Oil Resources Flashcards
What is marine pollution?
- The direct or indirect introduction by man of substances or energy to the marine environment that have a deleterious effects, or interfere with legitimate uses of the sea, or are a threat to human health. (GESAMP)
- Naturally occurring oil in the marine environment isn’t techniqually marine pollution
What is oil?
- Petroleum or ‘crude oil’ is a complex mixture of different hydrocarbons
- Hydrocarbons are organic compounds consisting of hydrogen and carbon atoms
- Simple or branched chains
- Aromatic hyrdocarbons: Cyclic molecular structure, rings: e.g benzene rings which confer greater toxicity
- PAHs are Polycyclic Aromatic Hydrocarbons, are very difficult to remove from the environment and are highly toxic
What are drilling muds and what happens to them?
Drilling ‘muds’ essential for effective recovery of oil
‘Muds’ and drill spoil were historically dumped on seabed, but are now retained on board for disposal
What is produced water and what happens to it?
Produced water’: either injected into drill hole for pressure balance, or existing reservoir water that becomes contaminated
•can include solutions of chemicals to intensify hydrocarbon extraction and separation of oil-water mixture
What pipeline connects to the North East?
- Norpipe Oil Pipeline commences at the Ekofisk facility.
- The pipeline has a diameter of 34” and is 354 kilometres long.
- It crosses the UK continental shelf and reaches land at Teesside in the UK.
- There is a connection point for the British fields about 50 kilometres west of Ekofisk.
- The pipeline commenced operations in 1975.
- Pipelines open up risks – blowout
- Valves can shit down damaged part of pipes
How much of the cargo transported to the UK was crude oil?
- 500 million tonnes of cargo transported to UK ports in 1996:
- 50% of which was crude oil and related products
Oil tankers in the transport of oil.
- Most common route – oil tankers
- Size of oil tankers and bussiness of shipping channels.
- Dead weight – all the weight a ship can carry
- Economies of scale
- Bigger size – one accident can cause a greater impact on the marine environment
- Second WW saw advent of T2: 16,400 tonnes deadweight
- 1959 : first 100,000 tonne capacity crude oil tanker
- 1960’s : VLCC Very Large Crude Carriers, capacity of 200,000 DWT
- Today: ULCC Ultra-large crude carrier has capacity of 500,000 DWT
Giv some examples of oil tanker incidents
- Eagle Otome 2010 Texas 462,000 gallons
- Prestige 2002 Spain 20 million gallons
- Braer 1993 Shetland 85,000 tonnes
- Exxon Valdez 1989 Alaska > 10 million gallons 37,000 -104,000 tonnes
- (11-32 million gallons)
- Atlantic Empress 1979 Tobago 87 million gallons
- Amoco Cadiz 1978 France 68 million gallons
- Torrey Canyon 1967 England 36 million gallons 120,000 tonnes
Exxon Valdez – famous for changing a whole swath of legislation, famous for occuring on th pristine Alaskan Coastline.
Talk about double skins on vessels.
- Traditionally tankers had a single skin of steel plate and used the oil tanks for ballast
- Following Exxon Valdez, US and then IMO has insisted on double skins; this often means ballast tanks are located between oil and sea, so act as further buffer in the event of collision
- Exxon Valdez disaster off Alaska in 1989
37,000 tonnes of crude oil
Led to legislation for double skin requirement
Describe reducing operational discharge.
What transport associated routine operation cause the release of oil?
- Loading
- e.g. in 2007: loading of tanker at Statfjord oilfield Norway : 3000 metric tonnes§
- Unloading
- Ballasting
- Dry-docking
- Bilge and fuel
- Scrapping
Natural seeps
This pair of images includes a wide-area view of the Gulf of Mexico from the NASA’s Terra satellite in 2006 (top), and a close up (bottom) showing a series of natural crude oil seeps over deep water in the central Gulf.
Happens in a larger scale in the gulf of Mexico
Can be seen in reflection patterns
Give some stats about scources of oil pollution at sea
- Natural sources are around 10%
- Oil tanker incidences is relatively small
- Largest source comes from industry and domestic (runnoff) uses – 50 – 60 %
- Tanker operations – bilge cleaning
- Other shipping – big ships fuel tanks carry more fuel than tankers in the 1960’s
What are the different ways which oil breaks down when in the marine enviroment?
Spreading
- gravity , tides, wind
Evaporation
- Lighter, more volatile, more toxic fractions evaporate first. Will become heavier but less toxic.
- Dissolution (minimal) and dispersion
- Turbulence can disperse oil down into the water column, exposing it to different biota below the surface
Emulsification (oil in water and water in oil)
- Loss of volatilesLarger volume
- Chocolate mousse
- Heavier
- Less amenable to chemical dispersion and biodegradation
- Water in oil is nastyier, very high percentage of water, low surface areas for bacteria to act on oil (chocolate mouse) can form tar balls.
Chemical degradation and photo-oxidation, downside is that it tends to produce nasty toxic byproducts.
Biodegradation breaking down of organic molecules by bacterial activity, requires oxygen and various nutrients – slow progress.
How are fisheries at risl from oil pollution?
- Mobility makes evaluation of effects difficult
- Safe from surface slicks
- Evidence of enzyme degradation of hydrocarbons – can break some down.
- ‘tainting’ of flesh from oil makes fish unmarketable.
- Will effect benthic spawning grounds as eggs will float to the surface
- Dispersed oil can affect vulnerable egg and larval stages. If gravel beds were to become tainted early life stage commercial species can be removed.
