Fossil Fuels

Remains of ancient organisms Accumulated, compacted, modified Estimated less than 0.1% of matter incorporated

Fuel-forming Reactions Not well understood –Many products –coal, kerogen hard to characterize Fragmentations –loss of small molecules: H 2 O, CO 2 Condensation and Polymerization

Oil Most versatile fuel source –Easy to transport –Easy to refine –Many different derivatives –Refined product burns without residue

Forming Oil Dead plankton settle to sea floor –Incorporated in mud –Decomposes anoxically Becomes kerogen in oil shale Water, pressure, heat  chemical change –Bitumen, Oil,Gas

Oil Deposits Oil seeps to surface  destroyed Must be trapped underground Must be recoverable

Recoverable Oil Source rock: organic matter subjected to proper conditions Reservoir rock: porous and permeable Cap rock: impermeable

Oil from Shale Large recoverable deposit in Green River Formation Heating oil shale: retorting Product similar to crude oil

Coal Created from swampy plant residue Compacts, decays anaerobically Compression and heating “matures” coal

Forming Coal

Coal Rank Peat Lignite Sub-bituminous Bituminous Anthracite Graphite Low maturity High maturity Low %C High %C Low energy High energy

Worldwide Coal Mostly from Carboniferous Lots of swamps, warm climate Later sea-covered –Sulfate-reducing bacteria acted on deposits –Put sulfur compounds in coal –Pollution upon combustion!

Wyoming Coal Wyoming arid during Carboniferous WY coal is Cretaceous –Low grade –Never subsequently sea-covered –Low-sulfur

US Coal Production

Gas Principally CH 4, some C 2 H 6 May include CO 2 Formed in all stages of organic degradation Can be associated with coal or oil

Gas Hydrates Ice-like complexes of water and methane –water framework with methane in voids Stable at low temperatures and high pressures –Found in permafrost, marine sediments Estimated to be world’s largest fossil fuel resource