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Fluid flux in fractured rock of the Alpine fault hanging-wall determined from temperature logs in the DFDP-2B borehole, New Zealand

Fluid flux in fractured rock of the Alpine fault hanging-wall determined from temperature logs in the DFDP-2B borehole, New Zealand
Fluid flux in fractured rock of the Alpine fault hanging-wall determined from temperature logs in the DFDP-2B borehole, New Zealand

Sixteen temperature logs were acquired during breaks in drilling of the 893m-deep DFDP-2B borehole, which is in the Alpine Fault hanging-wall. The logs record various states of temperature recovery after thermal disturbances induced by mud circulation. The long-wavelength temperature signal in each log was estimated using a sixth-order polynomial, and residual (reduced) temperature logs were analyzed by fitting discrete template wavelets defined by depth, amplitude, and width parameters. Almost two hundred wavelets are correlated between multiple logs. Anomalies generally have amplitudes <1°C, and downhole widths <20m. The largest amplitudes are found in the first day after mud circulation stops, but many anomalies persist with similar amplitude for up to 15 days. Our models show that thermal and hydraulic diffusive processes are dominant during the first few days of re-equilibration after mud circulation stops, and fluid advection of heat in the surrounding rock produces temperature anomalies that may persist for several weeks. Models indicate that the fluid flux normal to the borehole within fractured zones is of order 10−7 to 10−6 m s−1, which is 2–3 orders of magnitude higher than the regional flux. Our approach could be applied more widely to boreholes, as it uses the thermal re-equilibration phase to derive useful information about the surrounding rock mass and its fluid flow regime.

aquifer, geothermal, groundwater, hydrogeology, permeability
1525-2027
1-16
Janku-Capova, Lucie
23b7a06a-c5d8-4b39-9ccc-bcc69f327d46
Sutherland, Rupert
96704929-bf2b-4eff-9e81-93edfad504b0
Townend, John
60be76ed-47bd-4c9a-92e1-2cba6fdad2e4
Doan, Mai Linh
c3133590-40bd-4b12-9282-4acd49ae9a2a
Massiot, Cécile
62d69e10-9dc5-4506-944a-535c510f3d90
Coussens, Jamie
10b295ab-dcbb-4111-baa0-d21e631d6af4
Célérier, Bernard
d51b3fa6-d780-47c6-bec5-1e2a527eecff
Janku-Capova, Lucie
23b7a06a-c5d8-4b39-9ccc-bcc69f327d46
Sutherland, Rupert
96704929-bf2b-4eff-9e81-93edfad504b0
Townend, John
60be76ed-47bd-4c9a-92e1-2cba6fdad2e4
Doan, Mai Linh
c3133590-40bd-4b12-9282-4acd49ae9a2a
Massiot, Cécile
62d69e10-9dc5-4506-944a-535c510f3d90
Coussens, Jamie
10b295ab-dcbb-4111-baa0-d21e631d6af4
Célérier, Bernard
d51b3fa6-d780-47c6-bec5-1e2a527eecff

Janku-Capova, Lucie, Sutherland, Rupert, Townend, John, Doan, Mai Linh, Massiot, Cécile, Coussens, Jamie and Célérier, Bernard (2018) Fluid flux in fractured rock of the Alpine fault hanging-wall determined from temperature logs in the DFDP-2B borehole, New Zealand. Geochemistry, Geophysics, Geosystems, 1-16. (doi:10.1029/2017GC007317).

Record type: Article

Abstract

Sixteen temperature logs were acquired during breaks in drilling of the 893m-deep DFDP-2B borehole, which is in the Alpine Fault hanging-wall. The logs record various states of temperature recovery after thermal disturbances induced by mud circulation. The long-wavelength temperature signal in each log was estimated using a sixth-order polynomial, and residual (reduced) temperature logs were analyzed by fitting discrete template wavelets defined by depth, amplitude, and width parameters. Almost two hundred wavelets are correlated between multiple logs. Anomalies generally have amplitudes <1°C, and downhole widths <20m. The largest amplitudes are found in the first day after mud circulation stops, but many anomalies persist with similar amplitude for up to 15 days. Our models show that thermal and hydraulic diffusive processes are dominant during the first few days of re-equilibration after mud circulation stops, and fluid advection of heat in the surrounding rock produces temperature anomalies that may persist for several weeks. Models indicate that the fluid flux normal to the borehole within fractured zones is of order 10−7 to 10−6 m s−1, which is 2–3 orders of magnitude higher than the regional flux. Our approach could be applied more widely to boreholes, as it uses the thermal re-equilibration phase to derive useful information about the surrounding rock mass and its fluid flow regime.

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More information

Accepted/In Press date: 5 May 2018
e-pub ahead of print date: 18 May 2018
Keywords: aquifer, geothermal, groundwater, hydrogeology, permeability

Identifiers

Local EPrints ID: 424194
URI: http://eprints.soton.ac.uk/id/eprint/424194
ISSN: 1525-2027
PURE UUID: d00e60fb-79c9-42f0-a870-89f30689304a

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Date deposited: 05 Oct 2018 11:34
Last modified: 27 Apr 2022 10:53

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Contributors

Author: Lucie Janku-Capova
Author: Rupert Sutherland
Author: John Townend
Author: Mai Linh Doan
Author: Cécile Massiot
Author: Jamie Coussens
Author: Bernard Célérier

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