Geoscience Reference
In-Depth Information
Oil and Gas Production
Oil and gas production involves pumping hydrocarbon liquids (petroleum and natural
gas), often together with large amounts of aqueous fluids (groundwater) that commonly con-
tain high amounts of dissolved solids and salts (“brine”), from the subsurface. In the United
States, oil and gas operators are required to manage these aqueous fluids through some
combination of treatment, storage, disposal, and/or use, subject to government regulations.
Commonly, these fluids, if not reused in the extraction process (see also Carbon Capture and
Storage, below), are disposed of by injection into the deep subsurface in wells that may be
located at some distance from the site of the oil or gas extraction (see also Chapters 3 and 4).
Fluids may also be produced from a well during “flow-back operations” after a well has
been hydraulically fractured. Hydraulic fracturing is a method of stimulating an oil- or gas-
producing geologic formation by injecting fluid underground to initiate fractures in the rock
to aid oil or gas production from the well. A portion of the fluid is later recovered from the
well and may be reinjected for additional hydraulic fracture treatments or managed through
storage, permanent disposal in an injection well, or treatment for disposal or beneficial use
similar to aqueous fluids that are normally produced directly from an oil or gas reservoir.
Injection of fluids related to hydraulic fracturing and injection of waste fluids into the sub-
surface for permanent disposal are two different processes described in detail in Chapter 3.
Oil and gas production (withdrawal) often includes fluid reinjection. The reinjected
fluid may be natural gas, aqueous fluids, or carbon dioxide (CO 2 ) used to help push more
oil and gas out from the rocks and to the surface; such reinjection is termed secondary re-
covery. Enhanced oil recovery, also known as tertiary recovery, uses technologies that also
aid in increasing the recovery of hydrocarbons from a reservoir by changing the properties
of the oil (primarily aiming to lower the viscosity of the oil so that it flows more easily).
The most common EOR techniques involve injecting CO 2 or hydrocarbons, or heating the
oil through steam injection or combustion. The injection of fluid to facilitate oil and gas
production, similar to fluid injection for geothermal systems, has the potential to generate
induced seismic activity. To date, EOR has not been associated with induced seismicity,
although felt seismic events have been documented in connection with waterflooding for
secondary recovery. The withdrawal of oil and gas has also been associated with induced
seismic activity. All of these technologies and examples of induced seismic activity are
described further in Chapter 3.
Carbon Capture and Storage
Carbon capture and geologic storage is the separation and capture of CO 2 from emis-
sions of industrial processes, including energy production, and the transport and perma-
nent storage of the CO 2 in deep underground formations. Currently five different types of
 
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