Fossil Fuels PDF

FOSSIL FUELS  At the end of the lesson, learners are expected to: Describe how fossil fuels are formed (S11ES-Id-10) ENERGY  FOSSIL FUELS Formed by natural processes such as anaerobic decomposition of buried dead organisms Age of the organisms and their resu...

FOSSIL FUELS  At the end of the lesson, learners are expected to: Describe how fossil fuels are formed (S11ES-Id-10) ENERGY  FOSSIL FUELS Formed by natural processes such as anaerobic decomposition of buried dead organisms Age of the organisms and their resulting fossil fuels sometimes exceeds 650 million years old Contain high percentages of carbon include coal, petroleum and natural gas  WHAT IS SEDIMENTARY ROCK? Most of the rocks that form layers at Earth’s surface New layers increase the pressure on older layers. Over time, water flows through the compacted sediments.  WHAT IS SEDIMENTARY ROCK? Most of the water on Earth contains dissolved minerals which stick to the sediments. Eventually they form a kind of cement that holds together all the bits of rock to form new rock.  COAL started forming over 350 million years ago transformation of organic plant matter combustible black or brownish- black sedimentary rock occurring in rock strata in layers or veins called coal beds or coal seams  the harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure composed primarily of carbon along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen Coalification is the formation of coal from plant material by the processes of diagenesis and metamorphism also known as bituminization or carbonification CONDITIONS TO TURN INTO FOSSIL FUELS Need for saturated environment Need for anaerobic environment Pressure Temperature Time  Geological Time For The Formation of Coal 360 million to 290 million years ago- Carboniferous (“coal-bearing”) Period less than 65 million years ago- Tertiary Era-generally less mature ✓Lignite-still contains a high content of volatile matter (bitumen and decayed wood) and has a lower carbon content  Geological Time For The Formation of Coal Recent accumulations (from 10,000 years ago to today) ✓Peat- very rich in fibrous debris, not buried deep enough to contain elemental carbon  THE DIFFERENT TYPES OF COAL ranked according to their carbon and volatile matter content a. Anthracite- 86 to 98% pure carbon and 8 to 3% volatile matter The highest rank of coal used to heat homes forms in regions of the world where there have been giant movements of the earth, such as the formation of mountain ranges b. Bituminous coal- 70 to 86% carbon and 46 to 31% volatile matter used to make coke, used in metallurgy c. Sub-bituminous coal- is 70 to 76% carbon and 53 to 42% volatile matter burned in industrial boilers  d. Lignite- 65 to 70% carbon and 63 to 53% volatile matter a low-grade fuel with a high moisture content that is used in industrial boilers  e. Peat - partially decomposed vegetation the lowest rank of coal It has a carbon content of less than 60% and is composed entirely of volatile matter important fuel in areas of the world including Scotland, Ireland, and Finland PETROLEUM AND NATURAL GAS FORMATION  Natural gas is naturally occurring hydrocarbon made up mainly of methane (CH4). It is colorless, odorless and tasteless Natural gas from the well is called wet gas as it contains liquid hydrocarbons and non-hydrocarbon gasses Methane and useful gasses will be separated from the mixture at the processing plant These other useful gasses include ethane, propane, butane, pentanes Crude oil is a mixture of many organic substances transported to a refinery, where it is separated by fractional distillation and other processes where oil is heated in a furnace The oil evaporates and goes into a fractionating column The vapor is then allowed to condense at various temperatures in the column How Oil and Gas Deposits are Formed When a living organism dies, it is generally recycled in one of two ways: a.It is eaten by predators, scavengers or bacteria b. Through exposure to ambient air or oxygen-rich water, it oxidizes ✓ the hydrogen, carbon, nitrogen, sulfur and phosphorus contained in the matter combine with oxygen atoms present in the air ✓ the organic matter breaks down into water (H2O), carbon dioxide (CO2), nitrates, sulfates and phosphates that nourish new plants The Slow Formation of Source Rock about 0.1% — escapes this fate sinks to the bottom of the sea or large continental lakes partly preserved in these poorly oxygenated environments, well away from tidal currents  It mixes with inorganic matter, such as clay particles and very fine sand, and with dead marine plankton (microscopic organisms) This mixture is transformed into dark, foul-smelling mud by anaerobic bacteria Mud that contains at least 1 to 2% organic matter may be transformed into source rock, which eventually produces oil and gas deposits  More specific requirements are necessary to enable the process to take place: ✓A hot climate that is conducive to the growth of large quantities of plankton ✓A location near the mouth of a major river carrying a lot of plant debris ✓No nearby mountains that could limit the volume of inorganic sediment within the rock.  Source Rock Subsidence The weight of accumulating sediment very slowly pushes the source rock further under the Earth's crust by a few hundred meters every million years or so. This gradual sinking is called subsidence and leads to the formation of sedimentary basins.  As it sinks below ground, the source rock is subjected to increasingly high temperatures, pressure increases by 25 bar every 100 meters on average. At one kilometer underground, the temperature is 50°C and pressure is 250 bar  nitrogen, sulfur and phosphorus atoms are gradually converted into kerogen, an intermediate material made up of water, carbon dioxide, carbon and hydrogen, which is then transformed into oil or gas.  How Oil and Gas Forms 2,000 meters deep, temperature reaches 100°C, kerogen starts to release hydrocarbons oil window - between 2,000 and 3,800 meters, it turns into oil  gas window - 3,800 and 5,000 meters, production of liquid hydrocarbons peaks The liquids produced become increasingly lighter and gradually turn into methane gas, the lightest hydrocarbon  8 to 10 kilometers, hydrocarbons are destroyed by the high temperature. animal origin- more oil than gas plant debris - mostly gas average sedimentation of 50 meters every million years, 60 million years to become liquid hydrocarbons  How Oil and Gas Migrate Starting out from the source rock where they are formed, hydrocarbon molecules, which are light, set off on an upward journey to the surface. They accumulate in porous rock and are blocked by impermeable rock, thereby creating oil and gas deposits.  The Slow Rise to the Surface of Oil and Gas Hydrocarbons are lighter than water, gas and oil rise upward by circulating between the mineral grains of the rock. This slow, constant movement away from the source rock is called migration.  Migration rate depends on the permeability of the rocks they cross and the size of the molecules: gas molecules rise more quickly than oil molecules, because they are smaller and more mobile.  migration loss- some hydrocarbon molecules are prevented from moving upward either because they dissolve in the water contained in the rock or because they adhere to the grains that make up the rock The Formation of Deposits in Reservoir Rock, Under Cap Rock A hydrocarbon deposit can only form in reservoir rock Hydrocarbon molecules may accumulate in large quantities in this porous, permeable rock  There are also empty spaces within the rock that determine its porosity. The higher the percentage of space within the rock, the more porous the rock, which can contain large quantities of fluids such as water, oil or gas. Pumice is an example of a porous rock.  The connectivity of spaces or pores is known as permeability, which is what allows fluids to circulate within the rock. Not all rock is both permeable and porous. Density Porosity Permeability  Hydrocarbon deposit will only form if the reservoir rock is capped by a layer of impermeable rock that prevents the oil or gas from rising vertically to the surface This cap rock forms a barrier and traps the hydrocarbons Ex. clay and crystallized salt (evaporite) layers, highly compact carbonates  Absence of Cap Rock hydrocarbon molecules will move through the reservoir rock and cannot accumulate Oil or gas that reaches the surface at the end of its migration is exposed to bacteria and ambient air. This triggers complex chemical reactions that convert them into water and carbon dioxide  However, when significant quantities of hydrocarbons arrive at the surface more quickly than the final degradation process, the heaviest molecules may remain in the ground in the form of viscous, almost solid bitumen, buried at depths of a few meters. But these bitumen deposits will quickly disappear when the hydrocarbons stop arriving at the surface to replenish them.  Two main types of trap: Structural traps- formed by changes in geological layers caused by the movement of tectonic plates. Reservoir rock is sometimes deformed until it forms a completely sealed space. These anticlinal traps are dome- shaped and the most common type of structural trap. Stratigraphic traps - made up of sedimentary layers that have not undergone tectonic deformation a cap rock completely seals off the reservoir rock Ex. salt domes  Conserving Hydrocarbons Once trapped, the hydrocarbons are still at risk of deterioration that could prevent the formation of a commercial deposit.  At depths of less than 1,000 meters ✓the accumulation can be infiltrated by meteoric water which contains bacteria and oxygen that come into contact with the gas and oil, triggering chemical reactions that separate them into water and carbon dioxide. ✓After a period of time, the initial oil is significantly degraded, leaving only viscous, solid hydrocarbons that are more difficult to extract than non- degraded oil or gas.  Below 1,000 meters ✓the temperature is in most cases higher than 50°C ✓traps located deep underground can be affected by tectonic activity that can cause fractures and faults in the rock, breaking the seal and letting the hydrocarbons leak out of the trap  Hydrocarbon traps can contain: Oil with significant quantities of dissolved gas gas dissolved in the crude oil will be turned into liquefied petroleum gas (LPG), used primarily as fuel  Gas with light liquid hydrocarbons known as condensate that will be refined naphtha, used as a feedstock in the petrochemical industry kerosene, a fuel used in aviation  Fossil Fuel Power Generation Electrical energy generation using steam turbines involves three energy conversions: extracting thermal energy from the fuel and using it to raise steam converting the thermal energy of the steam into kinetic energy in the turbine and using a rotary generator to convert the turbine's mechanical energy into electrical energy ADVANTAGES AND DISADVANTAGES Coal We mine coal out of the ground- underground mining and surface mining. Advantages Reliable source of energy. We can rely on it day and night, summer and winter, sunshine or rain, to provide fuel and electricity.  Disadvantages Mining is one of the most dangerous jobs in the world. Coal miners are exposed to toxic dust and face the dangers of cave-ins and explosions at work. can also cause the ground to cave in and create underground fires that burn for decades at a time When coal is burned, it releases many toxic gases and pollutants into the atmosphere. Petroleum Petroleum is a liquid fossil fuel. It is also called oil or crude We drill through the earth to access the oil. Some deposits are on land, and others are under the ocean floor. Once the oil has been drilled, it must be refined. Oil contains many chemicals besides carbon, and refining the oil takes some of these chemicals out.  Advantages We use oil for many things. About half of the world’s petroleum is converted into gasoline Energy denser, cleaner than coal can be processed and used in liquid products such as nail polish and rubbing alcohol, or solid products such as water pipes, shoes, crayons, roofing, vitamin capsules, and thousands of other items  Disadvantages Burning gasoline is harmful to the environment Possibility of an oil spill  Natural Gas Found in deposits a few hundred meters underground In order to get natural gas out of the ground, companies drill straight down. Some companies use a process called “hydraulic fracturing,” using high-pressure water to split apart the rocks underground. This releases the natural gas that is trapped in rock formations.  can send acid down the well to dissolve very hard rock can also use tiny grains of glass or sand to prop open the rock and let the gas escape used for heating and cooking can also be burned to generate electricity can be turned into liquid natural gas (LNG), which is much cleaner than any other fossil fuels  Advantages “cleaner” fossil fuel than oil or coal When natural gas is burned, it releases lower carbon dioxide per amount of energy used  Disadvantages Extracting natural gas can cause environmental problems Fracturing rocks can cause mini- earthquakes The high-pressure water and chemicals that are forced underground can also leak to other sources of water Methane is a huge greenhouse gas Looking to the Future Can we run out of fossil fuels? It is very important for people to use less coal, oil, and natural gas. Removing fossil fuels from the ground pollutes the environment. So does burning them. But there is an even simpler reason for people to find other sources of energy. Fossil fuels are nonrenewable resources. This means that we use them much more quickly than nature makes them. Remember: coal, oil, and natural gas take millions of years to form. Even if people could remove every drop of oil from the ground, eventually all the oil would be gone. References: http://www.openlearningworld.com/World_Geography/imgs/figure_7.3.3.jpg) https://www.nationalgeographic.org/encyclopedia/non-renewable-energy/