Oil and Gas

• Non-renewable resources - rate of formation < rate of consumption

• Formed from dead tropical marine plankton
• Formed over millions of years in anaerobic conditions with heat and pressure
• Moves from kerogen to oil shales to tars to heavy oils then light oils then diesel and petrol and eventually natural gas
• Young oil is more viscous - doesn't run - hard to extract
• Stored in porous reservoir rocks eg. Sandstone
• Cap rock needed above to contain the deposits - impermeable rock
• California - Lake View Gusher, Micricopa
• Primary recovery whereby the oil and gas comes to the surface under its own pressure(a gusher)
• Pressure is created by water below or gas above, or both
• Secondary recovery - pumping down water or gas to increase the pressure
• Tertiary recovery - attempts to increase the mobility of the oil making it less viscous
• Involves injecting stream or detergents in to the reservoir rock to make the oil flow more readily


Problems of oil recovery:
• Young oils too viscous to flow
• Oil deep below surface (5km) difficult to reach as friction increases and pumping fluids in to carry out rock fragments becomes harder
• Oil beneath deep water (2km) hard to exploit as anchoring floating rig is hard
• Oil that is very viscous or in impermeable rock will not flow to the extraction well
• Many oil fields are too small to be exploited profitably

Uses:
• Range of different uses - very versatile
• Main uses
 - building and process heating
 - vehicle fuels
 - electricity generation and petrochemicals

Environmental Impacts:
• Exploration
 - seismic surveys - affects whales
 - explosions to test for oil - habitat disturbance
 - benthic species - sea bed species
• Extraction
 - leaks eg. BP oil spill
 - anchoring rigs - destroys sea bed - benthic species
• Transport
 - pipelines - habitat destruction
 - fuel for transport
• Process
 - air pollution - fractional distillation
 - energy intensive
• Use
 - fuels - petrol/diesel - nitrous oxide = acid rain
 - habitat destruction - building petrol stations
• Waste
 - air pollutants
 - plastics - don't biodegrade

Future:
• As oil and gas become exhausted we are needing to use technology to find and extract oil and gas in new ways
• Oil sands and shales eg. Alberta, Canada
• Drilling in deep water eg. Gulf of Mexico - deep water horizon
• Drilling in difficult environments eg. the North Sea
• Drilling in harsh climates eg. the Artic
• Fraking eg. in USA

• These less conventional methods of extracting oil are likely to have greater environmental impacts and as they are more expensive ways of extracting the resources global prices are likely to increase