Bio1110 Chapter 24 Petroleum
  1. Fossil fuels power today's economies and is refined into many energy-dependent products.
    • Fossil fuels (petroleum, coal, natural gas) are nonrenewable
      Ancient organisms died and became buried in sediment with low oxygen levels. The partially decomposed biomass undergo chemical changes under heat and pressure. The buried fossil fuels buildup over time and are harvested by drilling or excavations.

    • Crude oil is refined into a wide variety of products.

      A furnace heats the crude mixture; the vapor rises in a distilling tower where various fractions are siphoned.

      The heaviest products are recovered above 600°C: asphalt, grease, wax.

      Subsequent fractions yield diesel fuel, kerosene, jet fuel, and gasoline.

      The lightest fraction (requires lowest temperature to boil) is liquefied petroleum gas.

  2. Fuel reserves are declining and require increasingly more costly techniques to extract.
    • • Most of the world's conventional reserves of oil as well as natural gas are located in the Middle East.

      Political instability in that region makes access to these fossil fuels uncertain.

    • Petroleum (oil) is a nonrenewable resource, and deposits close to the surface are already harvested.

      The world peak production of oil has probably already occurred, yields are expected to decline in coming decades.

    • Conventional oil reserves are extracted by drilling wells.

      Primary production occurs when the first 15% of the oil flows upward naturally from rock pressure.

      Secondary production uses an injection well to pump water into the reserves to recover up to 20% of the oil.

      Tertiary production injects steam or CO2 to recover up to 60% of the oil.

    • • The Deepwater Horizon spill of 2010 has severe short-term impacts on marine ecosystems.

      Excess and toxic compounds can pass up the food chain by bioaccumulation and biomagnification.

      Top predators such as sperm whale are especially at risk.

      The long-term consequences of such spills are unknown.

    • Hydraulic fracturing (fracking) techniques can be used to recover natural gas as well as oil buried in shale underground deposits.

      1. A well is drilled and extended horizontally.

      2. Explosives fracture the rock.

      3. Hydraulic pressure is applied to the fractures.

      4. Escaping gas is collected.

      Side effects of shale gas and shale oil recovery may include contamination of soil and groundwater.

  3. Unconventional oil reserves are still plentiful but also hard to extract.
    • • North America has large amounts of unconventional oil deposits.

      Oil sands (tar sands) are sand deposits containing viscous bitumen.

      This form of degraded petroleum must be mined and requires special refining processes.

      Oil shale is sedimentary rock filled with kerogen - the precursor to the major fossil fuels.

      This low-grade fuel must be mined followed by heating the rock.