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Fracture-pattern growth in the deep, chemically reactive subsurface

Abstract:
Arrays of natural opening-mode fractures show systematic patterns in size and spatial arrangement. The controls on these factors are enigmatic, but in many cases the depth of formation appears to be critical. Physical, potentially depth-dependent factors that could account for these variations include confining stress, fluid pressure, and strain rate; these factors are common inputs to existing fracture models. However, temperature-dependent chemical processes likely exert an equally important control on patterns, and such processes have not yet been rigorously incorporated into models of fracture formation. Here we present a spring-lattice model that simulates fracturing in extending sedimentary rock beds, while explicitly accounting for cementation during opening of fractures, and for rock failure via both elastic and time-dependent failure criteria. Results illustrate three distinct fracturing behaviors having documented natural analogs, which we here term fracture facies. “Exclusionary macrofracturing” occurs at shallow levels and produces large, widely spaced, uncemented fractures; “multi-scale fracturing” occurs at moderate depth and produces partially cemented fractures having a wide range of sizes and spacings; and “penetrative microfracturing” occurs at great depth and produces myriad narrow, sealed fractures that are closely and regularly spaced. The effect of depth is primarily to accelerate both dissolution and precipitation reactions via increased temperature and porewater salinity; the specific depth range of each fracture facies will vary by host-rock lithology, grain size, strain rate, and thermal history.
Publication status:
Published
Peer review status:
Peer reviewed

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Publisher copy:
10.1016/j.jsg.2023.104915

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Role:
Author
ORCID:
0000-0002-4129-6755
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Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Role:
Author
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Institution:
University of Oxford
Division:
MPLS
Department:
Earth Sciences
Role:
Author


Publisher:
Elsevier
Journal:
Journal of Structural Geology More from this journal
Volume:
173
Article number:
104915
Publication date:
2023-07-11
Acceptance date:
2023-07-08
DOI:
EISSN:
1873-1201
ISSN:
0191-8141


Language:
English
Keywords:
Pubs id:
1493155
Local pid:
pubs:1493155
Deposit date:
2023-07-18

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