In situ permeability and scale dependence of an active accretionary prism determined from cross-borehole experiments

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doi: 10.1029/2018GL078304
Author(s): Kinoshita, C.; Saffer, D. M.
Author Affiliation(s): Primary:
National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
Pennsylvania State University, United States
Volume Title: Geophysical Research Letters
Source: Geophysical Research Letters, 45(14), p.6935-6943. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0094-8276 CODEN: GPRLAJ
Note: In English. 52 refs.; illus., incl. sketch map
Summary: Permeability controls fluid flow in the Earth's crust and affects a wide range of processes including advective transport and pore pressure generation. However, in situ measurements of permeability are few, especially in active tectonic settings or at scales relevant to regional flow. We analyze formation fluid pressure records from oceanic boreholes in the Nankai accretionary prism offshore southwest Japan, focusing on unexpected responses to drilling operations conducted at boreholes ∼100 m to the northeast. We develop a 2-D numerical model of transient fluid flow and conduct a parametric grid search to define hydraulic diffusivity. A value of 0.19-0.46 m2/s (corresponding to a permeability of 9.8×10-13 to 2.4×10-12 m2) yields the best fit to observed pressure responses. Together with laboratory measurements on core samples and drillstrem tests reported in previous studies, our analysis indicates a strong scale dependence of permeability, likely reflecting the presence of permeable faults and fractures. Abstract Copyright (2018). American Geophysical Union. All Rights Reserved.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Accretionary wedges; Asia; Boreholes; Crosscorrelation; Crust; Deformation; Diffusivity; Far East; Faults; Fluid flow; In situ; Japan; Kumano Basin; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Numerical models; Offshore; Pacific Ocean; Permeability; Pore pressure; Statistical analysis; Subduction zones; Transport; Two-dimensional models; West Pacific
Coordinates: N331700 N331900 E1363900 E1363800
Record ID: 2019039672
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom