Chapter 14 Fossil Fuels Geology

oil shales characteristics

(poorly named) always sed. rock need not be shale; potential fuel is kerogen: formed by remains of plants,algae, and bacteria Physical prop of kerogen: must be crushed and heated to distill out the hydrocarbon as "shale oil" refined as crude oil to produce liquid pet. products

how do oil and gas deposits form?

1. large accumulation of organic matter =marine microorganisms rich in carbon and hydrogen 2. quick burial ( to protect it from the air so it wont destroy it) 3. Pressure and temp increase causes chemical change: large organic (heavy) hydrocarbon molecules broken into smaller (lighter) molecules Temp range 50-100 degrees Celsius 4. repetition of 3: brings maturation of hydrocarbon: asphalt→oil→gasoline→gas

How many years of US oil consumption do the large oil deposits of the Alaska north slope represent?

2 yrs

% of oil used in the US thats imported?

50%

US oil and gas reserves last at current consumption rates?

6 months?? check

sources of oil spills

600,000 tons per year; large catastrophic ones • Come from drilling offshore, accidents →largest source of oil spills; tanker accidents • War (Persian gulf) = destruction of pipelines and refineries

% of US energy from fossil fuels?

83%

coal strip mines; mountain top removal description impact

??

differences and similarities among oil shales and tar sands

??

oil shale and tar sand distribution in North America US abundance?

??

Environmental impacts of oil/gas exploitation and processing

??? find

environmental impacts of mining related to coal use and extraction

Co2 from coal burning > Co2 from oil or gas risk? global warming sulfur in coal > 3%; desirable 1% or less pyrite bound in organic compounds when burned So2 (gas) kills aquatic life • When the sulfur is burned along with the coal, sulfur gases notably (So2) are produced; these gases are extremely poisonous and are extremely irritating to eyes and lungs. These gases also react with water in the atmosphere to produce sulfuric acid (very strong) this acid then falls to earth as acid rainfall; acid rain falling into stream and lakes can kill fish and other aquatic life. It can acidify soil, stunting plant growth. It can dissolve rock (limestone or marble) corroding away buildings and monuments

characteristics of the different types of coal

Combustible product formed under suitable conditions 1. Peat: can form at the earths surface 2. Lignite: further burial with more heat, pressure, and time gradually dehydrates the organic matter and transforms the spongy peat into soft brown coal and then into 3. Bituminous coal (harder) 4. Anthracite (harder)

characteristics of gasification products

Gasification: coal + steam; gas= less heating power than natural gas; underground gasification: less disturbance, mine thin beds. makes a mixture of carbon monoxide and hydrogen w little methane typically only pumped where produced

enhanced recovery method

Something good=well is already built→ no time delay Something bad=ground subsidence or groundwater pollution

methods of clean up/treatment for oil spills

Treatment: clam seas, but non very effective (barriers to contain skimmers pick up) 1. Soak peat moss or wood shavings 2. Burn it (not easy) 3. Sink it (chalk, sand) →bad below 3. Use detergent (toxic); Hope: development of "oil hungry" organisms

cracking

breaking large hydrocarbon molecules to obtain lighter ones (gasoline); from heavier compounds of crude oil

crude oil

contains a mixture hydrocarbon compounds

fossil fuels

energy sources formed from the remains of ancient living organisms. Include: oil, natural gas, coal, and fuels derived from oil shale and tar sand

Structural trap

fold, fault, salt dome (petroleum trapped against an impermeable salt dome, which has risen up from a buried evaporite deposit)

how does coal form?

from remains of land plants, swampy anaerobic conditions (oxygen is nearly or absent)

reservoir rock

from where oil is extracted; porous and permeable, oil displaces water and floats on top; needs to be trapped by an impermeable rock (oil and gas may keep rising up to the earth's surface)

oil shales exploitation and environmental impact

large amnt to be proceed bc its at the surface or near strip mining problem with increased volume requires H20 the dry conditions wld make revegetation esp difficult after strip mining; not economical now could be a long term resource US=2/3 of known oil shale reserves

light hydrocarbons

light oils (gasoline, hense) bottled gas (butane) natural gas ( methane)

primary recovery method

little pumping

methane gas hydrates

major new potential sources of natural gas. Gas (usually methane) hydrates are crystalline solids of gas and water molecules; contained in permafrost and deep sea sediment; abundant but how to exploit them is still unclear; concern about greenhouse effect, particularly from coal bed methane.

characteristics of liquefaction products

making a liquid feasible, still not competitive with petroleum. Yield: 70% original coal; promising. makes gasoline and fuel oil

Stratigraphic reef

petroleum accumulated in a fossilized ancient coral reef

secondary recovery method

pump water

tar sands

sed rocks containing a very thick semi solid tar like petroleum called bitumen: may represent very immature pet deposits deposits where light hydrocarbons migrated tech and environmental concerns = to oil shales Canada has large tar sand deposits (exports to the US)

refining

separation of hydrocarbons for different uses

geopressurized natural gas

thousands of meters below the surface, conditions are sufficiently hot that any oil would have been broken down to natural gas; this natural gas, under a lot of pressure exerted by the overlying rock, may be dissolved in the water filling the pore spaces in the rock (much like carbon dioxide is dissolved in a bottle of soda) pumping this water to the surface is like taking off the bottle cap: the pressure is released and the gas bubbles are out. Enormous quantities of natural gas might exist in these geopressurized zones; estimates from 150-200 trillion cubic feet. *drilling problems -potential unknown

heavy hydrocarbons

waxes (paraffin), residual oils. medium oils (kerosene, des. fuels, jet fuels, power plants, domestic/idustrial boilers)

source rock

where oil is formed; fine grained clastic sedimentary rocks, low permeability. Black, gray, green = good source rocks brown or tan= not useful

coal gasification and liquefaction

• Coal can be converted to liquid or gaseous hydrocarbon fuels gasoline or natural gas by causing the coal to react with steam or with hydrogen gas at high temp these conversion processes are called gasification (when the product is gaseous) liquefaction (when the product is liquid fuel) both intended to transform coal into cleaner burning more versatile fuel

limitations to coal distribution

• Time to depletion: 200 y if exclusively coal is used; more otherwise • Drawback: not versatile (as petroleum or natural gas), not clean cant be used in modern transportation

Coal in the US

• U.S.= 30% of the worlds reserves (unused and unmined) coal provides 25% of the total energy today in the U.S.