What are unconventional resources?

Shale gas

Natural gas produced from shale reservoirs is known as shale gas.

Shale is one of the earth's most common sedimentary rocks. It is a fine-grain rock composed mainly of clay flakes and tiny fragments of other minerals. Shale can be a gas reservoir, but only formations with certain characteristics are viable for exploration.

Shale oil

There are two meanings of the term “shale oil.”

The first meaning of “shale oil” is tight oil contained in petroleum-bearing formations of low permeability, often shale or tight sandstone. Production from tight oil formations requires the same hydraulic fracturing process, and often uses the same horizontal well technology used in the production of shale gas.

The other meaning of "oil shale" refers to synthetic crude oil derived from oil shale rock fragments rich in kerogen. Kerogen oil is an abundant resource containing organic-rich matter that is the source material for petroleum. This form of oil shale is produced by pyrolysis, hydrogenation or thermal dissolution. These processes convert the organic matter within the rock (kerogen) into synthetic oil and gas.

Coal bed methane

Coal bed methane (CBM) is another form of unconventional gas, formed by the decomposition of organic material found in coal that is too deep or too poor quality for commercial mining.

Although occasionally found at shallow depths, CBM is often buried 1,000 to 2,000 meters underground. It is most often produced using vertical wells, although horizontal drilling is becoming increasingly common in some areas.

To extract the gas, water is pumped out of the coal seam to reduce the pressure that holds gas in the seam. CBM is not very soluble in water and easily separates from the coal seam as pressure decreases, allowing it to be piped out of the well separately from the water. The water removed during the depressurization process is then re-injected into the subsurface.