Page 17 - Geothermal Energy Systems Exploration, Development, and Utilization

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Preface

The book presents basic knowledge about geothermal technology for the utilization
of geothermal resources. It helps to understand the basic geology needed for the
utilization of geothermal energy and describes the methods to create access to
geothermal reservoirs by drilling and the engineering of the reservoir. The book
describes the technology available to make use of the earth’s heat for direct use,
power, and/or chilling, and gives the economic and environmental conditions
limiting its utilization. Special emphasis is given to enhanced or engineered
geothermal systems (EGS), which are based on concepts that bring a priori less
productive reservoirs to an economic use. These concepts require the geothermal
technology described here. The idea of EGS is not yet very old. Therefore, this book
aims to provide a baseline of the technologies, taking into account the fact that due
to a growing interest in EGS, a dynamic development may increase the specific
knowledge to a large extent in the near future.
The book begins with a large-scale picture of geothermal resources, addressing
expressions of the earth’s heat sources and measured heat flow at different places
world wide. This leads to conceptual models with a geological point of view
influencing geothermal reservoir definitions based on physical parameters like
porosity, permeability, and stress distribution in the underground, indicating that
geothermal applications can be deployed anywhere, but some locations are more
favorable than others.
The second chapter addresses the characterization of geothermal reservoirs
and the implications of their exploration. A best practice for the exploration of
EGS reservoirs is still to be determined and the different methods in geology,
geophysics, and geochemistry have a strong local character. Some methods are
successful in exploring conventional geothermal reservoirs like the magnetotel-
lurics, whereas for EGS, seismic methods become more and more important.
An overall conceptual exploration approach integrating the geophysical measure-
ments into a geological model taking into account the earth’s stress conditions
is addressed in this chapter, but it has to be further developed in future
contributions.
The baseline know-how of EGS drilling given in the third chapter, is based on
a few case studies and therefore, somewhat different from hydrocarbon drilling

Geothermal Energy Systems. Edited by Ernst Huenges
Copyright  2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 978-3-527-40831-3