Evolution of fracture permeability through reactive flow at elevated temperatures

Hideaki Yasuhara, Amir Polak, Yasuhiro Mitani, Avrami Grader, Phillip Halleck, Derek Elsworth

Research output: Contribution to journalConference article

3 Citations (Scopus)

Abstract

Flow-through experiments are conducted on a natural fracture in novaculite at a constant effective stress of 1.38 MPa and at staged temperatures of 20, 40, 80, and 120°C. Fluid and mineral effluxes are measured throughout the 3150-hr experiment, together with post-experiment imaging by X-ray CT and destructive fracture-casting by Wood's metal impregnation. These measurements are used to constrain the evolution of dissolution-driven changes in fracture structure, and related permeability under hydrothermal conditions. At 20°C the fracture aperture monotonically decreases from an initial aperture of 18.5 μm to 7.5 μm during the first 1494 hrs. This reduction is attributed to removal of mineral mass from bridging asperities. Subsequently, fracture aperture increases to 13 μm and is interpreted as a switching of dominant dissolution processes to free-face etching of the fracture void surfaces. The resulting rate of gaping increases with an increase in temperature. Post-experiment imaging by X-ray CT and by using the fracture cast independently constrains the resulting architecture of the evolved fracture porosity. No localized flow channel is apparent, despite the evolving hydraulic response which is suggestive of an evolving dissolution channel.

Original languageEnglish (US)
Pages (from-to)437-441
Number of pages5
JournalTransactions - Geothermal Resources Council
Volume29
StatePublished - Dec 1 2005
EventGeothermal Resources Council 2005 Annual Meeting - Reno, NV, United States
Duration: Sep 25 2005Sep 28 2005

Fingerprint

permeability
fracture aperture
temperature
dissolution
Temperature
dissolving
Dissolution
apertures
experiment
Minerals
etching
asperity
Experiments
minerals
channel flow
mineral
effective stress
efflux
Imaging techniques
X rays

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology
  • Geophysics

Cite this

Yasuhara, Hideaki ; Polak, Amir ; Mitani, Yasuhiro ; Grader, Avrami ; Halleck, Phillip ; Elsworth, Derek. / Evolution of fracture permeability through reactive flow at elevated temperatures. In: Transactions - Geothermal Resources Council. 2005 ; Vol. 29. pp. 437-441.
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Evolution of fracture permeability through reactive flow at elevated temperatures. / Yasuhara, Hideaki; Polak, Amir; Mitani, Yasuhiro; Grader, Avrami; Halleck, Phillip; Elsworth, Derek.

In: Transactions - Geothermal Resources Council, Vol. 29, 01.12.2005, p. 437-441.

Research output: Contribution to journalConference article

TY - JOUR

T1 - Evolution of fracture permeability through reactive flow at elevated temperatures

AU - Yasuhara, Hideaki

AU - Polak, Amir

AU - Mitani, Yasuhiro

AU - Grader, Avrami

AU - Halleck, Phillip

AU - Elsworth, Derek

PY - 2005/12/1

Y1 - 2005/12/1

N2 - Flow-through experiments are conducted on a natural fracture in novaculite at a constant effective stress of 1.38 MPa and at staged temperatures of 20, 40, 80, and 120°C. Fluid and mineral effluxes are measured throughout the 3150-hr experiment, together with post-experiment imaging by X-ray CT and destructive fracture-casting by Wood's metal impregnation. These measurements are used to constrain the evolution of dissolution-driven changes in fracture structure, and related permeability under hydrothermal conditions. At 20°C the fracture aperture monotonically decreases from an initial aperture of 18.5 μm to 7.5 μm during the first 1494 hrs. This reduction is attributed to removal of mineral mass from bridging asperities. Subsequently, fracture aperture increases to 13 μm and is interpreted as a switching of dominant dissolution processes to free-face etching of the fracture void surfaces. The resulting rate of gaping increases with an increase in temperature. Post-experiment imaging by X-ray CT and by using the fracture cast independently constrains the resulting architecture of the evolved fracture porosity. No localized flow channel is apparent, despite the evolving hydraulic response which is suggestive of an evolving dissolution channel.

AB - Flow-through experiments are conducted on a natural fracture in novaculite at a constant effective stress of 1.38 MPa and at staged temperatures of 20, 40, 80, and 120°C. Fluid and mineral effluxes are measured throughout the 3150-hr experiment, together with post-experiment imaging by X-ray CT and destructive fracture-casting by Wood's metal impregnation. These measurements are used to constrain the evolution of dissolution-driven changes in fracture structure, and related permeability under hydrothermal conditions. At 20°C the fracture aperture monotonically decreases from an initial aperture of 18.5 μm to 7.5 μm during the first 1494 hrs. This reduction is attributed to removal of mineral mass from bridging asperities. Subsequently, fracture aperture increases to 13 μm and is interpreted as a switching of dominant dissolution processes to free-face etching of the fracture void surfaces. The resulting rate of gaping increases with an increase in temperature. Post-experiment imaging by X-ray CT and by using the fracture cast independently constrains the resulting architecture of the evolved fracture porosity. No localized flow channel is apparent, despite the evolving hydraulic response which is suggestive of an evolving dissolution channel.

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