The mystery of Eternal Flames

‘Eternal flames’ are fires that burn due to an underground supply of natural gas. These strange phenomena can tell scientists about where natural gas can be found in underground rock layers and how it reached the surface, without having to drill into the ground.

Geologists at Indiana University Bloombington have been studying a spectacular eternal flame in Erie County, New York, which has been burning throughout recorded history.  The eternal flames come about as gas seeps from underground rock layers to the surface.  If there is a ‘macro seep’, this can be a large enough amount of gas to produce an eternal flame: a continuous stream of fire.  The eternal flames consist mainly of methane, this one in Erie County releases about 1 kg of methane a day, but also seems to have the highest ethane and propane concentrations of any known natural gas seep at 35%.

Researchers believe that the gas powering the flame comes from the Rhinestreet Shale (a stretch of rock), which is about 400m deep.  The paper published in Marine and Petroleum Geology is one of the first investigations of a natural shale gas seep (most originate from traditional reservoirs: more porous rocks like limestone).  The gas would have reached the surface through passages created by tectonic activity. There are also micro seeps, when not enough gas reaches the surface to form a flame, but natural gas seeps still account for 30% of the methane emissions into the atmosphere, the second biggest source after wetlands.

Shale is normally not very permeable so gas cannot reach the surface.  It is thought that artificial ‘fracking’ is the only way to provide passages to the surface, but this research shows that natural fractures may also be an effective way for gas to reach the surface. These naturally occurring shales have “naturally fracked” characteristics so are seen as potential sources of gas production amid the controversy into artificially fracking shale.  No doubt scientists will be on the look out for more as a future source of natural gas.

Picture of the flame: http://www.eurekalert.org/multimedia/pub/56309.php?from=239330