Speaker
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Hydrogen energy is expected to play a significant role in the energy transition, with geological storage poised to be one of the few economically viable options for enabling a large-scale hydrogen economy. However, there is a critical lack of research in H2 storage in carbonate rocks, particularly regarding the role of microporosity (<10 μm) and pore connectivity in residual trapping during imbibition.
The limitations in studying the role of microporosity arise from the low spatiotemporal resolution of lab-based micro-CT scanners in addition to the heterogenous nature of carbonate pore systems. Analogous research considering proxy fluids indicate that microporous phases can significantly stratify flow paths into complex geometries due to their hydrophilicity and high capillary entry pressure. These regions – when water-wet – can lower non-wetting phase residual saturations and boost wetting-phase relative permeabilities to aid recovery during waterflooding (Reynolds et al., 2017; Gao et al., 2019). Furthermore, the complexity of micro-porous carbonates is further exacerbated when wettability is considered. This is coupled with contact angle hysteresis which is typically accentuated in smaller pore sizes and heterogenous systems (e.g., van Rooijen et al., 2022).
To bridge the gap, pre-characterization work was conducted prior to high-resolution synchrotron X-ray imaging using lab-based X-ray micro-CT scanner to develop a null hypothesis and highlight regions of interest. An Estaillades carbonate mini-plug was imaged during two cycles of drainage and imbibition at reservoir conditions (10 MPa and 50 °C). During drainage, H2 pore occupancy pre-dominantly lies in the largest pores (macropores) with microporous phases acting as barriers that increase flow tortuosity unless their capillary entry pressure can be exceeded. However, during imbibition, we find that microporous phases may affect the phase connectivity, enhance brine flow and affect the residual saturation distribution. This is evidenced by the increase in residual saturation around a microporous-rich band where micro-macro links are greater and macroporous connectivity is reduced. Subsequent experiments conducted under synchrotron radiation will enable the visualization of H2-brine phase flow paths during drainage and imbibition to understand the dynamics of flow through heterogeneous carbonate pore systems.
| References | Bultreys, T., Stappen, J.V., Kock, T.D., Boever, W.D., Boone, M.A., Hoorebeke, L.V. and Cnudde, V. 2016. Investigating the relative permeability behavior of microporosity‐rich carbonates and tight sandstones with multiscale pore network models. Journal of Geophysical Research: Solid Earth. 121(11), pp.7929–7945. Burchette, T.P. 2012. Carbonate rocks and petroleum reservoirs: a geological perspective from the industry. Geological Society, London, Special Publications. 370(1), pp.17–37. Gao, Y., Raeini, A.Q., Blunt, M.J. and Bijeljic, B. 2019. Pore occupancy, relative permeability and flow intermittency measurements using X-ray micro-tomography in a complex carbonate. Advances in Water Resources. 129, pp.56–69. Reynolds, C.A., Menke, H., Andrew, M., Blunt, M.J. and Krevor, S. 2017. Dynamic fluid connectivity during steady-state multiphase flow in a sandstone. Proceedings of the National Academy of Sciences. 114(31), pp.8187–8192. Van Rooijen, W., Hashemi, L., Boon, M., Farajzadeh, R. and Hajibeygi, H. 2022. Microfluidics-based analysis of dynamic contact angles relevant for underground hydrogen storage. Advances in Water Resources. 164, p.104221. |
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| Country | United Kingdom |
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