[aruanan]

Oil doesn't migrate through "streams" or collect in "ponds." Maybe they dumbed this down for the general public, but it's grossly misleading and casts doubts on the seriousness of this study.

Actually petroleum does flow in streams and collect under regions of relatively more impermeable overburden. This would make a pond or pool of oil, albeit upsidedown. Water flows because of gravity. Petroleum flows because of pressure gradients. Water collects in places out of which it cannot flow and in which the porosity is overcome by the inflow. Petroleum collects under formations the porosity of which is insufficient to handle the flow. In places where such overburden doesn't exist, the oil and accompanying methane flows right out of the ground. In some places the porosity is such that the petroleum is blocked from reaching the surface but not the methane, resulting in people lawns or fields catching on fire.

[lawnguy]

Actually petroleum does flow in streams and collect under regions of relatively more impermeable overburden. This would make a pond or pool of oil, albeit upsidedown. Water flows because of gravity. Petroleum flows because of pressure gradients. Water collects in places out of which it cannot flow and in which the porosity is overcome by the inflow. Petroleum collects under formations the porosity of which is insufficient to handle the flow. In places where such overburden doesn't exist, the oil and accompanying methane flows right out of the ground. In some places the porosity is such that the petroleum is blocked from reaching the surface but not the methane, resulting in people lawns or fields catching on fire.

Well of course, everyone knows that :) (Hermione Grainger alert)!!