The recent discovery of natural gas in western Idaho has many Idahoans wondering if their drinking water wells will be protected from contamination. As gas wells are drilled, eager developers propose to pump tens of thousands of gallons of chemicals into the ground to fracture the rock and stimulate the flow of gas to their wells. These companies want to use a process called hydraulic fracturing or “fracking”. Fracking is an engineering technique that injects liquid (gel+sand+water) into a well at high pressure to create cracks in deep rock. These cracks allow natural gas to flow more freely into the well. The trouble with this type of chemical drilling is that it is exempt from many federal laws that protect public health and the environment and, for many years, the liquid contents injected into the wells have been treated as trade secrets by the industry.
Hydraulic fracturing, or fracking, wrenches open rock deep beneath the Earth’s surface, freeing the natural gas that is trapped inside. Gas recovery is a game changer, a bridge to the future. The gas, primarily methane, is cheap and relatively clean. But along with these promises have come alarming local incidents and national reports of blowouts, contamination and earthquakes. Fracking opponents contend that the process poisons air and drinking water and may make people sick. What’s more, they argue, fracking leaks methane, a potent greenhouse gas that can cause homes to explode. Research suggests methane leaks do happen. The millions of gallons of chemical-laden water used to fracture shale deep in the ground have spoiled land and waterways. There is also evidence linking natural gas recovery to earthquakes, but this problem seems to stem primarily from waste-water disposal rather than the fracturing process itself.
Hydraulic fracturing has been cranking up output from gas and other wells for more than 50 years. But not until fracking joined up with another existing technology, horizontal drilling, was the approach used to unlock vast stores of previously inaccessible natural gas. The real fracking boom has kicked off in just the last decade. Conventionally drilled wells tap easy-to-get-at pockets of natural gas. Such gas heats homes and offices, fuels vehicles and generates electricity. But as easily accessible reserves have been used up, countries seeking a steady supply of domestic energy have turned to natural gas buried in difficult-to-reach places, such as deep layers of shale.
Gas doesn’t flow easily through shale or other impermeable rock. Drilling a conventional well into such formations would gather gas only from a small area right around the well. For shale in particular, many formations in the United States extend hundreds of kilometers across but are less than 100 meters thick, hardly worth sending a vertical well into. Combining hydraulic fracturing with horizontal drilling offers a way to wrest gas from these untapped reserves. By drilling sideways into a rock formation and then sending cracks sprawling through the rock, methane can bubble into a well from a much larger area.
Today hydraulic fracturing is used in about nine out of 10 onshore oil and gas wells in the United States, with an estimated 11,400 new wells fractured each year. In 2010 about 23 percent of the natural gas consumed in the United States came from shale beds. While the immediate output is gas, the uptick in this type of extraction has also fueled fears over fracking’s potential dangers such as drinking water contamination. One of the most explosive issues, literally, is whether fracking introduces methane into drinking water wells at levels that can make tap water flammable or can build up in confined spaces and cause home explosions.
Studies are few, but a recent analysis suggests a link. Scientists who sampled groundwater from 60 private water wells in northeastern Pennsylvania and upstate New York found that average methane concentrations in wells near active fracturing operations were 17 times as high as in wells in inactive areas. Methane naturally exist in groundwater – in fact, the study found methane in 51 of the 60 water wells but the high levels near extracting sites were prominent. To get at where the methane was coming from, the researchers looked at the gas’s carbon, which has different forms depending on where it has been. The carbon’s isotopic signature, and the ratio of ethane to other hydrocarbons, suggested that methane in water wells near drilling sites did not originate from surface waters but came from deeper down. But how far down and how the methane traveled isn’t clear. ( Jackson, Proceedings of the National Academy of Sciences, Duke.) He proposed four possibilities.
- The first most contentious-the least likely-is that the extraction process opens up fissures that allow methane and other chemicals to migrate to the surface.
- A second possibility is that the steel tubing lining the gas well, the well casing, weakens in some way. Both scenarios would also allow briny water from the shale and fracking fluid to migrate upward. The well water analysis found no evidence of either.
- Third, newly fracked gas wells could also be intersecting with old, abandoned gas or oil wells, allowing methane from those sites to migrate. Many old wells have not been shut down properly. In some places in Pennsylvania, West Virginia and elsewhere (especially those with existing coal beds), methane turned up in well water long before hydraulic fracturing became widespread.
- A fourth possibility is that the cement between the well casing and the surrounding rock is not forming a proper seal. Cracking or too little cement could create a passageway allowing methane from an intermediate layer of rock to drift into water sources near the surface. Such cases have been documented. In 2007, for example the faulty cement seal of a fracked well in Bainbridge, Ohio, allowed gas from a shale layer above the target layer to travel into an underground drinking water source. The methane built up enough to cause an explosion in a homeowner’s basement.
Accompanying these concerns are worries that methane leaking into the air will have consequences for the climate and human health. Burning methane creates fewer greenhouse gas emissions and smog ingredients than other fossil fuels, so natural gas is considered relatively clean. But evidence suggests that methane frequently escapes into the air during drilling and shipping, where it acts as a greenhouse gas and traps heat. Such leaching undermines the gas’s “clean” status. A case report occurred near Arlington, Texas where there is recent fracking. Air analyses showed high levels of methane and other hydrocarbons in both the outdoor and indoor air. The family all became ill with chemical sensitivity. Breath analyses showed high levels of methane and other related chemicals. he patients moved out of the fracking area and gradually improved until they lost their chemically sensitivity and became functional again.
Methane leaking into the air can also cause ozone to build up locally, leading to worries about headaches, inflammation and other ills among people who live nearby. A typical fracked well uses between 2 million and 8 million gallons of water. At the high end, that’s enough to fill 12 Olympic swimming pools. Companies have their own specific mixes, but generally water makes up about 90 percent of the fracking fluid. About 9 percent are “proppants,” i.e., sand or glass beads that prop open the fissures. The other 1 percent consists of additives, which include chemical compounds and other materials (such as walnut hulls) that prevent bacterial growth, slow corrosion and act as lubricants to make it easier for proppants to get into cracks. As the gas comes out of a fracked well, a lot of this fluid comes back as waste.
Until recently, many companies wouldn’t reveal the exact chemical recipes of their fluids, citing trade secrets. A report released in April 2011 by the House Energy and Commerce Committee did provide some chemical data: From 2005 to 2009, 14 major gas and oil companies used 750 different chemicals in their fracking fluids. Twenty-five of these chemicals are listed as hazardous pollutants under the Clean Air Act, nine are regulated under the Safe Drinking Water Act and 14 are known or possible human carcinogens including naphthalene and benzene.
In addition to the fracking fluid, the flowback contains water from the bowels of the Earth. This “produced” water typically has a lot of salt, along with naturally occurring radioactive material, mercury, arsenic and other heavy metals.
It’s not just what you put into the well. The shale itself has chemicals, some of which are quite nasty. A report analyzing the risks associated with fracking was released by the Energy Institute. Waste-water is dealt with in different ways. Sometimes it is stored on-site in lined pits until it is trucked off. When these pits are open to the air, they can release fumes or overflow, with possibly hazardous consequences.
The Energy Institute report cites one case in West Virginia in which about 300,000 gallons of flowback water was intentionally released into a mixed hard-wood forest. Trees prematurely shed their leaves, many died over a two-year study period, and ground vegetation suffered. In 2009, leaky joints in a pipeline carrying waste-water to a disposal site allowed more than 4,000 gallons to spill into Pennsylvania’s Cross Creek killing fish and invertebrates. For obvious ethical reasons, controlled studies exposing people to fracking fluid don’t exist. And long-term population studies comparing pre- and post-fracking health have not yet been done. But these incidents and the known dangers of some of the chemicals used raise alarms about the possible consequences of human exposure.
Local geology in some areas may also allow fracking chemicals and produced water to seep up from deep below into water sources. A study published in July in the Proceedings of the National Academy of Sciences found a geochemical fingerprint of briny shale water in some aquifers and wells in Pennsylvania. Local geology probably also played a role in fracking fluid getting into drinking water in Pavillion, Wyoming, a site that has been at the heart of the fracking controversy.
Still, several reviews of where fracking chemicals and waste-water have done harm find that the primary exposure risks relate to activities at the surface, including accidents, poor management and illicit dumping. An accepted disposal route is injecting the water into designated waste-water wells. But that strategy can cause an additional problem: earthquakes. Hydraulic fracturing operations have been linked to some small earthquakes, including a magnitude 2.3 quake near Blackpool, England, last year. But some agree such earthquakes are extremely rare, occurring when a well hits a seismic sweet spot, and are avoidable with monitoring. There were multiple quakes in a fracking area in Oklahoma in the year 2013.
Of greater concern are earthquakes associated with the disposal of fracking fluid into waste-water wells. Injected fluid essentially greases the fault, a long-known effect. In the 1960s a series of Denver earthquakes were linked to waste-water disposal at the Rocky Mountain arsenal, an Army site nearby. Waste-water disposal was also blamed for a magnitude 4.0 quake in Youngstown, Ohio, last New Year’s Eve.
A study headed by W. Ellsworth of the U.S. Geological Survey in Menlo Park, California, documents a dramatic increase in earthquakes in the Midwest coinciding with the start of the fracking boom. From 1970 to 2000, the region experienced about 20 quakes per year measuring at or above magnitude 3.0. Between 2001 and 2008, there were 29 such quakes per year. Then, there were 50 in 2009, 87 in 2010 and 134 in 2011.
But the earthquakes weren’t happening near active drilling. They seemed to be clustered around waste-water wells. It is hard to look back without pre-quake data and figure out what triggers a single earthquake, notes Ellsworth. There are several pieces of the geology equation that, if toggled, can tip a fault from stable to unstable. A recent study examining seismic activity at waste-water injection wells in Texas linked earthquakes with injections of more than 150,000 barrels of water per month. But not every case fit the pattern, suggesting the orientation of deep faults is important. Ellsworth advises that injection at active faults be avoided. Drill sites should be considered for their geological stability, and seismic information should be collected. Only about 3 percent of the 75,000 odd hydraulic fracturing setups in the United States in 2009 were seismically monitored.
Ultimately, unless people are willing to cut way back on their energy use, the risks associated with natural gas recovery have to be weighed against the risks that come with coal, nuclear power and other energy sources.