Ch. 12: Energy and Mineral Resources Flashcards
Stages in formation of hydrocarbons:
Organic-rich sediments buried, heated just enough to develop & release hydrocarbons
Liquid and gaseous hydrocarbons migrate up through porous and permeable rock
Become trapped by impermeable feature like a fault, an overlying shale at the top of a
fold, or the cap rock of a salt dome
Reservoir remains intact until hydrocarbons can be extracted
Nonrenewable resources
Fossil fuels: coal, petroleum, and natural gas
Renewable resources
solar; wind; hydroelectric
Oil and Natural Gas industry: Traps
porous, permeable reservoir where hydrocarbons accumulate
impermeable cap rock below which hydrocarbons are trapped
Types: folds; faults; salt domes
Shale Oil and Hydraulic Fracturing
The “Oil Age”: historically, about three centuries of use before it runs out
“Peak Oil”: production rate of an oil reservoir is a bell-shaped curve
The Oil “Crunch”: the rate of new discovery of new
reserves has not kept pace with the consumption of oil
Coal problems
Problems with coal use include environmental
damage from mining and air pollution from
burning it.
• No such geologic material as “clean coal”
Oil or Tar Sands
Mixtures of clay, sand and bitumen (a viscous tar)
• Oil in oil sands is much more viscous and cannot
be pumped out
Several large deposits of tar sands around the world
• Largest reserve in Alberta, Canada
– Obtaining oil from tar sands requires large amounts
of energy and has significant environmental
drawbacks
– Planned distribution is via Keystone Pipeline
Nuclear energy
– Fuel comes from energy released by nuclear fission
(splitting atoms)
• Resulting controlled chain reaction releases heat
used to drive steam turbines
• U235 is the only naturally occurring isotope that is
readily fissionable
–Primarily fuel used in nuclear power plants
–Rare element in Earth’s crust
Plant safety
– Disposal of spent fuel rods, contaminated materials
• Skyrocketing costs for safety features
–Plants cannot explode like bombs, however
the escape of radioactive debris during a
meltdown is a major hazard
How is electricity generated in Maryland?
Mostly coal
Bauxite
Principal ore of aluminum
– Forms in rainy tropical climates from chemical
weathering
– Requires huge amount of electricity to separate
aluminum from bauxite
- Most bauxite is extracted by massive strip
mining in underdeveloped countries
– It hasn’t been mined in the US since 1981
– Requires a huge amount of electricity to extract aluminum from bauxite
Oil
crude oil that is drilled out of a well Refined into gasoline, heating oil, propane, etc.
Natural gas
gaseous material that comes out of a well;
Distinct odor is added during refining process for safety
Sedimentary Basins
Sedimentary basins may form in active or passive
tectonic settings.
Depositional and thermal history of a sedimentary basin
determines the formation of hydrocarbons.
1. Foreland Basin: Mt belt pushes down on earth
2. Rift Basin: fault produces narrow troughs
3. Intracontinental basin: basin forms
4. Pasive margin basin: subsidence occurs at edge of ocean
oil trap
an environment that allows for
economically significant amounts of oil and gas to
accumulate underground.
–All traps have two basic conditions:
»A reservoir rock—A porous, permeable unit
»A cap rock—An impermeable unit that traps
the oil and gas
reservoir rock
A porous, permeable unit
cap rock
An impermeable unit that traps
the oil and gas
Seismic reflection
is able to create an image of the
subsurface by bouncing sound off layers.
This technique permits geologists to look for potential
traps below the earth’s surface without drilling.
Drilling
Expensive drilling is required to tap into a potential trap.
A diamond rotary bit pulverizes rock.
Heavy mud encases the pipe to reduce the risk of highpressure blowouts.
Steel casing protects aquifers and surface water supplies.
Shale Oil and Hydraulic Fracturing
Because shale is impermeable, it is shattered by
hydrofracturing (“fracking”) to release the natural gas
from the shale.
1. After a hole is drilled, high pressure fluid is pumped into the segment of hole.
2. The pressure pushes open cracks and forms new
ones
3. Sand injected with the fluid keeps the cracks from
closing.
4. Natural gas seeps into the pipe and flows to the
well.
Coal Mining
The type of coal mining used depends on the depth of
the coal seam. Deposits near the surface are strip mined,
which removes the overlying rock and soil.
For deeper coal seams, underground mining is required.
Surface or mine
Solar Energy
Direct use of the Sun’s rays to supply energy.
• Passive solar collectors –South-facing windows
• Active solar collectors
–Solar hot water
–Trough solar collectors
–Photovoltaic (solar) cells convert the Sun’s
energy directly to electricity
Solar energy is by far the most abundant source of energy to Earth’s surface. However, solar energy is hard to use because it is diffuse, highly variable on a seasonal and daily basis, and difficult to store and then convert into more usable forms of energy.
Wind Energy
Converting the kinetic energy of a moving air mass
(wind) into other forms of energy to perform work
– Wind turbines supply 3%of world electricity
Hydroelectric Power
Generated by falling water used to drive turbines
to produce electricity
– Most energy is produced at large dams, but…
• Dams have finite lifetimes
• Limited sites to construct dams
• Environmental challenges
Geothermal Energy
– Power generated by tapping into underground steam
and hot water
– Can be used for heating and to generate electricity
