This industry comprises establishments primarily engaged in (1) the exploration, development, and/or the production of petroleum from wells in which the hydrocarbons will initially flow or can be produced using normal or enhanced drilling and extraction techniques or (2) the production of crude petroleum from surface shales or tar sands or from reservoirs in which the hydrocarbons are semisolids. Establishments in this industry operate oil wells on their own account or for others on a contract or fee basis.
Performing oil field services for operators on a contract or fee basis--are classified in Industry 21311, Support Activities for Mining; The combined activities of crude petroleum and natural gas extraction--are classified in Industry Group 2111, Oil and Gas Extraction, based on the primary activity of the establishment; and Refining crude petroleum into refined petroleum and liquid hydrocarbons--are classified in Industry 324110, Petroleum Refineries.