Presented by the University of Kentucky’s Center for Applied Energy Research
Vol. 23 No. 3/2012
Fracture Stimulation of Shale Gas Wells Is it Dangerous?
Brandon Nuttall, Kentucky Geological Survey Gas produced from low-permeability organic-rich shale has revolutionized the energy outlook in the United States. The total shale gas resource is estimated to be as much as 3,000 trillion cubic feet (Tcf) by the Energy Information Administration and the United States Geological Survey. Estimates of proven reserves likely exceed 97 Tcf. Exploration and development of these resources has increased petroleum liquids production, significantly reduced oil imports, and electric utilities are now turning to natural gas for new generation. Geologists have long recognized organicrich shales as petroleum-source rocks, but the combination of horizontal wells and fracture stimulation has unlocked the resources from these rocks. However, these technologies are not without controversies associated with the chemicals used, the potential for groundwater pollution, flaming faucets, and earthquakes. Oil and gas accumulations have four main properties: a reservoir, a seal that forms a trap, a source rock, and a migration pathway to connect the source and reservoir. Reservoirs are rocks characterized by a similar depositional system, structural set-
An underground source of drinking water (USDW) that is hundreds of feet below ground and a fracture stimulated horizontal well that is thousands of feet underground (not to scale). The illustration shows the well to be cemented from surface to the top of the gas shale. There are several rock units and sealing zones between the gas shale and the water source.
ting, porosity, permeability, pressure, and fluids. Seals are low porosity, low-permeability rocks that confine fluids in the reservoir. A source rock contains sufficient organic matter to generate hydrocarbons. In a reservoir, porosity is a measure of the total volume of void space in a rock and defines the available volume for fluid storage. Po-
rosity can occur within and between grains and in fractures. Permeability is a measure of the resistance to fluid flow within the rock and varies with the viscosity of the fluid. In gas shales, micrometer-scale and smaller pores, nanodarcy-scale permeability, and organic content contribute to make the shale a reservoir, trap, and source. continued on page 3
Revealing New Energy in a New CAER Building Energy research became more energy efficient as the University of Kentucky opened its newest energy research building this summer - a living laboratory devoted to renewable energy and energy storage. The $20.8 million laboratory building allows CAER to expand research devoted to Kentucky’s growing renewable energy industries, including biomass and biofuels, electrochemical power sources (like capacitors and batteries), and distributed solar-energy technologies.
What does the public think about energy, or does it? see page 2
At a press conference in August, Kentucky’s Governor Steve Beshear said, “It makes good sense for all buildings-not just those devoted to energy research-to be as energy-efficient as possible. Smart energy usage in buildings saves money and resources. Most importantly, the people inside this building are performing critical work in advanced energy research. Their efforts will undoubtedly impact Kentucky’s future in energy innovation.” continued on page 5
What does the public think about energy, or does it? Marybeth McAlister - Editor, Energeia
“Why aren’t we using more solar energy?” “I don’t think about energy unless I’m at the gas pump.” “If development of renewables was viable, companies would be doing it.” These were some of the questions and statements on energy made by “ordinary people” in a discussion I heard recently. For reasons that had nothing to do with my job, I was one of the people observing from behind the glass as a focus group met. Ten people had been chosen to participate. They were not told beforehand that they would be talking about energy issues facing the nation. They came from all walks of life; (accountant, midwife, administrative assistant, stay-at-home mom, student); were different ages (from their 20s – 60s); had varying levels of education (from high school through college graduates); and were of different races and genders. The discussion, led by a facilitator, lasted around two hours. Their only commonality, unlike most people who are reading this editorial, was they did not work in the energy field. Their connection to energy was that they are energy consumers. They hear about energy through the media, pay their heating and electric bills, drive cars, and recycle. However, it is not their top daily priority. It was a fascinating two hours. The octopus-like topic of energy produced a sprawling discussion. When prompted by the facilitator regarding how much time they devoted to thinking about the topic, most people admitted that they only think about it when they have to pay for it. As one man said, “I’m not an engineer. I don’t
know how to fix these problems.” Other than paying for energy, the other major impact on their lives seemed to be in recycling. That and other individual actions (combining trips, energy conservation, etc.) have become part of their lives. It was interesting that most agreed they would “put up with” paying a little more if it were for the greater good and that good could be measured. There is a general awareness that our dependence on fossil fuel is a looming problem. Many people spoke up about our complicated relationship with the Mideast. They admitted that we can’t be isolationists, yet were anxious about our dependence on foreign oil. The role of government to incentivize business for technology advancements in all types of energy sources was seen as important and needed to move innovative ideas forward. There was a “future” focus to the discussion. They agreed that there needs to be a long-range plan, “a bigger solution” and Americans must be willing to make tradeoffs and pay more. Some commented that the U.S. infrastructure isn’t sustainable given its citizens’ style of living and expectations. But when it came to how to make changes for our country’s future, the answers were all over the place. Some admitted that they did not like being told what to do, while others supported legislation to regulate consumers’ habits. Some thought we were only looking at short-term
“This matters to me because I have grandkids. What will their grandkids use for energy?”
solutions as a nation and that we needed a long-term solution to energy, looking at a variety of sources. Several thought Alaska was a good place for more energy sources. Petroleum exploration there was something they were willing to support as long as it was safe. Nuclear energy was suspiciously absent from conversation until the facilitator prompted discussion about its potential use. Nobody was strictly against nuclear, but all shared a “not in my backyard” mentality. In spite of Japan’s not-so-distant Fukushima break down, in general the group would again support the use of safe nuclear energy development. One woman put it succinctly when she said, “I can make individual consumption decisions, but can’t affect/change policy.” They see it as not their jobs to tackle this thorny issue. As long as the individual makes his or her day-to-day efforts, in their minds, they have done enough. At the end of the discussion, these folks left with the topic of energy at a much higher place in their consciousness – for now. But we can’t get everyone in the country to spend two hours in a focus group. That means it is up to local, state, and federal energy researchers and policy makers to push toward solving the multi-faceted energy issues. For most Energeia readers, that means the onus is on you.
“Americans can’t keep up this lifestyle forever. Developing countries want the things they see us have.”
Fracture Stimulation of Shale Gas Wells cont. Oil and gas are produced by drilling wells. A standard vertical well contacts only a small part of the reservoir. In conventional reservoirs with good porosity and permeability, this is usually adequate to produce oil and gas. A horizontal well is drilled so that more of the producing formation is exposed to the well bore along laterals that follow the bedding of rock units. When a horizontal lateral is completed by using fracture stimulation, or “fracing,” a maximum volume of the producing reservoir now has flow paths for oil and gas to move from the pores where it is stored to the well bore where it is produced at the surface. Well construction is a key component to protecting underground sources of drinking water. Standards and specifications are set forth by regulation and practices established over more than 150 years of drilling; in Kentucky, the main statute is KRS 353. Well construction begins with driving a large diameter pipe, “conductor,” into bedrock to prevent collapse of the material into the borehole. As the well is deepened, successively smaller diameter pipe, called casing, is installed to support the borehole and prevent the entry of undesirable fluids (including fresh water). In Kentucky, KRS 353 specifies that one string of casing must be installed through the deepest known fresh water zone and cemented to the surface in the annulus between the casing and the inner wall of the borehole. While drinking water standards include water that is 1,000 ppm or less total dissolved solids (TDS), the Safe Drinking Water Act defines fresh water as 10,000 ppm TDS or less for the purpose of protecting the resource. During drilling, air or specially engineered fluids are circulated down the drill pipe and exit through nozzles on the bit. This fluid then lifts rock material to the surface. The engineered fluids, “mud,” are designed to lubricate and cool the bit, support the borehole before casing is installed, prevent the exchange of fluids between the rock units and the borehole, and prevent high pressure reservoir fluids from reaching the surface in an uncontrolled manner. When the well reaches the planned total depth,
a continuous recording of the geophysical properties of the rocks is acquired and used to determine the most promising zones for producing hydrocarbons. Modern conventional (i.e., vertical) shale gas completions typically include a “long string” of casing set and cemented in over the entire shale interval. Horizontal wells have an advantage over vertical wells; they contact significantly more of the reservoir than a vertical well and can be steered to maximize the number of intersections with naturally occurring fractures. Multiple horizontal wells can be drilled from the same surface site thus minimizing the total surface disturbance required for drilling and production. In horizontal wells, the long string of casing is often set in a non-producing, sealing unit above the shale. A special bit that is powered by the fluids pumped through it, a downhole motor, is added to the drill string. Behind the motor is an assembly that includes an angled, bent, section that enables turning the well from vertical to horizontal. Several technologies are available for acquiring information that allows steering the bit to arrive at a planned target location. While it is possible to run casing and cement it in a horizontal lateral, most horizontal shale wells in Kentucky are not cased through the lateral. Once a well is constructed, it must be “completed.” In a vertical well that is cased and cemented across the shale, a tool is lowered into the borehole and used to perforate the casing and cement at selected depths. In a horizontal well, expanding devices, packers, are used to isolate sections of the lateral and the well is treated through ports positioned along the string of tools. Successive packers are set and ports opened along the lateral enabling the well to be stimulated in stages. Fracture stimulation refers to the use of energized fluids to overcome the mechanical strength of rocks, thus inducing fractures that propagate away from the well bore. In the 18th century, shallow water wells were typically fracture stimulated with black powder explosives. The first oil well in Kentucky to be explosively frac-
tured was drilled in 1888. Many of Kentucky’s oil and gas wells were completed with nitroglycerine and gelled explosives. Today, ANFO and TNT are the most commonly used explosives. Water-based or hydraulic fracturing was first used in 1946 in Kansas and the technique was introduced in eastern Kentucky shale wells in 1966. Kentucky’s shales include clay minerals that absorb water causing the clays to expand. Experiments determined that nitrogen could be energized and used for fracturing and since the 1970s, Kentucky shale gas wells have used nitrogen. Today, small amounts (thousands of gallons) of water are added to the nitrogen to create a foam. Carbon dioxide (a cryogenic frac) and propane have also been used for fracture stimulations. The goal of fracture stimulation is to create a network of pathways to maximize communication between the reservoir and the wellbore. To that end, fluids used in hydraulic fracturing often contain additives. Depending on various factors, the fluid is typically 90 to 95 percent (or more) water. The hydraulic fracture stimulations employed in the Marcellus shale (New York, Ohio, and Pennsylvania) can use as much as 3 to 5 million gallons of water. Sand is added to the mixture. The sand is transported into the induced fractures and when the pressure used for the treatment is released, the sand remains to prop the fractures open. The mixture of sand and water is typically 99 percent of the total volume pumped. The remaining volume of fluids contains a number of chemical additives. Corrosion inhibitors, usually petroleum products, are added to protect the steel casing. Thickeners like guar gum are added to increase the sand-carrying capacity of the water. Friction reducers enhance fluid entry into the reservoir. Breakers, usually enzymes or oxidizers, are added to lower the viscosity so the sand tends to stay where it is placed. Biocides prevent the growth of bacteria that over time would reduce flow efficiencies. Acids are used to clean up the perforations and changes in pH can be used as triggers to initiate the actions of enzymes or oxidation. Many of continued on page 4
continued...Fracture Stimulation of Shale Gas Wells - Is it Dangerous? these additives are certainly toxic. Ethylene glycol, for example, is a commonly used corrosion and scale inhibitor. Some, like the biocides, water softeners, and many others, are used in household cleaning products. The chemicals used are tailored to specific reservoir conditions; not all are used in every stimulation. The controversy over the nature of these additives has led to the creation of a voluntary chemical registry for hydraulically fractured wells. FracFocus.org is a web site sponsored by the Interstate Oil and Gas Compact Commission and the Groundwater Protection Council. In addition to a registry of chemical additives with their material safety data sheets, operators are listing the chemicals used in individual wells that can be accessed and queried by several criteria. Colorado, Texas, Louisiana, Montana, and North Dakota have made reporting to FracFocus.org mandatory and other states are considering similar legislation. Drinking water quality can be impaired through both natural and man-made processes. In the subsurface, rocks contain varying amounts of fluids including oil, gas, fresh, and salt water that can seep to the surface. In Kentucky, underground sources of drinking water generally occur at depths of less than 1,000 feet. Natural salt, oil and gas and fresh water springs abound as evidenced by the number of places named for them. Pioneers often relied on these springs for the necessities of life and the Commonwealth has recognized their scenic, historic, and geologic importance. Oil and gas reservoirs are usually thousands of feet deep but can occur at the surface. As depth increases, water quality changes from drinkable at shallower depths to nasty at deeper depths. Under provisions of the Safe Drinking Water Act, water that contains 10,000 parts per million total dissolved solids or less must be protected. There are several ways things can go wrong and fluids or gas can leak into underground sources of drinking water.
Multiple impermeable and fluid-saturated zones between the stimulated zone and underground sources of drinking water indicate the improbability of direct contamination of drinking water with frac fluids from the deeper subsurface. It is more likely that in a poorly constructed well, casing and cement failures can lead to the contamination of groundwater with chemicals or gas. Poor construction of domestic water supply wells only exacerbates the problem. The fracture stimulation can propagate out of the intended zone if an unexpected natural fracture or old well bore is encountered. Kentucky has a plugging fund administered by the Division of Oil and Gas to remediate abandoned wells. The association between earthquake events and fracturing is being investigated in the Barnett shale in Texas and the Fayetteville Shale in Arkansas. A recent documentary implied these problems were pervasive and endemic to the production of shale gas. Out of the hundreds of thousands of fracture stimulated wells completed since the 1940s the incidence of well failures is very small. A suit against the EPA and the Alabama Oil and Gas Board alleging groundwater contamination and failure to regulate hydraulic fracturing in coal seams resulted in an EPA study that in 2004 concluded no direct evidence of water impairment to surface water quality from the practice. Recently, the U.S. EPA has investigated
drilling baseline water quality data made it impossible to determine if observed impairments to water quality were related to pre-existing conditions or hydraulic fracturing. In Pennsylvania, they held an oil and gas operator liable for remediation. The company signed a consent order to address the problem and in 2011, a Pennsylvania DEP review concluded the operator had fulfilled its obligations. One of the most dramatic scenes in the video was the ignition of methane in tap water. Prior to the release of the video, the Colorado Oil and Gas Commission investigated the incident and concluded the gas was biogenic methane sourced from the aquifer tapped by the domestic water supply well and not related to hydraulic fracturing. Many eastern Kentucky wells that serve as domestic water sources are similarly contaminated by biogenic methane produced from coals. In Texas, a similar incident was attributed to thermogenic gas co-produced with fresh water from a shallow reservoir known to be an oil and gas producer in the area and not from the deeper hydraulically fractured shale gas wells. More recently, small seismic events around Youngstown, Ohio were blamed on hydraulic fracturing. Similar claims have been made in both Texas and Arkansas. Studies conducted at the Rocky Mountain National Arsenal indicate water injection into an existing fracture system can induce seismic activity. Inves-
To date, Federal and state studies have found no direct or significant impact to shallow underground sources of drinking water that can be traced to hydraulic fracturing of much deeper gas shales. claims of degraded water quality in Pavilion, Wyoming and Dimock, Pennsylvania that included the presence of diesel and gasoline in groundwater. In these cases, the EPA concluded a lack of pre-
tigations by the National Science Foundation and the U.S. Geological Survey have found that seismic events may be associated with hydraulic fracturing, but these events are small. The few dozen events continued on page 5
of greater magnitude are associated with underground disposal of waste water and have not caused either structural damage or loss of life. Water disposal is regulated under the U.S. EPA Underground Injection Control program that has permitted tens of thousands of UIC Class I and II injection wells that exhibit no problems related to induced seismicity. The few wells with seismic problems may need review to change their injection rates and schedule or they may have to be abandoned. Neither condition condemns the operation of the vast majority of disposal wells. To date, Federal and state studies have found no direct or significant impact to shallow underground sources of drinking water that can be traced to hydraulic fracturing of much deeper gas shales. Regulation of well construction and surface discharges under the Safe Drinking Water
Act are adequate to prevent impairment risk to the public is small while the benof water supplies provided there is suffi- efits of developing vast domestic energy cient funding for inspection and enforce- resources is large. ment. Induced seismicity appears related to waste water disposal and not hydraulic fracturing. Oil and gas service companies are experimenting with alternatives to hydraulic fracturing (cryogenic and propane fracs) and are developing biodegradBrandon Nuttall is a geologist within the able alternatives to toxic energy and minerals section of the Kentucky additives. Certainly, water Geological Survey. resources can be affected He can be reached at: email@example.com by accidents or human error at ground level but the A Powerpoint presentation on this topic is posted in the KGS presentation library. Click here to view and download the presentation (see also the presentation notes pages).
Revealing New Energy in a New CAER Building cont. His remarks were echoed by Stella Fiotes, chief facilities management officer of the National Institute of Standards and Technology (NIST), which provided the majority of funding. “We’re excited to see this new laboratory open and begin hosting research into renewable energy and energy storage. This work will complement NIST’s measurement research in support of clean technologies and energy efficiency.” The building itself was the star of the show after the press conference, when toured by dignitaries. According to CAER director Rodney Andrews, “Our target was at least a 50 percent reduction in energy usage compared to similar facilities. The final percentage is 54. It is targeted to be LEED gold certified.” Energy reduction is accomplished through energy-saving features throughout the building, including an exterior and roof with twice the amount of insulation normally used. Windows contain a nanogel material that diffuses sunlight and provides the same insulation as brick walls. Among other features are geothermal heating and cooling, occupancy
sensors that turn off lights automatically when a space isn’t being used, and a ventilation system that recaptures energy. The facility was funded by a competitive grant from the U.S. Department of Commerce’s National Institute of Standards and Technology under the American Recovery and Reinvestment Act’s (ARRA) NIST Construction Grant Program. The award consisted of $11.8 million in federal funds, with matching resources of $3.5 million provided by the Commonwealth of Kentucky and $1.9 million from UK. An additional award of $3.5 million in state ARRA funds was provided by the Department of Energy to achieve LEED certification and insure that this new laboratory is a model for energy efficiency and renewable energy technologies. This funding has enabled UK to develop unique labs including a dry room designed for battery manufacturing
and testing, an open-access biofuels research lab, and state-of-the-art solar research facilities. The entire second floor is devoted to research performed by UK Department of Chemistry Professor John Anthony’s group, whose work includes organic thin-film transistors (for flexible flat-panel displays), organic solar cells (for low-cost electricity generation) and organic light-emitting diodes (for highefficiency lighting). “For nearly 150 years, the University of Kentucky has been an engine for growth in the Commonwealth continued on page 6
Biofuels researchers investigate algae for CO2 removal from coal-burning power plants.
of Kentucky transforming lives through education, research and service,” said UK President Eli Capilouto. “Today we are taking another major step forward in advancing our century-and-a-half old promise. The research and creative discoveries developed by our world-class engineers at UK’s Center for Applied Energy Research and in the cutting-edge laboratories in this new facility will bolster an essential industry and energize our Commonwealth’s economy.” In addition to housing non-fossil fuel research, the building is home to the Kentucky-Argonne Battery Manufac-
turing Research & Development Center laboratories, jointly affiliated with the Commonwealth of Kentucky, the Argonne National Laboratory in Chicago, the University of Kentucky, and the University of Louisville. This is a shared-use facility, with portions of the laboratory purposely designed and specially equipped to accommodate capacitor and battery manufacturing research and development.
Dr. John Anthony (right) alongside a CAER graduate student (left) demonstrate the capabilities of a vacuum evaporator.
Press Conference &
Grand Opening of Lab #2
David Drake, CAER Advisory Board Chairman
Eli Capilouto, University of Kentucky President
Stella Fiotes, Chief Facilities Management Officer, National Institute of Standards and Technology
Steve Beshear, Governor of Kentucky
Eric Isaacs, Argonne National Director Jim Gray, Mayor of Lexington
Greg Stumbo, Kentucky House of Representatives, Speaker of the House
CAER longtime Associate Director of the Clean Fuels and Chemical Group, Burt Davis has been selected as the 2013 American Chemical Societyâ€™s Energy & Fuels Division Distinguished Researcher Award in Petroleum Chemistry. Criteria used for the award include excellence in research in the broadly defined area of petroleum chemistry, as evidenced by publications, patents, invention or commercialization of new technologies, and leadership in the research area. Dr. Davis is also a former ACS Storch Award recipient from 2002. One of the ACS top awards, the Storch Award recognizes distinguished contributions to fundamental or engineering research on the chemistry and utilization of all hydrocarbon fuels, with the exception of petroleum.
Carbon Capture 101 Workshop
Organized by the University of Kentucky Center for Applied Energy Research This workshop will offer a series of informative technical presentations that will provide an overview of carbon capture technologies and recent research progress. The intended audience is primarily power industry engineers, professors, and scientists along with other key stakeholders wishing to become more informed in carbon management issues and recent technical advances.
Location: Hilton Downtown, Lexington, KY Date: February 4-5, 2013 Cost: $300 per attendee, $100 per students For registration, agenda, and other information, go to: http://www.caer.uky.edu/events/cmrg2012/home.shtml
Energeia is published online four times a year by the University of Kentucky Center for Applied Energy Research (CAER). The newsletter features aspects of energy resource development and environmental topics. Online subscriptions are free and may be requested by sending your email address to: Marybeth McAlister, Editor of Energeia, firstname.lastname@example.org. The mailing address is: CAER, 2540 Research Park Drive, Lexington, Kentucky 40511. Past issues of Energeia may be viewed on the CAER web site at www.caer.uky.edu Copyright 2012, University of Kentucky