THERMO-HYDRO-MECHANICAL MODELING OF WORKING FLUID INJECTION AND THERMAL ENERGY EXTRACTION IN EGS FRACTURES AND ROCK MATRIX

Conference · Sun Jan 01 04:00:00 EST 2012

OSTI ID:1042378

Podgorney, Robert; Lu, Chuan; Huang, Hai

Development of enhanced geothermal systems (EGS) will require creation of a reservoir of sufficient volume to enable commercial-scale heat transfer from the reservoir rocks to the working fluid. A key assumption associated with reservoir creation/stimulation is that sufficient rock volumes can be hydraulically fractured via both tensile and shear failure, and more importantly by reactivation of naturally existing fractures (by shearing), to create the reservoir. The advancement of EGS greatly depends on our understanding of the dynamics of the intimately coupled rock-fracture-fluid-heat system and our ability to reliably predict how reservoirs behave under stimulation and production. Reliable performance predictions of EGS reservoirs require accurate and robust modeling for strongly coupled thermal-hydrological-mechanical (THM) processes. Conventionally, these types of problems have been solved using operator-splitting methods, usually by coupling a subsurface flow and heat transport simulators with a solid mechanics simulator via input files. An alternative approach is to solve the system of nonlinear partial differential equations that govern multiphase fluid flow, heat transport, and rock mechanics simultaneously, using a fully coupled, fully implicit solution procedure, in which all solution variables (pressure, enthalpy, and rock displacement fields) are solved simultaneously. This paper describes numerical simulations used to investigate the poro- and thermal- elastic effects of working fluid injection and thermal energy extraction on the properties of the fractures and rock matrix of a hypothetical EGS reservoir, using a novel simulation software FALCON (Podgorney et al., 2011), a finite element based simulator solving fully coupled multiphase fluid flow, heat transport, rock deformation, and fracturing using a global implicit approach. Investigations are also conducted on how these poro- and thermal-elastic effects are related to fracture permeability evolution.

• Research Organization: Idaho National Laboratory (INL)
• Sponsoring Organization: DOE - EE
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1042378
• Report Number(s): INL/CON-12-24584
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
COUPLING
DEFORMATION
ENTHALPY
EXTRACTION
FLUID FLOW
FRACTURES
FRACTURING
GEOTHERMAL SYSTEMS
HEAT
HEAT TRANSFER
INJECTION
PARTIAL DIFFERENTIAL EQUATIONS
PERFORMANCE
PERMEABILITY
PRODUCTION
RESERVOIR ROCK
ROCK MECHANICS
ROCKS
SHEAR
SIMULATION
SIMULATORS
SOLIDS
SOLUTIONS
STIMULATION
TRANSPORT
VOLUME
WORKING FLUIDS
egs
geothermal
modeling