Core - Samples of subsurface rocks taken as a well is being drilled. The core allows geologists to examine the strata in proper sequence and thickness. Cracking - The process of breaking down the larger, heavier and more complex hydrocarbon molecules into simpler and lighter molecules, thus increasing the gasoline yield from crude oil. Cracking is done by application of heat and pressure, and in modern time the use of a catalytic agent. Crude oil - Liquid petroleum as it comes out of the ground.
Sour crude is high in sulfur content.
Sweet crude is low in sulfur and therefore often more valuable. Crude oil equivalent - A measure of energy content that converts units of different kinds of energy into the energy equivalent of barrels of oil. Cuttings - Chips and small rock fragments brought to the surface by the flow of drilling mud as it is circulated and examined by geologists for oil content.