Lecture 4: Migration from source to reservoir
We learned that oil results from kerogen, which in turn comes from organic matter. This oil is then present in source rocks. The source rocks get over-pressured and oil moves from the source rocks to the reservoir rocks. Reservoir rocks can be imaged with seismic by geophysicists, and this is also where human get the oil from. Here it is explained why migration happens, and some evidence of seepages which prove migration is given.
Primary migration is the migration from the source rock to ‘something else’, which is badly understood in science. The contradiction on pore sizes in source rocks and the sizes of the migrating molecules is explained. Moreover four possible primary migration mechanisms are discussed.
Secondary migration is the migration from ‘something else’ to the reservoir rock. This is much better understood than primary migration. Buoyancy resulting from density differences is the driving force. Some migration pathways are presented, and seals which finally stop the migration are explained.
The lecture is ended with a summary.
The above recorded lecture covers the following topics:
- Why migration? (In Petroleum Geoscience: paragraph 2.8 ‘Seepage of petroleum’)
- Primary migration
- Secondary migration
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Based on a work at https://ocw.tudelft.nl/courses/petroleum-geology/.