As part of our commitment to advancing well control and risk management in carbon capture and storage (CCS) projects, our well control experts were engaged by the Norwegian Ocean Industry Authority (Havtil) to assess the differences between CO2 and natural gas wells and their impact on flow simulations. The study aimed to assess the suitability of blowout modelling tools currently used in the oil and gas industry for simulating flow assurance in CO₂ storage wells.
The Norwegian Ocean Industry Authority oversees the issuance of licenses for CO₂ storage exploration and exploitation on the Norwegian Continental Shelf (NCS).
Our team conducted a detailed study on the dynamics of an uncontrolled CO2 blowout, including thermodynamic behavior, flow phase distribution, and CO2 well integrity risks and provided expert opinion on flow simulation software for CO₂ wells.
Client challenges: Understanding CO₂ blowout behavior
CO₂ behaves differently from hydrocarbons under high-pressure conditions. Simulating potential blowout scenarios helps in understanding the unique thermodynamic behaviors of CO₂, such as rapid phase transitions and cooling effects, which are essential for developing effective CO2 well control measures.
Requirements for tools to simulate CO₂ well flow
Most models used for simulating regular oil and gas reservoir flow operate in a steady-state and are not suitable for capturing transient behavior in CO2 wells and pipelines.
To accurately simulate a CO₂ blowout and estimate kill requirements, a transient multiphase model is required. This model must be capable of handling operational conditions near the critical point of CO₂, where the risk of numerical instabilities is high. Additionally, the model should be validated against operational data to ensure reliability. Currently, only a limited number of software simulation models in the industry meet these requirements.
Insights from simulations contribute to the development of industry guidelines for well control and best well integrity practices, promoting uniform safety standards across all CCS operations.
Ensuring compliance with environmental regulations and safety protocols is essential for CO₂ storage operations.
Our solutions
We evaluated the key factors essential in CO2 flow simulation and explored strategies for successfully killing a flowing CO₂ well.
The flow behavior of CO₂ under blowout conditions:
- CO2 has unique thermodynamic properties, including rapid phase transitions between gas, liquid, and solid states.
- Discussions around the equations of state (EoS) and thermodynamic models tailored for CO2 together with impurities and other fluids
- The risks of dry-ice formation during pressure drops, which could cause blockages in the wellbore and impact well control strategies.
- Recognising the potential for numerical instabilities in CO₂ simulations, limited validated transient multiphase models capable of handling high-pressure variations and rapid expansion effects.
Well integrity challenges and barrier performance in CO₂ injection wells
- We emphasized the risk of CO2 versus natural gas:
the highly corrosive nature of CO2 significantly affects the overall risk profile, and this underscores the critical need to maintain well integrity throughout the entire lifecycle of a CO2 injection well, from design and drilling to long-term operation.
Uncertainties during a CO2 well blowout and kill operation
- We considered the complex interactions of CO₂ with water, oil, gas, and injected chemicals, to highlight that well control measures accounted for potential phase changes, hydrate formation, and chemical react ions require modifications in CO2 well blowout and kill operations.
The results
Independent CO₂ blowout simulation study: supporting safe and sustainable CCS operations
The study emphasised the importance of using transient multiphase models for CO2 well simulations, as steady-state models are inadequate for capturing dynamic well control scenarios.
By addressing the limitations of current CO₂ blowout simulation models, our work has helped operators and regulators understand potential gaps, refine risk assessments, and develop effective well control strategies for CCS projects.
Our findings contribute to improving industry knowledge, ensuring safer and more reliable CO₂ well operations on the Norwegian Continental Shelf. The results of our study were presented at the 2025 Well Control Seminar, where industry professionals gathered to discuss best practices, lessons learned, and new advancements in blowout prevention and well control technology.
