The Oil Drum

This is a little technical meander that occurs with some regularity, on Saturdays. It is largely for background information, and is a very simplified explanation of what happens in drilling oilwells and for related underground resources. Because the series is now getting longer, references to earlier posts are given at the back end of this one. And to explain the title, and give an indication of today's topic; one of the nastier jobs in early coal mines was given to a man called a Penitent. He would wrap himself in wet rags and crawl along the floor holding a long stick with burning rags on it, ahead of him, and up against the local mine roof. The intent was to burn dangerous pockets of methane before they got large enough to explode.

There is a debate in Los Angeles about the risks involved in extending the subway from Wilshire Boulevard to the sea. The major concern is with methane pockets. Because

Millions of years ago, the L.A. Basin was under the Pacific, and centuries of dead sea life created rich reserves of fossil fuel. By the early 20th century, the fuel was being pumped out in a maze of active oil fields. Today, many of the old pumps are gone, but significant pockets of explosive methane and other subterranean gases remain.

The Fairfax area -- home to the bubbling La Brea tar pits -- poses a particularly vexing problem for diggers.