It appears that the North Carolina General Assembly is going to take up the issue of hydraulic fracturing or “fracking” again in this legislative session.  I’ll leave the details of the political process to other fora, but I will be addressing the technical, energy, and environmental issues here in Common Science. 
Last August I published a primer on the basics of fracking called “To Frack or Not to Frack”.  As background for this column, let me give you the nickel summary.  Fracking is the practice of pumping a high pressure mixture of water, sand, and chemicals into an oil or gas well to fracture the underground rock formations.  These fractures make it easier for the oil or gas to reach the well bore so they can be extracted to the surface.  Fracking was invented by Haliburton in 1947 and has been employed in 90% of all oil and gas wells drilled in the United States since then.  The oil and gas industry frequently quotes this statistic as unassailable proof of the safety of the technology.  As I’ll discuss below, this statement glosses over some key issues.
Most of the fracked wells from 1947 until 2005 were for liquid petroleum.  What you are reading about in the paper these days, and what the NC General Assembly will be discussing, is fracking of natural gas wells.  Natural gas and petroleum both come from the decomposition of ancient algae and bacteria which were buried under ground at high temperature and pressure.  (I covered this process in detail in “Petroleum: 300 Million Years of Sunlight”.)  The bacteria and algae which were buried at the greatest depths were converted to natural gas which composed primarily of methane.
Once the natural gas was formed, much of it began to migrate towards the surface through porous rock formations.  Some made it all the way to the surface and was released into the atmosphere, and some encountered an impervious layer of rock during its rise to the surface and collected there.  These pockets of natural gas are what gas companies have traditionally been trying to locate. 
The OPEC inspired energy crisis of the 1970’s gave life to the U.S. domestic natural gas industry, driving a large expansion.  Then things began to go wrong in 2005 when supply from the traditional gas wells was no longer keeping up with demand.  During the course of a year, the price of natural gas increased by a factor of 4 or 5.  This trend, had it continued, would have had significant and potentially devastating impacts on U.S. industry and consumers who use natural gas for cooking and heating.
What reversed this trend was fracking.  Much of the natural gas that formed underground over the eons is still trapped in small, unconnected rock cavities from which it is unable to escape and migrate towards the surface.  In fracking, the gas company drills down into  these formations and then drills horizontal holes through them which can be as long as five miles.  Fracking fluid is then pumped into the horizontal holes at high pressures, fracturing the rock formation.  About 60% of the fracking fluid is pumped back out, and then the natural gas begins to flow.  The recovered contains a wide variety of toxic additives and needs to be treated with great care.  The water also contains dissolved methane, some of which escapes into the atmosphere.
Published anti-fracking literature tends to focus on the potential for a fracture propagating from the methane-containing rock formation all the way to the water table, thereby polluting the local water supply.  In my column from last August, I suggested that this was an unlikely path since the gas to be fracked tended to be thousands of feet lower than the water table, way too large of a gap to be bridged by single fractures which tend to be less than 500 feet long.  I suggested that the real threats were the more mundane issues of proper management of the water after it was pumped back out of the well and also the design and construction of the well bore.  As I will explain below, it turns out I was right.
The well bore is the most important part of the gas well in terms of protecting the water supply.  Just like a water well, a gas well has a double pipe design.  The gas flows up through the inner pipe.  The space between the outer and inner pipe is filled with concrete to prevent leaks either in or out.  Proper installation is also important to prevent leaks along the outside of the outer pipe.
With that background in hand (sorry, that was bit more than the nickel summary), let’s move to Pavillion, Wyoming, where in 2008 residents began complain about the taste and smell of their well water.  Approximately 170 natural gas wells have been drilled in the Pavillion area since 1960, 100 of which have been installed since 2003 as part of the fracking boom.  The EPA performed testing of both surface water and subsurface water in Pavillion during 2009 and released a draft report in December of 2011 (here is a link to the full report if you are interested).  The study showed significant, fracking-related contamination of the water both at the surface and underground.
In “To Frack or Not to Frack,” I posited that fracking could be performed in a way that protected drinking water, provided that the rock being fractured was located at a depth which kept it far away from the water table, that the casing around the well bore had proper design and installation, and that the water recovered from the well after the fracking process was handled with appropriate care.  The gas companies in Pavillion and the agencies charged with regulating them failed miserably on all three counts.
Let me start with the most egregious short-coming.  Domestic drinking water wells in Pavillion draw subsurface water from depths of up to 244 meters.  Fracking operations in the area were carried out at depths as shallow as 372 meters, a separation in depth of only 128 meters.  The lengths of individual fractures are dependent on conditions but are often longer than the 128. Allowing fracking with such a small separation in depth was simply inexcusable.  A frack which bridges the gap between the well and water table is almost certain to result in contamination.
The description of the installation and condition of the concrete well bore casings in the EPA report is enough to make an engineer weep.  Everything about them was sloppy and inadequate.  In some cases the annular space between the inner and outer well pipes was not even completely filled with concrete, let alone filled properly and tested prior to use.  The gas well necessarily must pass through the water table on the way to the fracturing zone.  Leaks from the casing provide an easy path for the natural gas to saturate the ground water. 
An examination of the surface waters also showed significant contamination, indicating that neither the waste water nor other solid wastes from the fracking process were handled properly.  We like to think that this sort of careless disregard for water quality and people’s health is only fodder for movies about things that happened long ago.  The EPA’s draft report is a strong reminder that without proper vigilance, things can still go horribly wrong.
I continue to believe that fracking can be done in a way that does not threaten our drinking water quality, but as our neighbors in Pavillion, Wyoming can tell us, careful monitoring and regulation will be required. The NC General Assembly must ensure that fracking operations are sufficiently removed in depth from the water table and that resources are provided to inspect well bore casing installations and that water and solid wastes are managed properly.
The question you might ask is “with all of these concerns and risks related to fracking, why not just ban the practice”?  This column is already long enough so I’ll save the full answer for later.  The short answer is that in the absence of fracking we would see a dramatic decrease in natural gas supply, a circumstance for which we are not even remotely prepared.
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