Fossil Fuels
Coal Facts
--Coal is an organic sedimentary or metamorphic rock derived from the accumulation and preservation of land plant material that grew in profuse amounts in wetlands (marches, swamps, bogs, and fens). --After deposition, the peat was rapidly buried by other sediment, usually sand and clay. --Enrichment of the carbon (coalification) occurred during diagenesis and subsequent metamorphism. --Peat, which is found in mires (AKA quagmires) - bogs and ferns - is not technically coal, but it is the precursor of true coal. --A bog is a mire that accumulates peat, a deposit of dead plant material—often mosses, and in a majority of cases, sphagnum moss. Fens are alkaline mires.
Anthracite coal
Anthracite is the highest rank of coal. It has a bright luster and breaks with a semi-conchoidal fracture.
Petrogenesis - How does coal form?
Coal forms from the accumulation of plant debris in a reducing, wetlands environment. When plant debris dies and falls into the "swamp" the standing water protects it from decay. Swamp waters are deficient in oxygen, which would react with the plant debris and cause it to decay, therefore allowing the plant debris to persist. In addition, insects and other organisms that might consume the plant debris on land do not survive well under water in an oxygen deficient environment.
coal
Coal shale and bituminous shale have less combustible material, but they do burn slowly. The boundary between coal and coal shale is 50 wt. % combustibles, but rarely is coal with > 30 wt. % non-combustibles used as a fuel. -Most coals are very heterogeneous, macroscopically and microscopically.
COnt
Countries like Canada, Venezuela, and United States all sit atop extremely large deposits of heavy oil and oil shale. In fact, it is estimated that there is more heavy oil in Venezuela then there is petroleum in the entirety of the Middle East. Canada is currently the world's leading producer of heavy oil and it is estimated that the heavy crude in Canada is enough to supply the entire world at current demand for well over 200 years. Most experts seem to agree that if the world has not already reached peak petroleum production, then it will do so within the next 20 years. Peak oil does not mean that petroleum reserves have run out, but that the maximum rate of petroleum extraction has been reached and that subsequent methods of extraction cannot increase the rate further. Over time, the total rate of petroleum output will decrease.
Petroleum Facts
Crude petroleum, a complex volatile mixture of hydrocarbons with some sulfur, nitrogen, oxygen, and trace metals, is the largest single source of energy in the world, accounting for approximately 35-40% (in oil equivalents) of the energy consumed in the world. It is also the building block for a large number of chemical products consumed globally. I will very briefly cover the following because I expect that you will be taking a petroleum geology course within the next two years: Classification Composition/Chemistry Formation Reservoirs/Traps Extraction/Production Refining World and US production/exports/imports Reserves Uses
Introduction
In 2009 the world's primary energy supplies were: Petroleum - 34.8% Natural Gas-23.8% Coal - 29.4% Hydroelectricity-6.6% Nuclear Power-5.5% Geothermal, Wind, and Solar Electricity - 1.7% -Alternatives must play a major role in the future since these primary fossil fuels are non-renewable and finite!
cont.
In the United States, primary production methods account for less than 40 percent of the oil produced on a daily basis, secondary methods account for about half, and tertiary recovery the remaining 10 percent. Extracting oil (or "bitumen") from oil/tar sand and oil shale deposits requires mining the sand or shale and heating it in a vessel or retort, or using "in-situ" methods of injecting heated liquids into the deposit and then pumping out the oil-saturated liquid. The petroleum industry is involved in the global processes of exploration, extraction, refining, transporting (often with oil tankers and pipelines), and marketing petroleum products. The largest volume products of the industry are fuel oil and gasoline.
coal consists of various types/ranks
Lignite - soft, brown - C = 60-75 wt %; O = 30-35 wt % Sub-bituminous - hard, brown - C = 75-83 wt %; O = 10-20 wt % Bituminous - soft, black - C = 75-90 wt %; O = 10-20 wt % High Volatile (AKA gas coal) Medium Volatile (AKA coking coal) Low Volatile Bituminous (AKA steam coal) Semi-Anthracite - C = 90-93 wt %; O = 1-4 wt % Anthracite - hard, black - C . 93 wt %; O = 1-2 wt % (METAMORPHIC)
COnt
OPEC currently accounts for approximately 73% of total world oil reserves, but Venezuela now holds the single largest share at 18%. Saudi Arabia holds the second-largest share at 16%. The Middle East retains the regional share title with 48%. By virtue of Venezuela's reserve gains, Central and South America has displaced North America for second place, at 20% of world reserves. North America is now third at 13%, in spite of the U.S. gain in reserves due to oil shales and oil sands formations. There are several major oil producing regions around the globe. The Kuwait and Saudi Arabia's crude oil fields are the largest, although Middle East oil from other countries in the region such as Iran and Iraq also make up a significant part of world production figures. The North Sea crude oil fields are still fairly full, and are arguably the second most influential oil field in economic terms. Texas, once the world's major oil region, is now almost completely dry.
Unconventional Oil Reservoirs
Oil Sands - These are reservoirs of partially biodegraded oil still in the process of escaping and being biodegraded, but they contain so much migrating oil that, although most of it has escaped, vast amounts are still present—more than can be found in conventional oil reservoirs. The lighter fractions of the crude oil are destroyed first, resulting in reservoirs containing an extremely heavy form of crude oil, called crude bitumen in Canada, or extra-heavy crude oil in Venezuela. These two countries have the world's largest deposits of oil sands.
Unconventional Oil Reservoirs Cont. Oil Shales
Oil shales are source rocks that have not been exposed to heat or pressure long enough to convert their trapped hydrocarbons into crude oil. Technically speaking, oil shales are not always shales and do not contain oil, but are fined-grain sedimentary rocks containing an insoluble organic solid called kerogen. The kerogen in the rock can be converted into crude oil using heat and pressure to simulate natural processes. The method has been known for centuries and was patented in 1694 under British Crown Patent No. 330 covering, "A way to extract and make great quantities of pitch, tar, and oil out of a sort of stone." Although oil shales are found in many countries, the United States has the world's largest deposits.
Peat
Peat: A mass of recently accumulated to partially carbonized plant debris. This material is on its way to becoming coal but its plant debris source is still easily recognizable.
Petroleum Classification
Petroleum is formed when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and subjected to both intense heat and pressure. In its strictest sense, petroleum includes only crude oil, but in common usage it includes all liquid, gaseous, and solid hydrocarbons. Under surface pressure and temperature conditions, lighter hydrocarbons -- methane, ethane, propane and butane -- occur as gases, while pentane and heavier ones are in the form of liquids or solids. However, in an underground oil reservoir the proportions of gas, liquid, and solid depend on subsurface conditions. An oil well produces predominantly crude oil, with some natural gas dissolved in it. A gas well produces predominantly natural gas. However, because the underground temperature and pressure are higher than at the surface, the gas may contain heavier hydrocarbons such as pentane, hexane, and heptane in the gaseous state. At surface conditions these will condense out of the gas to form natural gas condensate
Cont.
Plant debris accumulates very slowly, so accumulating ten feet of plant debris take a long time. The fifty feet of plant debris needed to make a five-foot thick coal seam would require thousands of years to accumulate. During that long time the water level of the swamp must remain stable. If the water becomes too deep the plants of the swamp will drown and if the water cover is not maintained the plant debris will decay. To form a coal seam the ideal conditions of perfect water depth must be maintained for a very long time. Therefore, the formation of a coal seam is a highly unusual occurrence. It can only occur under one of two conditions: a rising water level that perfectly keeps pace with the rate of plant debris accumulation a subsiding landscape that perfectly keeps pace with the rate of plant debris accumulation. Most coal seams are thought to have formed under condition #2 in a delta environment. On a delta large amounts of river sediments are being deposited on a small area of Earth's crust and the weight of those sediments causes the subsidence.
Cont. Uses of petrogenesis
Production of electricity To heat kilns that are used for concrete blocks and bricks Power source for factories Production of coke used in steel production Plastics Roofing Linoleum Synthetic Rubber Insecticides Paints Medicines Synthetic Fibers
Pyrolysis
Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen (or any halogen). It involves the simultaneous change of chemical composition and physical phase, and is irreversible.
classification of coal according to important properties
Reflectance (%) Volatile Matter (wt. %) (d.m.m.f. = dry mineral matter free) Vitrinite (wt %) - one of the primary components of coals and most sedimentary kerogens. Vitrinite is a type of maceral, where "macerals" are organic components of coal analogous to the "minerals" of rocks. Vitrinite has a shiny appearance resembling glass (vitreous). It is derived from the cell-wall material or woody tissue of the plants from which coal was formed. Chemically, it is composed of polymers, cellulose and lignin. Bed Moisture (wt %) Calories (kcal/kg or MJ/kg)
coal
Surface extraction of coal by essentially taking the entire hill/mountain down! This is a large coal seam!!
Cont.
Tectonic processes can provide the slow subsidence necessary for peat formation in orogenic and post-orogenic basins. Coalification requires; Time Temperature Increase Pressure Increase - lithostatic and sometimes tectonic Paleogeographical reconstructions of important coal basins of the Earth are hampered by the fact that no "giant wetlands exist today to test hypotheses. The Allegheny (Pennsylvanian) model is currently used to explain coal formation structures. It consists of disconformity bound stratigraphically repetitive sequences of sediments called "cyclothems." These were deposited in the following environments: Marine Shelfs Delta fronts Brackish Lagoons Delta Plains Broad Alluvial Plains
Lignite
The lowest rank of coal is "lignite". It is peat that has been compressed, dewatered and lithified into a rock. It often contains recognizable plant structures.
Petroleum Uses
The primary uses of crude oil to this point have been in the production of fuel. A single barrel of crude oil can produces the following components, which are listed by percent of the barrel they constitute. 42% Gasoline 22% Diesel 9% Jet Fuel 5% Fuel Oil 4% Liquefied Petroleum Gases 18% Other products While the transportation industry is responsible for using almost 80% of all crude oil produced, there has been great effort in the last two decades to produce electric vehicles capable of performance similar to that of petroleum powered vehicles. In its thickest form, the almost black petroleum is named bitumen, this is used for paving road, forming the blacktop, it is also an excellent water repellent and is used in roofing. It is also a major part of the chemical makeup of many plastics and synthetics. Possibly the most startling usage of petroleum for many people is its appearance in foodstuffs such as beer and in medications such as aspirin.
Petroleum Composition/Chemistry
The proportion of light hydrocarbons in the petroleum mixture varies greatly among different oil fields, ranging from as much as 97 percent by weight in the lighter oils to as little as 50 percent in the heavier oils and bitumens. The hydrocarbons in crude oil are mostly alkanes, cycloalkanes and various aromatic hydrocarbons while the other organic compounds contain nitrogen, oxygen and sulfur, and trace amounts of metals such as iron, nickel, copper and vanadium. Many oil reservoirs contain live bacteria. The exact molecular composition varies widely from formation to formation, but the proportion of chemical elements vary over fairly narrow limits as follows: carbon - 83-85% Hydrogen - 10 to 14% Nitrogen - 0.1 to 2% Oxygen - 0.05 to 1.5% Sulfur 0.05 to 6.0% Metals < 0.1%
Petroleum Formation
There were certain warm nutrient-rich environments such as the Gulf of Mexico and the ancient Tethys Sea where the large amounts of organic material falling to the ocean floor exceeded the rate at which it could decompose. This resulted in large masses of organic material being buried under subsequent deposits such as shale formed from mud. This massive organic deposit later became heated and transformed under pressure into oil. The temperature range in which oil forms is an "oil window"—below the minimum temperature oil remains trapped in the form of kerogen, and above the maximum temperature the oil is converted to natural gas through the process of thermal cracking. Sometimes oil formed at extreme depths may migrate and become trapped at a much shallower level. If temperatures get too high (usually >200oC), oil and natural gas are vaporized and destroyed.
Bituminous coal
This is a highly magnified view of bituminous coal in transmitted light. The large yellow object in the center of this image is a spore - a reproductive cell of the coal-forming vegetation. It is about two millimeters long. The spore was probably round before it became part of the coal-forming plant debris. It was squeezed flat after burial. The thin red bands running horizontally across this view are thin shreds of well-preserved woody material. The tiny yellow and orange particles are smaller spores and algal debris. The black material is either charcoal or opaque mineral matter. This coal does not contain a lot of well preserved wood. Instead it is mostly charcoal and mineral debris. The material in this view is representative of coal that formed under conditions that were not idea for the preservation of plant material.
Petroleum Reservoirs/Traps
Three conditions must be present for oil reservoirs to form: 1-a source rock rich in hydrocarbon material buried deep enough for subterranean heat to transform it into oil 2-a porous and permeable reservoir rock (high interconnectedness) for it to accumulate in 3-a cap rock (seal) or other mechanism (structural) that prevents it from escaping to the surface. Within these reservoirs, fluids will typically organize themselves like a three-layer cake with a layer of water below the oil layer and a layer of gas above it, although the different layers vary in size between reservoirs. The above process is influenced by underground water flows, causing oil to sometimes migrate hundreds of kilometers horizontally or even short distances downward before becoming trapped in a reservoir. When hydrocarbons are concentrated in a trap, an oil field forms, from which the liquid can be extracted by drilling and pumping.
Petrogenesis - How does coal form?
To form the thick layer of plant debris required to produce a coal seam the rate of plant debris accumulation must be greater than the rate of decay. Once a thick layer of plant debris is formed it must be buried by sediments such as mud or sand. These are typically washed into the swamp by a flooding river. The weight of these materials compacts the plant debris and aids in its transformation into coal. About ten feet of plant debris will compact into just one foot of coal.
coal
Underground mining using room and pillar technique
Petroleum Formation
Vast quantities of fossilized organic materials, such as zooplankton and algae remains, settled to sea or lake bottoms, mixing with sediments and being buried under anoxic conditions. As further layers settled to the sea or lake bed, intense heat and pressure build up in the lower regions. This process caused the organic matter to change, first into a waxy material known as kerogen, which is found in various oil shales around the world, and then with more heat into liquid and gaseous hydrocarbons via a process known as catagenesis. Formation of petroleum occurs from hydrocarbon pyrolysis in a variety of mainly endothermic reactions at high temperature and/or pressure
Petroleum Extraction and Distribution
Wells are drilled into oil reservoirs to extract the crude oil. "Natural lift" production methods that rely on the natural reservoir pressure to force the oil to the surface are usually sufficient for a while after reservoirs are first tapped. In some reservoirs, such as in the Middle East, the natural pressure is sufficient over a long time. The natural pressure in most reservoirs, however, eventually dissipates. Then the oil must be extracted using "artificial lift" means. Over time, these "primary" methods become less effective and "secondary" production methods may be used. A common secondary method is "waterflood" or injection of water into the reservoir to increase pressure and force the oil to the drilled shaft or "wellbore." Eventually "tertiary" or "enhanced" oil recovery methods may be used to increase the oil's flow characteristics by injecting steam, carbon dioxide and other gases or chemicals into the reservoir.
The BIG three
coal, crude oil, natural gas
Bituminous Coal
typically a banded sedimentary rock. In this photo you can see bright and dull bands of coal material oriented horizontally across the specimen. The bright bands are well preserved woody material, such as branches or stems. The dull bands can contain: mineral material washed into the swamp by streams, charcoal produced by fires in the swamp, or degraded plant materials. This specimen is approximately three inches across (7.5 centimeters). Photo by the West Virginia Geological and Economic Survey. - 50% of the US production of coal
