In my first series on this post [here](https://steemit.com/stemng/@michaelwrites/insight-into-the-world-of-crude-oil-from-digging-to-refining-to-a-look-at-other-by-products-part-i-exploration-of-oil), I spoke about how the oil and gas industry has in many ways helped our survivability in many regions including the one I am here. I am quite sure Nigerians aren’t the only one finding petroleum to be of great help. At least for now, a large percentage of the total masses using one automobile or the other has to depend on our precious oil. As a typical Nigerian, if you are not cooking with DPK (Dual Purpose Kerosene), then you are in for AGO (Automotive Gas Oil) to fuel large machines or you are using PMS(Premium Motor Spirit) to power your automobiles, generators, and some other machines. The everyday living is made convenient with CRUDE OIL. It is right to note I mentioned a great deal about the exploration of crude oil from the satellite imaging survey, to magnetometry and down to the most popular of all, seismological survey and to some other surveys. If you didn’t know before now, exploring is the first process in making sure petroleum is available. ## About right now, we’d move to types of oil wells that exist and the drilling methods and techniques that is been used. **Why is this needed?** We learn every day and part of the learning process is ensuring we fully acquaint ourselves with the technology that goes on around us. If you are a businessman or potential one thinking of going into this business, I think this and some other related areas are what you need to note. ## What is an oil well?

^{Wikimedia Creative Commons Attribution-Share Alike 4.0 International license: Pumping unit at an oil well}

An oil well is simply a deposit of oil. It is a well far below the ground whereby when struck, drilled or tapped releases crude oil. Some oil wells tend to release water simultaneously with oil and some other hydrocarbons. The wells, therefore, are divided into three classifications by what they produce which are; exclusive oil producing well, oil and gas producing well and well that produces only gas. Oil well is further divided by purpose: why do we need to dig this well? ## Injection well Injection well is a well that has to be induced to make production process go smoothly. This type of well uses water or gas to ensure the production is possible. In the water injection well, water is injected into the wells to up the pressure in the reservoir to excite the production. The same mechanism goes for the gas injection. The advantage the water and gas injection has is that it ensures the maximum harvest of oil. The production in this well is usually massive. Before water is used, it needs to be deoxygenated because oxygen commonly encourages corrosion or rusting and bacteria growth. The water is deoxygenated by adding ammonium bisulfite or sodium bisulfite as a salvaging agent for oxygen. If deoxygenation does not occur and the water is injected, it would affect the oil due to bacteria. ## Appraisal well: Appraisal well is a well drilled for the purpose of evaluation or researching. Prior to oil been harvested, an appraisal well is dug to run tests, get fluid samples, test the ability of the drills, do the mathematics behind exploring and the eventual gain that would come in after processing, and also other evaluations. ## Exploration well or Wildcat well The English say, when you explore a place, you are trying to find something you don’t know about. Isn’t that true? Same also exist in the production of oil. Exploration well is dug with the intention of discovering untapped resources in respect to oil and some other hydrocarbons. The exploration well is also known as a wildcat well (By wildcat, I am not referring to a big cat like Lion. xHaha). Further discussion about the exploration or wildcat well is that, since oil or gas hasn’t been gathered from this location before, Engineers and the drillers have to be at their best to ensure everything goes well.

^{Wikimedia Creative Commons Attribution-Share Alike 3.0 Unported license: Oil well (Authored by Belizian)}

## Conventional well or Vertical well and the Unconventional well Conventional well is the most common and earliest of all well. In the convention well, after picking a location for drilling, a reservoir is made beneath where the oil flows to. Here, drilling is done vertically/uprightly downward. By been vertical, oil flows directly without been hindered, While the unconventional well is the direct opposite of the conventional well. This method is usually employed to increase the harvest or production of the oil. A deposit is made horizontally to the well and the oil is steered in. This method help meets the target of the involved company and also ensure the well releases its entire product. Having gotten to know the kind of wells that exist and how they are they are gotten, shall we move on to the drilling technique used? The drilling technique is another major step-up tactic in getting of oil. After exploration is done, we can’t leave the oil to dwell underground without tapping it. Since crude oil and other hydrocarbon lie far beneath the ground, methods are used to get them up and running. Briefly, I will show you the overview of the method used. ![hr.png](https://cdn.steemitimages.com/DQmSg46djfmXa4rAvyeS8Dn8GtmVahqfmtABKkR3ppfdHHf/hr.png) ## Let start off with the drilling rig In drilling, a machine called **drill rig** is used to make drilling production possible and go smoothly. A drill rig is majorly made up of a drill bit, drill pipe and a drill string. As we know that rocks are usually very hard and so a drill bit is used in order to crush and cut through the subsurface of the rock structure until the reservoir or oil deposit is reached. A drill pipe, on the other hand, is joined to the drill bit to help or facilitate the process of drilling and are pipes also added to the drill string as the drilling goes deeper. The drill string is a column used to transfer fluid to the drill bit. The drill also ensures that maximum twisting force or torque reaches the drill bit. Once these instruments are together and coupled, the hole can be drilled on the surface. I know the layman would totally be clueless about the process involved even with the knowledge of the basic items. So, let have a look at how the ground is been dug.

^{Drill rig from Wikimedia under CC-BY-SA 3.0 license by blastcube}

The drill bit as a grinding machine is introduced as the most important instrument together with the drill pipe as talked about earlier and the drill collar to add weight to the bit. The drill collar ensures top performance from a bit, hold deviation and help stiffness. As human as we are, our body is useless without our bones. These bones articulated together are what give us shape and help us stand, so also is casing as related to drilling. It is set inside the well to support and stabilize, if the casing is absent, the rocks could cave in. Allow me call casing the well’s foundation. A turntable or a rotary table which serves as a medium whereby kelly transfers rotary motion and a kelly used for transferring rotary/circular motion from the table to the drill string are also used. In the process of breaking through the substrata, mud is passed out through the drill pipe and once the oil well is reached, the well’s foundation i.e casing is immediately cemented by putting the foundation pipe to prevent a collapse. Also as the hole goes deeper, so is drill pipe made available. Drilling is not a straightforward process; it is done bit by bit in order to ensure smooth running of the operation. The signal Engineers get to stop drilling is often gotten from mud. Once they start to see oil around the mud, they begin to feel good like someone who just hit gold, well; crude oil is gold here in Nigeria. The bit by bit drilling also comes with bit by bit casing. A gun is introduced here (not an AK47 but a perforating gun) to makes holes for easy passage of the crude oil in the casing pipe. The pressure in the well is usually enough for oil to flow upward but the opposite could be the case in abandoned or used wells. In this well, tubing is introduced to help or artificial systems can be used such as gas lift and pump jacks. ![hr.png](https://cdn.steemitimages.com/DQmSg46djfmXa4rAvyeS8Dn8GtmVahqfmtABKkR3ppfdHHf/hr.png) CONCLUSION There are other instruments that make up the drill rig like the derrick, mud pump, standpipe and a host of others. There could be a selection headache with the collar that helps the bit performance. So in choosing a collar, drillers check on the result or readings gotten from the site due to the previous drilling. For a new site that hasn’t been drilled before, choosing a collar could be a little laborious. Recently, drillers and Engineers have resolved to the use of the bit’s measurement or size and the diameter of the casing that would fit in into the hole. I only spoke majorly about onshore (land) operations. What about offshore (sea)? The type of rig system to use is determined by the floor of the ocean.

^{Semisubmersible oil drilling rig from wikimedia under Attribution 2.0 Generic (CC BY 2.0)}

Submersible rig and Semisubmersible rig are used where there are shallow waters. They are a mobile offshore drilling unit packed together with other drilling components. The rig and the equipment are supported by columns that go deep into the water. Semisubmersible rigs often find more use than the submersible because it is strong compared to the submersible. Semisubmersible is also used since they float, they can be easily transported to the site of operation. When a sea with deepwater or ultra-deepwater is to be dug, drillers use a drillship. A drillship houses its drilling rig and vessel where the oil flows into. A drill ship is usually very big it contains a helipad that transport workers and also convey supplies. A drillship serves as a multipurpose ship that drills and also transport oil compared to other types. The other advantage is that the ship floats and is semi-submersible.

^{Drill ship from Wikimedia under CC BY-SA 4.0 license by CARLOS TEIXIDOR CADENAS}

I hope you got exposed a little to how the oil and gas industry runs? Overall, we have read about oil exploration, types of well, and the drilling process. I would write about the recovery processes used in case oil production doesn’t reach the maximum and also about the separation techniques used to break crude oil into different products in a later post. THANK YOU. ![hr.png](https://cdn.steemitimages.com/DQmSg46djfmXa4rAvyeS8Dn8GtmVahqfmtABKkR3ppfdHHf/hr.png) If you write STEM (Science, Technology, Engineering, and Mathematics) related posts, consider joining #steemSTEM on steemit chat or discord [here](https://discord.gg/vwzWz3Z). If you are from Nigeria, you may want to include the #stemng tag in your post. You can visit this blog by @stemng for more details. ![DQmbLnWWa61dztWL9qkkXUABmnd3DpjbSrj7KHL3jH3c4tW.gif](https://cdn.steemitimages.com/DQmbX4famb5juYkNTu6NEm1C94T7PS1jiAsSws8VNqoEqo7/DQmbLnWWa61dztWL9qkkXUABmnd3DpjbSrj7KHL3jH3c4tW.gif) I'm a proud member of @promo-mentors where you get mentored and guided on how to make quality posts on steemit amongst other benefits. Do join us on [discord](https://discord.gg/jza4pJS). We anticipate your arrival. ![DQmTDLNSwrxM4R85rA2qsR18pugncTy5FDhVf5gJBoW5vLm.gif](https://cdn.steemitimages.com/DQmZnq2xDGwDJrmkozriE1TdKKT36We6aThGxZUVMWCETXz/DQmTDLNSwrxM4R85rA2qsR18pugncTy5FDhVf5gJBoW5vLm.gif) SOURCES * [Npd - Well definitions](http://www.npd.no/en/Topics/Wells/Temaartikler/Well-definitions/) * [Youtube](https://m.youtube.com/watch?v=7QwE7TWLb1c) * [Ilocis - Oil document](http://www.ilocis.org/documents/chpt75e.htm) * [Energy education - Oil well](http://energyeducation.ca/encyclopedia/Oil_well) * [Pass my exams - Drilling crude oil](http://www.passmyexams.co.uk/GCSE/chemistry/drilling-crude-oil-1.html)