You observe that oil floats on water. You do experiments which demonstrate that oil and water can move through sandstone but not shale. Isotopic and other compositional characteristics of oil suggest to you that it originates from an organic rich limestone which you have identified beneath the surface from drill-core samples taken in your region of study. You have observed that oil is often found in sandstone where the oil is kept from escaping upward to the Earth’s surface by a layer of shale.
Based on these observations, you formulate a theory for oil formation: small amounts of organic material changes to become tiny drops of oil. These drops of oil float upward through water-saturated sandstone, continuing to coalesce with other drops of oil until they reach a spot where they can no longer migrate upwards. Here, they accumulate.
Given this model, you are most likely to find oil at A, B, C, D, or E?
Second Puzzle:
Consider the cross-sectional view below. Where (at the surface) would you drill for oil?
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