The Role of Deformation Bands in Dictating Poromechanical Properties of Unconsolidated Sand and Sandstone
Abstract Cataclastic shear bands in sands and sandstones are typically stronger, stiffer, and exhibit lower permeability than the surrounding matrix, and therefore act as barriers to fluid flow. Previous work has quantified the reduction in permeability associated with these features; however, littl...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Wiley
2020-10-01
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| Series: | Geochemistry, Geophysics, Geosystems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2020GC009143 |
| _version_ | 1827771765266317312 |
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| author | Peter K. Miller Chris Marone Demian M. Saffer |
| author_facet | Peter K. Miller Chris Marone Demian M. Saffer |
| author_sort | Peter K. Miller |
| collection | DOAJ |
| description | Abstract Cataclastic shear bands in sands and sandstones are typically stronger, stiffer, and exhibit lower permeability than the surrounding matrix, and therefore act as barriers to fluid flow. Previous work has quantified the reduction in permeability associated with these features; however, little is known about the role of shear band structure in controlling the way they impact permeability and elastic properties. Here, we report on a suite of laboratory measurements designed to measure the poromechanical properties for host material and natural shear bands, over effective stresses from 1–65 MPa. In order to investigate the role of host material properties in controlling poromechanical evolution with stress, we sampled shear bands from two well‐studied sandstones representing structurally distinct end‐members: a poorly cemented marine terrace sand from the footwall of the McKinleyville thrust fault in Humboldt County, California, and a strongly‐cemented sandstone from the hanging wall of the Moab Fault in Moab, Utah. The permeability‐porosity trends are similar for all samples, with permeability decreasing systematically with increasing effective stress and decreasing porosity. The permeability of the host material is consistently >1 order of magnitude greater than the shear bands for both localities. For the unconsolidated case, shear bands are less permeable and stiffer than the host material, whereas for the consolidated case, shear bands are slightly less permeable, and wave speeds are slower than in the host. We attribute the differences between the McKinleyville and Moab examples to changes in structure of the nearby host material that accompanied formation of the shear band. |
| first_indexed | 2024-03-11T13:00:00Z |
| format | Article |
| id | doaj.art-c9e215a224b243999cc4cf22046e2516 |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T13:00:00Z |
| publishDate | 2020-10-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-c9e215a224b243999cc4cf22046e25162023-11-03T16:55:21ZengWileyGeochemistry, Geophysics, Geosystems1525-20272020-10-012110n/an/a10.1029/2020GC009143The Role of Deformation Bands in Dictating Poromechanical Properties of Unconsolidated Sand and SandstonePeter K. Miller0Chris Marone1Demian M. Saffer2Institute for Geophysics University of Texas Austin TX USADepartment of Geoscience and Center for Geomechanics, Geofluids, and Geohazards The Pennsylvania State University University Park PA USAInstitute for Geophysics University of Texas Austin TX USAAbstract Cataclastic shear bands in sands and sandstones are typically stronger, stiffer, and exhibit lower permeability than the surrounding matrix, and therefore act as barriers to fluid flow. Previous work has quantified the reduction in permeability associated with these features; however, little is known about the role of shear band structure in controlling the way they impact permeability and elastic properties. Here, we report on a suite of laboratory measurements designed to measure the poromechanical properties for host material and natural shear bands, over effective stresses from 1–65 MPa. In order to investigate the role of host material properties in controlling poromechanical evolution with stress, we sampled shear bands from two well‐studied sandstones representing structurally distinct end‐members: a poorly cemented marine terrace sand from the footwall of the McKinleyville thrust fault in Humboldt County, California, and a strongly‐cemented sandstone from the hanging wall of the Moab Fault in Moab, Utah. The permeability‐porosity trends are similar for all samples, with permeability decreasing systematically with increasing effective stress and decreasing porosity. The permeability of the host material is consistently >1 order of magnitude greater than the shear bands for both localities. For the unconsolidated case, shear bands are less permeable and stiffer than the host material, whereas for the consolidated case, shear bands are slightly less permeable, and wave speeds are slower than in the host. We attribute the differences between the McKinleyville and Moab examples to changes in structure of the nearby host material that accompanied formation of the shear band.https://doi.org/10.1029/2020GC009143deformation bandfaultspermeabilityseismic velocity |
| spellingShingle | Peter K. Miller Chris Marone Demian M. Saffer The Role of Deformation Bands in Dictating Poromechanical Properties of Unconsolidated Sand and Sandstone Geochemistry, Geophysics, Geosystems deformation band faults permeability seismic velocity |
| title | The Role of Deformation Bands in Dictating Poromechanical Properties of Unconsolidated Sand and Sandstone |
| title_full | The Role of Deformation Bands in Dictating Poromechanical Properties of Unconsolidated Sand and Sandstone |
| title_fullStr | The Role of Deformation Bands in Dictating Poromechanical Properties of Unconsolidated Sand and Sandstone |
| title_full_unstemmed | The Role of Deformation Bands in Dictating Poromechanical Properties of Unconsolidated Sand and Sandstone |
| title_short | The Role of Deformation Bands in Dictating Poromechanical Properties of Unconsolidated Sand and Sandstone |
| title_sort | role of deformation bands in dictating poromechanical properties of unconsolidated sand and sandstone |
| topic | deformation band faults permeability seismic velocity |
| url | https://doi.org/10.1029/2020GC009143 |
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