Energy Technologies: How They Work and Their Induced Seismicity Potential - Induced Seismicity Potential in Energy Technologies - page 42

FIGURE 3.4 Geysers seismicity maps in 10-year intervals show the expanding distribution of develop-
ment as illustrated by the increased numbers of green squares that indicate the locations of the operating
power plants. SOURCE: Preiss et al. (1996).
FIGURE 3.5 The locations of injection wells and the location and depth distribution of seismic events in
the southeastern part of The Geysers area during 1997-1998. Map on the left shows injection wells in
1998. The middle map shows the total number of recorded seismic events from the period 1997-1998
with the line of cross section (figure on the right). The cross section shows the positions of three geothermal
wells with the location at depth of the seismic events (red dots). SOURCE: Beall et al. (1999).
began deliveries in 1997 and 2003. The annual amount of water injected followed the same
trends until new sources of water other than condensate were developed, allowing recent
injection to become nearly equal to the annual production levels.
The method of injection at The Geysers is unusual because of the extremely low fluid
pressures in the deep underlying reservoir. No surface pressure is needed to inject; the
water simply falls down the injection well as though through a partial vacuum because
the fluid pressures in the reservoir are incapable of supporting a liquid level to the surface.
Consequently, without elevated bottom-hole pressures, the primary cause of the induced