A drop of Oil (Part 2)

| How oil is formed | How oil is found | Getting the oil out | Refining | Uses |
How oil is found.
In order to find oil, oil companies use skilled scientists, called geologists, and geophysicists, combined with some of the world's most advanced technology, to identify areas where oil should be, and how it could be extracted.
Geologists are experts in rocks and their formation and geophysicists understand the physical characteristics of rocks. Working together, using their combined knowledge and experience, they locate sites where they think oil may have been formed, and trapped many years ago. For example, oil is likely to be held within reservoirs of limestone or sandstone, and it will need to have an impermeable cap rock, such as shale. Also, the Earth’s crust must have moved in such a way that the oil or gas reserves have been unable to escape. Once they have located likely sites they need to undertake deeper study and investigation. Various techniques are used to conduct an intensive ground study. A seismic exploration uses shock waves to produce a survey, which can be made to look like a map of the earth's surface, by sending shock waves down into the earth's crust. As shock waves travel at different speeds, and at different angles through different types of rock it is possible for the survey team to collect the signals, using geophones, to produce a three dimensional map of the site.

"A seismic exploration uses shock waves to produce a survey, which can be made to look like a map of the earth's surface, "

The map of the site will then either prove or disprove the scientists  thoughts about whether the site has supplies of oil or not.
If a new oil reserve has been located then it is up to a new team of people to decide whether or how to go into full scale oil production. This team consists of economists, scientists, and engineers all of whom have experience in the tapping of new reserves. This team try and calculate how much oil is in the ground, how much of that oil can be brought to the surface, what it would cost to get the oil to the surface, and then how can it be transported to the refinery. This team do not look purely at the cost issues, as they must also consider other issues, such as the safety of the operation, the effect it could have upon the environment, and the length of time that they may be able to tap the oil resource.
Different sites require different types of equipment to withdraw the oil.
The oil itself is not always the same. Some sites may have thick heavy crude oil, whilst on other sites the oil is light and almost colourless. Generally crude oil (i.e. unprocessed oil straight from the ground) is similar to a thin brown treacle. You need more specialist equipment to lift a thick oil than a thin oil. Thus the thickness and form of the oil will effect the cost of it's extraction. Additionally the quality of the crude oil can vary. Crude oil of high quality is more valuable than low quality crude. Thus if the oil is of a high quality then it is more likely to be drawn up from the ground than a supply of low quality. The location of the oil can also vary. Because the oil is formed and held by certain rock formations underground, it can be found at different depths in the earth's surface and under the sea, as well as under the land. 
It is a lot harder, and more expensive to drill for oil under the sea but it is possible because many different types of oil drilling platforms can be used. Oil found under the land is easier to extract and less expensive, and thus the majority of oil that we use is actually extracted by land based platforms from rocks found below. Oil is normally found a long way away from where it can be refined and used. This means that the team assessing the viability of a site must also consider how they are going to transport the oil from the site to the refinery. Pipelines are commonly constructed to take the oil either directly to the refinery, or to a local port where the oil can be loaded onto a super tanker and then shipped to the refinery. The cost of transportation can be considerable and again must be fully considered.
Once these issues have all been considered they make a decision as to how to proceed. If the oil is relatively easy, and cost effective to draw out then they will proceed with setting up all the equipment to go into full scale production.

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