3. Bedrock hydrocarbons

3.1 Bedrock: a highly heterogeneous medium

The definition of a bedrock differs according to the scale at which it is described. On a small scale (millimetric, centimetric or even metric), bedrock is the level or levels containing the organic matter which, through transformation, produces hydrocarbons. On a larger scale (metric or decametric, and sometimes even hectometric), bedrock is considered to be all the levels containing organic matter that form a distinct sedimentary unit, including banks that do not contain organic matter (figure 9 )