Oil drilling from sea floor in search of Black Gold
Introduction
In the previous articles we learned how the process of drilling initiates and how it is carried out in the great depths of oceans. When this drill reaches the oil inside the ground, it may seem a bit daunting in front of the immense pressure of the subterranean oil stream. Its not an easy task and has to be done with utmost concern to prevent marine pollution and structural harm to the oil platform.
The oil that we procure is not of the purest form. The oil from the rig is sent to refineries onshore for the refining process. But before all this, its a tough task to take oil out of the well itself. Let’s take a closer look at the whole process.
When the drill strikes the oil
When the drill hits oil, an interesting process takes place. A cylindrical or rectangular casing known as “production casing” goes to the bottom of the shaft. This production casing when reaches the bottom of the shaft, caps the reservoir to form an enclosed chamber. This may sound odd as there is oil every where around so why to take a limited quantity? The aim over here is not to block a certain amount of oil, but to obstruct the flow so that the oil doesn’t come out with high pressure. This casing is later perforated for the oil to flow inside the casing. This is done to reduce the pressure and to assure that the oil inside the casing doesn’t get exhausted.
Initially the pressure in the casing is enough to push them up to the platform but as the level decreases the pressure also decreases. Pumps are then used to get the oil out of the casing. Pressurized water and steam is also used for this purpose. The oil is also heated with the help of superheated steam so that it flows easily.
Refining
If the oil that comes out is in pure form then it is directly transported with the help of tankers or sub sea pipelines. But this is never the case. The oil that comes out is a mixture of crude, water sediments and natural gas. For this reason, the oil is transported to the shore where the refinement of oil takes place in petroleum refineries. There are also ships that are made for this purpose, which pre-refine the oil before sending it to the oil refineries on land.
Almost all the platforms are provided with natural gas refining facilities. This is because; natural gases are of two types- wet natural gas and dry natural gas. Wet natural gas contains vaporized liquids which need to be refined and removed before it is transported. Whereas Dry natural gas is free of any such liquids and thus it can be transported immediately though Sub Sea pipelines for storage or further refinement.
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Time to Terminate
Petroleum companies would have been extremely lucky if the stock beneath would never end. But the sad part is that it does end and when it does, it is time to close shop. This generally happens when the well becomes dry or the investment in the project overweighs the quantity procured. This is the time, when companies pull the plug. The platform is first detached from the foundation with the help of explosives. It is then towed to the shore to get it scraped. Later on, the divers cut the casting above the sea surface and cover it with concrete. Remains of the platform are bound to stay at the site.
Recently, there has been too much opposition made against offshore drilling due to incidents of marine pollution. The pictures given below show the process of detachment of the oil platform from the bottom of the sea floor while the other picture at the extreme right shows an aerial view of the oil pollution that has occurred during this process.
References
Deep Challenge: Our Quest for Energy Beneath the Sea by Clyde W. Burleson
Image Credits
https://www.engineerlive.com/media/images/large/large_0903654001222425901__119908_fullsize.jpg
https://surfpioneer.com/blog/wp-content/uploads/2008/08/offshoredrilling.jpg
https://www.treehugger.com/offshore-drilling-rig-examples.jpg
https://www.hydrocarbons-technology.com/projects/sunrise/images/sunrise2.jpg
https://www.hydrotrole.co.uk/images/offshore-drill.jpg
https://www.amsbowfishing.com/images/features/articles/shark%20journal/oil-rig.jpg
