In this paper, we describe the various morphologies of hydrocarbon residue found in the Miocene Monterey Formation in California. Scanning electron microscope photomicrographs clearly show various shapes of hydrocarbon droplets in microchannels in the Monterey Formation and hence provide insight not only into the shape of hydrocarbon droplets during migration, but also about the migration pathways themselves. The small (5-10 micrometers) diameter droplets are observed to have various shapes that include spherical droplets, amalgamated droplets, sausage-shaped droplets, and elongate rod-shaped droplets. Observations suggest that hydrocarbon droplets move through the rock matrix into microchannels where they coalesce into larger droplets and then move into larger fractures. Different morphologies are simply a result of amalgamation of simple droplets during migration.

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