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Title: Geomechanical characterization of Newberry Tuff

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USDOE Office of Energy Efficiency and Renewable Energy (EERE)
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Journal Article: Publisher's Accepted Manuscript
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Journal Volume: 63; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-03 21:59:20; Journal ID: ISSN 0375-6505
Country of Publication:
United Kingdom

Citation Formats

Wang, Jihoon, Jung, Woodong, Li, Yawei, and Ghassemi, Ahmad. Geomechanical characterization of Newberry Tuff. United Kingdom: N. p., 2016. Web. doi:10.1016/j.geothermics.2016.01.016.
Wang, Jihoon, Jung, Woodong, Li, Yawei, & Ghassemi, Ahmad. Geomechanical characterization of Newberry Tuff. United Kingdom. doi:10.1016/j.geothermics.2016.01.016.
Wang, Jihoon, Jung, Woodong, Li, Yawei, and Ghassemi, Ahmad. 2016. "Geomechanical characterization of Newberry Tuff". United Kingdom. doi:10.1016/j.geothermics.2016.01.016.
title = {Geomechanical characterization of Newberry Tuff},
author = {Wang, Jihoon and Jung, Woodong and Li, Yawei and Ghassemi, Ahmad},
abstractNote = {},
doi = {10.1016/j.geothermics.2016.01.016},
journal = {Geothermics},
number = C,
volume = 63,
place = {United Kingdom},
year = 2016,
month = 9

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.geothermics.2016.01.016

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  • U.S. Geological Survey Newberry 2 was drilled to a depth of 932 m within Newberry caldera. The bottom-hole temperature of 265/sup 0/C is the highest reported temperature of any drill hole in the Cascades region of the United States. The upper part of the stratigraphic section pentrated by Newberry 2 consists of caldera fill below which are increasingly more mafic lavas ranging from rhyodacite at 501 m to basalt at 932 m. Measured temperatures shallower than 300 m are less than 35/sup 0/C, and rock alteration consists of hydration of glass and local palagonitization of basaltic tuffs. Incipient zeolitization andmore » partial smectite replacement of ash and pumice occurred throughout the pumiceous lithic tuffs from 300 to 500 m. Higher-temperature alteration of the tuffs to chlorite and mordenite occurs adjacent to a rhyodacite sill at 460--470 m; alteration minerals within the sill consist of pyrrhotite, pyrite, quartz, calcite, and siderite. Below 697 m the rocks are progressively more altered with depth mainly because of increased temperature along a conductive gradient from 100/sup 0/C at 697 m to 265/sup 0/C at 930 m. Fluid inclusions in quartz and calcite indicate that temperature in the past have been higher than at present, most likely due to local confining pressures between impermeable lava flows.« less
  • No abstract prepared.
  • We developed a hydraulic fracturing simulator by coupling a flow simulator to a geomechanics code, namely T+M simulator. Modeling of the vertical fracture development involves continuous updating of the boundary conditions and of the data connectivity, based on the finite element method for geomechanics. The T+M simulator can model the initial fracture development during the hydraulic fracturing operations, after which the domain description changes from single continuum to double or multiple continua in order to rigorously model both flow and geomechanics for fracture-rock matrix systems. The T+H simulator provides two-way coupling between fluid-heat flow and geomechanics, accounting for thermoporomechanics, treatsmore » nonlinear permeability and geomechanical moduli explicitly, and dynamically tracks changes in the fracture(s) and in the pore volume. We also fully accounts for leak-off in all directions during hydraulic fracturing. We first validate the T+M simulator, matching numerical solutions with the analytical solutions for poromechanical effects, static fractures, and fracture propagations. Then, from numerical simulation of various cases of the planar fracture propagation, shear failure can limit the vertical fracture propagation of tensile failure, because of leak-off into the reservoirs. Slow injection causes more leak-off, compared with fast injection, when the same amount of fluid is injected. Changes in initial total stress and contributions of shear effective stress to tensile failure can also affect formation of the fractured areas, and the geomechanical responses are still well-posed.« less
  • Newberry 2 was drilled in the caldera floor of Newberry Volcano, Oregon, by the US Geological Survey during 1979-81. The maximum temperature measured was 265C at the bottom of the hole, 932 m below the surface. Rocks recovered fr9om the drill hole are divided into three intervals on the basis of hydrothermal alteration and mineral deposition: (1) 0-290 m consists of unaltered, largely glassy volcanic material, with present temperatures ranging from 20 to 40C; (2) 290-700 m consists of permeable tuff layers, tuff breccia units, and brecciated and fractured rhyodacitic to dacitic lava flows, with temperatures ranging from 40 tomore » 100C; (3) 700-932 m consists of impermeable andesitic to basaltic lava flows that generally show little effect of alteration, interlayered with permeable hydrothermally altered flow breccia, with temperatures gradually increasing from 100 at 700 m to 265C at 932 m. Hydrothermal alteration throughout the system is controlled by rock permeability, temperature, composition of geothermal fluids, and composition and crystallinity of host rocks. Rock alteration consists mainly of replacement of glass by clay minerals and, locally, zeolites, partial replacement of plagioclase phenocrysts by calcite +/- epidote +/- illite, and whole-rock leaching adjacent to fluids channels. Open-space deposition of hydrothermal minerals in fractures, vesicles, and interbreccia pore space is far more abundant than replacement. A cooling shallow convection system in the upper 700 m is indicated by the occurrence of hydrothermal minerals that were deposited in a slightly higher temperature environment than presently exists. Below 700 m, the heat flow is conductive, and fluid flow is controlled by horizontal lava flows. Homogenization temperatures of secondary quartz fluid inclusions were as high as 370C.« less