How much methane is emitted from oil and natural gas systems? What are the major emission sources?
According to the EPA Inventory of U.S Greenhouse Gases and Sinks: 1990-2007 report, dated April 2009, methane emissions from oil and natural gas systems make up two percent of total greenhouse gas emissions in the United States. Methane emissions occur in all sectors of the natural gas industry, from drilling and production, through gathering and processing and transmission, to distribution. These emissions occur through normal operation, routine maintenance, fugitive leaks, system upsets, and venting of equipment. In the oil industry, some underground crude contains natural gas that is entrained in the oil at high reservoir pressures. When oil is removed from the reservoir, associated natural gas is produced. Additionally, the inventory shows that the oil and natural gas industry emitted 331 billion cubic feet (Bcf) of methane in 2007. Of this amount, 37% was from production operations, 10% from processing, 31% from transmission and storage systems, and 22% from distribution systems.
