Page 18 - Geothermal Energy Systems Exploration, Development, and Utilization

XVI Preface
with reference to issues like large diameter holes, deviated wells, and mitiga-
tion of formation damage. The latter is also important for drilling conventional
geothermal reservoirs, which to a great extent follow standards in operation and
completion. The knowledge of underground physical conditions, especially the
magnitude and direction of the local stress, is important for reliable drilling
into EGS reservoirs. Awareness of the stress conditions is also a prerequisite
for starting hydraulic fracturing treatment which is addressed in a following
chapter.
In the fourth chapter, techniques and experiences from several EGS sites are
described providing a set of methods available for addressing the goal of increasing
well productivity. The case studies cover several geological environments such as
deep sediments and granites. Significant progress was made in the last few years
in recovering enhancing factors in the order of magnitudes. Chances and risks of
companion effects of the treatments, such as induced seismicity, are addressed and
will be a subject of forthcoming research.
In the fifth chapter, the state-of-the-art numerical instruments used to simulate
geothermal reservoirs during exploitation are given in different case studies.
Different coupled processes such as thermal–hydraulic or hydraulic–mechanical,
including coupled chemical processes, are discussed. The development of the
coupling of thermal, hydraulic, mechanical, and chemical processes is ongoing,
hence the chapter provides the basics.
The benefits of using geothermal energy technologies for the direct use and
conversion of the earth’s heat into chilling or heating power (as required), are
described in the sixth chapter. Technical solutions for all tasks within the goal of
energy provision exist, and approaches for improving the performance of system
components are given. Special emphasis is given to techniques that can assure
reliable and efficient operation at the interface of underground fluids with technical
components. Processes like corrosion and scaling have to be addressed and they
are still a subject of future research.
The economic learning curve is shown in the seventh chapter that provides some
methods to analyze the risks of a project. A decision-making methodology is given
for several stages of the project. Environmental aspects are discussed, and results
of life cycle assessment with illustrations of greenhouse gas emissions are reported
in the chapter.
The final chapter discusses the possibility of geothermal deployment as a part
of future energy provision and an important contribution to the mitigation of
CO 2 emissions. The technological, economic, and political factors controlling
such deployment are discussed and should provide some assistance for decision
makers.
The book was compiled by the authors, but also significantly improved by
competent reviewers. Therefore, we like to thank Magdalene Scheck-Wenderoth,
Albert Genter, Dominique Bruel, Claus Chur, Don DiPippo, Wolfram Krewitt, and
Harald Milsch for their excellent comments on the different chapters. In addition,
we acknowledge the funds received from the EU commission, for example, for the
projects ENGINE and I-GET, and the German government, especially, the Federal