# Vocabulary Back to [[Abiogenic Oil and the Fossil Fuel Debate]] - **Abiogenic / abiotic petroleum:** hydrocarbons formed without biological precursors, for example from CO₂ or carbonate plus hydrogen. - **Biogenic (thermogenic) petroleum:** hydrocarbons formed when buried organic matter (kerogen) is cracked by heat over geological time. - **Microbial (bacteriogenic) gas:** methane made by microbes at shallow depth. - **Kerogen:** insoluble organic matter in sedimentary rocks; the precursor of oil and gas. - **Source rock:** an organic-rich rock (often shale) that has generated petroleum. - **Oil window:** the temperature range, very roughly 60–150 °C, in which kerogen yields oil ⚠️ (approximate range, general knowledge). - **Migration (primary / secondary):** the movement of petroleum out of the source rock, then through carrier beds into traps. Kutcherov's chapter denies lateral migration. - **Trap / reservoir / seal:** the geometry, porous rock and cap rock that hold petroleum. - **Biomarkers ("chemical fossils"):** molecules with skeletons inherited from living organisms, such as porphyrins (from chlorophyll), steranes (from sterols) and hopanes (from bacterial hopanoids). - **δ¹³C, δ²H:** stable-isotope ratios. In thermogenic gas, δ¹³C increases from C1 to C4. Abiogenic gas shows a reversed trend ([Sherwood Lollar 2002](https://doi.org/10.1038/416522a)). - **C1–C4:** methane, ethane, propane and butane. - **Serpentinization:** reaction of water with olivine-rich (ultramafic) rock that produces H₂, which can reduce CO₂ to methane. - **Fischer-Tropsch-type (FTT) synthesis:** catalytic formation of hydrocarbons from CO or CO₂ plus H₂. - **Asthenosphere:** a weak, ductile layer of the upper mantle, roughly 100–200+ km deep. - **Outgassing (degassing):** the release of volatiles from Earth's interior. The chapter misspells it "outgrassing". - **Diamond-anvil cell / split-sphere apparatus:** high-pressure laboratory devices that reproduce mantle pressures. - **Fossil fuel:** first recorded in 1759 for fuel "dug up" (Latin *fossilis*). Today it means coal, oil and gas formed from ancient organisms ([Etymonline](https://www.etymonline.com/word/fossil)). - **Peak oil:** the point of maximum production, followed by decline. It does not mean "running out". - **Observed decline rate:** the year-on-year production drop of fields past their peak. - **Geologic (natural) hydrogen:** H₂ generated underground, for example by serpentinization or radiolysis, and explored as a resource. - **Deep hot biosphere:** Thomas Gold's term for microbial life deep in the crust. - **Russian-Ukrainian theory:** the deep abiogenic petroleum school founded by N. A. Kudryavtsev in 1951.