Study was initiated by Altera Infrastructure after around 10 years of engagement in studies of marine transport of CO₂ and lately also in CCS (Carbon Capture and Storage).

Altera’s huge knowledge base from more than 30 years of building and operating Floating Production Storage and Offtake units (FPSO’s) and a large fleet of Dynamic Positioned shuttle tankers, has been used to study a “reversed process” of large scale shuttling of CO₂, directly offshore with offloading to a floating unit and continuous injection for permanent storage in a subsea saline aquifer on the Norwegian Continental Shelf. Large scale CCS solutions will be mandatory to meet the commitments in the Paris Agreement and the goal of keeping global warming below 2 °C.

What was the project objective?
The objective of the Stella Maris Feasibility Study has been to verify feasible technical solutions and a coarse cost estimate for large scale shuttling, offshore loading, intermediate storage and continuous injection of liquid CO₂ for permanent storage in subsea saline aquifers.
Focus has been to verify “maximum size solutions” for the CO₂ tanks on the shuttle tanker, the offshore offloading system and for the required intermediate storage capacity and FSIU (Floating Storage and Injection Unit) tank sizes.

What has the project done in terms of activities?

The objective has been achieved by performing the following activities (CTRs):
01A Study Administration
01B Information Survey
01C Risk Screening
01D Interface Information
01E Regulatory Compliance
01F CO₂ Logistic assessment
02 B Design, risk and safety review
02C Tank Containment
02D CO₂ Overall Process Flow
02E Carrier Loading and Cargo Handling Arrangement
02F Offshore Loading System
02G FSIU Cargo Handling System
02H FSIU CO₂ Conditioning and injection System

Partners involved performing the above scope of work has been Moss Maritime AS, TGE Marine Gas Engineering GmbH, Sevan SSP AS, APL Norway AS, DNV GL AS.

In addition to the technical Partners, the project has also had an “advisory” Reference Group with representatives from Equinor, Total, SINTEF and Low Carbon Shipping.

What has the project achieved ? Did the project achieve its objective ?
Evaluation of technical feasible solutions for the CO₂ process flow and tank containment has been be performed for:
• Loading of the Shuttle Tanker at shore.
• Cargo handling / conditioning in transit.
• Offshore offloading to the FSIU.
• Cargo handling / conditioning during FSIU storage.
• Conditioning and pumping onboard the FSIU for injection into the reservoir.

Within each of these five areas, the goal has been to verify available technology and / or products that can be developed further into defining a commercial concept design for the whole logistic system covered by the Stella Maris Project.

The overall conclusion from the feasibility study work is that 10 million tons pr year of CO₂ is possible to be transported and injected by use of:
• 3 off DP shuttle tankers; each with a capacity of around 50.000 m3 of liquid CO₂ at approximately 6.5 barg pressure and minus 48 oC temperature.
• Offshore offloading system with a 16” loading hose.
• 1 off FSIU with storage capacity of about 73.000 m3 of CO₂.

Based on the individual Partner’s engineering work and risk reviews performed, the study has not identified any technical showstoppers. The project has reached its objective of demonstrating feasible solutions by use of “known technology” for the proposed Stella Maris concept.

Future plans?
Altera’s high-level post evaluation of findings from the Feasibility Study, has identified several areas of the base case concept where cost can be further reduced.

These matters will be analysed in the planned Concept Selection and Definition phases of the Stella Maris project. Key items/areas to be addressed are:
• Optimization of the tank arrangement for the shuttle tanker
• Optimization of the offloading system for shuttle tanker
• Optimization of the offshore offloading system
• Optimization of the main dimensions for the shuttle tanker
• Optimization of the tank arrangement for the FSIU
• Optimization of the hull for the FSIU
• Low-manned/un-manned operation of the FSIU.