In situ measurements of fluid flow in DSDP holes 395A and 534A; results from the DIANAUT Program

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doi: 10.1029/91GL02947
Author(s): Morin, Roger H.; Hess, Alfred E.; Becker, Keir
Author Affiliation(s): Primary:
U. S. Geol. Surv., Denver, CO, United States
Univ. Miami, United States
Volume Title: Geophysical Research Letters
Source: Geophysical Research Letters, 19(5), p.509-512. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0094-8276 CODEN: GPRLAJ
Note: In English. 16 refs.; illus.
Summary: The DIANAUT program provided the first opportunity to directly measure vertical fluid flow in ocean boreholes by means of a high resolution thermal flowmeter. Measurements of volumetric flow rate were obtained in DSDP (Deep Sea Drilling Project) Holes 395A and 534A. These results identified a total flow of 2300 L/hr of seawater entering Hole 395A from the seafloor that diminished to about 550 L/hr at a depth of 251 meters below seafloor (mbsf), indicating that approximately 3/4 of the original downward flow had exited the borehole and entered the open formation across the upper 140 m of basement. This information allows the upper oceanic crust at this site to be delimitated into three hydrologic units, with basalt permeabilities of 3.0 × 10-14 m2 near the sediment/basement interface decreasing sharply as a function of depth to values much less than 10-16 m2 below 440 mbsf. It is estimated that approximately 108 L of seawater have entered this well since it was drilled in 1975. Quantitative flow measurements in Hole 534A were inconclusive because of technical problems with the flowmeter packer. Nevertheless, results showed that borehole fluid was moving upward and out into the open ocean at a rate on the order of a few hundred liters per hour, roughly one order of magnitude less than that determined for Hole 395A and moving in the opposite direction. There is good correlation between these field measurements and the attendant temperature logs from each well, and the results provide strong evidence of important mass-transport processes associated with the diverse submarine hydrologic systems in the upper oceanic crust. Copyright 1992 by the American Geophysical Union.
Year of Publication: 1992
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; 20 Geophysics, Applied; Atlantic Ocean; DIANAUT; DSDP Site 395; DSDP Site 534; Deep Sea Drilling Project; Fluid dynamics; Geophysical surveys; IPOD; Leg 109; Leg 45; Leg 76; Leg 78B; Ocean Drilling Program; Ocean floors; Surveys; Techniques; Temperature logging; Well-logging
Coordinates: N224521 N224521 W0460454 W0460454
N282036 N282036 W0752254 W0752254
N224521 N233102 W0445651 W0460454
N220000 N230000 W0430000 W0470000
N224521 N224521 W0460454 W0460454
Record ID: 1992021889
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