HOW OIL DRILLING WORKS
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How does oil drilling work?

The process of drilling for oil is one of the most fascinating, and one of the most controversial in the world. Whether oil rigs are set up in the ocean and possibly destroying sea life, or whether drillers are digging into the ground looking for black gold, it seems there are always problems that come with this type of work. It’s true that oil drilling can destroy sea and land habitats of many of our important creatures and that oil can also possibly seep into the ground where it is being drilled and that this can cause further environmental problems. But oil drilling is an essential part of our world and the results from it allow us to function in society the way we do.

The amount of oil that we need to live is amazing. In 2005, the United States produced 9 million barrels of crude oil a day within the country, while it still obtained 13.21 million barrels a day from other countries. This oil then needs to be refined so that it can be turned into gasoline, kerosene, and many other important gases and substances. And when you consider how much oil is needed to run our cars, heat our homes, and all the other vital practices that we need, it’s understandable why we need to drill for so much. Because we need so much oil, it’s critical that the oil practices used are constantly being controlled and kept up so that the oil wells can continue to drill the vital liquid that we need and new drilling stations are being set up all the time.

How Oil is Formed and Located

You may never guess it but oil is formed from the tiny animals and plants that lived and died in the seas between 10 million and 600 million years ago. Once these different life forms died, they sank into the bottom of the ocean and settled into the sand and mud. Because in these deep layers there was almost no oxygen present, if any, microorganisms broke down the life forms into organic layers that are filled with carbon. These layers then mix in with the other sediments to form source rock, which is very fine shale.

As more organisms die and settle down into the sediment at the bottom of the water, it creates pressure on the organisms that are already settled, and at the same time, it also creates heat which is transferred to the organisms which are now source rock. It is this heat and pressure that then turns the source rock into crude oil and natural gas. This oil then flows out of the source rock and collects into bigger pools of harder rock such as limestone or sandstone. This rock is then called reservoir rock. When the Earth moves, it then traps the oil and gas between other layers of hard rock such as granite or marble, which are impermeable.

It is up to geologists to find and locate good oil sources around the earth. They do this by examining and analyzing different soil surfaces looking for places that might be suitable for an oil trap. Satellite images and sometimes shallow drilling of an area are also used to help geologists determine good sources of oil supply. Gravity meters are also used to help detect small subtle shifts in the earth’s gravitational pull and they also use magnetometers, which are extremely sensitive and are used to measure any changes in the earth’s magnetic field. Both of these help geologists to understand where there is flowing oil. Sniffers, which are electronic noses, are also used to help smell for hydrocarbons.

Seismology is also used to send shock waves throughout the layers of rock and analyze the shock waves that are sent back. Seismic shocks can be sent in a number of different ways. A compressed air gun can be used to send pulses of air into water; thumper trucks are sometimes used to plunge heavy plates into the ground, and explosives are also sometimes drilled into the land and set off, and this method can be done on land or in water. Whichever method of seismology is used, these shock waves go so deep that they actually reach the underside of the surface of the Earth. These waves travel through the rock, and then back again so that the waves can then be measured and analyzed. The shock waves are detected by tiny microphones and detectors that can pick up vibrations, which are called hydrophones or seismometers, respectively. They are analyzed so that the geologists can study the type of rock and the density of the rock, which can be determined depending on how quickly the shock waves came back after being passed through the ground or water.

Once geologists think that they have found oil, the area is marked with GPS markings or if it’s on water, with buoys in the water. These processes of finding oil may be highly debatable but they are much better than they have been in years past.

Preparing to Dig

But once the oil has been found either in land or water, it’s more than a matter of simply setting up drills and getting to it. There are many procedures that first must be set into place. The land must first be surveyed to determine what the boundaries of both the land and the oil are. This will help determine if the oil lies on more than one plot of land. Environmental studies may also be done to determine the impact any drilling will have on the environment and, if the oil is not within the same country as those drilling for it, legal jurisdiction may need to be obtained. Once all of these measures have been taken care of, a team of drillers will begin to prepare the site to be drilled.

First, the site of the land needs to be cleared and leveled and if necessary, access roads are also sometimes built. It’s essential that there is water near the drilling site. If there are no water sources nearby, a water well will have to be built to provide the water source. A reserve pit is also drilled so that any excess rock, dirt, or debris that’s collected during the drilling can be disposed of. The reserve hole is lined with plastic to protect the environment from any accidental leaks or seeps and if the location is an environmentally sensitive area, this waste will need to be disposed of off site.

The rig is what the huge machine is called that is used to drill for the oil. This rig will need to be set up but first, the location needs to be prepared for the rig and the main hole. To prepare for the rig, first a cellar must be dug, which is a rectangular hole in which most of the work will be done. Within this hole workers can go about their jobs and use this as a place for work tools and other equipment need along the way. Once the cellar is in place, the drilling team will then begin drilling the main hole. This usually requires a small drilling truck and not the entire rig. Even the main hole isn’t just one long hole down into the ground though. It starts with a hole that’s quite shallow and is lined with conductor pipe. Other holes will also be drilled around the cellar and around this shallow area so that equipment and other things can be stored. Once all of the holes have been drilled, the rig can then be set up.

The Rig

The oil rig is the grand structure that most of us associate with oil drilling. Whether we’ve seen the great machines hovering over the waves in the water or if we’ve seen them taking up massive amounts of land for one hole, these oil rigs are surely hard to miss. They have many different components, each of which is vital to the entire operation of oil drilling. The power system of an oil rig consists of large diesel engines that burn diesel engine in order to keep the drill functioning. Another power source that oil rigs generally use are generators, which will supply electrical power to the rig.

The mechanical system of the rig is powered by motors and the mechanical system consists mostly of the hoisting system and the turntable. The hoisting system is made up of a winch that has a large steel cable on it, a block and tackle pulley, and a receiving area where extra cable is kept. This hoisting system is used to pull up very heavy loads. The turntable is part of the drilling equipment and it helps to turn the engine. The crew will also need to use a lot of rotating equipment that’s used mainly for rotary drilling, the main type. This equipment consists of: a swivel, a kelly, a turntable, a drill string, and drill bits.

The swivel holds the drill string in place while drilling is in operation. This swivel allows the drill string to rotate as well as creates a pressure-tight seal around the hole that’s being drilled into. The kelly is simply a multi-sided pipe that usually has 4 or 6 sides and this is the piece of equipment that allows the drill string and the turntable to rotate. The turntable, also sometimes called the rotary table, is also used to deliver the rotating motion to the other parts of the machine and to keep it going. The drill string is just a long series of piping that fits around the drill pipe and puts pressure on the drill bits. The drill bits are simply the ends of the drill that are used to bust through the rock.

Casing is another piece of equipment that’s important to all oil rigs, regardless of the type of drilling that’s being done. This casing is just a piece of large pipe that is inserted to the hole. This is done for many reasons but it’s mainly done so that the hole does not collapse and so that mud can be mixed up and delivered to where it needs to go via the circulation system.

Drilling mud is a type of mud that’s made from clay, water, chemicals, and weighting materials. It comes from the mud and dirt that’s being created from the drill bit and it’s taken to other parts of the machine. There are many different components of an oil rig’s circulation system that’s used to deliver this specialized mud. The pumps first work to pull the mud out of the mud pits and send them to the drilling equipment. There are many pipes and hoses that all work together to get the mud from the pits to where it needs to go. The mud-return hole will also indicate that there is enough mud and it will send mud back to the mud pits. The shale shaker is just what it sounds like! It shakes out the rock and other debris from the mud and the shale slide will deliver anything that’s not mud to the reservoir hole. The mud pits are simply pits where mud is mixed together and delivered to the drilling pieces and a mud-mixing hopper is where the mud is mixed once more before being returned to the mud pits.

The derrick is what’s most noticeable about an oil rig and it’s because this is the large piece of equipment that stands very tall above the rest of the rig. This is what holds the actual drill during drilling and it’s extremely tall so that new pieces of pipe can always be added. And lastly, there’s the blowout preventer. Blowouts can happen when sudden rushes of air or oil come up and bubble out over top the surface. The preventer works to prevent this from happening and that’s done by placing high-pressure valves either under the rig on land or at the bottom of the sea floor. These valves relieve the pressure that drilling lines can sometimes create thereby, causing a blowout to occur.

Once the rig has been set up and drilling is ready to commence, a surface hole must first be dug. This hole will reach down to just above where the oil is in the land. This surface hole can be as shallow as just a few hundred feet deep, or it can be deep, reaching thousands of feet deep. The team will begin drilling this surface hole by placing the drill bit, collar, and drill pipe into the hole. Once the kelly and the turntable have been installed and are ready, drilling can then begin. As drilling continues the mud will start to flow through the pipe and out of the bit to squeeze the rock cuttings out of the hole. As the hole gets bigger and deeper, new sections of pipe will be added to accommodate it. Once the surface depth has been reached, the drill pipe, collar, and drill bit will all be removed.

The next step after creating the surface hole is to fit it with casing. Using a top plug and drill mud, the team will then create a cement slurry to pour around the casing and fill up the casing so that there is only cement between the casing and the outside of the hole. After the cement has been given proper time to harden, it will then be tested.

Extracting the Oil

In the movies it’s common to see men shouting and hugging each other as black oil shoots up from a hole and pours down on them. Realistically though, this is not how oil is extracted and it’s actually a sign that something serious, such as a blowout, has occurred. In order to avoid this from happening, the hole must be dug, tested, and then dug again. This occurs throughout the entire process and takes a lot of time. Once the team believes that they have gotten close enough to the reservoir rock, it is tested to determine if it is indeed reservoir rock. Once it has been determined that it is, the well will continue to be dug and completed until they reach oil.

Once oil has been reached, it will flow into the casing. This is done by lowering a perforating gun into the casing which will punch small holes into it so that the oil can move into the casing. Once the casing has been perforated, a small tube is then inserted into the casing so that oil and gas can move up the well. Outside of this tube is a device called a packer, which creates a seal around the tube. Lastly, the tubing is connected to another device called a Christmas tree at the top of the well. This Christmas tree has many valves on it that better regulates and controls the oil flowing out of the well. Now the oil is ready to be moved from the hole into the well.

This process happens when acid or proppants are dropped down into the casing to make the oil start flowing through the perforations in the casing. Once the oil starts flowing into the casing, the rig can be removed and pumps can be placed over the hole. The pumps are also large structures but they have one simple job – pump the oil from the hole into the well.

Because oil is a natural resource that comes from the ground, there is a limited supply of it. It’s estimated that we will have enough oil for the world’s needs for approximately 60-95 years but conserving the oil that we currently have is extremely important to make sure that we still have more for many, many years to come.

An Oil Rig

 

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