Skip to main content

Benefits and Risks of Shale Gas Development (updated April 14, 2015)

L. M. Cathles, Professor in Department of Earth and Atmospheric Sciences


From student projects in a class I taught in 2010 and 2011, from my own (unfunded) research, and from discussions with colleagues inside and outside of Cornell, I have accumulated a good deal of material that could be of use to those seeking to understand issues involved in the Marcellus gas resource.  As a resource geologist I have felt a responsibility to be involved in this new (to the north eastern area of the U.S.) resource issue, and this blog puts the material in an accessible form.

This blog consists of short answers to questions with links to supporting material (immediately below), plus (at the end) spreadsheets, literature summaries, and links to more information.  (log of recent blog changes)

Questions Addressed (quick summaries with links to detailed material below the list)

  1. How big is the Marcellus resource?
  2. What is its geological story and why is it full of gas with no water?
  3. Does natural gas leak naturally?
  4. What are the upsides of gas recovery?
  5. What are the downsides?
  6. Will the water required for fracking deplete our water supplies?
  7. Why may the returned water contain radioactive elements like radium and how can this be handled or avoided?
  8. How much will traffic be increased and will there be road damage?
  9. Is natural gas good or bad for global warming?
  10. Will gas development be ugly?
  11. What are the alternatives?
  12. Has there been gas drilling or production in Tompkins County before?
  13. How do capillarly seals prevent flow and contain high pressure gas in the Marcellus?
  14. What do ground water chemistry studies in northeastern Pennsylvania tell us about methane leakage?
  15. Strategic considerations (Which fossil fuel posses the greatest risk?)
  16. Health Issues
  17. Overview/Summary/Recommendations
  18. Review of related papers not related to natural gas leakage (which are reviewed in Section 9)

1. How big is the Marcellus resource?

Quick A: Enough to supply the gas needs of the US for >20 years and, if produced over 30 years), equivalent to four hundred  1 GW nuclear power plants, or a wind farm covering the entire area underlain by the Marcellus with towers 240 m apart in rows separated by 800 m.  Here’s why.

2. What is its geological story?

Quick A:  The Marcellus was deposited as a very organic-rich mud 400 million years ago, which was then  buried and cooked to oil and then gas between 350 and 300  million years ago as the Appellachian mountains formed.   The gas became highly overpressured and fracked its way out.  As it continued to generate gas it dried itself out, like a hair blower.  In most places the Marcellus shale contains no water today- just gas.  The gas has been incarcerated, commonly in a highly overpressured state, for the last ~300 million years by capillary seals (the kind that arise when water and gas are mixed in the irregular plumbing of your intestines and give you gas indigestion).  If the Marcellus is hydrofractured it will be for the second time.  When the hydrofracing is done, capillary seals will keep whatever gas is left incarcerated for hundreds of millions of years. Powerpoint slides telling this story and more are here.  An excellent video presentation by J A Harper, Pennsylvania State Geologist is here.

3. Does natural gas leak naturally?

Quick A:  Anywhere substantial organic material is buried methane is generated (by bacteria or by cooking) and is leaking.  Remember how swamp gas was blamed for UFO sightings years ago?  Gas seeping under a stream in Fredonia, New York led to its capture and use 38 years before Drake drilled his well in Pennsylvania.  Natural leaks in Azerbaijan sustain “eternal flames” and probably account for the eternal flames of Nebakanezer.  Gas noticed on a Sunday school outing led to the discovery of Spindletop (one of our largest discoveries).   There is a gas fire under a waterfall in the Shale Creek Preserve at Chestnut Ridge Park, NY.  Gas was leaking in Dimock County Pa and it was possible to light the water on fire decades before gas drilling started there.  Natural leakage is  common, and natural – as you will see from these images.  A video presentation by me on this general subject can be viewed here.

4. What are the upsides of gas recovery?

Quick A: At $5 per thousand cubic feet, about $30,000 worth of producible natural gas lies under each acre of land overlying the Marcellus.  The Marcellus could supply 1/3rd of the total  present US energy needs (oil, gas, coal, hydro, renewables) over the next 20 years, and could significantly reduce our energy dependence on foreign sources.  Gas is a cleaner fuel when used in power generation or transportation.  Substitution of natural gas for coal and some oil could take us 40% of the way to the reduction of greenhouse gas emissions from substituting zero carbon energy sources.  Because gas will be a cheaper fuel than oil or coal if Marcellus-type resources are tapped, gas substitution will tend to happen automatically for economic reasons, and low energy costs will make U.S. manufactures more competitive.  The distributed nature of the gas royalties and the economic stimulus to the region is perhaps the best way to assure that our struggling farms survive and the rural character of upstate New York is maintained.    Taxes will flow to local, regional, and state governments.  Hiking pathes along pipelines could be a permanent legacy.  There are many real benefits to natural gas development. (No additional material).

5. What are the downsides?

Quick A:  Just about every downside has been articulated and rearticulated:  Drinking water could be depleted and what remains contaminated; the associated truck traffic could damage roads; the area could be industrialized; habitats could be fragmented; noise and air pollution could damage health; tourists and students could be repelled; natural gas could be worse than coal from a global warming perspective.  Many think these negatives mandate that we seek our energy from clean sources like wind or solar, but there are challenges with these sources also.  These issues are discussed in the points below.

6. Will the water required for fracking deplete our water supplies?

Quick A:  The water needed sounds like a lot when measured in billions of gallons, but stream flows are not measured in billions of gallons for a reason- the numbers are too big.  Instead streamflows are measured in cubic feet per second, and if put in these terms the amount of water that could be used for fracking is trivial.  We will not deplete our water supply.  Here’s why.

7. Why could the returned water contain radioactive elements like radium. How can these contaminants be handled or avoided?

Quick A:  Organic rich material tends to be uranium rich, and the first water soluble product of uranium decay is radium.  Its decay time is a small fraction of uranium’s, so its abundance is a small fraction of uranium’s, but it behaves like calcium and thus can accumulate in bones.  The good news is it can be detected and removed easily, as it is currently where drinking water requires it.  Attention will need to be paid to contaminants like radium (as well as others) in return water.  It might be possible to eliminate contamination by spillage of return water entirely, however, by fracking with gelled propane or some other non-aqueous fluid that would break down to gas.  Recovery of the gas could be greater if this is done because capillary barriers to gas recovery will not be formed if no water is injected.  Here’s some ellaboration.

8. How much will traffic be increased and will there be road damage?

Quick A:  Traffic during development will increase about 4%, but its impact can be minimized by restricting it to non-commuting hours.  “Heavy loads bend reoads” and the trucks involved in fracing will damage roads.  Means to pay for repairs need to be planned. There is a lot of information available on road use and damage.  Here is some of it .  Many more details are summarized here (see slides 41-51) and the corresponding notes here.

9. Is natural gas good or bad for global warming?

Quick A:  Using natural gas in place of coal and oil will reduce global warming and pollution.  There has been a long debate about whether enough natural gas could leak during its extraction and distribution that it would be more damaging than coal for global warming and push the world toward dangerous climate tipping points.  We now know that these fears are not warranted.  In the long term substituting gas for coal in electricity generation and oil in transportation will reduce warming by more than 40% of what is possible by transitioning immediately to zero carbon energy sources even if the natural gas leakage rate is very high.  Even if the leakage rate were 14% of consumption, a leakage far higher than any have suggested, the same temperatures would be reached in the short term as if natural gas were not substituted- they would just be reached a few years sooner.  Thus no tipping points that would not be encountered anyway will be reached.  Substituting gas in the short term can do no harm, and in the long term it very significantly reduces global warming because burning natural gas in preference to coal puts so much less CO2 into the atmosphere.  A diagram and one page elaboration can be found here).

We are already seeing the greenhouse benefits of substituting gas for coal.  The latest EPA report shows that the U.S. emissions of CO2 and CH4 are declining dramatically.  This link connects to an Excel spreadsheet that plots this data, and provides links to its sources.  Data and plots showing how natural gas is displacing coal in electricity generation in the U.S. are given.  The drop in U.S. CO2 emissions is at least 50% due to the substitution of natural gas for coal in electricity generation (see discussion by John Hanger here).  Methane leakage has plummeted to 1.7% after holding steady at 2.5% of natural gas production from 1990 to 2007.

The above statements are documented in an extensive primer on atmospheric chemistry and greenhouse warming that is summarized here with links to an extended discussion including simple spreadsheet methods for calculating atmospheric greenhouse gas concentrations and climate forcing.

This discussion replaces my previous discussion which focused on now irrelevant leakage rates.  The previous discussion which is available here, summarizes the exchange I had with Robert Howarth, a spreadsheet that implements his Global Warming Potential methods of analysis, a paper fully describing a proper way to calculate greenhouse climate change,  and a review of recent papers addressing methane leakage.

10. Will gas development be ugly?

Quick A: Here are some pictures (ground and from the air) I took on a tour of the Dimock Pennsylvania  area (the heart of shale gas development) in 2010.  The blue slate quarries farmers used to supplement their income over recent decades are more visable today and more permanent in the future than the gas drilling pads wil be.  See the pictures here and judge for yourself.  I believe it is clear the long term inpact on the countryside will be very small.

11. What are the alternatives?

Quick A:  With what energy source would you replace  the AES Cayuga coal electrical facility?   This is the question I posed to my “Energy and Mineral Resources of the Earth” class in the 2010 and 2011 fall semesters.  In 2010 the class answer was a mix of wind and natural gas in the near term, phasing into nuclear in the longer term.  In 2011 the class  recommended half wind and half coal for now and nuclear in the longer term.  They felt shale gas is currently so contentious that, as a practical matter natural gas is off the option table.   The land needed for wind and solar is substantial.   The land requirement of the various options for replacing the 350 MW AES facility are summarized here and the 2010  class recommendations here.  The detailed reports by the wind, solar, nuclear, and natural gas 2010 groups are at these links.  The 2011 class built on the work of the previous class and assembled a great deal of web material that can be readily accessed by the links they provide.  They considered pipelines, road damage, water contamination, wildlife fragmentation,  and managing the intermittency of wind, recommending compressed air storage as the best option for our area.  A summary with links to the reports of the 2011 class and their extensive references is here.

The viability of coal as an energy source was not addressed by the students, but depends (in the climate context) on  being able to sequester the CO2 generated.  Sequestration will require a large subsurface volume of porous sandstone, and the risk of escape of the CO2, which is deadly in high concentrations, will be of public concern.  Some elaboration is given here.

12. Has there been gas drilling or production in Tompkins County before?

Yes.   New York State has a long history of gas production.  William Hart dug a 27 ft deep pit to collect gas for his store in Fredonia in 1821 (38 years before the Drake well in Pennsylvania).  Gas drilling began in Tompkins county in 1888.  New York State Department of Environmental Conservation documents show that about 100 gas, brine (and two geothermal) wells have been drilled in Tompkins County since then.  Tompkins County had commercial gas production in the 40’s.  About 100 gas wells were drilled in Tompkins County starting in 1888.  A July 31, 2012 Guest Viewpoint column in the Ithaca Journal details this history.  Supporting scanned material supplements the DEC data base.

13. How do capillarly seals prevent flow and contain high pressure gas in the Marcellus?

The normal rules of fluid flow change completely when two fluid phases (say gas and water) are present in the pore space.  Everyone who has experienced gas indigestion knows this.  Gas bubbles in the sediments must deform to pass through the small pores of a fine sediment layer, and this requires pressure.  The gas bubbles pressed up against the pores prevents to flow of water.  The pressure drops at many fine layers combine to contain overpressured fluid such as the gas in the Marcellus and can do so for very long periods of time because they are virtually indestructible: when broken they re-heal because they depend only on grain size differences and the presence of two fluids (water and gas).  A few slides introduce these concepts here, a video illustrating the principles is here, more discussion can be found here and here, and a broad view of how capillary seals changed the rules of subsurface fluid flow when plants developed and hydrocarbons first appeared in the subsurface can be found here.  A full paper discussing these issues is reviewed here (Engelder et al (2013)) and a link to a pre-print of the paper is provided.

14. What do ground water chemistry studies in northeastern Pennsylvania tell us about methane leakage?

They tell us mostly about how meteroric water (rainfall) infiltrates in upland areas, circulates through the subsurface dissolving methane, and then upwells under low-lying areas.  This is the normal and expected subsurface circulation pattern.  The ground water chemistry illustrates how methane is removed from the subsurface and moved to topographically low areas by circulating water (see USGS topical report here).

This normal and expected pattern has been found in water well samples in northeastern Pennsylvania, but the analysts gave it a very different interpretation, suggesting that the topographically low areas are low because of fractures that connect donward to the Marcellus and allow upward methane leakage from the Marcellus that could be exacerbated by hydrofracturing.  Warner et al.’s (2012) data and interpretation is summarized here.

The suggestion that cross-formation leakage from the Marcellus to surface aquifers that is outside of engineering control is a serious suggestion because it means we may not be able to control leakage. It has been addressed vigorously.

A recent DOE study looked for leakage of the kind Warner et al. suggested in an ideal location where a portion of the Marcellus that was about to be hydrofractured was overlain by a convention gas reservoir and therefore wells were available to monitor any upward pressure pulses and gas and water contamination that might result from hydrofracturing.  None were found, as summarized here.

A second paper showed from noble gas analysis that 93 of 113 drinking water well samples in the same area that had elevated methane content acquired their methane by the natural ground water circulation described above.  Twenty of the samples had elevated methane levels because of leaks from nearby gas wells. Not only could the geochemistry distinguish clearly between well leaks and naturally-acquired ground water methane, but it could also show that in about half the well leak cases the gas had come up the well annulus from Upper Devonian shales, and in the other half Marcellus gas had leaked from the production casing.  In one case the geochemistry showed that the gas was introduced as the result of a packer failure.  In no cases was there evidence of gas migration up through the stratigraphy from the hydrofractured portions of the Marcellus.  The authors state strongly: “Noble gas data appear to rule out gas contamination by upward migration from depth through the overlying geological strata triggered by horizontal drilling or hydraulic fracturing.”  More discussion can be found here.

Finally there are good physical reasons why gas and water should not leak from the treated portions of the Marcellus.  Powerful capillary forces will keep them incarcerated just as these forces have kept the Marcellus gas incarcerated for over 200 million years (see discussion here).

The important conclusions from these papers are: only a relatively small portion of the methane introduced into aquifer drinking water is from gas wells (most is natural), the leakage comes from well defects that are under engineering and regulatory control not from enhancements in the natural leakage which would be outside engineering and regulatory control, and noble gas chemistry can be remarkably informative regarding the origin of elevated methane in drinking waters and the nature of the well leakage if that is its cause.

15. Which fossil fuel poses the greatest global warming risk?

Coal poses the greatest risk.   Estimates of the resource base of oil, natural gas, and coal (e.g., the amounts of these fuels that could possible be recovered) show that it is coal could add 6.6 PAL of CO2 to the atmosphere, whereas oil and gas could together add about 2 PAL.   A PAL is the mass of CO2 in the pre-industrial atmosphere.  Given the far greater potential of coal to add CO2 to the atmosphere, a wise strategy would be to encourage the developing world to focus first on fuels other than coal in the hope that lower carbon energy sources will become available before much of the coal resource is tapped.  More discussion is available here and in section 17 below.

16. Health Issues

Gas emissions from wells, trucks, and equipment can impact health.  But a detailed 2010 National Research Council Study indicates that air pollution associated with shale gas development will be far outweighed by the reduction of pollution associated with the conversion of coal to gas electricity generation.   This report is summarized here, but briefly the report calculates that the U.S. health impact from life cycle use of coal (90% used in electricity generation) is $62 billion per year. The life cycle (non-climate) health impact of natural gas is 20 times less.  Thus replacing gas for coal in electricity generation would save ~$59 billion in health damage per year.

A study of 9 old Michigan coal electrical plants (summarized here) provides a specific illustration.  The 9 plants cost Michigan $1.5 billion and the U.S. (the pollution spills across state boundaries) $5.4 billion per year in extra health costs.  In Michigan the plants cause 176 additional pre-mature deaths each year (660 in the U.S.), 76 additional cases of chronic bronchitis (280 in the U.S.) , and  68,000 additional asthma exacerbations (250,000 in the U.S.).  Against these numbers that the health impacts of the temporary air pollution associated with drilling, site preparation, and initial production of natural gas are very minor.  The one study that exists in the peer-reviewed literature examining the impact of air emission from shale gas operations suggests benzene and ethylbenzene are the main contributors to cancer risk.  It finds that levels of these pollutants are elevated near drilling operations, but only to about the levels that exist in urban areas of the U.S. (p 10 of report by Public Health England).  And unlike the urban environment these contaminants disappear when the drilling is finished.

The City of Ft. Worth commissioned the Eastern Research Group (ERG) to quantify health risk from hydrocarbon leakage related to Barnett gas production within city limits.  The surveying and monitoring spanned 2 months.  Eight sites were selected and monitored (1 background, one downwind of major highways, 2 in pre-production areas, 3 in high gas activity areas, and 1 in a medium production area. Forty weather and meterological stations near and in the city were used to define wind directions and carry out dispersion modeling.  Point source emissions at 338 sites and at least 10% of the all the components at each site that could leak were also monitored.  The conclusions: (1) no observed emissions during fracking or well drilling but some during well completion, (2) three fourths of emissions were associated with well pads, (3) extremely good repeatability of total leakage between first and second surveys at two sites, (4) strong leaks at some tank hatches, (5) most frequent leaks were at pneumatic valve controllers, and (6) no significant identified health threats.

None of this is to say that spills of fracking and particularly return fluid are not serious.  They are.  If animals drink the return fluids, as they are inclined to do because they like the saltiness, they can get very sick and die.  A good description of this in the reviewed literature is summarized here.  The cases described relate to leaks and volatile emissions from containment pits which could not happen now that return fluids are contained in tanks with closed loop feeds.  Nevertheless, the cases described are instructive, and it is clear that very careful attention needs to be paid to protecting animals when spills occur, to placing pads so that risks are minimized, to adopting procedures such a closed loop fluid handling systems and protective barriers under all pads that minimize or eliminate the risk of water spillage, and to eliminating additives that are particularly harmful.

Finally, when considering health economic impacts should not be forgotten.  The BBC reported recently on a study published in the Journal of Psychology that showed the economic crisis led to an acceleration in suicides and estimated, for example, that the economic crisis led to 4,750 additional suicides in the U.S. and 7,950 more in Europe.  Delaying resource prosperity may thus also have health impacts.

17.  Summary/Overview/Recommendations

A 2 1/2 page letter to Governor Andrew Cuomo summarizing the analysis in this blog and arguing that it is time to lift the moratorium and allow counties that choose to do so to develop their natural gas resources is reproduced here.  A critical part of the letter is a figure showing the global warming trajectory from 1600 to 2211 AD.  The figure illustrates how warming can be reduced by substituting natural gas for coal and some oil and shows that even with leakage as unrealistically high as 14% of consumption using gas will not expose us to any climate tipping points and will produce a significantly cooler planet in the long term.

A November 19th power point presentation to the Hudson-Mohawk Geologist Association directly assessing the climate, water and health implications of Marcellus development.

A power point presentation April 22, 2014 to the Joint Landowners Coalition of New York addresses the issues of global warming and water contamination from a scientific perspective.  Recommendations are made for obtaining the greatest benefit from natural gas development, including making provisions such that pipeline easements could be used as hiking trails.

A Future Rx showing how the 2011 plateaued world population of 10.5 billion  can live sustainably for 100’s of centuries can be read in this paper.

18. Review of publications not related to methane leakage

Recent papers on earthquakes, colloid-assisted contaminant transport, and the risk of treatment waters leaving treated shales are reviewed here.

Spreadsheet resources in the blog

  1. An excel greenhouse gas calculator that can be used to calculate the comparative impact of gas and coal as a function of leakage, GWP (time period), and electrical generation efficiency.  The method is that of Howarth et al. (2011).
  2. Spreadsheet graphics that plot recent trends in U. S. CO2 and CH4 emissions.
  3. spreadsheet that presents 3 future fossil fuel use scenarios, calculates the greenhouse gas emissions from them, predicts future atmospheric greenhouse gas concentrations assuming 55% of anthropogenic CO2 remains in the atmosphere and methane is in equilibrium with its emission rate from fossil fuel and agricultural sources, and provides graphical comparisons to convolution predictions.

Literature reviews:

  1. Review of gas leakage papers in Section 9.  Water papers are reviewed in Section 14.
  2. Review of other relevant papers mentioned in Section 18.
  3. Excellent comprehensive review in August 2014 issue of Elements (vol 10, nbr 4).

Links where more information can be found:

The Pennsylvania Dept. Env. Protection Oil and Gas website –wells can be located geographically and their permit numbers obtained

The PA oil and gas reporting website –using the permit number, gas or oil production information on a particular well can be obtained.  Also information on the quantity and mode of disposal of solid and liquid wastes from the well can be obtained.  These are very useful and easy to use web sites.

Paleontological Research Institute Marcellus Outreach

Cornell Cooperative Extension

Cornell Water Resources Institute

Penn State Extension

Joint Landowners Coalition of New York (see video tab on right bar)

Hydrologist Don Siegel, Syracuse University

Physicians Scientists & Engineers for healthy Energy

Andrew Revkin Dot Earth blog

Energy in Depth

Council on Foreign Relations blog

The Enterprise Blog