Page 299 - Introduction to Petroleum Engineering

ACTIVITIES 287
The working fluid is circulated through the preheater, vaporizer, turbine, and
condenser. The working fluid is warmed up in the preheater and vaporized in the
vaporizer. The high‐pressure working fluid vapor drives a turbine. Mechanical energy
from the turbine is transformed into electrical energy by the generator. The working
fluid vapor is condensed by the air‐cooled condenser and recycled through
the preheater.
Heat is transferred from the primary produced fluid to the working fluid in the
vaporizer and again in the preheater. The cooler primary fluid is injected into a
formation. If the formation is the geothermal reservoir, the cooler injected fluid can
reduce the temperature of the geothermal reservoir over time. A heat source like
the Hawaii hotspot provides geothermal heat to overcome the cooling effect of
reinjected fluid.
The PGV facility is located near residential communities. During the early days
of the venture, well failures and gas emissions resulted in serious health concerns.
Geothermal fluids are highly toxic and corrosive. Well failures can be caused by
corrosion of tubing and casing and exposure to excessive heat by encountering
magma or lava. A well failure can result in the emission of produced gases into the
environment. Emissions from geothermal water and steam include benzene, hydrogen
sulfide, ammonia, mercury vapor, methane and other hydrocarbons, carbon dioxide,
arsenic, radon, and radioactive materials that emit alpha and beta emissions. Several
of these chemicals can adversely affect human health. For example, hydrogen sulfide
can be fatal at 700 ppm, and the PGV wells contained from 750 to 1100 ppm.
Several practices have been implemented to protect the environment in response
to community concerns. The footprint, or areal size, of the facility has been mini‑
mized and the facility is surrounded by noise reduction enclosures. A closed system
is designed to reinject 100% of the produced geothermal fluid, and the entire system
is designed to achieve near‐zero emissions. Continuous monitoring systems have
been built to detect undesired emissions.

14.6 ACTIVITIES

14.6.1 Further Reading
For more information about reservoir flow modeling and reservoir performance, see
Gilman and Ozgen (2013), Fanchi (2010b), Satter et al. (2008), Carlson (2003), and
Towler (2002).

14.6.2 True/False
14.1 Geostatistics is a method for spatially distributing reservoir parameters.
14.2 Data preparation for a flow model study is usually the quickest and least
important step in the process.
14.3 A simulation study can help coordinate activities as a modeling team gathers
the resources it needs to determine the optimum plan for operating a field.