New Research on Fracking and Contamination of Drinking Water

Scientists have found and investigated methane in drinking water wells near fracked gas wells in the Marcellus Shale. Fracking or hydraulic fracturing as it is more properly known involves the pressurized injection of fluids commonly made up of mostly water and chemical additives into a geologic formation. The pressure used exceeds the rock strength and the fluid opens or enlarges fractures in the rock. As the formation is fractured, a “propping agent,” such as sand or ceramic beads, is pumped into the fractures to keep them from closing as the pumping pressure is released. The fracturing fluids (water and chemical additives) are partially recovered and returned to the surface or deep well injected. Natural gas will flow from pores and fractures in the rock into the wells allowing for enhanced access to the methane reserve.

Over the past few years, the use of hydraulic fracturing for gas extraction has increased and has expanded over a wide diversity of geographic regions and geologic formations beyond its original use in old oil and gas fields to revitalize them. By January of 2013, the daily production of methane (CH4) in the United States had increased 30% from January 2005 to about 70 billion cubic feet of gas each day. As fracking has expanded at what seems a breakneck speed in some regions, so has a public and regulatory concern about the possible environmental consequences of fracking and horizontal drilling. These concerns include air pollution from the operation of heavy equipment, human health effects for workers and people living near well pads from chemical exposure, noise and dust, induced seismicity from the disposal of fracking fluids, and increased greenhouse gas emissions from poor well head control and continued use of hydrocarbons.

However, the biggest health concern remains the potential for drinking water contamination from fracturing fluids, natural formation waters, and stray gases. While geologists and engineers believed that in hydraulic fracturing the intervening layers of rock prevent a fissure from extending into the water table, this had not been studied and there were reported instances of contamination of drinking water wells in areas that had been fracked. Only in the past three years has the potential to contaminate drinking water wells been studied. In a small group of studies (listed below) that were primarily in the Marcellus region of Pennsylvania, peer-reviewed studies found no evidence of salts, metals, or radioactivity beyond naturally occurring concentrations in drinking water wells near shale gas wells. However, in the latest studies they did find increased levels of methane in groundwater wells.

Methane gas occurs naturally in groundwater aquifers in most geological sedimentary basins. Methane gas exists in a dissolved state in the groundwater underground and will “bubble out” when pumped to the surface. For those on private water well supplies, spurting taps is a typical indication of this phenomenon. Methane present in groundwater can be a result of biogenic activity or can be from coal gas beds or from deeper shale gas. Biogenic methane is produced by subsurface bacteria and commonly occurs naturally in groundwater aquifers used for water well supplies. Thermogenic methane gas is produced at greater depths through high pressure and temperature processes and is characteristic of deep oil and gas reservoirs that conventional and shale gas wells tap into. Methane gas typically contains trace amounts of ethane. The proportion of methane to ethane in a gas can help determine its origin. Biogenic gas typically contains above 1,000 times more methane than ethane, but thermogenic gas has higher levels of ethane. In addition, isotope data can also be used to help determine whether a gas is biogenic or thermogenic. In the most recent research paper from the scientists at Duke University, University of Rochester and California State Polytechnic University (1) used these ratios to examine the occurrence and source of methane in drinking water wells in northeastern Pennsylvania.

A total of 81 samples from drinking water wells were collected in six counties in Pennsylvania (Bradford, Lackawanna, Sullivan, Susquehanna, Wayne, and Wyoming), and results were combined with 60 previous samples from a 2011 study by Stephen G. Osborn et al. (2). Dissolved methane was detected in the drinking water of 82% of the houses sampled (115 of 141 samples). Methane concentrations in drinking water wells of the homes closest to the gas wells were six times higher on average than concentrations for homes farther away. All of the 12 houses where CH4 concentrations were greater than 28 mg/L (the threshold for immediate remediation set by the US Department of the Interior) were well within a mile of an active shale gas well. Concentrations of ethane (C2H6) and propane (C3H8) were also higher in drinking water of homes near the shale gas wells.

The scientists concluded that the combined results suggest that natural gas, derived at least in part from thermogenic sources (the shale gas) was present in some of the shallow water wells less than a mile away from natural gas wells. The scientist pointed out that the two simplest explanations for the higher dissolved gas concentrations measured in the drinking water are faulty or inadequate steel casings and/or imperfections in the cement sealing (also known as the grouting) between casings and rock that keep fluids from moving up the outside of the well. In 2010, the Pennsylvania Department of Environmental Protection (DEP) issued 90 violations for faulty casing and cementing on 64 Marcellus shale gas wells; 119 violations were issued in 2011.

The scientist believed based on their isotopic analysis and previous studies that the cause of the elevated levels of methane (CH4) in the groundwater was due to imperfections in the cement grouting on the wells. Faulty cement grouting can allow methane and other gases from intermediate layers to flow into, up, and out of the void between the steel casing and the grouting into shallow drinking water layers. The geochemical and isotopic compositions of stray gas contamination in this scenario would not fully match the target shale gas, and no fracturing chemicals or deep formation waters would be expected, because a direct connection to the deepest layers does not exist; and this is consistent with their findings. Faulty grouting is believed to be the most likely cause of the scientists’ findings. Legacy or abandoned oil and gas wells (and even abandoned water wells) though a potential source of contamination, were unlikely to be the cause in this instance. Historical drilling activity was negligible within the study area making this mechanism unlikely there. Though, in 2000, the Pennsylvania DEP estimated that it had records for 141,000 of the 325,000 oil and gas wells that had historically been drilled in the state.

In another study by Duke University and the US Geological Survey no evidence of drinking water contamination from methane from shale gas was found in a part of the Fayetteville Shale in Arkansas (7). That shale has a less fractured geology than the Marcellus and good confining layers above and below the drinking water aquifers. Ultimately, we need to understand why, in some cases, shale gas extraction contaminates groundwater and how to ensure that contamination does not happen with a high level of certainty in susceptible geology. Well construction and maintenance needs to be studied, optimized and carefully regulated before further expansion of shale gas development.

1. Jackson, RB, Vengosh, A, Darrah, TH, Warner,  NR, Down, A, Poreda, RJ, Osborn, SG, Zhao, K, Karr,JD (2013) Increased stray gas abundance in a subset of drinking water wells near Marcellus shale gas extraction PNAS 2013 ; published ahead of print June24, 2013, doi:10.1073/pnas.1221635110
2. Osborn SG, Vengosh A, Warner NR, Jackson RB (2011) Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing. Proc Natl Acad Sci USA 108(20):8172–8176.
3. DiGiulio DC, Wilkin RT, Miller C, Oberley G (2011) Investigation of Ground Water Contamination Near Pavillion, Wyoming (US Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, Ada, OK), p 74820.
4. Warner NR, et al. (2012) Geochemical evidence for possible natural migration of Marcellus Formation brine to shallow aquifers in Pennsylvania. Proc Natl Acad Sci USA 109(30):11961–11966.
5. Chapman EC, et al. (2012) Geochemical and strontium isotope characterization of produced waters from Marcellus Shale natural gas extraction. Environ Sci Technol 46(6):3545–3553.
6. Boyer EW, et al. (2012) The Impact of Marcellus Gas Drilling on Rural Drinking Water Supplies (The Center for Rural Pennsylvania, Harrisburg, PA)
7. Kresse TM, et al. (2012) Shallow Groundwater Quality and Geochemistry in the Fayetteville Shale Gas-Production Area, North-Central Arkansas, 2011 (USGS), US Geological Survey Scientific Report 2012–5273 (Lafayette Publishing Service Center, Lafayette, LA).

Natural Gas, Energy and the Environment

It is a dream of some for the United States to become “energy independent.” For others the dream is to convert our nation to renewable energy sources. These two ideas or dreams are related, but we are not about to jump from oil dependence to solar and wind, and the resurgence of atomic power plants in the United States may not come to fruition after the post Tsunami reactor disaster in Japan. Many think that the way to progress is to move from oil and coal fired electrical generating plants to cleaner natural gas plants and from there to more renewable sources of power. Clearly, all your eggs in one basket mega power plant strategy is not the optimal plan.

Our ability to recover natural gas buried a mile or more beneath the earth has increased. Advances in horizontal drilling which allows a vertically drilled well to turn and run thousands of feet laterally through the earth combined with advances in hydraulic fracking, the pumping of millions of gallons of chemicals and water into shale at high pressure have increased our ability to recover natural gas from shale. Hydraulic fracking is a technology that was unknown 60 years ago. In the past decade the advances in drilling and fracking technology have been adapted to exploit gas in the Barnett shale in the Fort Worth Basin in Texas and applied to a series of major shale gas deposits that could not have been viable without the advances in drilling and fracking. The Fayetteville shale, the Haynesville shale, the Marcellus shale reserves all in the United States and the Horn River shales in Canada are now accessible. At the current rate of natural gas consumption North America is reported to have a 100-year supply of proven, producible reserves and even with expanded use of natural gas, there is more than a generation of currently accessible reserves.

A large swath of Pennsylvania, New York and West Virginia sit atop the Marcellus Shale, which is the third-largest natural gas field currently known in the world. The Marcellus Shale alone is estimated to be 500-trillion-cubic-feet of gas reserve. This resource could heat our homes for a generation or more, and power our electrical generating plants, even fuel cars either directly or through plug in hybrids. The possible impacts to our economy and environment are far reaching. The potential risks are also far reaching. http://www.absoluteastronomy.com/topics/List_of_natural_gas_fields

In hydraulic fracking on average 2-3 million gallons of chemicals and water is pumped into the shale formation at 9,000 pounds per square inch and literally cracks the shale or breaks open existing cracks and allows the trapped natural gas to flow. While geologists and engineers believe that there is little risk that the fracking “water,” a mix chemicals and water, will somehow infiltrate groundwater reserves though a fissure created by the fracking there are other routes of contamination and impact. It is believed that the intervening layers of rock would prevent a fissure from extending thousands of feet to the water table, there are other risks in how we build wells and fracture the shale. There have been documented cases of seepage into drinking water wells through improperly sealed or abandoned drilling wells. There are also places where groundwater is only several hundred feet above the gas reserves as they are in Wyoming and groundwater is more easily directly impacted by fracking.

Though it is unlikely that the strontium and barium and radioactive materials that occur naturally in the brine in the Marcellus shale, will flow from the shale through a crack or fissure up thousands of feet to the groundwater supplies, there are still other routes of contamination a portion of the fracking water is recovered and reused, disposed or stored. In fact, there have already been several high-profile cases of groundwater contamination. According to the PA Department of the Environment surface spills and shoddy construction practices (by Cabot Oil) allowed natural gas from a shallow deposit above the Marcellus to drift into the drinking-water wells of 14 Pennsylvania residents. The state is currently investigating traces of toluene, ethylbenzene and xylene chemicals that are sometimes used in fracking and are common in fuel found in some of the drinking water wells in the area. These could easily be long present contaminants from leaking underground storage tanks, but the residents did not regularly test and document their water quality historically.

According to the US Geological Survey in 2000 the United States used about 323 billion gallons per day of surface water and about 84.5 billion gallons per day of ground water. Although surface water is used more to supply drinking water and to irrigate crops, ground water is vital in that it not only helps to keep rivers and lakes full, it also provides water for people in places where visible water is scarce and rural areas. To survive over time, a population must live within the carrying capacity of its ecosystem, which represents a form of natural capital. One of the most important elements is potable water. Without water there can be no life. As populations grow water is needed for drinking, bathing, to support irrigated agriculture and industry. In the quest for fuel and wealth we can not forget our need for water.

The recharge of groundwater and the possibilities for its abstraction vary greatly from place to place, owing to rainfall conditions and the distribution of aquifers (rock and sand layers in whose pore spaces the groundwater sits). Generally, groundwater is renewed only during a part of each year through precipitation, but can be abstracted year-round. Provided that there is adequate replenishment, and that the source is protected from pollution, groundwater can be abstracted indefinitely.

Groundwater forms the invisible, subsurface part of the natural water cycle. Any attempt to accurately model the groundwater component of the water cycle requires adequate measurements and observations over decades. The computer models in common use in the United States only address the shallower groundwater and surface water interactions; GSFLOW (USGS) and ArcHydro (ESRI) are two commonly used models. Proper study and modeling of groundwater has not yet been done, rules of thumb and common knowledge assumptions are utilized instead of facts to assess the risks to water. This is irresponsible when pumping 2-3 million gallons of chemically laced water a mile into the earth. In hydraulic fracking water is pumped into the shale formation at 9,000 pounds per square inch and literally cracks the shale or breaks open existing cracks and allows the trapped natural gas to flow. To reach the gas deposits requires drilling though a couple of miles of earth and rock using “common knowledge” that our groundwater will not be impacted. In addition, natural gas which is methane and a significant greenhouse gas, escapes from the well heads due to imperfect operations, grouting and sealing. It is estimated that between 1% and 8% (depending on who is doing the estimating)of the natural gas escapes in this way.

This past spring, the Shale Gas Subcommittee of the Secretary of Energy Advisory Board was created to identify the measures that can be taken to reduce the environmental impact and improve the safety of shale gas production utilizing fracking. Their report was issued today after 90 days. The report had a rational approach to regulation recommending disclosure, testing, evaluation and modification of regulation and practices based on the information and data obtained. The report is to some extent a collection of the best regulatory framework among the states and covers little new ground overlooking some of the significant questions. This is a work product of a subcommittee at the Department of Energy that reports to the Secretary of Energy. EPA will be the regulatory agency and is currently engaged in a multi-year study of hydraulic fracturing. http://www.shalegas.energy.gov/resources/081111_90_day_report.pdf