Oil and Gas Industry Sectors: Downstream Sector


This article is the final entry in a series of MXD Process blogs outlining the three primary sectors of the oil and gas industry- upstream, midstream, and downstream. The upstream arm of the business includes finding oil and natural gas deposits, evaluating the quality of the deposit, and drilling through the layers of rock to bring the substance back up to the surface. After the oil and/or gas is acquired, it moves into the midstream phase; which handles the transportation, storage, and wholesale marketing of crude oil or raw natural gas. Finally, the downstream industry refines and treats the oil or gas into its final product. Refining oil is a complex procedure that extracts the proper components and filters out the other elements that aren’t useful or desirable for the product’s intended purpose. The crude oil that enters a refinery can be concocted into any number of different fuels and sources of energy, and the chemical composition of the oil changes greatly from start to finish.

Distinguishing Crude Oil Qualities

Crude oil is usually a thick liquid with a dark brown or black color. There are two essential qualities of the crude oil that determine its price. One of these is the “specific gravity” of the oil. This is defined by the oil’s thickness and weight. Depending on these factors, the oil will be classified as either heavy, intermediate, or light. Heavier oils require more work to refine than the lighter ones. The other key characteristic is an oil’s sulphur content. Some refer to oil with a lower sulphur content as “sweet” oil, while others that contain greater amounts of oil are described as  “sour”. Sulphur is a harmful substance to fuels and other refined oil products, so sour oils will be more difficult to refine than sweeter ones. Essentially, oils with a lower density and sulphur content are the ones with the greatest quality and highest price tag.

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How Oil Refineries Work

As one article puts it, an oil refinery is basically like a large machine that alters the density of the crude oil. Different products demand different densities, so there isn’t just one universal weight sought by all types of manufacturers. According to recently compiled statistics, the United States produces 15.4 million barrels of petroleum each day on average- a barrel contains 42 gallons, which adds up to 647 million gallons of petrol manufactured per day. Within the refinery, there are three stages through which the crude oil is formed into the desired product. First comes the distillation phase; in which heat is applied to the oil in order to separate the petrol. It begins in the crude tower (also known as the fractioning tower) where a furnace heats the oil, dividing the different elements of the oil from one another depending on their specific boiling point. Substances like gasoline are light, so they rise to the top of the tower. Heavier things like asphalt boil at a higher temperature and sink to the bottom. Around the time that the temperature hits the 730-850 degrees Fahrenheit range, the heavier components will start to break, or crack; and seems proper that this phase is known as “cracking”. The heavier materials are harmful to the structure of the crude tower, so they are transitioned to another section called the vacuum tower. As one might conclude, there is a vacuum operating here; and the appropriate amount of pressure is applied to cool the matter and break it down.

The conversion stage is the next step in the process of refining oil. Just as the name suggests, this is the phase in which the materials produced by the distillation phase are transformed into products like gasoline and other fuels. Chemicals are mixed in, catalysts are added to improve the efficiency of the item and expedite the manufacturing process, and heat and pressure are applied again. The coker section works with the heavier components that came from the vacuum tower, using heat and pressure in order to separate the substances into a lighter and useable form. In the hydrocracker, the medium-weight elements derived from crude oil are processed by using hydrogen and other catalysts to break the substances from one another. A machine called the fluidized catalytic cracker applies chemicals that fractures larger molecules into smaller pieces that are more useful. Some molecules are too light to be suitable for gasoline; so these are put through a process called alkylation that combines the lighter molecules with one another and gives them the necessary weight to be used in fuel.

After a long journey through the refinery, the different types of matter produced by the distillation and conversion phases can be blended and mixed; and the end result of this is the formation of petrol and other products. Mixer Direct is proud to design and manufacture explosion-proof mixing equipment for the petrochemical industry. Finally, the oil that was once hundreds of feet underground has been purified and perfected into the products that power the world. It also important to note that although it can take as little as a week for the oil to be drilled, transported, and refined, there are different variables that can change the timeline. Refineries receive massive quantities of oil every day, so it might take a few days to work through the backlog of crude oil. All that is left is distribution. Fuel can be to gas stations that are owned by the same company that operates the refinery, but is also sold to smaller companies that have a contract with a manufacturer to sell their product exclusively. Natural gas is refined and purified in a different facility and uses different ways of producing their product, but the procedure is effectively quite similar to the process by which crude oil is refined. At the most basic and fundamental level; the refining process and other related fields seek to break up the crude oil or raw natural gas into different components, extracting the proper substances and removing the ones that aren’t desirable for the product’s purpose.







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