Energy and Material Resources

1
Energy and Material Resources
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Natural resources

• Most geologists are employed in looking for some
  kind of resource.
• Resources range from petroleum to precious metals
  to water.

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Resource

• A material that is both useful and available in
  useable quantities.
• A renewable resource is one that is produced
  faster than it is depleted.

4
Reserves

• Resources that are identifiable and recoverable
  under today's economic conditions
• Conditional resources Not economical to recover
  at the moment.

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Resource vs. Reserve

• Resource Already been discovered and can be
  mined economically.
• Reserve Entire amount of a given material that
  may become available in the future.

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Fig. 22.1
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Energy Mix in the U.S. 18501997
Fig. 22.3
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Photosynthesis andFossil Fuels
Fig. 22.4
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Fossil fuels

• Decayed organic material (plants)
• Must have relatively rapid burial

• FOSSIL FUELS ARE A NONRENEWABLE RESOURCE

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Hydrocarbons oil and gas

• Oil formation
• 1) Relatively large quantity of organic matter
• 2) Rapid burial (before oxidation)
• 3) Subsequent chemical reactions f(P,T)
  transform decaying organic matter into
  hydrocarbons.

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How do oil and gas deposits form?

• Production of large amounts of organic material
  (mainly microscopic plants and bacteria).
• Preservation in a reducing (oxygen-poor)
  depositional environment (e.g., restricted ocean
  basin).
• Burial causes increased heat and pressure,
  resulting in maturation (the physical and
  chemical breakdown of organic matter into a
  liquid or gaseous hydrocarbon compound) in a
  source rock.

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Theres more

• Migration of fluids out of the source rock into a
  more permeable reservoir rock.
• Trapping of fluids must occur by encountering an
  impermeable seal.
• In short, you need
• Production
• Preservation
• Maturation
• Migration
• Trapping

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Thermal conditions ofoil formation

• Relatively narrow temperature range
• 50200C (also depends on time)
• Temperature and duration determine type of
  hydrocarbon (oil vs. gas).
• Duration of process could last millions of years

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Environments ofoil formation

• Continental shelf
• Continental rise
• Some non-marine basins

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Reservoirs

• For oil to be useful, it must accumulate in
  concentrated and accessible areas. Such spots
  are called reservoirs.
• Accumulation is possible because oil and gas are
  low-density fluids that can migrate through the
  pore space in rocks.

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Reservoirs

• To create a reservoir, the migration of the
  fluids is retarded by cap rock.
• Cap rocks Reservoir rocks
• shale sandstone
• gypsum limestone
• salt
• limestone

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Trap

• Combination of cap rock and reservoir rock
  favorable for petroleum accumulation
• Anticlinal trap
• Stratigraphic trap
• Fault trap
• Salt dome trap

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Anticlinal Trap
Fig. 22.5
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Fault Trap
Fig. 22.5
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Stratigraphic Trap
Fig. 22.5
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Salt Dome Trap
Fig. 22.5
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Dry Holes

• Many potential reservoirs exist that are free of
  hydrocarbons.
• Source rocks may have enough organic matter but
  may never have been hot enough.

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How do we explore for oil?

• Map surface geology
• (use surface geometry to interpret subsurface
  conditions).
• Seismic exploration
• (good way to get lots of information but subject
  to interpretation).
• Drilling, coring
• (more detailed information from smaller
  arealike seismic, very expensive).

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How much oil is left?
Fig. 22.6
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How much oil is left?

• Proven reserves 700 billion barrels (over half
  in Middle East).
• Petroleum resources 2 trillion barrels.
• 1997 consumption 70 million barrels per day.
• At this rate, reserves will last between 25 and
  80 years.

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This assumes no increase in the rate of
consumption, but

• Between 1985 and 1995, consumption of oil in the
  world increased by 16.
• The increase in Latin America was 30.
• The increase in Africa was 40.
• The increase in Asia was 50.

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Coal

• Coal is usually formed in swamps.
• 1st stage - peat (high C, high H20).
• P,T ? loss of gases, toward higher C.
• Ranks of coal Anthracite hard
• Bituminous
• Subbituminous
• Lignite soft

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Coal

• High sulfur is badH2SO4 is produced during
  burning.
• Coal ash.
• Principle coal producing areas in United States
  are Appalachia, Wyoming, New Mexico, and Colorado.

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Coal
Fig. 22.9
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Formation of Coal
Fig. 22.8
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Strip Mining Coal in Indiana
Fig. 22.10
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Strip Mining Coal in Indiana
Fig. 22.10
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Alternatives to fossil fuels
Nuclear energy Advantage Virtually
inexhaustible supply Disadvantage Disposal of
nuclear waste
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Alternatives to fossil fuels
Solar energy Advantage Virtually inexhaustible
supply Disadvantage Very expensive with current
technology (solar cells, hydrothermal, wind
power)
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Solar Cells
Fig. 22.11
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Alternatives to fossil fuels
Geothermal energy Advantage Cheap and
clean Disadvantages Cannot be transported long
distances
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Geothermal energy

• Must have a concentrated heat source near the
  surface magma chamber with porous rocks above
• Cool water pumped into hot rocks, hot water or
  steam extracted (rocks may be as cool as 80C)
• Producing Iceland, France
• Experimenting New Mexico, California

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Geothermal Energy to Electricity
Fig. 22.12
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World Energy Demand1971-2030
Fig. 22.13
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Mineral deposits

• If deposited in concentrated volume, we get veins
  or lodes.
• If deposited in large volume, we get disseminated
  deposit.

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Disseminated Deposits
Copper Mine in Utah
Fig. 22.19
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Veins
Chromite bands in South Africa
Fig. 22.20
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Mineral deposits

• Hydrothermal deposits minerals deposited from
  hot waters usually associated with igneous
  intrusions
• These fluids carry low temperature ions. When
  the fluids cool off (near surface) the solubility
  goes down and minerals with Pb, Fe, Hg, Cu, Zn,
  Ag, Au, etc. are precipitated.

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Hydrothermal Ore Deposits
Fig. 22.16
Gold and silver ores in a quartz vein.
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Metal Sulfide Ores
Fig. 22.17
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Copper Sulfide Ores
Malachite
Chalcopyrite
Chalcocite
Fig. 22.18
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Sedimentarymineral deposits

• Banded iron formations (layers of iron in rock
  formations)
• Placers (accumulation of heavy minerals by
  physical sorting in rivers)
• Clays
• Sand and gravel

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PrecambrianBanded Iron Deposits (Aus.)
Fig. 22.21
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Hydrothermal Vent Systems
Fig. 22.22
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Manganese Nodule
Fig. 22.24
Chip Clark
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EEZs
Fig. 22.25
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Kanai National Wildlife Refuge