The movie Gasland portrays hydraulic fracturing as a cause of water well contamination, while industry supporters assert that there has never been a documented case of hydraulic fracturing causing contamination of groundwater. So what are the facts?
Gasland showed individuals lighting their faucets on fire, explained that the individuals' water wells were contaminated with methane (the principal component in natural gas), and suggested that hydraulic fracturing had caused the contamination. The water wells probably did contain methane, but determining the cause of the contamination requires some investigation. And to understand those investigations, it helps to understand a little about the ways methane can be formed.
Methane is a flammable gas that is formed in one of two ways. First, it can be produced by bacteria during the decomposition of organic matter. This is the process that creates the methane found in landfills, swamps (called swamp gas), and in the intestines of cattle and other animals. Methane produced in these biological processes is called "biogenic" methane. When biogenic methane is formed underground, it generally is formed at fairly shallow levels ─ not more than a few hundred feet underground. It has been well documented for years that a high proportion of water wells in some parts of the country contain significant amounts of biogenic methane.
The second way methane can be formed is through the thermal decomposition of organic matter under high temperatures and pressures. Methane created by this thermal process is called "thermogenic" methane. Thermogenic methane is created when organic matter is buried deep underground by the accumulation of more and more sediment under the right circumstances. Over thousands of years, the combination of high temperatures and pressures caused by the organic material being buried deep underground can lead to the formation of thermogenic methane.
Biogenic methane and thermogenic methane molecules are chemically the same, but scientists can tell the difference between the two types of methane by a couple of means of "chemical fingerprinting." The first is isotopic analysis of the carbon atoms found in methane. All carbon atoms have the same chemical properties, but a small fraction of carbon atoms have a different number of neutrons in the atomic nucleus than do most carbon atoms. Because the fraction of carbon atoms that have the "odd" number of neutrons is different for thermogenic and biogenic methane, scientists can tell the difference between the two types of methane by using isotopic analysis.
Also, the process that creates thermogenic methane also generally leads to small amounts of other hydrocarbons, such as ethane, propone, and butane. The process that creates biogenic methane creates very little ethane, and no propane or butane. Thus, scientists sometimes can "fingerprint" methane as being thermogenic or biogenic based on the presence or absence of other hydrocarbons.
The methane recovered in natural gas drilling is thermogenic, not biogenic. Thus, the presence of biogenic methane in a water well generally would not be caused by natural gas drilling, whereas the presence of thermogenic methane might be caused by drilling activity (though in some places, thermogenic natural gas naturally seeps to the earth's surface, so that the presence of thermogenic methane in a water well is not sufficient by itself to prove that oil and gas activity is the cause).
Gasland discussed three water wells located in Colorado, and also discussed two additional places in Colorado where gas was seeping to the surface in the West Divide Creek area. The Colorado Oil & Gas Conservation Commission, the arm of state government that regulates the oil and gas industry, investigated the contamination and has posted a report of its findings on its website. Through testing, the Commission conclusively established that three of the five locations (two of the water wells and one of the seeps) contained biogenic methane that was unrelated to oil and gas activity.
Of the remaining two locations, the water well contained both biogenic and thermogenic methane, while the seep contained thermogenic methane. That left the question of what caused thermogenic methane to contaminate the water well and the seep. The Commission concluded that oil and gas activity was the cause, but that the contamination had not been caused by hydraulic fracturing. Rather, the problem had been caused by improper well construction (the casing and cementing of the natural gas wells).
This result is consistent with statements previously made in the Oil & Gas Law Brief that standards for casing and cementing wells is an issue that should be discussed, but that hydraulic fracturing rarely, if ever, is a problem. Further, the Colorado result is consistent with investigations of water well contamination in other places. Those investigations repeatedly conclude either that oil and gas activity was not the cause of the contamination, or that oil and gas activity was the cause, but that the specific activity that led to the problem was a well construction problem, not hydraulic fracturing. Lisa Jackson of the EPA and other officials in the Obama administration have stated that they are unaware of any documented cases of groundwater being contaminated by hydraulic fracturing. Numerous other government agencies have reached similar conclusions.
And I recently attended a major conference where a representative of the Natural Resources Defense Council stated that he advocates several reforms relating to the oil and gas industry (including mandatory disclosure of hydraulic fracturing fluid composition, spill prevention, and more attention to well construction standards), but that he does not think the threat of groundwater contamination by the hydraulic fracturing process itself is an issue.
In short, many knowledgeable people assert that all the energy that is being poured into the debate over hydraulic fracturing would be better spent on other safety issues.