Transcript Document
Sedimentary Environments Fossil Sedimentary rocks record environmental information Continental Shelf 10-15K feet of compacted sand and mud Lithification: Compaction and cementation At depth, SiO2 and CaCO3 go into solution, water is driven out (dewatering). This solution permeates throughout open pore spaces, forming a cement. Cemented Sandstone SiO2 cement Cemented Limestone CaCO3 cement Classification of Sedimentary Rocks Clastics Increasing water energy Clastic Sedimentary Rock Fast Stream Fast moving water does not allow clay-sized particles to accumulate. They stay in suspension. Larger particles, like pebbles, drop through the water column and accumulate. Breccia Biogenic rocks - Limestone Accumulation of dead critters. Shallow, warm, marine environment. Limestone Thin Section Fossils cemented together by CaCO3 cement. Biogenic rocks - Coal Accumulation of organic material in a swampy environment. Anaerobic, dark, murky water. Lagoon Care for a swim? Chemical rocks - Evaporite - Salt What happens when salty water evaporates? Salt Flat Wet in the spring and early summer Water evaporates in late summer and fall Chemical rocks - Chert Microcrystalline silica Deep water ocean environment, too cold for CaCO3 precipitation. Continental Slope Transatlantic Cable Turbidity Current Turbidite Layers Sea level facies change Mud Sand North Carolina OIL Oil Well Offshore Oil Rig Oil Traps Oil & gas are less dense, so they migrate toward the surface. Oil Traps Salt Dome Salt is very impermeable Salt is also less dense than the country rock, so it too is migrating toward the surface. Oil Formation Maturation Given many thousands of years, a stack of mud and organic remains many kilometers thick may pile up on the sea floor, especially in nutrient-rich waters. Given enough time, the overlying sediments that are constantly being deposited will bury these organic remains and mud so deeply that they will eventually be turned into solid rock. It is believed that high heat and intense pressure help along various chemical reactions, transforming the soft parts of ancient organisms found in the deep-sea sludge into oil and natural gas. At this point, this ooze at the bottom of the ocean turns into source rock. Reservoir Rock High porosity Low porosity Oil must be allowed to move between pore spaces: permeability Stratigraphic Trap Oil migrates into ‘traps’ Oil rig: Gulf of Mexico Gulf of Mexico 130 active drilling rigs 4,489 producing oil wells 3,813 producing gas wells Worldwide Offshore Oil Rigs North Sea: 88 Gulf of Mexico 215 S. Asia: 25 Far East: 23 Latin America 109 Pacific Rim: 42 West Africa: 42 November 2001 Middle East: 33 Known Oil Reserves QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Oil Consumption Oil Consumption United States: 19.6 million barrels per day. 25% of world total. World: 75 million barrels daily and rapidly increasing. How much is left? Forecasted at 40 years (2K billion barrels). World Oil Consumption QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. What A Barrel Of Crude Oil Makes (42 gallons) Product Gallons per barrel gasoline 19.5 distillate fuel oil 9.2 (Includes both home heating oil and diesel fuel) kerosene-type jet fuel 4.1 residual fuel oil (Heavy oils used as fuels in industry, marine transportation and for electric power generation) 2.3 liquefied refinery gasses 1.9 still gas 1.9 coke 1.8 asphalt and road oil 1.3 petrochemical feedstocks 1.2 lubricants 0.5 kerosene 0.2 other 0.3 Oil makes gas, right? 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