Shale oil extraction

Shale oil extraction is a specialized industrial process used to produce unconventional oil. This process targets a substance called kerogen, which is found within oil shale rocks. Kerogen is a solid organic material that can be converted into liquid shale oil. This conversion is vital for energy production when traditional crude oil is scarce. It also helps nations improve their energy security by using local resources.

To turn kerogen into oil, scientists use several chemical methods. The most common method is pyrolysis, also known as retorting. In pyrolysis, the shale is heated in an environment without any oxygen. This heat causes the kerogen to decompose into two different substances. The first is shale oil vapor, which can be condensed into liquid. The second is a non-condensable oil shale gas. Other methods include hydrogenation, which uses hydrogen, and thermal dissolution, which uses solvents.

Extraction technologies are categorized by where the work happens. Ex situ processing occurs above ground. In this method, the oil shale is mined from the earth and moved to a facility. The rocks are often crushed into small pieces to increase their surface area. This helps the heat work more efficiently. In contrast, in situ processing happens in place. Heat is applied to the shale while it remains deep underground. The resulting oil is then pulled up through wells, just like conventional crude oil.

Different machines and methods are used to transfer heat to the shale. Some methods use internal combustion, where the heat comes from burning materials inside the retort. Others use indirect heating, where a heat source is kept outside the retort. Heat can also be delivered through gas, solid materials, or even radio waves and microwaves. For example, vertical retorts often use gas to carry heat to the shale. Horizontal retorts might use rotating drums to move the material through the process.

History shows that humans have studied this process for centuries. The Assyrian physician Masawaih al-Mardini wrote about extracting oil from bituminous shale in the 10th century. Much later, in 1684, the English Crown granted the first formal patent for this extraction. Modern industrial methods began in the 19th century. Alexander Selligue invented a process in France in 1838. James Young later improved these techniques in Scotland. By the late 1800s, extraction plants were operating in Australia, Brazil, Canada, and the United States.

The industry has seen many ups and downs due to global oil prices. In the mid-20th century, the discovery of large conventional oil reserves caused the industry to shrink. However, high petroleum prices in the early 21st century sparked new interest. As of 2010, major industries were operating in Estonia, Brazil, and China. In 2008, these three locations produced approximately 930,000 tonnes of shale oil. This amount equaled about 17,700 barrels per day.

While shale oil provides energy, the process has notable side effects. Pyrolysis produces a solid residue known as spent shale. This residue contains minerals and a carbon residue called char. If the char is burned off, it leaves behind oil shale ash. Both spent shale and ash can be reused to make cement or bricks. However, critics raise concerns about environmental management. They focus on issues like air pollution, waste disposal, and the extensive use of water.