In the journey towards a sustainable future, Carbon Capture Utilisation and Storage (CCUS) has become a potential near term solution to abate Carbon Dioxide (CO2) emissions while progress is made to reduce our reliance on fossil fuels. After CO2 emissions are captured (and if they are not utilised), they must be safely stored deep within geological formations and kept there indefinitely with no leakage. This practice prevents the release of CO2 into the atmosphere, helping to safeguard our planet for future generations from the warming effect of this greenhouse gas.

THE IMPORTANCE OF SAFE STORAGE

CO2 storage is underpinned by the following key principles:

GEOLOGICAL INTEGRITY

When selecting a site for CO2 storage, key characteristics are a permeable storage unit (to inject CO2 into) and impermeable cap rocks (to prevent the upwards and sideward migration of CO2). Sound familiar? This is why depleted oil and gas reservoirs have been identified as good potential CO2 storage sites, along with saline aquifers and other geological formations. It is worth noting that there is an additional risk associated with using depleted oil and gas reservoirs for storing CO2. Historic drilling will have penetrated the cap rock, meaning every well drilled is a potential leak point that will need a thorough assessment before CO2 injection can begin.

Merlin have utilised their geoscience and reservoir engineering skills to support clients with workflows which evaluate these properties, their uncertainties and the risks associated with containment. By modelling plume migration through containment structures, a clear understanding of the storage potential and integrity can be established.

Dynamic simulation of CO2 injection in saline aquifer over thousands of years

Given the period of time we are storing CO2 over, it is also important for us to understand how CO2 storage changes over time. The picture above shows three different types of trapping mechanisms (structural, residual and solubility), how much CO2 is trapped via each method, and how this varies over time. The trapping mechanism is important as it helps companies and their stakeholders understand the geological integrity of each storage site (ensuring the trapped gas does not seep to other unintended locations) prior to making final investment decisions.

LONG-TERM CONTAINMENT

Over long time periods, the stored CO2 undergoes a process known as mineralisation. During this process the CO2 reacts with minerals within the geological formation, transforming into stable, mineralised compounds. This process ensures the long-term containment and immobilisation of CO2.

MONITORING AND VERIFICATION

Robust monitoring and verification protocols are implemented to track the movement and behaviour of the stored CO2. This continuous surveillance provides assurance that the CO2 remains securely stored and does not pose any environmental risks.

MERLIN’S COMPREHENSIVE EXPERTISE IN SAFE CO2 UNDERGROUND STORAGE

At Merlin Energy Resources Limited, we bring a wealth of expertise to the forefront of CCUS projects. Our capabilities extend far beyond the initial capture of CO2. We excel in performing a range of critical analyses, including:

• Storage Site Analysis: Thorough evaluation of geological formations to identify optimal storage sites.
• 3D Geological Modelling: Precise mapping and modelling of subsurface structures for accurate storage planning.
• Top Seal Integrity Evaluation: Ensuring the impermeability of cap rocks to prevent CO2 migration.
• CO2 Injection Analysis: Assessing the feasibility and effectiveness of injection processes.
• Plume Migration Evaluation: Understanding the movement of CO2 within geological formations.
• Geochemical and Geomechanical Coupled Dynamic Modelling: In-depth simulations to predict CO2 behaviour and its interaction with subsurface structures.

By leveraging these advanced techniques, we ensure that the CO2 captured is securely stored, contributing to a more sustainable and environmentally responsible future.

A TESTAMENT TO ENVIRONMENTAL STEWARDSHIP

Safe underground storage of captured carbon stands as a testament to our collective commitment to environmental stewardship. By safeguarding our planet from the detrimental effects of CO2 emissions, we pave the way for a future where industrial progress and environmental preservation coexist harmoniously.

Stay tuned for the next episode in our CCUS series, where we will explore Merlin Energy’s vision for supporting the global effort towards Net Zero emissions.

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