New evidence for age variation and scale effects of permeabilities of young oceanic crust from borehole thermal and pressure measurements

Keir Becker, Earl E. Davis

Research output: Contribution to journalArticle

45 Citations (Scopus)

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.

Original languageEnglish (US)
Pages (from-to)499-508
Number of pages10
JournalEarth and Planetary Science Letters
Volume210
Issue number3-4
DOIs
StatePublished - May 30 2003

Fingerprint

scale effect
Observatories
pressure measurement
Pressure measurement
boreholes
Boreholes
oceanic crust
crusts
permeability
borehole
Packers
Water
Pressure sensors
Temperature sensors
Flow of fluids
Drilling
Flow rate
basements
temperature profile
temperature profiles

Keywords

  • Hydrothermal circulation
  • Marine hydrogeology
  • Ocean Drilling Program
  • Oceanic crust
  • Permeability

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

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title = "New evidence for age variation and scale effects of permeabilities of young oceanic crust from borehole thermal and pressure measurements",
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.",
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AU - Davis, Earl E.

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AB - 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.

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