Perhaps no image captures the fear of hydraulic fracturing and gas extraction more than this one; tap water burning because natural gas has seeped into an underground aquifer and is coming out of the pipes of people’s homes. Images like this were key parts of the “Gasland” movies and even got a mention on The Simpsons, with Marge screaming “Our water was on fire!”.
I’ve covered the history of hydraulic fracturing and the development of the modern natural gas fracking boom, so now there’s no where else to go but the controversial parts, and this is at the top of the list.
The scariest idea for how natural gas could get into people’s water involves the modern fracking process directly. The basic idea is – pumping high-pressure fluids into the ground to fracture a geologic unit could open fractures throughout the entire ground, letting gas flow upward that completely contaminates anything above, including aquifers that hold drinking water.
Fortunately, one of the things we can actually say with confidence about the current fracking boom is that this has literally never happened and it simply should never happen. The geology and the geophysics are actually our friends.
For these shale gas units to exist the first place they must be buried with strong units on top of them. If that weren’t the case, then the pressure that built up in these formations would have instead leaked out towards the surface. That hasn’t happened in part because the units are buried beneath enough rock to hold the pressure.
To hydraulically fracture a geologic unit, high-pressure fluids are pumped in, but that pressure is simply not enough to overcome the huge pile of rocks on top of the shale. Fluids can cause small to moderate fractures to form, but the pressures required to break through several kilometers of rock are enormous and its more than is being pumped into these wells.
This reality is one that has been used as a strong argument by the natural gas industry – it is literally impossible for the fracking process to cause gas to migrate upward. There has never been a single reported example of aquifer contamination from gas or oil leaking upwards through fractures generated by fracking and there is unlikely to ever be one.
Of course, if that were the end of this post this wouldn't be much of a story to tell, because in fact this situation is more complicated. People’s homes do have water that started flaming after the starting of drilling. These families have even faced defamation lawsuits from energy companies for publicly blaming energy companies for the contamination. What’s the deal with that?
The answer to that actually comes from something other than the fracking process, it comes from the drilling process itself.
The units that overlie the shale source rocks actually are virtually impenetrable during fracking, but getting to those units requires drilling a very deep hole in the ground. If that hole isn’t perfectly sealed then it can serve as a direct conduit to bring gas from deep into aquifers.
A 2014 study by Duke University, which hosts a research group that has been very active on understanding these unconventional gas extraction techniques, used trace components called noble gases found mixed with natural gas as a fingerprint to track contamination back to its source. They sampled about a hundred sites throughout Texas and Pennsylvania, located 8 wells that had leaked, and were able to track each one back to failures in the casing, the material that lines the well (full details here http://tmblr.co/Zyv2Js1R2EPXV).
Natural Gas in groundwater actually does occur naturally. It does leak up from units at depth and companies do manufacture equipment to remove gas that naturally occurs in groundwater. However, gas shouldn’t leak out from fracking operations during the fracking, so for years otherwise innocent homeowners have had major issues verifying that contamination in their groundwater came from the nearby drilling operations. This has been, to say the least, trying for these families, who had their water contaminated and wound up part of a political debate in the process of trying to get retribution for the actual damage done to their property.
Quite simply, the failures found in the Duke study are unacceptable. The study was specifically looking at sites with potential failures, so we can’t simply say that large numbers of wells do leak, but the problem is that even a 1% leak rate is unacceptable. If 10,000 wells are drilled and 1% leak, that’s still 100 leaks, and 10s of thousands of new wells are being drilled every year. There are strong suggestions that many of the leaks are associated with inexperienced drilling companies or times when the techniques were being developed and things have improved already, but the number of cases where people have seen increased methane in groundwater is high enough that this problem needs continuing focus. Every time I write a post on this topic I stress; this is a major issue. Preventing leaks from well casings is something that can and must be done better for this to be a moderately safe source of energy.
When that isn't done, when the quality control isn't as good as it should be, the end result isn't just methane contamination, it's also political pressure. These stories have happened and denying them or failing to correct them hurts the reputation of the industry. Failed seals don't just hurt the people nearby, they hurt the industry too; a high number of leaks is a great reason to simply shut an industry down or ban it across large areas, states, or eve nations. If you're in the oil and gas industry, even if your company is doing things right, a failed seal from a different company can put you out of business, so this should matter to everyone.
Finally, there is one more side to the issue of leaking casings, and like several issues with gas extraction this one is the comparison to regular gas wells. Every single natural gas well, including the millions of conventional wells already drilled around the country, is a source for a potential similar leak. Some of the largest gas leaks around the country are found not associated with fracking but instead are found in an area where methane is being extracted from a coal bed (http://tmblr.co/Zyv2Js1SqNqZp).
One of the remarkable things about the current fracking boom compared with natural gas extraction over the past century is that modern day gas extraction is actually being done with fewer wells. By tapping a large area of a source reservoir from a single well, fewer vertical wells are actually necessary. Per unit of gas extracted, per unit of energy available, the modern methods for unconventional gas extraction are actually at less risk of leaking gas than classic techniques.
The reality that we’ve run into again is…if we are actually going to use fossil fuels as an energy source, modern methods for unconventional gas extraction are less risky than the techniques employed for the last century.
Of course, that statement would be small comfort to a family that had their water contaminated and then faced opposition when they tried to seek restitution for their losses.
Hopefully you’ve gotten a bit of a conflicted story from this post, because there are parts of this story that should bother you and there are parts that do bother me.
Image credit: NBC/Huffington Post http://huff.to/1nY38bJ
Read more: http://bit.ly/1q9Cpq1
http://energy.wilkes.edu/pages/159.asp
http://www.eia.gov/dnav/ng/ng_enr_wellend_s1_a.htm
http://www.pnas.org/content/111/30/10902
http://www.sciencedaily.com/releases/2014/…/140915095851.htm
Previous articles in this series: http://on.fb.me/1yhKcYu