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Title: Discrete element modeling of rock deformation, fracture network development and permeability evolution under hydraulic stimulation

Abstract

Key challenges associated with the EGS reservoir development include the ability to reliably predict hydraulic fracturing and the deformation of natural fractures as well as estimating permeability evolution of the fracture network with time. We have developed a physics-based rock deformation and fracture propagation simulator by coupling a discrete element model (DEM) for fracturing with a network flow model. In DEM model, solid rock is represented by a network of discrete elements (often referred as particles) connected by various types of mechanical bonds such as springs, elastic beams or bonds that have more complex properties (such as stress-dependent elastic constants). Fracturing is represented explicitly as broken bonds (microcracks), which form and coalesce into macroscopic fractures when external and internal load is applied. The natural fractures are represented by a series of connected line segments. Mechanical bonds that intersect with such line segments are removed from the DEM model. A network flow model using conjugate lattice to the DEM network is developed and coupled with the DEM. The fluid pressure gradient exerts forces on individual elements of the DEM network, which therefore deforms the mechanical bonds and breaks them if the deformation reaches a prescribed threshold value. Such deformation/fracturing in turnmore » changes the permeability of the flow network, which again changes the evolution of fluid pressure, intimately coupling the two processes. The intimate coupling between fracturing/deformation of fracture networks and fluid flow makes the meso-scale DEM- network flow simulations necessary in order to accurately evaluate the permeability evolution, as these methods have substantial advantages over conventional continuum mechanical models of elastic rock deformation. The challenges that must be overcome to simulate EGS reservoir stimulation, preliminary results, progress to date and near future research directions and opportunities will be discussed. Methodology for coupling the DEM model with continuum flow and heat transport models will also be discussed.« less

Authors:
; ;
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
DOE - EE
OSTI Identifier:
1017880
Report Number(s):
INL/CON-10-20152
TRN: US201113%%624
DOE Contract Number:  
DE-AC07-05ID14517
Resource Type:
Conference
Resource Relation:
Conference: Stanford Geothermal Workshop,Stanford, CA,01/31/2011,02/04/2011
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; DEFORMATION; FLOW MODELS; FLUID FLOW; FRACTURES; FRACTURING; HYDRAULIC FRACTURING; HYDRAULICS; PERMEABILITY; PRESSURE GRADIENTS; SIMULATION; SIMULATORS; STIMULATION; TRANSPORT; DEM; fracture flow; geothermal

Citation Formats

Deng, Shouchun, Podgorney, Robert, and Huang, Hai. Discrete element modeling of rock deformation, fracture network development and permeability evolution under hydraulic stimulation. United States: N. p., 2011. Web.
Deng, Shouchun, Podgorney, Robert, & Huang, Hai. Discrete element modeling of rock deformation, fracture network development and permeability evolution under hydraulic stimulation. United States.
Deng, Shouchun, Podgorney, Robert, and Huang, Hai. Tue . "Discrete element modeling of rock deformation, fracture network development and permeability evolution under hydraulic stimulation". United States. https://www.osti.gov/servlets/purl/1017880.
@article{osti_1017880,
title = {Discrete element modeling of rock deformation, fracture network development and permeability evolution under hydraulic stimulation},
author = {Deng, Shouchun and Podgorney, Robert and Huang, Hai},
abstractNote = {Key challenges associated with the EGS reservoir development include the ability to reliably predict hydraulic fracturing and the deformation of natural fractures as well as estimating permeability evolution of the fracture network with time. We have developed a physics-based rock deformation and fracture propagation simulator by coupling a discrete element model (DEM) for fracturing with a network flow model. In DEM model, solid rock is represented by a network of discrete elements (often referred as particles) connected by various types of mechanical bonds such as springs, elastic beams or bonds that have more complex properties (such as stress-dependent elastic constants). Fracturing is represented explicitly as broken bonds (microcracks), which form and coalesce into macroscopic fractures when external and internal load is applied. The natural fractures are represented by a series of connected line segments. Mechanical bonds that intersect with such line segments are removed from the DEM model. A network flow model using conjugate lattice to the DEM network is developed and coupled with the DEM. The fluid pressure gradient exerts forces on individual elements of the DEM network, which therefore deforms the mechanical bonds and breaks them if the deformation reaches a prescribed threshold value. Such deformation/fracturing in turn changes the permeability of the flow network, which again changes the evolution of fluid pressure, intimately coupling the two processes. The intimate coupling between fracturing/deformation of fracture networks and fluid flow makes the meso-scale DEM- network flow simulations necessary in order to accurately evaluate the permeability evolution, as these methods have substantial advantages over conventional continuum mechanical models of elastic rock deformation. The challenges that must be overcome to simulate EGS reservoir stimulation, preliminary results, progress to date and near future research directions and opportunities will be discussed. Methodology for coupling the DEM model with continuum flow and heat transport models will also be discussed.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2011},
month = {2}
}

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