Formation of Fossil Fuel Resources

Vocabulary flashcards covering key terms related to the origin, types, and geologic processes involved in forming coal, oil, and natural gas.

Fossil Fuels

Energy-rich substances (coal, oil, natural gas) derived from ancient plant and animal remains converted by heat and pressure.

Coal

A sedimentary rock formed from compacted plant material; burned for energy and classified by rank.

Lignite

Brown, soft, crumbly coal of lowest rank; high moisture, low carbon, low calorific value.

Sub-bituminous Coal

Intermediate-rank soft coal with 71–77 % carbon and higher calorific value than lignite.

Bituminous Coal

Black, dusty soft coal (77–87 % carbon) that burns with a smoky flame; common strip-mined fuel.

Anthracite

Hard, shiny, dust-free high-rank coal; low volatile content, burns with smokeless flame.

Peat

Water-logged, partially decayed plant matter (≈60 % carbon) that can become coal with more heat and pressure.

Brown Coal

General term for lignite and low-rank coals with 60–71 % carbon and high moisture.

Coal Rank

Classification of coal (peat → lignite → sub-bituminous → bituminous → anthracite) reflecting increasing heat, pressure, and carbon content.

Calorific Value

Amount of energy released during combustion of a fuel, measured in kJ/kg for coal ranks.

Petroleum

General name for naturally occurring solid, liquid, and gaseous hydrocarbons; includes crude oil, natural gas, and asphalt.

Hydrocarbon

Compound composed only of hydrogen and carbon atoms; building blocks of petroleum.

Methane (CH₄)

Simplest hydrocarbon and main component of natural gas.

Crude Oil

Liquid mixture of hydrocarbons formed from organic matter and extracted before refining.

Natural Gas

Gaseous hydrocarbons (methane, butane, propane, etc.) produced with or separate from oil.

Plankton

Microscopic marine plants and animals whose remains commonly generate oil and gas.

Organic Mush

Accumulation of dead plankton on an oxygen-poor seabed that initiates petroleum formation.

Black Shale

Fine-grained sedimentary rock containing >5 % organic matter; potential petroleum source rock.

Kerogen

Solid, waxy organic material in source rocks that converts to oil (~90 °C) and gas (~150 °C) upon heating.

Oil Window

Temperature range (~90–150 °C) where kerogen changes into liquid oil and then gas.

Source Rock

Organic-rich rock (e.g., black shale) that has generated oil or gas through burial heating.

Reservoir Rock

Porous, permeable rock (e.g., sandstone) that stores and transmits petroleum.

Oil Trap

Geologic configuration that blocks petroleum migration, allowing accumulation in a reservoir.

Structural Trap

Oil trap created by deformation such as folds or faults (e.g., anticline, fault trap).

Anticline (Dome) Trap

Upward-arched fold capped by impermeable rock where gas and oil accumulate at the crest.

Fault Trap

Oil accumulation where impermeable rock is displaced against a reservoir by a fault, sealing hydrocarbons.

Impermeable Cap Rock

Rock layer that prevents upward movement of oil and gas, sealing a trap.

Permeable Rock

Rock with interconnected pores allowing fluids like oil, gas, or water to flow through it.

Migration (Oil & Gas)

Upward movement of buoyant petroleum from source rock toward reservoir and trap.

Diagenesis

Early stage (surface–few hundred meters) where anaerobic bacteria convert organic debris into sticky matter and biogenic gas.

Catagenesis

Burial stage (3–5 km) where heat and pressure transform organic matter into kerogen and liquid petroleum.

Metagenesis

Deep, high-temperature stage (>3 km) where kerogen yields thermogenic gases and carbon-rich residue.