1) The document discusses enhanced geothermal systems (EGS), which artificially create underground reservoirs in hot rock with low permeability by hydraulically fracturing the rock and circulating water to extract geothermal energy. 2) Developing an EGS plant involves finding a suitable hot rock site, drilling injection and production wells to create a fracture network between the wells, and operating the reservoir by circulating water to generate electricity via a turbine. 3) EGS could potentially provide a significant amount of the world's energy needs from the abundant heat in the Earth's crust, though developing the technology poses technical challenges compared to conventional geothermal.

1. GEOL602-Global & Regional Tectonics
Presentation – I
Enhanced Geothermal Systems
[EGS]
Omar A. Radwan
PhD Student – Geosciences Dept. - KFUPM
Olasolo, P., Juárez, M. C., Morales, M. P., & Liarte, I. A. (2016).
Enhanced geothermal systems (EGS): A review. Renewable and
Sustainable Energy Reviews, 56, 133-144.

2. Outline
• Thermal gradient
• Enhanced Geothermal Systems (EGS)
Introduction
• Finding a site
• Creating the reservoir
• Operating the reservoir
Development of a geothermal plant
Case Study

3. Introduction
• The mean thermal gradient stands at
an increment of between 25 °C and
30 °C per km of depth
• Three different resource quality
levels:
• Low-grade: with an estimated
geothermal gradient of 30 °C/km
• Medium-grade: with an
estimated geothermal gradient
of 50 °C/km
• High-grade: with an estimated
geothermal gradient of 70 °C/km
• For instance, the regions of Alsace (eastern France) and Rhineland-
Palatinate (western Germany) with a thermal gradient in the first 1000
metres depth of up to 100°C/km of depth.

4. Introduction
• Geothermal system
• Enhanced Geothermal
System
• EGS
• A.K.A. Engineered
Geothermal Systems

5. Development of a geothermal plant
EGS plant comprises
complex above-ground and
underground facilities.
• The above-ground power
plant accounts for a
significant proportion of
the overall cost of a
commercial EGS plant.
• Artificially created
underground
geothermal reservoir,
where research and
studies into EGS are
mainly concentrated.
Operating
the
reservoir
Creating
the
reservoir
Finding a
site

6. Development of a geothermal plant
Finding a site
• Assess the temperature
gradient, permeability, in-situ
stress directions of the resource,
rock mechanical properties, and
whether fluid is present.
Determine if the necessary
characteristics to create an EGS
reservoir are present.

7. Creating the reservoir
• Drill an injection well into hot rock with
limited fluid content and/or permeability
• Inject water at sufficient pressure to create a
fracture network.
• Continue operation until there is enough
fractured volume to create a reservoir (flow
rate, temperature, volume, and
sustainability).
• Drill a production well into the fracture
network, intersecting the created flow paths.
The resulting circulation loop allows water to
flow through the enhanced reservoir, picking
up in situ heat. The hot water is then pumped
to the surface through the production well.
Development of a geothermal plant

8. Operating the reservoir
• At the surface, the water flashes
to steam, or it heats a working
fluid that produces vapor.
• The steam/vapor turns a turbine
to create electricity.
• The original geothermal water is
recycled into the reservoir
through the injection well to
complete the circulation loop.
Development of a geothermal plant

9. • It has been estimated that the total heat available in the crust of the
earth, is around 540x107 EJ (EJ=Exajoules=1018 J).
• If we could use just 1% of this amount to meet global energy needs
(which come to around 500 EJ per annum) it would provide us with all
the energy that the planet requires for 2800 years at a constant
consumption rate.
• However, this energy is continuously being renewed by heat received
from various sources.
Development of a geothermal plant

10. Case Study