The mitigation of the current climate crisis depends on the effective integration of renewables, hydrocarbons, long-term subsurface storage of greenhouse gases, such as CO2, and promising new hydrogen (H2) fuel economy. The latter emerging technology builds on, and will extend, techniques developed for Capture Usage and Storage (CCUS). Norway and UK lead the existing and planned large scale CCUS projects in Europe, repurposing previous oil and gas extraction sites and infrastructure (e.g., four UK Energy clusters will deploy CCUS at scale by 2030). CCUS is of growing global interest. International action plans (e.g. Brazil, Indonesia and Malaysia) now aim to implement onshore and offshore CCUS to achieve ambitious Net Zero emissions targets. This timely and innovative project aims to connect UK expertise in environmental science and CCUS to new partnerships in these countries, exporting knowledge and experience, and conducting research to address global challenges concerning geological CO2 and H2 storage.
A successful CCUS project requires efficient subsurface storage in mechanically stable formations. This requires detailed, multi-scale characterization of subsurface rocks to determine their CO2 storage capacity, changes in their mechanical behaviour during injection and storage, and the capacity to monitor the onset of leakage and possible fluid migration. Novel technologies have been developed by the UK project team to quantitatively characterise and monitor CCUS activities from laboratory- to field-scale; however, application of these techniques has focused on the exceptional offshore European sites that largely target sandstone formations, barely reactive to CO2. Proposed targets of international partners (and potential, but previously disregarded UK targets) involve more reactive to CO2 lithologies, e.g. carbonates, basalts, shales and coal beds. Brazil's CCUS plan includes all these lithologies as potential reservoir targets, which are all well-represented in the Paraná Sedimentary Basin, Sao Paolo, and the required experience and infrastructure in place (the oil and gas majors' commitment) for rapid and effective CCUS implementation. The diverse CO2-fluid-rock reactions that CO2 injection can trigger in these more reactive formations include combined mineral dissolution and precipitation mechanisms, which can jeopardize reservoir integrity, limit injection capacity and transmission efficiency. The UK project components have previously shown how similar mineralogical changes can be detected at the laboratory scale based on their distinct geophysical character, and monitored in real-time, thus enabling early warning. This project (EHMPRES) seeks to develop an accurate methodology to detect CO2-induced mineral changes occurring simultaneously with pore fluid substitution, using new rock samples from Paraná Sedimentary Basin, to provide the first detailed characterisation of CO2-reactive CCUS sites. The methodology involves a combined laboratory assessment of the chemical, hydraulic and mechanical properties of CCUS candidate samples, to provide the necessary understanding of CO2-rock geochemical and geomechanical interactions, together with the associated geophysical signatures, for informing remote geophysical monitoring using seismic and electromagnetic methods. EHMPRES will establish a new international collaboration between world-leading experts in CO2 storage and reservoir characterization from NOC and IEE/USP, essential to enable interpretation of reactive geological complexes targeted for CCUS. Our findings will be extendable to H2 storage (with an increasing demand worldwide) and CO2-enhanced geothermal recovery, both conceptually similar strategies to CCUS. This project will form the basis of a long-term UK-São Paulo state collaborative network to develop and validate tools to assess a wide range of reactive reservoirs for storing gas worldwide, reinforcing the UK leadership in CCUS research.