Formation of Oil
Formation of Oil Exploration, Production, and Refinement Uses: Past and Present Politics Environmental Consequences Future Projections Oil Home FSEM Home	What is Oil: Oil is a naturally occurring chemical made up of carbon and hydrogen atoms.  This type of chemical is called a hydrocarbon.  How Is Oil Formed: Millions of years ago, plants and animals living in the ocean absorbed energy from the sun and stored this energy in their bodies in the form of carbon.  As these animals died, their bodies sank to the bottom of the ocean where they were covered with layers of sediment deposits. (Source:  http://geology.50megs.com/cgi-bin/i/energy/fuels/trap.gif) As these layers of sediment increased the heat and pressure exerted on these remains began to rise.  The degree of heat and the amount of pressure, along with the type of biomass, directly influence whether oil or natural gas is formed.  As heat increases, a lighter gas is formed.  If the temperature raises to an even higher heat, or if the biomass is predominantly plant material, natural gas is formed.  (Source:  www.adventuresinenergy.org) (Source:  http://geology.50megs.com/cgi-bin/i/energy/fuels/mature.gif) What is an Oil Reservoir: After oil is formed, it travels from the source rocks, where it was formed, through tiny pores in the surrounding rock until it either seeps through the rock onto the surface or is trapped beneath a layer of impermeable rock or clay and forms a reservoir.  (Source:  http://geology.50megs.com/cgi-bin/i/energy/fuels/migration.gif) Reservoirs range in depth below the surface.  Some are only hundreds of feet below, while others have been discovered at depths greater than 30,000 feet.  Others are discovered offshore, and are covered with thousands of feet of water on top of tens of thousands of feet of sediment.  The majority of reservoirs are made up of oil, gas, and water.  These fluids are generally separated into layers due to the influence of gravity and differences in density.  Gas, being the less dense of the three, migrates to the top, followed by oil and then water.   (Source:  The Society of Petroleum Engineers, http://www.spe.org/spe/jsp/basic_pf/0,,1104_1008218_1109092,00.html)  Facts About Oil Deposits: 70% of oil deposits were formed in the Mesozoic age, 20% were formed in the Cenozoic age, and 10% were formed in the Paleozoic age.  These differences are the result of many factors,  The Mesozoic climate was primarily tropical worldwide, plankton were very abundant in the ocean, the ocean bottoms stagnant and anoxic (preventing the occurrence of decomposition), and organic-rich muds accumulated and formed later source rocks. Facts About Oil Reserves: 75% of the world's oil reserves are located in the Middle East's Persian Gulf.  This is because the Persian Gulf was once the on the boundary of the Tethys Seaway were tropical reefs were abundant, but the bottom was an extremely anoxic environment.  The closing of this seaway also produced many structural traps. Oil reserves throughout the world (1996):  1 trillion barrels Saudi Arabia → 30% Iraq → 12% United Arab Emirates → 11% Kuwait → 11% Iran → 11% Subtotal → 75% Venezuela → 6% FSU → 6% Mexico → 6% United States of America → 2% China → 2% Other → 3% The United States of America consumes 30% of the world's oil (Source:  http://www.geo.wvu.edu/~kemmer/g3/Lec13Text.htm) BACK                         Quick Navigation                        FORWARD Formation    Exploration, Production, and Refinement    Uses: Past and Present Politics    Environmental Consequences    Future Projections