Page 51 - Geothermal Energy Systems Exploration, Development, and Utilization

1.3 Conceptual Models of Geothermal Reservoirs 27

114°00′
Cascade Arc
Juan
de Basin
Fuca and Boundary of
great basin 42°00′
range
Mendocino Walker
F. Z. Lane
MTJ
San Andreas
Fault SIERRA NEVADA
Walker lane
Pacific
plate SAN ANDREAS FAULT
0 Ma 0 100 mi.
ECSZ
0 100 km
Figure 1.14 Geothermal fields in the Great terminus of the Walker Lane dextral shear
Basin, western United States. Most of the zone (dark grey). Black spots, high temper-
◦
activity is concentrated in the transtensional ature geothermal systems (>160 C); open
◦
northwestern Great Basin within NE-trending circles, low temperature systems (<160 C);
belts oriented orthogonal to the extension di- ECSZ, eastern California shear zone.
rection and radiating from the northwestern

◦
has drilled on Paralana 1B down to 1.8 km, which suggests 200 Cat3.6 km,that
−1
◦
is, more than 50 Ckm . In that case, the reservoir should be the Infracambrian
detrital sedimentary sequences.
1.3.2
Porosity, Permeability, and Fluid Flow in Relation to the Stress Field

The permeability of the continental crust is defined by the capacity of the geological
medium to transmit fluid. It constitutes a critical geological parameter for the
definition of the geothermal reservoir as it plays a fundamental role in heat and
mass transfer (Manning and Ingebritsen, 1999). This parameter is related to two
basic properties of the rocks:

1) The porosity is the ratio of pore volume to the total volume. The intrinsic
permeability is the measure of the fluid flow through the pore network of
the rock and will be directly correlated to the porosity. These parameters are
directly linked to the packing of the minerals within the rocks, which is a result
of the nature, size, sorting of the minerals and elements, and of the compaction
and diagenetic history. Sedimentary rocks such as limestone, sandstone, or