Oil Shale

Definition - What does Oil Shale mean?

Oil Shale is a sedimentary rock that has naturally occurring mixture of organic chemical compounds called as “Kerogen” which when heated yields crude oil. Many people get confused by the terms Oil Shale and Shale Oil; however, both are completely different. Oil Shale is a sedimentary rock that contains possibilities of storing rich amount of hydrocarbons in it. They can be treated as the immature source rocks and hydrocarbon reservoirs called as shale reservoirs. Whereas Shale Oil is the crude oil produced from these shale reservoirs.

Petropedia explains Oil Shale

Oil Shale deposits are found across the globe in large quantities; however, so to extract crude oil and natural gas at a commercial level from such shale reservoirs, an E&P organization has to have expertise and technology advancements in the field of hydraulic fracturing and horizontal drilling.

Oil Shale is considered to be the immature source rock that consists of Kerogen which is the mixture of organic chemical compounds that actually form a portion of the sedimentary rock. Few kerogens release natural gas or crude oil when heated. High concentrations of kerogen in a rock such as shale form a Source Rock.

There are three types of Source Rock:

  • Type 1 Source Rock- During deep burial when they are subjected to thermal stress they generate waxy crude oil. The algae which remains in deep lakes (in anoxic conditions) is the major source of formation of type 1 Source Rock.
  • Type 2 Source Rock- During thermal crack they produce both oil and gas. In the marine environment, under the anoxic condition, the deposition and preservation of bacterial remains form these types of rocks.
  • Type 3 Source Rock- They are formed by decomposition of terrestrial plant material.
Shale oil produced from Oil Shale is known as unconventional crude oil and the gas generated along with the shale oil is called as Shale Gas.

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