EESC V2200 - Fossil Fuels as Energy Sources

Lecture 10: Fossil Fuels as Energy Sources

Origins of fossil fuels.
- Importance of structure.
  - Most of world's reserves of oil and natural gas contained in deformed rocks (fig).
  - Most coal exploited from relatively undeformed sedimentary strata.
- Importance of depositional environment.
  - A few large oil fields in lake (lacustrine) sediments.
  - Mostly sediments with lots of marine organic matter yield large amounts of oil and gas.
  - Importance of high productivity and good preservation (low oxygen or anoxic basins).
  - Coal forms from peat which accumulates in bogs and swamps (fig).
  - Freshwater swamps are low in sulfate and thus the goal generated is lower in sulphur.
- Importance of burial and thermal reactions.
  - Burial preserves the organic carbon from oxidation and predation.
  - Chemical changes accompany conversion from plants to peat, thence to lignite, to sub-bituminous coal, bituminous coal, and semi-bituminous coal, finally to anthracite coal, and ultimately to graphite.
  - As heating progresses at higher and higher temperatures (fig).
    - carbon content increases.
    - oxygen and hydrogen content decrease.
    - CH₂O ^__> C^o + H₂0.
  - Petroleum not produced in conversion of terrestrial organic matter to coal.
- Petroleum: Importance of essential ingredients.
  - Good source rock formed where biological productivity was high (shales).
  - Reservoir with good porosity and permeability (sands, carbonates).
  - Traps need effective seals (anticlines, pinch outs, unconformities) (fig), (fig).
  - Salt domes make good traps (fig).
  - Large closure of a broad anticline can make for a giant oil field (fig).
- Relation of burial temperature and petroleum genesis.
  - Oil and gas are generated in a thermal window (fig).
  - Oil window from 75 to 175 deg C.
  - Gas window from 175-235 deg C.
  - Most compaction already achieved in upper 3 km before burial in the thermal windows with an average thermal gradient of 25 deg C/km.
  - shales are generally impermeable and need fractures for oil to be released.
  - the quantity of oil shale is very large.
  - oil and gas which escapes from shale during its genesis may move through more permeable strata (carrier beds) into reservoirs driven by gravity (bouyancy).
Fossil fuels and world energy.
- Historical energy use.
  - Although fossil fuels supply most of the world's energy today, that has not always been the case.
  - Wood, animal dung (renewable sources) was the dominant energy source until second half of 19th century (fig).
  - In the not-too-distant future, fossil fuels will cease to be the dominant source.
  - Why? Because we will have run out of them (non-renewable) (fig).
- World's energy production in 1995 was 8,000 million metric tonnes of oil equivalent or about 331 quadrillion Btu (knowns as "quads"). About 60% of the total (206 quads) is from oil and gas. Another 90 quads are produced from coal. Total fossil fuel energy production is greater than 90% of total energy production.
  - Fossil fuels are therefore by far the most important sources of energy for the world as a whole.
  - Energy production in the world is extremely uneven.
    - The United States, with 5% of the world's population, produced nearly 25% of the world's energy.
    - China, with 20% of the world's population, produces less than 10% of the worlds energy.
  - Greatest oil production is in the Middle East.
  - Second greatest oil production is in North America, but since 1987 there has been a falling production in the USA and in the Former Soviet Union.
  - The balance has been made up by substantial increases in Europe and the Middle East.
    - Production by area since 1973 (chart).
    - Production by country since 1987 (table).
- World's energy consumption is predominantly oil, natural gas and coal.
  - United States consumes 25% the World's total energy budget (fig).
  - World's energy demand continues to rise after stalling in the early 1970's when consumption in the Former Soviet Union began to decline.
  - World's energy cost is presently more than $500 billion/year, a substantial fraction of the global economy.
    - Prices for crude oil remained quite static at low levels (few $/barrel) for a hundred years before rising in 1973 with the OPEC oil embargo. (Crude prices since 1861 (chart)).
  - World's total energy demand has grown in line with population growth (World consumption all sources per capita since 1972 (chart)).
- Production and Reserves of coal.
  - China, United States and former Soviet Union are most prolific coal producers.
    - Production and consumption by area, 1987 & 1997 (chart).
    - Production by country since 1990 (table).
  - Coal is used locally.
  - We mine coal at a prodigous rate.
  - Proven Reserves are very large, enough to last for about 220 years.
  - We have a comfortably long time to enjoy coal, but at a large environmental expense.
  - The burning of coal contributes greatly to greenhouse CO₂ buildup and acid rain.
- Production and reserves of crude oil and natural gas.
  - World distribution of oil and gas very uneven.
    - Oil Proven Reserves at end of 1997 (map).
    - Natural Gas Proven Reserves at end of 1996 (map).
  - A significant fraction already extracted from countries such as the United States.
  - Since 1990, new discoveries, additions and revisions have broadly matched the world's production.
    - Proven Reserves of Oil by year (chart).
    - Proven Reserves of Natural Gas by year (chart).
  - Reserves to production ratios are higher for natural gas than for oil.
  - Saudia Arabia's reserves are by and large the greatest for oil.
    - Ratio of reserves to production for oil (chart).
  - Russia's reserves are the greatest for natural gas.
    - Ratio of reserves to production for Natural Gas (chart).
  - Oil production has peaked in the United States, despite intense exploration. Most giant oil fields have aleady been discovered except possibly in deep-water areas such as the Gulf of Mexico.
    - Production by area since 1972 (chart).
    - Production by country since 1987 (table).
  - World's reserves for natural gas will provide another 80 years of consumption at present rates.
  - Since reserves are unequally distributed, large amounts of oil and gas must be transported to the consumers by ships and pipelines.
  - Oil is easier to transport across the ocean than natural gas.
  - Gas must be transported in liquified state by special ships. Principal overseas routes are to Japan (65%). Principal overland imports through pipeline are to the US (25%) and Germany (20%).
- A forecast for fossil fuels.
  - There will be no worldwide shortage of fossil fuels during the next century.
  - Their cost will not increase dramatically for several more decades, but the price might be volitile.
  - Shortages of oil and large price fluctuations will occur in less than two decades.
  - On the timescale of hundreds of years, the outlook for continued availability of fossil fuels is bleak (fig).

Supplementary materials

All of the charts, tables, and maps illustrating fossil fuel statistics are from the web version of the BP Amoco Statistical Review of World Energy 1999 produced by BP Amoco.

Click here for definitions.

Click here for conversion factors.

Or see the BP Statistical Review of World Energy Appendices page for both definitions and conversion factors.

Click here for downloadable data from the BP Statistical Review of World Energy website.

Updated December 2, 2004
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The Solid Earth System

EESC 2200

Lecture 10: Fossil Fuels as Energy Sources

Supplementary materials