Tight oil in the context of Directional drilling

Oil shale is an organic-rich fine-grained sedimentary rock containing kerogen (a solid mixture of organic chemical compounds) from which liquid hydrocarbons can be produced. In addition to kerogen, general composition of oil shales constitutes inorganic substance and bitumens. Based on their deposition environment, oil shales are classified as marine, lacustrine and terrestrial oil shales. Oil shales differ from oil-bearing shales, shale deposits that contain petroleum (tight oil) that is sometimes produced from drilled wells. Examples of oil-bearing shales are the Bakken Formation, Pierre Shale, Niobrara Formation, and Eagle Ford Formation. Accordingly, shale oil produced from oil shale should not be confused with tight oil, which is also frequently called shale oil.

A 2016 estimate of global deposits set the total world resources of oil shale equivalent of 6.05 trillion barrels (962 billion cubic metres) of oil in place. Oil shale has gained attention as a potential abundant source of oil. However, the various attempts to develop oil shale deposits have had limited success. Only Estonia and China have well-established oil shale industries, and Brazil, Germany, and Russia utilize oil shale to some extent.

The 2010s oil glut was a significant surplus of crude oil that started in 2014–2015 and accelerated in 2016, with multiple causes. They include general oversupply as unconventional US and Canadian tight oil (shale oil) production reached critical volumes, geopolitical rivalries among oil-producing nations, falling demand across commodities markets due to the deceleration of the Chinese economy, and possible restraint of long-term demand as environmental policy promotes fuel efficiency and steers an increasing share of energy consumption away from fossil fuels.

The world price of oil was above US$125 per barrel ($790/m) in 2012, and remained relatively strong above $100 until September 2014, after which it entered a sharp downward spiral, falling below $30 by January 2016. OPEC production was poised to rise further with the lifting of international sanctions against Iran, at a time when markets already appeared to be oversupplied by at least 2 million barrels (320,000 m) per day.

The Vaca Muerta Formation, commonly known as Vaca Muerta (Spanish for dead cow), is a geologic formation of Late Jurassic to Early Cretaceous age, located in the Neuquén Basin in northern Patagonia, Argentina. It is well known as the host rock for major deposits of shale oil and shale gas.

The large oil discovery in the Vaca Muerta Formation was made in 2010 by the former Repsol-YPF. The total proven reserves are around 927 million barrels (147.4×10^ m), and as of 2014 YPF's production alone was nearly 45,000 barrels per day (7,200 m/d). In February 2012, Repsol YPF SA raised its estimate of oil reserves to 22.5 billion barrels (3.58×10 m). The US EIA estimates total recoverable hydrocarbons from this Vaca Muerta Formation to be 16.2 billion barrels (2.58×10 m) of oil and 308 trillion cubic feet (8.7×10^ m) of natural gas, more than even the Neuquén Basin's hydrocarbon-rich Middle Jurassic Los Molles Formation holds.As of 2017, there were almost 500 fracking wells, one of the most fracked sites outside North America, and as of October 2024, there were over 1500 fracking wells.

Shale oil is an unconventional oil produced from oil shale rock fragments by pyrolysis, hydrogenation, or thermal dissolution. These processes convert the organic matter within the rock (kerogen) into synthetic oil and gas. The resulting oil can be used immediately as a fuel or upgraded to meet refinery feedstock specifications by adding hydrogen and removing impurities such as sulfur and nitrogen. The refined products can be used for the same purposes as those derived from crude oil.

The term "shale oil" is also used for crude oil produced from shales of other unconventional, very low permeability formations. However, to reduce the risk of confusion of shale oil produced from oil shale with crude oil in oil-bearing shales, the term "tight oil" is preferred for the latter. The International Energy Agency recommends to use the term "light tight oil" and World Energy Resources 2013 report by the World Energy Council uses the term "tight oil" for crude oil in oil-bearing shales.