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.