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162 Geothermal Energy: Renewable Energy and the Environment

10,000.0
0°C

1000.0 350°C
1 400°C

100.0 300°C
Liquid 250°C
Pressure (bars) 10.0 150°C
200°C

1.0 100°C Vapor
20% 40% 60%
0.1 3 50°C 2 2 *
Liquid + Vapor 80%
25°C
0.01
0 500 1000 1500 2000 2500 3000 3500
Enthalpy (kJ/kg)

FIGUre 9.7 Pressure–enthalpy diagram for a representative hydrothermal system. Most hydrothermal sys-
tems have reservoir conditions enclosed by the shaded field.

X R

d

Water flow
toward
the well

FIGUre 9.8 Schematic representation of the flow field and geometrical relationships for a producing well.
The indicated dimensions X R and d are the depth to the top of the geothermal reservoir and the distance being
considered from the well edge, respectively. The shaded regions diagrammatically represent the top and bot-
tom of the reservoir.