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Title: Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling

Authors:
;
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1348253
Grant/Contract Number:
DOE-DE-343 EE0002761
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Geothermics
Additional Journal Information:
Journal Volume: 62; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-03 22:00:01; Journal ID: ISSN 0375-6505
Publisher:
Elsevier
Country of Publication:
United Kingdom
Language:
English

Citation Formats

Gan, Quan, and Elsworth, Derek. Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling. United Kingdom: N. p., 2016. Web. doi:10.1016/j.geothermics.2016.04.009.
Gan, Quan, & Elsworth, Derek. Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling. United Kingdom. doi:10.1016/j.geothermics.2016.04.009.
Gan, Quan, and Elsworth, Derek. 2016. "Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling". United Kingdom. doi:10.1016/j.geothermics.2016.04.009.
@article{osti_1348253,
title = {Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling},
author = {Gan, Quan and Elsworth, Derek},
abstractNote = {},
doi = {10.1016/j.geothermics.2016.04.009},
journal = {Geothermics},
number = C,
volume = 62,
place = {United Kingdom},
year = 2016,
month = 7
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.geothermics.2016.04.009

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  • A multiple interacting continua (MINC) technique which can describe fluid and heat flow in fractured reservoirs, including effects of phase transitions between steam and liquid water is discussed. MINC is a generalization of the ''double porosity'' concept developed for ground water systems and later adapted to petroleum reservoirs. The approach employs a highly idealized description of a fractured medium, but the method is applicable to more general fracture geometries. In order to develop the MINC method into a tool for practical field applications, however, much more sophisticated and realistic representations of the geometry of fractured reservoirs are needed.In particular, statisticalmore » aspects of observed fracture distributions should be incorporated into the model.« less
  • Vapor-dominated geothermal reservoirs produce saturated or superheated steam, and vertical pressure gradients are close to vapor static. These observations have been generally accepted as providing conclusive evidence that the liquid saturation must be rather small (<50%) in order that liquid may be nearly immobile. This conclusion ignores the crucial role of conductive heat transfer mechanisms in fractured reservoirs for vaporizing liquid flowing under two-phase conditions. We have developed a multiple interacting continuum method (MINC) for numerically simulating two-phase flow of a homogeneous fluid in a fractured porous medium. Application of this method to reservoir conditions representative of The Geyers, California,more » and results from an analytical approximation show that, for matrix permeability less than a critical value (roughly-equal2.5 to 5 microdarcies), the mass flux of water from the matrix to the fractures will be continuously vaporized by heat transported due to conduction. This gives rise to production of superheated steam even when the matrix has nearly full liquid saturation. Simple estimates also show that heat-driven steam/water counterflow can maintain a nearly vapor static vertical pressure profile in the presence of mobile liquid water in a reservoir with low vertical matrix permeability. The implication of these findings is that the fluid reserves of vapor-dominated geothermal reservoirs may be larger by a factor of about 2 than has generally been believed in the past.« less
  • DFNWORKS is a parallelized computational suite to generate three-dimensional discrete fracture networks (DFN) and simulate flow and transport. Developed at Los Alamos National Laboratory over the past five years, it has been used to study flow and transport in fractured media at scales ranging from millimeters to kilometers. The networks are created and meshed using DFNGEN, which combines FRAM (the feature rejection algorithm for meshing) methodology to stochastically generate three-dimensional DFNs with the LaGriT meshing toolbox to create a high-quality computational mesh representation. The representation produces a conforming Delaunay triangulation suitable for high performance computing finite volume solvers in anmore » intrinsically parallel fashion. Flow through the network is simulated in dfnFlow, which utilizes the massively parallel subsurface flow and reactive transport finite volume code PFLOTRAN. A Lagrangian approach to simulating transport through the DFN is adopted within DFNTRANS to determine pathlines and solute transport through the DFN. Example applications of this suite in the areas of nuclear waste repository science, hydraulic fracturing and CO 2 sequestration are also included.« less
  • DFNWorks is a parallalized computational suite to generate three-dimensional discrete fracture networks (DFN) and simulate flow and transport. Developed at Los Alamos National Laboratory over the past five years, it has been used to study flow and transport in fractured media at scales ranging from millimeters to kilometers. The networks are created and meshed using dfnGen, which combines fram (the feature rejection algorithm for meshing) methodology to stochastically generate three-dimensional DFNs on the basis of site specific data with the LaGriT meshing toolbox to create a high-quality computational mesh representation, specifically a conforming Delaunay triangulation suitable for high performance computingmore » finite volume solvers, of the DFN in an intrinsically parallel fashion. Flow through the network is simulated in dfnFlow, which utilizes the massively parallel subsurface flow and reactive transport finite volume code pflotran. A Lagrangian approach to simulating transport through the DFN is adopted within dfnTrans, which is an extension of the walkabout particle tracking method to determine pathlines through the DFN. Example applications of this suite in the areas of nuclear waste repository science, hydraulic fracturing and CO2 sequestration are also included.« less
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