This major group includes establishments primarily engaged in: (1) producing crude petroleum and natural gas; (21 extracting oil from oil sands and oil shale; (3) producing natural gasoline and cycle condensate; and (4) producing gas and hydrocarbon liquids from coal at the mine site. Types of activities included are exploration, drilling, oil and gas well operation and maintenance, the operation of natural gasoline and cycle plants, and the gasification, liquefaction, and pyrolysis of coal at the mine site. This major group also includes such basic activities as emulsion breaking and desilting of crude petroleum in the preparation of oil and gas customarily done at the field site. Pipeline transportation of petroleum, gasoline, and other petroleum products (except crude petroleum field gathering lines) is classified in Transportation and Public Utilities, Major Group 46, and of natural gas in Major Group 49. Establishments primarily engaged in petroleum refining and in the production of lubricating oils and greases are classified in Manufacturing, Major Group 29.