America’s push for clean energy has certainly been a source of intense debate – the safety of off-shore drilling, the hidden costs of ethanol subsidies, even the aesthetics of wind farms. New evidence is set to increase the intensity on yet another topic – the debate over hydraulic fracturing.
Hydraulic fracturing is a process where internal fluid pressure is used to extend cracks, or fractures, into a rock formation. It can occur in nature, but in man-made operations fractures are made deep in the earth by pumping fluid (mostly water) and a proppant (such as sand) out the bottom of a well. The proppant prevents the fracture from closing back up after the injection of fluid stops. Chemicals are sometimes added to the pumping fluid to aid in the process. These fractures allow the gas or liquid trapped in the rock formation to flow back through the fracture, up the well and out for production.
More commonly known as “fracking”, the technique is used to release natural gas from shale rock formations. These formations, especially common on the East Coast and in Canada, have provided thousands of new, well-paying jobs. Fracking has allowed natural gas companies to access enormous reserves of natural gas, previously thought inaccessible and prohibitively expensive to drill. In fact fracking has allowed drillers to tap what is potentially the world’s largest known reserve of natural gas in the Marcellus and Utica shale deposits, stretching from New York to Georgia.
As with any new technology however, there are potential consequences. Lawmakers and regulators have debated the safety of the largely unregulated fracking industry, but with little definitive evidence either way…until now. A study by Duke University has concluded that fracking does indeed lead to methane contamination in drinking water. Methane is the primary component in natural gas and is not lethal to consume. However, high concentrations are explosive.
The study determined that fracking causes methane to leak into drinking water. Water sources within a kilometer were found to have significant levels of methane, more than 17 times higher than wells located further from drilling sites. Furthermore, it was determined that the source of the methane was the much older methane released from the bedrock, versus newer methane produced naturally in the environment.
The exact reason for this is unclear, but a Cause Map can lay out the possible areas needing further investigation. For instance, the frack chemicals might enter the water supply accidentally during the drilling process. Spills could also contaminate surface water, or chemicals could migrate into the water supply.
The study indicates that chemical migration is most likely what’s happening. Surface spills, which have happened, are not a major contributor to the wide-spread methane contamination; so that cause can be left in the Cause Map but won’t be investigated further for our purposes. Furthermore, the study produced no evidence that the drilling process itself was causing the contamination; so that block can be crossed off the Cause Map.
That leaves one possibility – migration. The chemicals (including methane) could migrate in two different ways – through the well casing or through the bedrock. The study’s authors felt it was unlikely that chemicals were migrating thousands of feet through bedrock, so migration from well casings experiencing high pressure flow is more probable. While more evidence is needed, it is possible that the well casings are weakened by the fracking process which pushes sand through the casings at high pressure.
An EPA study looks to definitively determine fracking’s impact on drinking water, and specifically human health. However that study is not scheduled to be completed until 2014. Until then, lawsuits and tighter regulations are likely to dominate headlines.