Wednesday, August 03, 2011


Bridge Energy is planning to do some drilling in Payette County in an effort to determine whether there are viable natural gas fields available there.  As part of that, they intend to conduct fracking operations.

Various articles about fracking are available here.

Anyway, the articles frequently mention that, in addition to the water pumped at high pressure into the ground, the companies also inject chemicals.  I have been wondering why, until I read this article about petroleum.  It's nice written and well worth a read if you're interested in this at all.

The new gas deposits are contained in porous rock, kind of like a sponge.  Fracturing the rock allows the gas to escape.  The rock containing the gas is porous, but it also must be permeable, i.e., the pockets of gas must be somewhat connected so that all (or most, or at least much) of the gas will flow out once it's fractured.  Here's the money quote from the article:
Another involves fracturing the reservoir rock by pumping fluids and sand into it under high pressure. The fluids open cracks, and the sand keeps them open to let out the petroleum. This can overcome low permeability, and in the eastern U.S. states large new reserves of natural gas have been found through such techniques. Treating the wellbore with various acids or solvents can also raise permeability.
So, I guess the acids and solvents dissolve some rock and create or enlarge the connections among the gas pockets so that the gas will flow out faster.

Well.  That's odd.  Knowing the reasons for injecting acids and solvents into the ground doesn't really make me feel any better about the risks to the ground water. 


fortboise said...

The recent NYT story (which the Statesman picked up and put on the front page this week) about there being one demonstrated incident of groundwater contamination had a (generic) diagram showing the "vast" vertical separation between the deposits they're after, and aquifers.

So, something might not go wrong, but we do know something could, and has gone wrong in the past.

The thing about drilling is that it connects things one way or the other. Done right, it isolates the connection "as needed." As Macondo showed us--just last spring and summer--it's not always done right.

After you've satisfied your curiosity about fracking, you can try wrapping your head around underground coal gasification.

Anonymous said...

Popular Mechanics had a very nice explanation of fracking this past issue. Ground water contamination can occur when the gas deposit is close to the ground water, which does occur in certain locations like Wyoming. The most common scenario is when the company drilling down does not properly seal off the borehole with what basically amounts to a sleave of concrete as they drill deeper to get the gas. Material then seaps up the hole created by the drill and contaminates the aquifer above it. PA officials sued Chesapeake energy for such an incident. When I weigh the risk of an accident against our continued funding of wahabist to buy their oil, I think we should continue to develop these resources.