Explanation of Categories and Peak Oil

Conventional vs. Unconventional: Gas and Oil

Conventional and unconventional are the two main types of categories for oil and gas. They both differ from each other in many ways within the terms of oil and gas.

The geology of conventional and unconventional gas and oil

Conventional Gas

Conventional gas and oil flow naturally through rocks, which is easy to collect. Conventional gas is “… gas that is trapped in structures in the rock...caused by folding and/or faulting of sedimentary layers.” (1) Conventional gas comes from an organic rock that has compressed marine or terrestrial organic debris. This debris is heated by the pressure put on it, which creates hydrocarbons. The hydrocarbons move to the pores in permeable rocks seeking lower levels of pressure, and thereby become available for extraction (1). The gas moving toward the well is referred to as a "natural flow". (6) Conventional gas is considered a “natural gas” because of how easy it is to be pumped to the surface. (2) B

Unconventional Gas

Unlike conventional gas, unconventional gas is not as easy to extract. Unconventional gas is the gas that is trapped inside the impermeable rock that does not migrate out. (1) This gas is impossible to obtain using normal methods due to the low permeability of the rock where there are poorly connected pores. (2) To retrieve the gas, one must drill horizontally into the well, stimulating the pores to connect and allowing the gas to flow into a well bore - a hole to aid the recovery of natural resources. (1,6)

Unconventional gas comes in three forms: shale gas, tight gas, and coal seam gas. The most common is shale gas, which is gas that is trapped in a source rock such as a fine-grained rock or an organic-rich rock. (1,2) Tight gas is found in sandstones and limestone. (2) Coal seam gas is methane gas found in coal seams that are being held by water pressure. Coal seam gas is usually closer to the surface than the other two unconventional gasses. In order to extract coal seam gas, you must first remove the water applying pressure to the gas. (1)

Conventional Oil

In today’s culture, oil is a global commodity. Throughout the years, oil production has peaked and prices continue to rise. Oil, too, comes in the two categories of conventional and unconventional. Conventional oil comes in liquid form and is extracted from natural gas production. Conventional oil is easy to extract because of the way it raises to a peak underground. (5) Crude oil, a mixture of natural hydrocarbons and impurities, is classified as a conventional oil. (3)

Unconventional Oil

Unconventional oil comes in lower quality forms that are not as easy to extract. This type of oil is expensive and slow to produce. Although it is harder to extract, unconventional has a wider variety of liquid sources. Some examples are shale oil, heavy oil and tar sands. These two categories of oil are not always fixed though. (3)

Because of advancements in technology, some unconventional oils can become conventional oils as they are easier to extract than before. Both conventional and unconventional oil and gas are found all over the world, with the bulk of the oil demand coming from china. (3)

chart of conventional vs unconventional oil

(This shows the yearly average of millions of barrels per day of conventional and unconventional liquid oils)

Peak Oil

The Oxford Dictionary states that peak oil is “the hypothetical point in time when the global production of oil reaches its maximum rate, after which production will gradually decline.” Over time, extracting oil becomes harder, which in turn raises costs and lowers the production. The term usually applies on a global scale, but can be applicable within countries and towns. Although the demands for oil and gas grow higher and higher each year, production is falling. A lot of pressure to produce large amounts of oil at low cost comes with extracting oil, expediting peak oil.

some possible future oil production scenarios


  1. http://www.nt.gov.au/d/Minerals_Energy/index.cfm?header=What%20is%20the%20difference%20between%20Conventional%20and%20Unconventional%20Gas?#
    1. http://www.aer.ca/about-aer/spotlight-on/unconventional-regulatory-framework/what-is-unconventional-oil-and-gas
  2. http://www.iea.org/aboutus/faqs/oil/
  3. https://people.hofstra.edu/geotrans/eng/ch5en/appl5en/oilgasreservestypes.html
  4. http://benergypartners.com/Facts_About_Crude_Oil.html
  5. http://www.eon.com/content/dam/eon-com/en/downloads/ir/20100205_Unconventional_gas_in_Europe.pdf

Elizabeth Jemo

Last Updated: May 10, 2017