Fossil Fuels Flashcards
What are the different forms of petroleum?
Gas, oil, tar sand and oil shale
What’s the significance of fossil fuels having high energy density?
Transportation cheaper, easier to produce higher temp, small amount of fuel
What are the high temperatures produced from coal commonly used for?
Smelting of ores, generation of electricity
How do fossil fuels impact the level of technological development?
Many applications that use energy have been developed to use fossil fuels such as cars, trucks, ships, aircraft and most power stations
Why are significant amounts of coal and oil unexploitable?
Deposits are too deep, found in small amounts or located in areas which are difficult to reach
Where is natural gas contained?
Trapped in fine grained impermeable shale deposits
What is oil shale?
Fine grained sedimentary rock containing solid hydrocarbons
What does oil shale yield?
Oil and combustible gas upon destructive distillation
Why can availability be limited?
Economic viability, unacceptable pollution, habitat damage and extraction processes can cause local earth tremors
What is the basis of most of the world’s energy?
Crude oil
How is coal formed?
Plant remains accumulate and undergo bacterial decay, this is buried by sediment at high temp and pressure, increasing carbon content and the plant material is metamorphosed into coal
How can coal be mined?
Open-cast mining, adit mining and deep mining
What are the features of open cast mining?
Heavily mechanised, more economically viable and coal must be close to the surface
What is Adit mining and why is it no longer extensively used?
Removing coal horizontally from a valley and creating cooling heaps on the valley, Aberfan 1966 is an example of why it’s unsafe
What are the features of deep mining?
Labour intensive so relatively expensive
How does deep mining work?
A vertical shaft is sunken into the ground, the miners then dig horizontal galleries away from the shaft. The coal is then removed up the shaft and separated from spoil
What are some other environmental damages caused by coal?
Habitat loss, transport and ground subsidence
How does petroleum form?
Phytoplankton die and sink to sea floor, where they are preserved from immediate decomposition by anoxic black muds, most crude oil forms at temps of approx 100C with increased pressure
What forces oil to the surface when pipes are drilled?
Natural pressure of gas above the oil or by water beneath the oil
What conditions need to be met for oil and gas to be trapped underground as reserves?
Trapped by layers of impermeable rock, antiform trap
What are the environmental impacts of oil extraction and transport?
Oil pollution, marine seismic surveys and habitat damage caused by pipeline construction
What pollution is caused by burning of fossil fuels?
CO2, CO, NOx, SO2, smoke particulates, ash
What are the main uses of crude oil?
Liquid vehicle fuels, gas fuels for heating and petrochemicals
What are the main uses for natural gases?
Domestic and industrial heating, electricity generation and chemicals
What are the main uses of coal?
Electricity generation and iron and steel industry
Coal gasification
Coal that is too deep to be mined can be burnt underground under controlled conditions to produce a mixture of fuel gases including hydrogen, carbon monoxide and methane
Coal liquefaction
Converting coal to liquid hydrocarbons by directly using convents or indirectly using gasification then chemical changes to convert gaseous hydrocarbons to liquid
When is oil difficult to extract?
Very deep below the surface (>5km) ad friction increases and pumping becomes harder, the oil is beneath deep waterways it is hard to anchor a floating rig at these depths, the oil is very viscous or is trapped in impermeable rock, the oil field is too small to be economically exploited
What are some environmental impacts of oil extraction?
Oil spills, drilling mud for lubrication can cause pollution, surplus gas burned to reduce risk of explosion releases pollutants
What is primary oil recovery?
Use of natural pressure to force oil to the surface. 5-30% recovery rate.
How is natural pressure created on oil reserves?
Water under the oil forcing it upwards, gas above the oil expanding to create downward pressure when drills penetrate oil and bubbles of gas dissolving in oil expanding as oil begins to move towards the surface creating extra pressure
What is secondary recovery of oil?
Once initial pressure begins to drop a second well is added nearby and either gas is pumped or water is injected
How does CCS link to oil recovery?
Pump CO2 to recover oil as well as storing CO2
What is the recovery rate of secondary oil recovery?
40%
What is tertiary recovery?
Reducing viscosity of oil, 60% recovery rate.
What’s the process for tertiary recovery?
Injecting steam into the void from previous extraction, controlled underground combustion, injecting chemicals such as detergents or solvents to reduce surface tension
How is bacteria used in tertiary oil recovery?
Reduce the permeability of rock to force oil out, produce CO2 to increase pressure and react with the oil to reduce viscosity
What are the advantages of directional drilling?
Many wells drilled from single platform, drill underneath areas not usually possible, follow weak or soft rock strata for speed and recovery rate
What are subsea production wells?
Located on the seabed and have no platform at the sea surface, they allow operations in water up to 2000m deep
What are ROVs and AUVs?
Remotely operated vehicles and autonomous unmanned vehicles used to carry out seabed surveys and inspect underwater production equipment and pipelines
What is fracking?
High pressures used to open fissures in surrounding shale rock so that oil and gas can flow towards the recovery well.
When is fracking used?
Large volumes of crude oil and natural gas are trapped in the pore spaces of shale rocks, which have low permeability
What are the potential environmental issues with fracking?
Natural gas may enter aquifer, chemical injected may enter aquifers or reach surface and cause pollution, toxic metals may become mobile, large volumes of water needed and earthquakes occurring that would have eventually happened
What is unconventional oil?
Liquid hydrocarbons from tar sands and oil shale
How are tar sands extracted?
Sands are quarried using large excavators, the sand is then treated with hot water, to produce oil droplet emulsions that can then be separated
In-situ uses steam injection, solvent or controlled combustion is deep deposits
How is oil removed from oil shales?
Heating the shales to drain off the fluid hydrocarbons
What’s the issue with tar sand and shale oil?
Extraction is expensive so current estimates of economically recoverable reserves are low
What are the new technologies for natural gas?
Enhanced gas recovery, fracking, methane hydrate
What is enhanced gas recovery?
Injection of CO or N2 around the edge of the gas field to maintain pressure and gas flow
What is methane hydrate?
Solid ice-like crystalline solid found in locations at low temperatures (polar regions) or high pressures (oceanic sediments)
What’s the benefit of methane hydrate?
Potentially yield more methane than conventional natural gas resources
What are some proposed extraction methods for methane hydrate?
Water heating- melt hydrate to release CH4
Depressurisation- drilling into sediments causes pressure to drop so CH4 gradually dissociates
CO2 injection- Hugh pressure causes CO2 to displace methane
What are the features of fossil fuels?
Chemical energy (easy conversion), high energy density, finite resources, available resource, level of technological development, political and international trade and economic issues
