Geology is the science that deals with the structure and history of the earth and its life forms, especially as recorded in the rocks.  This science is essential to the petroleum industry, for it is used to predict where oil accumulations may occur.  Petroleum geology involves those aspects of geology associated in the discovery and production of petroleum.  Petroleum geology involves all aspects of geology and other related disciplines such as geophysics, paleontology, geochemistry, and other engineering fields.

The first principle is that the present is key to the past; i.e., the processes acting on the earth today are the same as those that operated in the past.