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Title: A Thermoplasticity Model for Oil Shale

Several regions of the world have abundant oil shale resources, but accessing this energy supply poses a number of challenges. One particular difficulty is the thermomechanical behavior of the material. When heated to sufficient temperatures, thermal conversion of kerogen to oil, gas, and other products takes place. This alteration of microstructure leads to a complex geomechanical response. In this work, we develop a thermoplasticity model for oil shale. The model is based on critical state plasticity, a framework often used for modeling clays and soft rocks. The model described here allows for both hardening due to mechanical deformation and softening due to thermal processes. In particular, the preconsolidation pressure—defining the onset of plastic volumetric compaction—is controlled by a state variable representing the kerogen content of the material. As kerogen is converted to other phases, the material weakens and plastic compaction begins. We calibrate and compare the proposed model to a suite of high-temperature uniaxial and triaxial experiments on core samples from a pilot in situ processing operation in the Green River Formation. In conclusion, we also describe avenues for future work to improve understanding and prediction of the geomechanical behavior of oil shale operations.
Authors:
ORCiD logo [1] ;  [2] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Stanford Univ., Stanford, CA (United States)
Publication Date:
Report Number(s):
LLNL-CONF-667671
Journal ID: ISSN 0723-2632; PII: 947
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Rock Mechanics and Rock Engineering
Additional Journal Information:
Journal Volume: 50; Journal Issue: 3; Conference: Presented at: Fifth International Conference on Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geosystems, Salt Lake City, UT (United States), 25-27 Feb 2015; Journal ID: ISSN 0723-2632
Publisher:
Springer
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
04 OIL SHALES AND TAR SANDS; 58 GEOSCIENCES; Rock Mechanics; In Situ Processing; Oil Shale; Thermoplasticity
OSTI Identifier:
1378546