Permeability of a decollement zone: Results from a two-well experiment in the Barbados accretionary complex

Elizabeth Screaton, Bobb Carson, Earl Davis, Keir Becker

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Abstract

Fault zones are hypothesized to play a major role in focusing fluid expulsion from accretionary complexes. A small number of previous investigations have examined the hydrogeologic properties of these fault zones using borehole packer or submersible-based slug and constant rate flow tests. While these single-well experiments yielded the first data on the permeability of active fault zones, they could only investigate a small area around the borehole and could not ensure reliable determination of formation storage properties. Recent data from an unplanned experiment in the decollement zone of the Barbados accretionary prism demonstrate the potential for multiple-well hydrogeologic tests. Pressure data from a sealed borehole show a clear signal of drilling activity ∼45 m away. Analysis of the pressure response suggests that decollement zone permeability lies between 1.0 and 1.2 × 10-14 m2. This permeability is ∼2-4 orders of magnitude greater than overlying and underlying sediment and thus appears sufficient to focus fluid flow along the decollement zone. This inadvertent test evaluated fault zone hydrogeologic parameters over a larger radius and longer timescale and at pressures closer to in situ than previous single-well tests.

Original languageEnglish (US)
Article number2000JB900220
Pages (from-to)21403-21410
Number of pages8
JournalJournal of Geophysical Research C: Oceans
Volume105
Issue numberB9
StatePublished - Sep 10 2000

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ASJC Scopus subject areas

  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography
  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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