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Title: Modeling Dynamic Helium Release as a Tracer of Rock Deformation

Here, we use helium released during mechanical deformation of shales as a signal to explore the effects of deformation and failure on material transport properties. A dynamic dual-permeability model with evolving pore and fracture networks is used to simulate gases released from shale during deformation and failure. Changes in material properties required to reproduce experimentally observed gas signals are explored. We model two different experiments of 4He flow rate measured from shale undergoing mechanical deformation, a core parallel to bedding and a core perpendicular to bedding. We also found that the helium signal is sensitive to fracture development and evolution as well as changes in the matrix transport properties. We constrain the timing and effective fracture aperture, as well as the increase in matrix porosity and permeability. Increases in matrix permeability are required to explain gas flow prior to macroscopic failure, and the short-term gas flow postfailure. Increased matrix porosity is required to match the long-term, postfailure gas flow. This model provides the first quantitative interpretation of helium release as a result of mechanical deformation. The sensitivity of this model to changes in the fracture network, as well as to matrix properties during deformation, indicates that helium release can bemore » used as a quantitative tool to evaluate the state of stress and strain in earth materials.« less
Authors:
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ;  [2]
  1. Univ. of Montana, Missoula, MT (United States). Dept. of Geosciences
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Geomechanics Dept.
  3. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Applied Systems Research Dept.
Publication Date:
Report Number(s):
SAND-2017-4431J
Journal ID: ISSN 2169-9313; 652815; TRN: US1800243
Grant/Contract Number:
AC04-94AL85000; NA0003525
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Solid Earth
Additional Journal Information:
Journal Volume: 122; Journal Issue: 11; Journal ID: ISSN 2169-9313
Publisher:
American Geophysical Union
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES
OSTI Identifier:
1411603