Close your eyes and imagine a tar pit. What comes to mind? Many of us picture a black, molasses-like lake with preserved saber-toothed tigers.
These naturally occurring asphalt seeps-turned-tourist traps have formed for over thousands of years as crude oil from underground petroleum deposits slowly seeped to the surface through fissures and faults. They're of great interest to scientist, geology lovers and school-aged children alike.
Then there are the industrial tar pits, better known as oil sands, tar sands and bituminous sands. And, to no one's surprise, they're of great interest to energy companies. But just like the name suggests, this black gold doesn't gush from a geyser; it's actually in the sand itself.
Oil sands are a type of unconventional petroleum deposit. They consist of a mixture of roughly 90 percent sand, water and clay and around 10 percent bitumen — a heavy, viscous form of petroleum.
The dark, sticky sands look similar to topsoil, are viscous when warm and freeze as solid as concrete in cold temperatures.
But calling them "tar" pits or "tar" sands is misleading — the thick, black substance isn't tar, but rather bitumen, which is composed of a mixture of hydrocarbons. It's petroleum that exists naturally in a solid or semisolid state.
But unlike conventional oil or petroleum, which is in natural liquid form, bitumen needs to be separated from the sand before it can be used.
Are There Oil Sands in the United States?
While there are oil sand deposits in the U.S., they are not as extensive or well-known as the major oil sands deposits in Canada, particularly in the province of Alberta. (The Athabasca oil sands in Alberta are one of the most significant oil sands deposits globally.)
In the U.S., the most significant oil sands deposits are found in Utah, particularly in the eastern part of the state, in the Uinta Basin. The oil sands in Utah contain bitumen, similar to the Canadian oil sands, and they have been the subject of some commercial oil production and development efforts.
However, Canada's oil sands industry is much larger than the one in the U.S., where various challenges — including economic factors, environmental concerns and regulatory issue — impact expansion.
On the other hand, the development of unconventional oil resources, such as shale oil and tight oil, has gained more prominence in the U.S. energy landscape due to advancements in hydraulic fracturing (fracking) technology, which has led to a significant increase in domestic oil production.
Oil Sands Production
Extracting oil from oil sands is a complex and energy-intensive process. The primary method used is called "in-situ" extraction, which involves injecting steam and solvents into the ground to heat the bitumen, making it easier to extract.
Another method, known as open-pit mining, is used when the oil sands are located close to the surface. In this case, large equipment is used to remove the overlying material and access the oil sands.
Once the bitumen is extracted, it goes through various processes to separate the bitumen from the sand, water and other impurities. The resulting bitumen can then be upgraded into synthetic crude oil through additional refining processes.
Oil sands have been a significant source of oil production, but they are also a subject of environmental concern due to the energy-intensive extraction process and the potential for habitat disruption, water contamination and greenhouse gas emissions associated with their extraction and processing.
Carbon dioxide emissions are a major concern. To produce one barrel of synthetic crude oil from oil sands, approximately 295 pounds (134 kilograms) of carbon dioxide are emitted into the atmosphere. To put that into perspective, the U.S. alone consumed approximately 19.89 million barrels of petroleum per day in 2021.
Efforts have been made to develop more environmentally sustainable methods for oil sands operations and to mitigate the environmental impacts of this resource.
The World's Petrol Supply
More than 2 trillion barrels of the world's petroleum lies in oil sands, though most will never be dug and processed because it's too deep [source: Strauss Center]. Oil sands are found worldwide, from Canada to Venezuela and, as you might imagine, in the Middle East.
However, Canada holds the third-largest crude oil reserves globally, trailing behind Saudi Arabia and Venezuela.
In total, Canada possesses a substantial reserve of 171 billion barrels of oil, with the majority — roughly 165 billion barrels — classified as oil sands reserves. This accounts for approximately 10 percent of the world's total crude oil reserves. It's estimated that Alberta may have as much as 161 billion barrels of recoverable oil, as well as exponentially more that can't be tapped until the development of new technologies for retrieval.
So how do you go about straining oil from sand? Next, we'll look at how bitumen is extracted, processed and transformed into some surprising products you use every day.
Squeezing Oil From Sand
Most bitumen is refined for use in gasoline, jet fuel and home-heating oil, but petroleum also makes its way into more than 3,000 products you might not expect: ballpoint pens, lipstick, flying discs, even T-shirts. Before it can be used for anything, though, it first needs to be extracted from the sand and then processed.
There are a few different ways to mine bitumen. Shallow reserves, which make up about 20 percent of oil sands, are recovered through surface mining, which is mining through open pits [source: Energy Education]. The process of surface mining differs a bit from company to company but generally includes conditioning, separation and froth treatment.
Conditioning starts the process of separating sand and bitumen and breaks apart any large pieces of oil sands. The oil sand is mixed with warm water — called a slurry — and transported by pipeline to an extraction facility. Here, the slurry is put through a separation process where sand sinks to the bottom and impure bitumen froth rises to the top.
The froth is steamed, de-aerated and diluted with naphtha (a flammable hydrocarbon mixture) to remove any lingering solids and promote flow. Diluted bitumen is processed in inclined plate settlers (IPS) and centrifuges — both methods further clean the bitumen.
And after all that, extraction is finished.
Deeply deposited bitumen reserves aren't reachable through open-pit digging and are recovered using in-situ techniques, like steam-assisted gravity drainage (SAG-D). This method involves injecting steam into wells within the oil sand. The intense temperature and pressure separate the bitumen and water from the sand, and the bitumen — rendered soft with the heat — surfaces while the sand stays put.
Other in-situ techniques include toe to heel air injection (THAI), a relatively new process that combines both vertical and horizontal air injections into underground wells, and a vapor extraction process (VAPEX), similar to SAG-D — but with solvent injections instead of steam.
Upgrading bitumen, which is a heavy, thick and highly viscous form of petroleum, involves a refining process to convert it into lighter and more valuable products like synthetic crude oil. This process is typically carried out in specialized facilities such as bitumen upgraders.
Preparation: Bitumen is usually mixed with a diluent, such as natural gas condensate or naphtha, to reduce its viscosity and enable easier transport and processing. This mixture is often referred to as "diluted bitumen" or "dilbit."
Heating: The diluted bitumen is heated to break down the heavy molecules and reduce its viscosity. This can be done in a coker, where the feedstock is thermally cracked under high temperatures.
Distillation: The heated bitumen is then distilled to separate it into different fractions based on boiling points. Lighter components like gases, naphtha and diesel are separated from the heavier ones.
Hydroprocessing: The remaining heavy fractions are subjected to hydroprocessing, where hydrogen is added under high pressure and temperature conditions. This process helps remove impurities like sulfur, nitrogen and metals, while also breaking down heavy hydrocarbons into lighter ones.
Fractionation: After hydroprocessing, the upgraded bitumen is further separated into different fractions, which can include synthetic crude oil, diesel and other valuable products.
Additional treatments: Depending on the desired end products, additional treatments such as desulfurization, de-asphalting and hydrogenation may be employed to improve the quality and value of the products.
Product storage and transportation: The upgraded products are then stored and transported to various markets and refineries for further processing or distribution.
Recovering bitumen and transforming it into synthetic crude oil is dirty work, literally and environmentally. The mining and processing needed to produce a single barrel of upgraded synthetic crude oil uses between 2 to 4 barrels of water, an amount of natural gas equal to what's needed to heat a home for four days.
Additionally, oil-sand extraction and processing operations were responsible for 81 million metric tons of Canada's greenhouse gas emissions in 2022 [source: SP Global]. Mining also puts rivers and forests (including Canada's boreal forest, one of the world's largest intact ecosystems) at risk.
As if that's not enough to worry about, two Canadian toxic dumps for tailings, the heavy metal–rich waste created during the separation process, can be seen from space [source: National Observer].
Canada is trying to deal with the environmental ramifications of rendering oil sands by requiring oil companies to refill old pit mines and plant trees. Efforts to lower fossil-fuel dependency, however, would lessen the need for energy-intensive, low-yield mining and minimize the blights that result from extraction.
This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.
Frequently Answered Questions
How oil sands are formed?
Oil sands are formed from the remains of organisms that lived in marine environments and were buried under sediment. Over time, the organic matter was converted into petroleum.