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°-The basis of oil and gas is created (small oil and gas molecules form)°-At 120, lots of oil starts to rise. °-As we rise in temperature We are maturing the organic matter. °-Complex reactions in organic matter to break into simpler molecules. The heating break the complex molecules into simple ones. °-St high temperature: the shale releases oil and gas.°-Oil and gas rise (when the oil shale reaches a certain temperatures). (the liquid is a lot less dense than the rock, so it will rise). Water density: 1g/ml; oil is less dense than water. Oil: 0.85°°The Oil Window°°°°-At around 100 degrees, we see oil°-Above 165 degrees, we lose oil, and get mostly NG. °-Most of NG tends to come from reservoirs that are at greater depths °-It’s about TIME and temperature. At the oil window, things have been buried for 100M years. °-Crude oil can be heated up to 300 degrees (it won’t break down if you heat it up rapidy). But with enough time, at a high temperature, things will happen. °-Oil window: 4-6 km°-Anything further down (9+) is turned into graphite. °
°Oil Migration and Entrapment
°°°°-The source bed gets folded, a fault gets formed (reverse) °-Faulting causes fracturing, a migration pathway develops, oil migratesupwards. °-A trap forms and oil accumulates beneath the seal/cap rock. (The oil rises until it is resting on the reservoir rock. °-Oil moves up the fault, collects in reservoir rock. The oil is trapped there. °°Types of Oil and Gas Traps:°1) Anticline trap: oil and gas rise to the crest of the fold (up to the seal rock)°°2) Reverse fault trap: oil rises to where it’s sealed in
°°°3) Unconformity °°The Origin of Coal°-Peak of coal: hot planet (300M)- lots of forest, lots of coal)°-Don’t see any coal older that 440M years. No plants, no coal. °°The Formation of Coal°-The vegetation of swamps must fall and be buried in an oxygen-poor environment. °-Compaction and partial decay of the vegetation transforms it into peat. (Is a form of energy in other parts of the world)°-To transform peat into coal, the peat must be buried deeply (4-10km) by overlying sediment. °-At a certain depth, the weight of overlying sediment compact the peatand squeezes out any remaining water. °-Temperature increases with depth, deeply buried peat gradually heats up.°-Heat accelerates chemical reactions that gradually destroy plant fibersand release elements in the form of gas. °-The gases seep out of the peat layer, leaving behind a residue concentrated with carbon. Once the carbon proportion of the residue exceeds 50%, the deposits become coal. °-Process continues, highest grade coal: anthracite. °°Phanerozoic Ice Ages and CO2°°-Impact of burning fossil fuels°
°°°Graph:°-Temperature are in relative terms to present day°-Left side: deltao18: Measure of the isotopic composition of oxygen. (2 isotopes: o16 and o18)Ocean water has a consistent o16 o18 ratioRatio changes as temperature of ocean changesWith water vapour, o16 goes with it. The heavier isotope stays behind.