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The radiator-enhanced geothermal system; benefits of emulating a natural hydrothermal system

Markus Hilpert, Bruce D. Marsh and Peter Geiser
The radiator-enhanced geothermal system; benefits of emulating a natural hydrothermal system
Interpretation (Tulsa) (November 2016) 4 (4): SR35-SR48

Abstract

We have developed a novel enhanced geothermal system (EGS) called radiator EGS (RAD-EGS). This system attempts to emulate naturally occurring hydrothermal systems by creating a vertically oriented heat exchanger or vane in the deep subsurface, mimicking a radiator in an internal combustion engine. Water is injected at the bottom of the vane and produced on the top. We propose to build the RAD-EGS in hot sedimentary aquifers (HSAs) with high-permeability vane(s) created in the plane defined by Sh (sub max) and S (sub 1) (vertical). We have evaluated 3D heat-transfer simulations to better understand the fluid and heat flows that may occur in RAD-EGSs. The simulations account for subsurface heterogeneity including the presence of underlying basement rock, an overlying confining layer, and an ambient hydraulic gradient, which causes background groundwater flow. Our simulations indicate that our induced upward flow in the vane significantly prolongs the lifetime of RAD-EGS when compared with downward flow because hydraulic short circuiting is avoided. Within the vane, convection may occur, and its onset is analyzed in terms of a characteristic Rayleigh number. A critical aspect of RAD-EGS, therefore, is that thermal recharge does not rely solely on heat conduction from the surrounding wall rock, which is typical for EGS built in hot dry rock (HDR). Instead, recharge is also due to heat advection through the surrounding water-saturated aquifer, substantially prolonging the lifetime of the thermal reservoir. Moreover, fluid losses as typical for EGS built in HDR do not occur. It is also possible that cold water injected at the bottom of the vane may sink into deeper rock layers, which displaces hot water from the surrounding aquifer into the RAD-EGS. We suggest that mimicking a natural hydrothermal system is a successful EGS strategy via RAD-EGS.


ISSN: 2324-8858
EISSN: 2324-8866
Serial Title: Interpretation (Tulsa)
Serial Volume: 4
Serial Issue: 4
Title: The radiator-enhanced geothermal system; benefits of emulating a natural hydrothermal system
Affiliation: Johns Hopkins University, Department of Earth and Planetary Sciences, Baltimore, MD, United States
Pages: SR35-SR48
Published: 201611
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 37
Accession Number: 2017-004713
Categories: Economic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Secondary Affiliation: Global Geophysical Services, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201704
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