Risk-based approach to CO2 transportation and storage infrastructure Integrity
Operators planning CO₂ transportation and storage infrastructure are not starting from a blank page. Established integrity-management practices from conventional oil and gas such as threat assessment, engineering analysis, mitigation and quantitative risk assessment provide a strong foundation to build on. The challenge is determining which assumptions remain valid for CO₂ service and where additional testing, analysis or historical data is needed.
CO₂ can interact with infrastructure and the surrounding environment differently than conventional natural gas or liquid products. Those differences can impact:
- material performance,
- failure behaviour,
- release consequences, and;
- the effectiveness of mitigation measures.
Applying conventional design and integrity practices without evaluating these impacts can leave important uncertainties unresolved.
A risk-based approach to assessing the integrity of CO2 transportation and storage infrastructure can address a broad range of threats and help the operators determine which threats are the most significant, especially when there is little industry data or experience available on asset performance with CO2
The project team needed more than data from u00a0pure COu2082 decompression behavior; t needed evidence that reflected the exact expected fluid properties for the proposed pipeline.
Start with What Operators Already Know
Many threats affecting conventional pipelines will continue to apply to CO₂ transportation systems. Established approaches to identifying, assessing and managing threats such as mechanical damage and external corrosion remain relevant.
Three categories of information are important to understand and manage the integrity of a CO2 transportation or storage asset:
- Established practices from oil and gas that remain applicable
- Existing methods from oil and gas that require adjustment for CO₂ conditions
- Knowledge gaps that require testing or additional analysis
CO₂ Changes the Integrity Questions
Integrity management connects the probability of failure with the potential consequences of that failure. CO₂, and the impurities entrained with the CO2 from the capture process, can influence both sides of that assessment.
On the probability side, operators need to understand how the transported or stored CO₂ may interact with materials and equipment under expected service conditions. Impurities such as hydrogen, hydrogen sulfide, water, NOx and SOx that are entrained in the CO2 in the carbon capture process can form corrosive products that accelerate material loss and cracking in pipelines and wells. Operators also need to determine whether conventional models accurately represent the loading and failure mechanisms that may occur in CO₂ service.
On the consequence side, the heavier-than-air nature of CO2 means that release behaviour of CO₂ differs from that of conventional natural gas. Release and dispersion models must represent the condition of the CO₂, the nature of the release and how the released gas moves through the surrounding environment. In addition, impurities in the CO2 can alter the impacts of the gas. These factors affect how potential consequences are estimated and how emergency, mitigation and integrity decisions are supported.
Important questions to consider include:
- How could CO₂ composition, including low concentration impurities, and operating conditions affect materials and equipment?
- Which failure mechanisms should be represented in the integrity assessment?
- How will the system respond if containment is lost?
- Do available release and dispersion models accurately predict release dispersion?
- How effective are the available prevention and mitigation measures?
- What additional training is required for operators and emergency response personnel?
Closing Information Gaps Before Deployment
One of the challenges facing CO₂ projects is the limited amount of publicly available performance data for infrastructure in CO2 service. Analytical models can help operators evaluate possible conditions, but those models rely on assumptions about material response, failure behaviour and release characteristics.
Testing provides a way to examine those assumptions under controlled conditions. Depending on the question, an operator may need material testing, structural testing, equipment qualification or flow and release testing to benchmark and refine the models.
Full-scale testing might be required to reveal behaviour that is not apparent in component or bench-scale testing.
C-FER combines testing and modelling so that each strengthens the other:
- Analytical models help identify influential conditions and parameters that can be used to design an effective testing program
- Test results provide data for calibrating and validating models.
- Validated models can be used to assess operating scenarios that cannot practically be reproduced experimentally.
For example, shock-tube testing is used to assess how low concentration impurities affect the decompression behaviour of CO2. C-FER uses models of the decompression behaviour to design a shock tube testing program that considers a range of operating variables and impurity composition. The results of the shock tube tests are then used to refine the models to reduce errors and expand model to cover a broader range of operating conditions. Finally, the models are built into a reliability-based framework that considers the uncertainties in the model, the input parameters and the operating condition to describe the range of possible gas behaviour in a variety of scenarios.
Fracture Control Shows Why Validation Matters
Running ductile fracture is one example of a CO₂-specific integrity concern that demonstrates the importance of combining analysis with full-scale testing and risk-based assessment.
In a CO₂ pipeline, an improper combination of pipe material properties, CO2 composition and pipeline operating conditions can allow a small crack to grow rapidly and propagate along the pipeline. This can produce a large gas release that is distributed along a pipeline which can cause more damage and increased threat to the public. The threat of a propagating fracture can be managed through rigorous design of the pipeline, including the addition of fracture-arrest technologies that strengthen the pipe to stop a crack before it travels an excessive distance and thereby reduce the potential impact of the event.
C-FER is evaluating the performance of a fracture-arrest technology through full-scale testing. The project will help determine whether the technology performs its intended function under representative conditions and will provide performance data that can be incorporated into integrity and risk decisions.
Turning Technical Information into Risk-Informed Decisions
Quantitative risk assessment provides a framework for bringing together potential failure mechanisms, release consequences and mitigation effectiveness. C-FER adapts risk-assessment practices developed for conventional oil and gas facilities and pipelines to account for the different conditions introduced by CO₂.
This can support decisions involving:
- Material and equipment selection
- Design and operating procedures
- Fracture-control strategies
- Inspection, repair and replacement activities
- Incorporation of new risk-mitigation technologies
- Emergency response procedures
As new information becomes available, the risk-based models can be updated, and decisions re-examined and activities modified to maintain a tolerable risk level. The result is an integrity-management process that evolves with the asset from design and commissioning through operation and maintenance.
How C-FER Helps Operators with CO₂ transportation and storage Challenges
C-FER supports CO₂ transportation and storage operators as they adapt established integrity-management practices to new operating conditions.
C-FER helps operators:
- Identify where conventional integrity practices remain applicable and where CO₂-specific evaluation and integrity management is required
- Develop analytical, release and dispersion models
- Conduct small- and large-scale tests to support material and equipment selection decisions
- Apply quantitative risk assessment to CO₂ transportation and storage assets to support design and integrity management decisions
C-FER brings together pipeline integrity experience, risk analysis, engineering modelling and specialized testing. This combination helps operators adapt current practices and equipment to the new challenges of CO2 pipelines and underground storage.
C-FER’s helps build the technical foundation for integrity management decisions by clarifying what is already known, identifying what still needs to be tested, and providing evidence that supports safe, risk-informed decision making.
Contributor
Daniel Fujinaga, BSc
Engineering Manager, Integrity Management & Structures
Daniel Fujinaga the engineering manager for C-FER’s Integrity Management & Structures department. He holds a Bachelor of Science in Materials Engineering from the University of Alberta. Daniel’s expertise includes cathodic protection, materials engineering and data analysis.
