This diagram shows the separation of gas, oil and water. They are trapped between impermeable rocks, which have formed an anticline.
Locating the oil
Usually, crude oil is found underground in reservoirs called ‘traps’. A common type of trap is an anticline. An anticline is when the layers of rock fold, causing an upwards curve. Crude oil is often found in these anticlines. The picture below shows examples of anticlines.
The walls of rocks show the outer edges of an anticline
An anticline is something that geologists, people who specialise in earth and rocks, look for when investigating oil locations. Anticlines are made when the movements of the earth causes the strata of rocks to fold up. A syncline is when the strata folds down. It is easier to see anticlines using aerial photographs taken from the height of an aeroplane. This saves time spent on searching the surface.
Geologists also tap rocks to see if the proposed place does have oil. The rocks with oils in them should sound different to those without. They also sample the rocks, to observe the fossils in them, as there are some fossils, which aid in the process of oil production.
We can also use seismic waves, which is mainly a method to sketch out the structure of the reservoir of oil. Geologists and geophysicists work together and places explosives several feet below the ground. When they are set off, sound waves either go straight up to the geophones, which pick up the waves, or they go further down and bounce off a different rock boundary, reflecting them back to the geophones. The geologists and geophysicists study the time differences in the reflected waves and create a formation for the anticline. If looking under water, they use an air gun to replace the explosives and hydrophones, which substitutes the geophones.
Extracting the oil
Extracting the oil is done by drilling and is an expensive job to do. This only happens when geologists and geophysicists are absolutely certain that there is oil to be found. This is an example of drilling equipment. The drilling company sets this up on the site. Once all the equipment is set up, they begin the drilling using a drill bit to cut through the layers of rocks. These are often tipped with diamond or tungsten carbide to make it hard, and easier to drill through difficult levels of rocks.
The bits also circulate mud (a mixture of water, clay, weighting materials and chemicals), which flushes out the rock cuttings, and bring them back to the surface.
There is also a chance for a ‘blow out’ when drilling for oil. You may see a ‘blow out’ illustrated on movies or cartoons, where the oil bursts out from the ground. Should this happen, the oil is wasted, and there is no profit. To reduce the risks, the mud is pumped down the drill string and balances the pressure of the crude oil and gas in the surrounding rocks.
What happens after
Once the oil is drained from the reservoir (which varies on each occasion), the crude oil that is made up of a mixture of substances, mainly hydrogen and carbon though, is then sent off to an oil refinery. The oil refinery fractionates the oil (divides it up according to molecular weight), which is heated in a distillation column and condensed at different temperatures to make different end products. The picture below illustrates the way oil is fractionated and the ending products due to different condensing temperatures.
The oil at the bottom has a higher boiling point, and is the ones with the heavier molecules. It is thick and hard to catch light. The oil at the top is gas which is thin, flammable and with light molecules.
Conclusion
After completing this report, I have found out a lot of information about oil. I understand the processes of locating and extracting crude oil and know how crude oil is changed into everyday items.
