Thursday, October 4, 2012

Burning ice

Did you know there is a type of ice that can burn while someone holds it? Don't believe me? Well, look at the picture below. It's not a trick!

Methane hydrate burning in someone's hands.
Alright so it's not really ice. But it looks and feels like ice. It's really methane hydrate, a specific type of gas hydrate. The word hydrate is a term used in organic chemistry to indicate that a substance contains  water. So a gas hydrate is a gas trapped in a ice-like cage of water molecules. It's really the methane burning while the water melts - not exactly burning ice but that's what it looks like!

A diagram of how gas hydrates form.

In addition to looking super cool when it burns, methane hydrates have some important impacts on energy and climate change. Methane hydrate forms in sediments beneath the ocean floor requiring low temperatures and high pressures to form but its usually located shallower than oil reservoirs. The methane hydrates are a problem for the guys drilling wells because it could blow-up. But methane is also a source of energy (natural gas) and ideally the methane hydrate could increase the amount of domestic energy products but we would need to figure out how to extract it. Methane is very bad for our atmosphere (actually worse than CO2) and if the methane hydrates were to melt and release the methane it could be the tipping point to start an even faster global warming.

In a paper published in a 1996 issue of  Science, one of the most highly regarded scientific journals, Steve Holbrook, Hartley Hoskins, Warren Wood, Ralph Stevens, and Daniel Lizarrale report their findings of the amount of methane hydrates in three wells located in the Blake Ridge area, offshore South Carolina. (I lived in SC for 10 years without knowing we had gas hydrates or any energy near!) This paper came out during the early investigations into methane hydrates and everyone was still unsure how much of this stuff was out there. These guys concluded that the volume of hydrates located in the area offshore of South Carolina had been over estimated and that global estimates could be 3 times too high. 
The location of Blake Ridge offshore of SC.
Methane hydrates are found by acquiring seismic data over the location. A seismic survey is where a boat tows a source (air gun - makes vibrations) and receivers (hydrophones - they listen for the reflected vibrations) over the ocean floor. The methane hydrates are found by the presence of a bottom simulating reflector (BSR) in the data. Basically the difference from the presence of gas hydrates creates a reflection that shows up as a line in the seismic profile. The image below depicts the data from the 1996 paper.
Seismic data of the bottom simulating reflector (BSR) highlighted in blue. 
So in 1996 it looked like estimates for methane hydrates were not going to be as large as originally thought but because they could actually provide us with energy and could cause more climate change the research continued. It was actually written into the Energy Act of 2005 that the research would keep getting funded. And now after years of more research the estimate of  global methane hydrate volume is around 700,000 Tcf (trillion cubic feet) which is enormous when compared to the 200 Tcf of worldwide natural gas reserves! Since 1996 lots of methane hydrate was found in the Arctic permafrost and Gulf of Mexico. The estimates from the seismic data were too simplified and the complexity of gas hydrates is now better understood. The first methane was produced from a well going through the permafrost in northern Canada in 2008. Experiments continue but it looks promising that this form of energy can be produced safely. But the future is never certain and with the worry of releasing too much into the atmosphere it is worth taking the risks to get more energy? What do you guys think? Are you just fascinated with the burning ice?