This excellent article starts with the massive Aliso Canyon methane leak in southern California and goes on to note that:
-About 10 percent of U.S. greenhouse gas emissions came from methane in 2012, and 30 percent of those emissions came not from fuel use, but from the extraction and distribution of oil and natural gas.
-Methane can leak almost anywhere in the natural gas supply chain. Studies show that it is leaking at almost every point in the supply chain — at drilling sites, along pipelines, at compression stations, at storage facilities like Aliso Canyon and along the networks of piping that deliver natural gas to homes. About the only thing unusual about the Aliso Canyon leak is its size.
The article quotes BU researcher Nathan Phillips extensively, and this article has much more detail about the Aliso Canyon methane storage field leak and its health effects. Check them both out!