In
petroleum geology,
source rock refers to rocks from which
hydrocarbons have been generated or are capable of being generated. They form one of the necessary elements of a working
petroleum system. They are organic-rich sediments that may have been deposited in a variety of
environments including deep water marine,
lacustrine and
deltaic.
Oil shale can be regarded as an organic-rich but immature source rock from which little or no oil has been generated and expelled. Subsurface source rock mapping methodologies make it possible to identify likely zones of petroleum occurrence in sedimentary basins as well as
shale gas plays.