John Marston

About this Talk

John Marston provides an overview of where the amazing fossil fuels come from and how they were deposited.

He introduces the concept of the Magic 5, not the Los Angeles Lakers, but the five main events that must occur for oil to trapped within our planet.

1. Source Rock. John introduced the concept of the process of capturing the suns energy through photosynthesis and building up of the resulting material (kerogen) to form a Source Rock. He outlined that although the process of depositing source rocks continues today, much of the source rock that generated the oil being consumed today was deposited during the Mesozoic, over 100 million years ago, during a period when the Carbon Dioxide content of the atmosphere was over 1000 ppm. The reduction of the Carbon Dioxide content in the atmosphere was in part due to absorption by organic life and subsequent deposition of those Carbon Dioxide molecules into source rocks.

2. Maturation. Over time the source rock is buried by later sediments and increase in temperature, the source rock begins to break down. This thermal degradation or cracking releases shorter chain hydrocarbons from the original large and complex molecules found in the kerogen.

The hydrocarbons generated from the source rock are expelled, along with other pore fluids, due to the continuing effects of compaction and start moving upwards towards the surface, a process known as migration.

3. Reservoir Rock. As the oil migrates from the source rock it moves through a permeable rock known as a reservoir rock.

4. Trap. If the reservoir rock outcrops at the surface and the oil can migrate through the rock it will seep out at the surface. If its route is blocked it will become trapped below the surface.

5. Timing. If all the above steps occur in the right order then oil will become trapped in geological structures below the ground.

Wilmington Oil Field

John then introduced the local oil field, the Wilmington Oil Field, that is located very close to Manhattan Beach, California. The field is the third largest in the USA, after Prudoe Bay and the East Texas oil fields. It was discovered in 1930 and is estimated to have ultimate recoverable reserves of around 3 billion barrels. Of this some 400 million barrels has yet to be recovered. The red lines on the map below are freeways.

About John Marston

John is a long time Manhattan Beach resident and worked as a Petroleum Engineer from 1983 to 2000.