HOW AND WHERE DID OIL COLLECT IN ROCKS?
The hydrocarbons, or oil and gas droplets, were buried by countless tons of sediments that accumulated on ancient sea bottoms. As these sediments hardened into sedimentary rocks, the hydrocarbons were squeezed into whatever empty spaces were available in the rocks. As the layers of sedimentary rocks later became folded and broken, oil and gas droplets and salt water moved upward through any interconnecting open spaces. Some droplets escaped to the surface as “seeps,” but many were trapped when they came up against a nonporous barrier. Gas, being lighter than either oil or water, was trapped at the top, and oil was stopped in the middle, above the salt water. An accumulation of this kind is termed a “pool” or a “field.”