As is the case in most fields of science, a geologist can choose to specialize in a wide variety of categories, including petroleum geology. Professionals involved in the field of petroleum geology play a critical role in the identification of natural oil and gas deposits under the earth, invaluable resources for humans and organizations all over the world. The primary job a petroleum geologist is tasked with involves reading signs both above and below the earth's surface that indicate oil and gas reserves.
For example, petroleum geologists are trained in the identification of geological folds. A fold occurs when pressure from faults beneath the surface cause one or more flat earth surfaces to bend and curve. This pressure can often be attributed to oil or gas deposits. Petroleum geologists can further specialize their services by excelling in areas of sedimentology and stratigraphy, structural geology, geochemistry, or paleogeography.