The development of natural gas resources in Pennsylvania has increased exponentially in the past two years. The area currently being explored is called the Marcellus Shale – a formation which extends across much of Pa. and neighboring states (See Map: PDF or image).
The shale is a dense, fine-grained rock formation that was created over 350 million years ago by the repeated deposits from ancient oceans. It contains trapped within it the remains of Devonian-era organic matter, long since turned to methane – the form that natural gas takes before it is processed.
The gas found in the shale is not trapped in large cavities, but rather in the pores of the rock itself. It is not possible to extract the gas from shale using conventional drilling methods. Instead, the rock must be fractured to release the trapped gas and to create spaces into which it can flow.
The development of horizontal drilling allows for several horizontally drilled well bores to branch off from a single, vertically drilled well. Hydraulic fracturing — which uses fluid to create and enhance cracks in the rock formation to allow trapped gas to escape — made formerly unreachable sources of fossil fuels not only reachable, but economical as well. (For a brief description of the drilling process, see sidebar.)
In a May 2008 report published in the industry newspaper American Oil & Gas Reporter, Penn State researchers Terry Engelder and Gary Lash described what a few early investors in the development of the Marcellus Shale already suspected – that the potential production of shale gas could be massive, even making up for dwindling resources elsewhere. Engelder and Lash estimated that the Marcellus Shale contained almost 50 trillion cubic feet of recoverable gas resources, making it the largest shale gas deposit in North America.
By this time, more energy companies had begun to invest in the Marcellus’ prospects. Between 2007 and 2010, the number of drilled gas wells in Pennsylvania went from one to over 2,000 (see National Geographic’s “Mapping a Gas Boom”). ‘Unconventional’ fossil fuel sources were a boon to U.S. energy needs. In 2009, the U.S. became the largest natural gas producer in the world.
As Pennsylvania began to emerge as a leading source of shale gas, public scrutiny over the costs, rather than the benefits, of shale gas production increased. The drilling activity in the Marcellus Shale is taking place in the most densely populated area of the country.
One issue has been the risk of gas ‘migration.’ After residents of Dimock, PA. reported that their drinking water was discolored, cloudy, smelled bad and was causing health problems like dizziness and skin lesions, tests by the DEP revealed elevated levels of methane in the water aquifer (see Photo). Further investigation found that improperly cemented well bores were the cause of the contamination.
Another issue is the content of the fracturing fluid itself. Though less than one percent of the total volume of fracturing fluid is composed of additives, millions of gallons of fluid are used for each fracturing event, so the volume of additives can be in the thousands of gallons. One argument for increased regulation of the gas industry centers on the toxicity of many of these additives, which can include potent carcinogens like benzene, as well as chemical compounds that act as endocrine disruptors.
There is another issue surrounding the water used in fracturing — not what goes in, but what comes out. The waste stream created by drilling in the shale has three main components: drill cuttings, which are the bits of rock carved out by the drill; drilling ‘mud,’ which is a friction-reducing liquid used to keep the drill cool; and brine, which is naturally occurring salty water trapped in the rock alongside fossil fuels.
Once a well has been fractured, the fracturing fluid returns to the surface, propelled by the force of subterranean pressure. Drill cuttings, drilling mud and brine are also returned to the surface with the fracturing fluid in a process called ‘flowback.’
The fluid is usually stored in large tanks and holding ponds at the well site. It is treated on site to separate out the solids and contaminants captured during flowback, then reused in another fracture or sent to nearby water treatment plants, where it is treated, filtered and released into waterways.
Shale also contains a variety of heavy metals, most notably uranium.The presence of radioactive material in the shale adds a twist to the already contested process of hydraulic fracturing.
Preliminary research by University of Buffalo geologist Tracy Banks and her colleagues, presented at the annual meeting of the Geological Society of America in Denver, Colorado, suggests that the process of hydraulic fracturing is having a previously unrealized effect on the radioactive material found in the shale.
Her team found that uranium is chemically bound to the trapped methane gas. In an emailed response to questions, Dr. Banks said that she believes “the drilling fluids and fracturing of the shale will mobilize uranium.” Additionally, the researchers found that the effect of the fracturing fluid on the mobilized uranium causes it to solubilize — become dissolvable in water.
The health risks suggested by these findings are not primarily related to uranium’s radioactive properties. As Dr. Banks explained, “Uranium is very weakly radioactive but it can still be toxic when its concentration is below a level detectable with a Geiger counter.”
The pursuit of U.S. energy independence, the rising cost of fossil fuels and the lower potential environmental cost of natural gas have increased the pressures to gas producing areas across the U.S. In Pennsylvania, the promise of big payoffs to leasing landowners as well as increased revenue from taxes and fees to local and state coffers during a time of serious economic shortfalls helped spur rapid growth of gas industry assets while federal and state regulators have struggled to keep up.
Though the method of extracting gas from unconventional sources using hydraulic fracturing has resulted in increased domestic energy independence and lower-cost, cleaner burning alternative to oil-based fuels, there is widespread concern over the lack of comprehensive understanding of the methods and materials used.
Response in the form of regulation has varied from state to state, since amendments in 2005 to the Clean Water Act exempted hydraulic fracturing fluids from EPA oversight, leaving states to maintain their own regulatory framework.
At the University of Buffalo, research continues into the effect of hydraulic fracturing on the uranium in the Marcellus Shale. In New York, a statewide moratorium on hydraulic fracturing is in place until updated permitting regulations can be established.
In comparison, Pennsylvania’s response has been less straightforward. The eastern third of the state falls under the purview of the Delaware River Basin Commission, which has the power to enact regulations to protect the waters of the Delaware Watershed. The DRBC declared a moratorium on drilling until it could draft new regulations to address the risks to water resources. Meanwhile, development continues apace across central and western parts of the Commonwealth.
In 2010, the DEP has logged more than one thousand violations by gas companies drilling in Pa., many involving improperly managed or damaged storage facilities, mishandling of waste materials and discharge of pollutants into nearby waters.
It remains to be seen whether the Clean Streams Law, the state’s primary platform for water pollution prevention, will provide sufficient protection in light of newly discovered risks. Dr. Yvette Bordeaux, Director of the Master’s Programs in Earth and Environmental Science at the University of Pennsylvania, succinctly stated the challenges: “The trick is to make sure that everybody does the right thing.”