Page 33 - Hydrocarbon
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20 Hydrocarbon Accumulations
fault
(impermeable)
oil/water
contact (OWC)
migration
hydrocarbon route
accumulation seal reservoir
in the
rock
reservoir rock
top of maturity
source
rock
Figure 3.1 Generation, migration and trapping of hydrocarbons.
Figure 3.2 Global plate con¢guration.
3.1.3. Source rocks
About 90% of all the organic matter found in sediments is contained in shales.For
the deposition of these source rocks several conditions have to be met: organic
material must be abundant and a lack of oxygen must prevent the decomposition of
the organic remains. Continuous sedimentation over a long period of time causes
burial of the organic matter. Depending on the area of deposition, organic matter
may consist predominantly of plant remnants or of phytoplankton. These are marine
