Shale Oil

With the conventional oil supply potentially decreasing, non-conventional oil supplies are being explored as some of the alternatives. Some of the sources of non-conventional oil include oil shale, tight oil, oil sands, tight oil, GTLs (gas-to-liquids) and biofuels. In this blog post I shall discuss shale oil in more detail.

Oil shale is an organic-rich fine-grained sedimentary rock that contains kerogen from which liquid hydrocarbons known as shale oil can be produced. Shale oil is known as a non-conventional oil as it has to be produced from the oil shale rock rather than directly being pumped out from beneath the Earth’s surface. Shale oil has the potential to be a substitute for crude oil but currently the costs of production of shale oil from oil shale are both not economically viable and environmentally unsustainable. Kerogen is an organic byproduct in oil formation or rather not full formed crude oil however it was formed more than 500 million years ago at the same time when crude oil formation occurred. Formations of kerogen can be graded and there is a great range of grades of the formations with some being up to 100 gallons of oil per ton. However such a high grade is rare and the approximately average grade of kerogen is 40 gallons a ton (Youngquist, 1998).

Kerogen forms in shallow marine embayments or in lakes, ponds and swamps. When pressure and temperature rises during organic decay of fossil fuels, the fossils are converted into insoluble mixture of extrememly large organic hydrocarbons, which are known as kerogen. As the process continues and the temperature increases molecules break off forming crude oil however kerogen deposits are left behind. This was discussed in my previous blog post on oil formation. The generation of crude oil from kerogen occurs naturally over geological timescales under the Earth’s surface however it requires a particular oil window which in turn requires specific high temperature of 70-160C. It may start to become obvious that in order to convert kerogen extracted from oil shale, high temperatures are necessary thus the environmental implications could be devastating. By extracting shale oil from oil shale we are basically trying to finish crude oil formation artificially in the matter of days or may be months compared to the natural processes that take millions of years. Environmental implications shall be discussed further in this post.

Oil shale itself occurs in many parts of the world including Canada, many European countries, China, Russia, South Africa, Australia, Brazil so on every continent (Youngquist, 1998). This means that potentially oil shale could be a solution to when recoverable crude oil resources become particularly scarse and Russia together with the Middle East have a monopolized market of very high oil prices as oil shale deposits are found everywhere so with appropriate technology, virtually every country could produce oil from oil shale.

Oil shale is not seen as an ideal alternative firstly due to geological factors- only a few beds are thick enough to mine it efficiently. Also economic costs due to geological reason as oil shale strata are very often found very deep below the surface and thus mining is very expensive. Furthermore recovery methods also add difficulties as once it is extracted, the rock must be blasted and crushed in a processing plant followed by heating to produce shale oil from kerogen at very high temperatures. High temperatures are not environmentally friendly plus require energy input thus costly. Water must also be supplied to the site as an additional hydrogen atom, which is extracted from water, has to be added to kerogen to convert it into shale oil. This means that a water source needs to be nearby the plant with a plentiful water supply or water needs to be transported to the plant, which yet again adds further costs and environmental implications. Finally the amount of waste material from this process of conversion is very large and thus would require a disposal site and needs stabilization to it does not contaminate the surrounding as shale has undesirable mineral compounds, which rain leaches. (Youngquist, 1998).  This creates another negative environmental impact and further increases costs yet again. Thus it becomes obvious as to why shale oil is not widely used.

However the original untreated kerogen shale oil could be used to burn as boiler fuel. Thus some countries actually use shale oil for electrical generation such as Estonia, where in 2005 95% of electricity is generated using shale oil (Estonian Energy in Figures, 2007). Other countries that also use shale oil include China, Brazil, Germany and Russia. Figure 1 below shows production of oil shale of several countries that utilize it and hence we assume that they do use it for something if money is being invested for its extraction.

Figure 1.

Source: USGS, 2005. Production of oil shale in millions of metric tons, 1880-2010.

Another advantage of oil shale is some of the byproducts it produces such as uranium, vanadium, zinc, alumina, phosphate, sodium carbonate minerals, ammonium sulfate and sulfur (USGS, 2005). The spent shale could also be used for making cement and this is undertaken by countries such as Germany and China.

Despite all the costs and environmental implications, shale oil has the potential to become a realistic substitute for crude oil we use now especially if the costs of its production are lowered. According to the US Department of Energy, it has been nearly two decade since any meaningful research has been done concerning shale oil (USDepartment of Energy, 2014) and the world has seen a lot of new technologies since so perhaps it is time to undertake some new research into the field and re consider it as one of the methods to obtain energy for our civilization.