The evolution of paleo-porosity in basalts: reversing pore-filling mechanisms using X-ray computed tomography

Macente, A. , Dobson, K.J., MacDonald, J. , Wadsworth, F.B. and Vasseur, J. (2022) The evolution of paleo-porosity in basalts: reversing pore-filling mechanisms using X-ray computed tomography. Transport in Porous Media, 145, pp. 697-717. (doi: 10.1007/s11242-022-01869-2)

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Often carrying a high-volume fraction of vesicles, basaltic rocks can be an important reservoir horizon in petroleum systems, and are considered an excellent candidate for CO2 storage by in situ mineral trapping. The frequency of amygdaloidal basalts in many sequences highlights the prevalence of mineralisation, but when the vesicle network has been filled, the basalts can act as impermeable seals and traps. Characterising the spatial and temporal evolution of the porosity and permeability is critical to understanding the petro-physical properties and CO2 storage potential of basalts. We exploit X-ray computed tomography (XCT) to investigate the precipitation history of an amygdaloidal basalt containing a pore-connecting micro fracture network now partially filled by calcite as an analogue for CO2 mineral trapping in a vesicular basalt. The fracture network likely represents a preferential pathway for CO2-rich fluids during mineralisation. We investigate and quantify the evolution of basalt porosity and permeability during pore-filling calcite precipitation by applying novel numerical erosion techniques to “back-strip” the calcite from the amygdales and fracture networks. We provide a semi-quantitative technique for defining reservoir potential and quality through time and understanding sub-surface flow and storage. We found that permeability evolution is dependent on the precipitation mechanism and rates, as well as on the presence of micro fracture networks, and that once the precipitation is sufficient to close off all pores, permeability reaches values that are controlled by the micro fracture network. These results prompt further studies to determine CO2 mineral trapping mechanisms in amygdaloidal basalts as analogues for CO2 injections in basalt formations.

Item Type:Articles
Additional Information:The XCT facility and AM were supported by Oil and Gas Innovation Centre. KJD was supported by NERC14 NE/M018687/2. JV was supported by European Research Council Advanced Grant 83422515 (EAVESDROP). This work was part supported by EPSRC EP/T023198/1 and NERC NE/T00908X/1.
Glasgow Author(s) Enlighten ID:MacDonald, Dr John and Macente, Dr Alice
Creator Roles:
Macente, A.Formal analysis, Methodology, Writing – original draft, Conceptualization
MacDonald, J.Methodology, Conceptualization, Supervision, Writing – review and editing
Authors: Macente, A., Dobson, K.J., MacDonald, J., Wadsworth, F.B., and Vasseur, J.
College/School:College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Transport in Porous Media
ISSN (Online):1573-1634
Published Online:19 October 2022
Copyright Holders:Copyright © 2022 The Authors
First Published:First published in Transport in Porous Media 145:697–717
Publisher Policy:Reproduced under a Creative Commons License

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