The American Association of Petroleum Geologists (AAPG) is one of the world's largest professional geological societies. AAPG works to advance the science of geology, especially as it relates to petroleum, natural gas, other subsurface fluids, and mineral resources; to promote the technology of exploring for, finding, and producing these materials in an economically and environmentally sound manner; and to advance the professional well-being of its members. AAPG was founded in 1917 and is headquartered in Tulsa, Oklahoma; currently almost one-third of members live outside the United States.