Borehole packer tests at multiple depths resolve distinct hydrologic intervals in 3.5‐Ma upper oceanic crust on the eastern flank of Juan de Fuca Ridge

Hydrogeologic Properties, Processes, and Alteration in the Igneous Ocean Crust

“…This is surprising at first because the long-term cross-hole response should be influenced by a much larger rock volume, extending perhaps 10-30 km from the borehole, and larger test volumes generally correspond to higher apparent permeability in heterogeneous/fractured rock systems such as the ocean crust (e.g., Clauser, 1992;Fisher, 1998;Guéguen, Gavrilenko, & Le Ravalec, 1996). Basement permeability estimated from this cross-hole response is also one to three orders of Becker and Fisher (2008), with additional data from Fisher et al (2008), Becker et al (2013), andWinslow et al (2013)). Most data are from packer experiments (P) and borehole thermal logs (T), but there was a single cross-hole test, as discussed in the text.…”

Physical properties of young (3.5 Ma) oceanic crust from the eastern flank of the Juan de Fuca Ridge: Comparison of wireline and core measurements with global data

“…The deeper (but still upper-crustal) interval is characterized by thinner zones having low bulk density and electrical resistivity. The entire upper crustal section around Hole U1301B is highly permeable Becker and Fisher, 2008], but wireline petrophysical data clearly distinguish between two regions within the upper crust (Figure 2). The high permeability of the upper crust at Site U1301B enables circulation of large quantities of fluids through the crust.…”

Site U1362

“…Initial shipboard processing of the data from the first injection period shows a good fit to the expected linear rise of pressure versus natural log of time predicted by the Theis (1935) formulation for an injection test. The slope of the log-linear response indicates a bulk permeability for the isolated zone of 2 × 10 -12 m 2 , the same as the average value reported by Becker and Fisher (2008) for a comparable section of basement in nearby Hole U1301B. This preliminary result needs to be refined with more sophisticated postcruise processing.…”