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Title: Thermal drawdown-induced flow channeling in a single fracture in EGS

Here, the evolution of flow pattern along a single fracture and its effects on heat production is a fundamental problem in the assessments of engineered geothermal systems (EGS). The channelized flow pattern associated with ubiquitous heterogeneity in fracture aperture distribution causes non-uniform temperature decrease in the rock body, which makes the flow increasingly concentrated into some preferential paths through the action of thermal stress. This mechanism may cause rapid heat production deterioration of EGS reservoirs. In this study, we investigated the effects of aperture heterogeneity on flow pattern evolution in a single fracture in a low-permeability crystalline formation. We developed a numerical model on the platform of GEOS to simulate the coupled thermo-hydro-mechanical processes in a penny-shaped fracture accessed via an injection well and a production well. We find that aperture heterogeneity generally exacerbates flow channeling and reservoir performance generally decreases with longer correlation length of aperture field. The expected production life is highly variable (5 years to beyond 30 years) when the aperture correlation length is longer than 1/5 of the well distance, whereas a heterogeneous fracture behaves similar to a homogeneous one when the correlation length is much shorter than the well distance. Besides, the mean production lifemore » decreases with greater aperture standard deviation only when the correlation length is relatively long. Although flow channeling is inevitable, initial aperture fields and well locations that enable tortuous preferential paths tend to deliver long heat production lives.« less
 [1] ;  [2] ;  [2] ;  [3] ;  [2]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Princeton Univ., Princeton, NJ (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Princeton Univ., Princeton, NJ (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0375-6505
Grant/Contract Number:
AC52-07NA27344; CBET-1133849
Published Article
Journal Name:
Additional Journal Information:
Journal Volume: 61; Journal Issue: C; Journal ID: ISSN 0375-6505
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Geothermal Technologies Office (EE-4G); National Science Foundation (NSF)
Country of Publication:
United States
15 GEOTHERMAL ENERGY; EGS; Thermal drawdown; Flow channeling; Aperture heterogeneity; THM coupling; GEOS
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1367999