Porosity in mudstones and its effectiveness for sealing carbon capture and storage sites

Alnajdi, N ORCID: 0000-0003-0676-9761 and Worden, RH ORCID: 0000-0002-4686-9428 (2023) Porosity in mudstones and its effectiveness for sealing carbon capture and storage sites Geological Society Special Publication, 528 (1). pp. 339-357. ISSN 0305-8719, 2041-4927

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Abstract

Mudstones represent top-seals for many carbon capture sites as they tend to have the correct petro-physical properties, including suitable porosity and pore-size distribution. The pore network of mudstones is thus pivotal for many carbon capture and storage (CCS) projects. The key to understanding the effectiveness of top-seals is an appreciation of the controls on the pore network. For this reason, schemes to classify pore body size, pore type and pore throat size are presented. Pore types include primary and secondary interparticle and intraparticle pores and pores associated with organic matter and fractures. The most relevant mudstone pore body sizes for CCS top seals are likely to be between,62 µm and 1 nm. Pore throat sizes are classified as nano-(,10 nm), transition-(10 nm–0.1 µm), meso-(0.1–0.625 µm), and macro-pore throats (.0.625 µm). Petro-physical, geochemical, and geomechanical properties control porosity and the CO<inf>2</inf> sealing integrity of mud-stones; these properties are, in turn, controlled by the rate and extent of compaction, mineral diagenesis and overpressure. The success of a CCS top-seal relies on pore throats in intact top-seal being sufficiently small, and fracture pressure (typically minimum horizontal stress, σ<inf>hmin</inf>) not being exceeded by CO<inf>2</inf> pressure. CO<inf>2</inf> sorption, especially by smectite in top-seals, may improve the nanoscale sealing efficiency of clay minerals. The systematic workflow presented here will help facilitate the new drive to understand mudstone properties, as they are essential for establishing safe and durable CO<inf>2</inf> containment.

Item Type:	Article
Uncontrolled Keywords:	37 Earth Sciences, 3705 Geology
Divisions:	Faculty of Science & Engineering > School of Environmental Sciences
Depositing User:	Symplectic Admin
Date Deposited:	27 Jan 2023 08:17
Last Modified:	24 Jan 2026 04:03
DOI:	10.1144/SP528-2022-84
Open Access URL:	https://www.lyellcollection.org/doi/epdf/10.1144/S...
Related Websites:	Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3167921
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