| Title | New evidence for age variation and scale effects of permeabilities of young oceanic crust from borehole thermal and pressure measurements |
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| Author | Becker, K; Davis, E E |
| Source | Earth and Planetary Science Letters vol. 210, issue 3-4, 2003 p. 499-508, https://doi.org/10.1016/S0012-821X(03)00160-2 |
| Links | Errata
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| Image |  |
| Year | 2003 |
| Alt Series | Earth Sciences Sector, Contribution Series 20120067 |
| Publisher | Elsevier BV |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Western offshore region |
| Subjects | marine geology; oceanic crust; permeability; boreholes; pressure-temperature conditions; hydrothermal systems; flow rates |
| Released | 2003 05 01 |
| Abstract | In 1996, long-term sealed-hole hydrological observatories with subseafloor temperature and pressure sensors were installed in four cased holes drilled by the Ocean Drilling Program into sedimented young
oceanic crust east of the Juan de Fuca Ridge. Data recovered over a year later showed that all four holes displayed temperature profiles indicative of vertical fluid flow immediately prior to their being sealed. Warm water was being produced from
basement in two cases, and cool ocean bottom water was being drawn into basement at the others. Linear flow rates of ~60-200 m/h were estimated from the perturbation of the temperature profiles relative to undisturbed geothermal gradients at the
sites. The pressure differentials driving the flow were also measured at the time of the observatory installations, allowing estimates of permeabilities of the upper crustal sections penetrated by the holes. Estimated permeabilities vary
systematically with age, ranging from about 10-10 m2 in the youngest site (0.9 Ma) to 10-12 m2 in the oldest site (3.6 Ma), confirming an apparent reduction of permeability with age determined with packer experiments at three of the same sites.
Combined with other estimates of permeabilities in the same holes using methods with different scales of investigation, the new permeability estimates also provide evidence for a significant scale dependence of permeability in the upper oceanic
crust. |
| GEOSCAN ID | 291438 |
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