Water Resources and Natural Gas Production from the Marcellus Shale

By Daniel J. Soeder1 and William M. Kappel2

Introduction What is the Marcellus Shale? Why is the Marcellus Shale an Important Gas Resource? he Marcellus Shale is a The Marcellus Shale forms Tsedimentary rock formation the bottom or basal part of a thick Organic matter deposited with deposited over 350 million years ago sequence of Devonian age, the Marcellus Shale was compressed in a shallow inland sea located in sedimentary rocks in the Appalachian and heated deep within the Earth over the eastern United States where the Basin. This sediment was deposited geologic time, forming hydrocarbons, present-day Appalachian Mountains by an ancient river delta, the remains including natural gas. The gas occurs now stand (de Witt and others, 1993). of which now form the Catskill in fractures, in the pore spaces This shale contains significant Mountains in New quantities of natural gas. New devel- York (Schwietering, opments in drilling technology, along 1979). The basin with higher wellhead prices, have floor subsided under made the Marcellus Shale an important the weight of the natural gas resource. sediment, resulting The Marcellus Shale extends in a wedge-shaped from southern New York across deposit (fig. 2) that Pennsylvania, and into western is thicker in the Maryland, West Virginia, and eastern east and thins to the Ohio (fig. 1). The production of com- west. The eastern, mercial quantities of gas from this thicker part of the shale requires large volumes of water sediment wedge to drill and hydraulically fracture the is composed of rock. This water must be recovered sandstone, siltstone, from the well and disposed of before and shale (Potter the gas can flow. Concerns about the and others, 1980), availability of water supplies needed whereas the thinner for gas production, and questions sediments to the about wastewater disposal have been west consist of finer- raised by water-resource agencies grained, organic- and citizens throughout the Marcellus rich black shale, Shale gas development region. This interbedded with Fact Sheet explains the basics of organic-lean gray Marcellus Shale gas production, with shale. The Marcellus the intent of helping the reader better Shale was deposited understand the framework of the as an organic-rich water-resource questions and concerns. mud across the Appalachian Basin before the influx of 1U.S. Geological Survey, MD-DE-DC Water Science Center, 5522 Research Park Drive, the majority of the Baltimore, MD 21228 younger Devonian 2U.S. Geological Survey, New York Water sediments, and was Figure 1. Distribution of the Marcellus Shale (modified from Science Center, 30 Brown Road, Ithaca, NY 14850 buried beneath them. Milici and Swezey, 2006).

U.S. Department of the Interior Fact Sheet 2009–3032 Printed on recycled paper U.S. Geological Survey May 2009 2 Water Resources and Natural Gas Production from the Marcellus Shale

Figure 2. West to east line of section A-A’ of Middle and Upper Devonian rocks in the Appalachian Basin. The Marcellus Shale is the lowest unit in the sequence (modified from Potter and others, 1980).

between individual mineral grains, and of the resource, estimating recoverable to intercept sets of existing, natural is chemically adsorbed onto organic gas, and determining the most effec- fractures within the shale (fig. 3), a matter within the shale (Soeder, 1988). tive technology for gas extraction. The network of flowpaths could be To produce commercial amounts of EGSP shale stimulation experiments created. natural gas from such fine-grained tested a wide variety rock, higher permeability flowpaths of hydrofracs and must be intercepted or created in the other techniques. formation. This is generally done using Results were some- a technique called hydraulic fracturing what uneven, and or a “hydrofrac,” where water under DOE concluded high pressure forms fractures in the that stimulation rock, which are propped open by sand alone was gener- or other materials to provide pathways ally insufficient to for gas to move to the well. Petroleum achieve commercial engineers refer to this fracturing shale gas production process as “stimulation.” (Horton, 1982). It From the mid-1970s to early was suggested that 1980s, the U.S. Department of Energy better success could (DOE) funded the Eastern Gas Shales be obtained by tar- Project (EGSP) to develop new tech- geting specific for- nology in partnership with industry mations in specific that would advance the commercial locations. The EGSP development of Devonian shale gas results did indicate Figure 3. Marcellus Shale drill core from West Virginia, 3.5 (Schrider and Wise, 1980). Goals of that if the hydraulic inches in diameter, containing a calcite-filled vertical natural the project included assessing the size fractures were able fracture. Photograph by Daniel Soeder, USGS. 3 Water Resources and Natural Gas Production from the Marcellus Shale

turned 90 degrees to penetrate long horizontal distances, sometimes over a mile, through the Marcellus Shale bedrock. Hydraulic fractures are then created into the rock at intervals from the horizontal section of the borehole, allowing a substantial number of high-permeability pathways to contact a large volume of rock (fig. 5). According to Range Resources (2008), one of the first major horizontal drill- ers of Marcellus Shale, these wells typically produce gas at a rate of about Figure 4. Wellhead price of natural gas since the mid-1970s to January 2009. [Source 4 MMCF (million cubic feet) per day. U.S. Energy Information Administration, 2009.] Over its lifetime, each horizontal well on an 80-acre surface spacing can be expected to produce a total of about In the mid-1980s, the Institute of Why is the Marcellus Shale 2.5 BCF (billion cubic feet) of gas at Gas Technology (IGT) in Chicago per- Being Developed Now? an estimated production cost of $1.00 formed some laboratory analyses on per MCF (Chernoff, 2008). EGSP shale samples (Soeder, 1988). Low prices for natural gas, and Published IGT lab measurements ineffective production technology did What are the Water-Resource found that a “gas-in-place” value for little to spark interest in Devonian Concerns About Developing the Marcellus Shale at pressures rep- shale gas in the 1990s, despite the Natural Gas Wells in the resentative of production depths may publication of the IGT Marcellus Marcellus Shale? be as high as 26.5 standard cubic feet gas-in-place estimates. Two factors of gas per cubic foot of rock (Soeder, working together have promoted the Substantial amounts of water are 1988). This greatly exceeded earlier current high levels of interest in the required for the drilling and stimula- gas-in-place estimates for Devonian Marcellus Shale. First, wellhead prices tion of a Marcellus Shale gas well. shale by the National Petroleum for gas have risen from values of less Fluids recovered from the well, includ- Council (1980), which ranged from than $2.00 per MCF (thousand cubic ing the liquids used for the hydrofrac, 0.1 to 0.6 standard cubic feet of gas feet) in the 1980s (fig. 4) to a peak and any produced formation brines, per cubic foot of rock. Although IGT of $10.82 per MCF in the summer must be treated and disposed of prop- analyzed only one sample of Marcellus of 2008 (U.S. Energy Information erly. Three important water-resource Shale, the large volumes of gas now Administration, being produced from this formation 2009). Although substantiate the early discovery of prices had declined significant gas reserves. to $5.15 per MCF in In 2008, two professors January 2009 due to at Pennsylvania State University and the economic down- the State University of New York turn, they are still (SUNY) Fredonia estimated that about substantially higher 50 TCF (trillion cubic feet) of recov- than a decade earlier. erable natural gas could be extracted The second from the Marcellus Shale (Engelder factor that spurred and Lash, 2008). In November 2008, interest in the on the basis of production information development of the from Chesapeake Energy Corporation, Marcellus Shale is a the estimate of recoverable gas from new application of the Marcellus Shale was raised to an existing drilling more than 363 TCF (Esch, 2008). technology known The United States uses about 23 TCF as directional drill- of natural gas per year (U.S. Energy ing, which involves Information Administration, 2009), steering a downhole so the Marcellus gas resource may be drill bit in a direction Figure 5. Combination of directional drilling and hydraulic large enough to supply the needs of the other than vertical. fracturing technology used for gas production from the entire Nation for roughly 15 years at An initially vertical Marcellus Shale in the Appalachian Basin (modified from the current rates of consumption. drillhole is slowly http://geology.com/articles/marcellus-shale.shtml). 4 Water Resources and Natural Gas Production from the Marcellus Shale

Shale gas production areas, but not yet fully implemented.

Transporting Fluids and Supplies

Large hydrofrac treatments often involve moving large amounts of equipment, vehicles, and supplies into remote areas (fig. 6). Transporting all of this to drill sites over rural Appalachian Mountain roads could potentially cause erosion, and threaten local small watersheds with sediment. Drill pad and pipeline construction also have the potential to cause similar problems. Of equal concern is the possibility for spills or leaks into water bodies as the fluids and chemical additives are transported and handled. Little is known about how a Marcellus Shale drilling “boom” might adversely affect the land, streams, and available Figure 6. A hydraulic fracturing stimulation in 2007 on a Marcellus Shale gas well showing water supplies in the Appalachian the amount of equipment involved. Basin. Even under current Marcellus gas production levels, complaints of rural road damage and traffic disrup- tion from drilling equipment have been concerns related to Marcellus Shale gallons of water per treatment (Harper, received, indicating that this could be gas production are: 2008). Many regional and local water a significant problem if carried out management agencies are concerned across thousands of active drill sites. • supplying water for well construc- about where such large volumes of tion without impacting local water water will be obtained, and what the Wastewater Disposal resources, possible consequences might be for local water supplies. Under drought For gas to flow out of the shale, • avoiding degradation of small conditions, or in locations with already nearly all of the water injected into the watersheds and streams as sub- stressed water supplies, obtaining the well during the hydrofrac treatment stantial amounts of heavy equip- millions of gallons needed for a shale must be recovered and disposed of. In ment and supplies are moved gas well could be problematic. Drillers addition to the problem of dealing with around on rural roads, and could face substantial transportation large bulk volumes of liquid waste, costs if the water has to be trucked in contaminants in the water may com- • determining the proper methods from great distances. plicate wastewater treatment. Whereas for the safe disposal of the large Similar shale gas operations in the the percentage of chemical additives in quantities of potentially contami- Barnett Shale of Texas have obtained a typical hydrofrac fluid is commonly nated fluids recovered from the hydrofrac water largely from ground- less than 0.5 percent by volume, the wells. water sources (Byrd, 2007). Water- quantity of fluid used in these hydro- supply concerns over the Barnett Shale fracs is so large that the additives in a These concerns are discussed in drilling have been brought up in the three million gallon hydrofrac job, for more detail in the following sections. past (see, for example, Francis, 2007). example, would result in about 15,000 Texas State and County agencies now gallons of chemicals in the waste. Water Supply closely monitor volumes of water used Hydrofrac fluids are often treated during drilling, and a consortium of with proprietary chemicals to increase Drilling requires large amounts Barnett Shale drilling companies have the viscosity to a gel-like consistency of water to create a circulating mud developed best management practices that enables the transport of a that cools the bit and carries the rock for water conservation, with the goal proppant, usually sand, into the frac- cuttings out of the borehole. After of keeping the pace of drilling and ture to keep it open after the pressure drilling, the shale formation is then production activities within the bounds is released (fig. 7). The viscosity of stimulated by hydraulic fracturing, of sustainable water use. Similar steps these fluids then breaks down quickly which may require up to 3 million have been discussed in Marcellus after completion of the hydrofrac, so 5 Water Resources and Natural Gas Production from the Marcellus Shale

the Oriskany or Potsdam Sandstones. A third disposal process used in Texas places the wastewater into an open tank to evaporate. The solids that remain behind are then disposed of as dry waste. Although this may be an effective technique in the deserts of the American Southwest, its usefulness in the humid climate of the Appalachians is questionable. A systematic study of the options for Marcellus Shale waste fluid treatment, disposal, or recycling could help to determine the best avail- able procedures. Summary

Natural gas is an abundant, domestic energy resource that burns cleanly, and emits the lowest amount Figure 7. Example of a gel used in hydrofracturing to carry proppant into a fracture. of carbon dioxide per calorie of any Photograph by Daniel Soeder, USGS. fossil fuel. The Marcellus Shale and other natural gas resources in the United States are important components of a national energy they can be easily removed from the other heavy metals, and radionuclides program that seeks both greater energy ground. The chemical formulations that significantly exceed drinking- independence and greener sources of required to achieve this are highly water standards (Harper, 2008). energy. Marcellus gas development researched and closely guarded, and The current disposal practice has begun in the northern Appalachian finding out exactly what is in these for Marcellus Shale liquids in Basin, with significant lease holdings fluids may present a challenge. The Pennsylvania requires processing them throughout Pennsylvania, West data publicly available on Marcellus through wastewater treatment plants, Virginia, southern New York, western Shale hydrofrac treatments indicate but the effectiveness of standard Maryland, and eastern Ohio. Because that a slickwater frac works best on wastewater treatments on these fluids of questions related to water supply this formation (Harper, 2008). These is not well understood. In particular, and wastewater disposal, however, types of hydrofracs employ linear gels salts and other dissolved solids in many state agencies have been and friction reducers in the water, and brines are not usually removed suc- cautious about granting permits, and utilize only small amounts of proppant, cessfully by wastewater treatment, some states have placed moratoriums relying instead on fracture surface and reports of high salinity in some on drilling until these issues are roughness to hold it open (Rushing Appalachian rivers have been linked to resolved. At the same time, gas and Sullivan, 2007). The potential the disposal of Marcellus Shale brines companies, drillers, and landowners problems for local wastewater treat- (Water and Wastes Digest, 2008). are eager to move forward and develop ment facilities caused by proprietary Another disposal option involves the resource. chemical additives in hydrofrac fluid re-injecting the hydrofrac fluids While the technology of drilling are unclear. back into the ground at a shallower directional boreholes, and the use of Along with the introduced depth. This is a common practice in sophisticated hydraulic fracturing chemicals, hydrofrac water is in close the Barnett Shale production area processes to extract gas resources contact with the rock during the course of Texas, and has been utilized for from tight rock have improved over of the stimulation treatment, and when some Marcellus wells drilled in West the past few decades, the knowledge recovered may contain a variety of Virginia (Kasey, 2008). Concerns of how this extraction might affect formation materials, including brines, in Appalachian States about the water resources has not kept pace. heavy metals, radionuclides, and possible contamination of drinking- Agencies that manage and protect organics that can make wastewater water supply aquifers has limited the water resources could benefit from a treatment difficult and expensive. The practice of re-injecting Marcellus better understanding of the impacts formation brines often contain rela- fluids, however. Another option might that drilling and stimulating Marcellus tively high concentrations of sodium, be to inject the waste fluid into deeper Shale wells might have on water chloride, bromide, and other inorganic formations below the Marcellus Shale supplies, and a clearer idea of the constituents, such as arsenic, barium, that are not used as aquifers, such as options for wastewater disposal. References Cited Horton, A.I., 1982, 95 stimulations in Schrider, L.A., and Wise, R.L., 1980, 63 wells — DOE reports on compar- Potential new sources of natural gas: Byrd, C.L., 2007, Updated evaluation ative analysis of stimulation strategy Journal of Petroleum Technology, for the Central Texas Trinity Aquifer in eastern gas shales: Columbus, v. 32, no. 4, p. 703–716, DOI Priority Groundwater Management OH, Northeast Oil Reporter, 10.2118/7628–PA. Area, Priority Groundwater p. 63–73, February 1982. Management Area File Report: Schwietering, J.F., 1979, Devonian Austin, TX, Texas Commission on Kasey, Pam, 2008, New drilling efforts shales of Ohio and their eastern and Environmental Quality, Water Rights raise questions: Charleston, WV, southern equivalents: Morgantown, Permitting and Availability Section, The State Journal, August 14, 2008, WV, Report METC/CR–79/2, pre- Water Supply Division, 160 p. accessed March 16, 2009 at http:// pared for U.S. Department of Energy statejournal.com/story.cfm?func=vie under contract EY–76–C–05–5199, Chernoff, Harry, 2008, Investing wstory&storyid=42542. West Virginia Geologic and in the Marcellus Shale, article on Economic Survey, January 1979. 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March 16, 2009 at http://www.fwbusi- com/PressReleases.asp. or visit our Web site at: nesspress.com/display.php?id=5838. http://md.water.usgs.gov Rushing, J.A., and Sullivan, R.B., Harper, J.A., 2008, The Marcellus 2007, Improved water frac increases Shale — an old “new” gas reser- production: Houston, TX, E&P Fact Sheet 2009–3032 voir, in Pennsylvania Geology: Magazine, Hart Energy Publishing, Pennsylvania Department of September 2007, accessed January Conservation and Natural Resources, 28, 2008 at http://www.epmag.com/ v. 38, no. 1, 20 p. archives/features/661.htm.