Establishments primarily engaged in performing oil and gas field services, not elsewhere classified, for others on a contract or fee basis. Services included are excavating slush pits and cellars; gradings and building of foundations at well locations; well surveying; running, cutting, and pulling casings tubes, and rods; cementing wells; shooting wells; perforating well casings; acidizing and chemically treating wells; and cleaning out, bailing, and swabbing wells. Establishments which have complete responsibility for operating oil and gas wells for others on a contract or fee basis are classified according to the product extracted rather than as oil and gas field services. Establishments primarily engaged in hauling oil and gas field supplies and equipment are classified in Division E, Transportation and Public Utilities. Establishments primarily engaged in oil and gas field machine shop work are classified in Manufacturing, Industry 3599.