Monday, May 9, 2011

Updated: Comments on Duke University Study Regarding Methane Contamination of Water Wells

Duke University released today a study of methane contamination of water wells, finding that gas drilling has contaminated some water wells with methane.  The study also concludes that frack fluids have not contaminated water wells.   See

The Duke findings are consistent with DEP findings that gas had migrated from some drilling sites to water wells, but that no case of frack fluids returning from depth to contaminate water wells had happened in Pennsylvania.

The Duke University study looks at 68 water wells in 5 counties, with Bradford and Susquehanna counties in Pennsylvania a main area of inquiry. Samples of the water wells were taken in July and September 2010.

The study concludes that methane contamination of a water well is 17 times more likely if the water well is within 1 kilometer of gas drilling.

When I served as Secretary of the Department of Environmental Protection, DEP documented cases of gas migration from Marcellus wells around Dimock in Susquehanna county and in Bradford county.

Duke also finds that the gas migrating is thermogenic and is not biogenic gas or gas that is encountered when a water well itself is sunk. This too is consistent with DEP conclusions. 

DEP furthermore found that the gas that was migrating in the Dimock area was Devonian gas located at about 1,000 to 3,000 feet.  Devonian gas is above Marcellus gas.  DEP concluded that the Devonian gas had not been isolated as a result of poor drilling practices.

Bradford and Susquehanna counties have had many more gas migration problems than counties in Southwest Pennsylvania.  Had Duke University done this study in Washington, Greene, and counties in the Southwest it would have reached different conclusions.  The reasons for the geographic difference in the incidence or rate of gas migration include geological differences in the counties, quality of gas drilling in the respective areas, or some of both.

In the case of 19 water wells contaminated by methane from drilling around Dimock, 14 of the 19 had methane removed by December 2010.   DEP required the drilling company to plug and repair gas wells that reduced the gas migration. At some water wells there were measurable declines in methane contamination shortly after gas wells were repaired or plugged.

Furthermore a settlement in December 2010 between DEP and the drilling company required payments to the families near Dimock where gas had contaminated their water wells that averaged $200,000.

DEP also proposed new gas drilling rules in 2009 that became final in February 2011.  The new rules raise standards for the design, construction, and operation of gas wells to reduce gas migration pollution.

Gas migration has been a problem in Pennsylvania for decades, well before the first Marcellus well was drilled in 2005. The new, strong rules and the attention to this problem make this the time to reduce it sharply.


  1. Did I read this wrong?

    Average and maximum methane concentrations were higher in shallow water wells within
    approximately 3,000 feet (1000 meters) of active shale‐gas wells. Isotopic data and other
    measurements for methane in the drinking water were consistent with gas found in deep
    reservoirs such as the Marcellus and Utica shales at the active sites and matched gas
    geochemistry from shale‐gas wells sampled nearby. The study found no evidence of
    contamination from hydraulic fracturing fluids or saline produced waters.30

  2. John,

    When you first posted, you said, “Duke also finds that the gas migrating is not Marcellus gas, but shallower gas that is encountered during drilling.  This too is consistent with DEP conclusions.”

    Then in your updated blog you said, “Duke also finds that the gas migrating is not Marcellus gas, but shallower gas (Middle Devonian) that is encountered during gas drilling on the way to the Marcellus.  The shallower gas is thermogenic, is migrating as a result of poor gas drilling, and is not biogenic gas or gas that is encountered when a water well itself is sunk. This too is consistent with DEP conclusions.”

    But in reading the study by Osborn, Vengosh, Warner, and Jackson, it says, “In active gas-extraction areas (one or more gas
    wells within 1 km), average and maximum methane concentrations
    in drinking-water wells increased with proximity to the nearest
    gas well and were 19.2 and 64 mg CH4 L−1 (n 1/4 26), a potential
    explosion hazard; in contrast, dissolved methane samples in neighboring nonextraction sites (no gas wells within 1 km) within similar
    geologic formations and hydrogeologic regimes averaged only
    1.1 mgL−1 (P < 0.05; n 1/4 34). Average δ13C-CH4 values of dissolved
    methane in shallow groundwater were significantly less negative
    for active than for nonactive sites (−37 7‰ and −54 11‰,
    respectively; P < 0.0001). These δ13C-CH4 data, coupled with the ratios
    of methane-to-higher-chain hydrocarbons, and δ2H-CH4 values,
    are consistent with deeper thermogenic methane sources such as
    the Marcellus and Utica shales at the active sites and matched gas
    geochemistry from gas wells nearby.”

  3. You may be right. I saw the reference to Middle Devonian gas at page 3. When I was at DEP we identified the gas in Dimock to be "Devonian" gas found at about 1,000 to 3,000 feet. This was gas found before reaching the Marcellus gas and had a different signature.

  4. I further updated the posting to reflect your feedback. Thank you for the feedback.

  5. I just read the paper - it is OK, but it still seems like it is trying to scare people by using words like explosion and asphyxiant. I suppose this is to be expected. Expect to hear the word asphyxiant a lot in the next few years. They also did not do their homework on the geology - they could have learned that the companies encounter a lot of shallow gas on the way down pretty easily. They could also have learned that microseismic shows no fractures forming within 3000 feet of the fresh water. One more important point is that gas found at 2000 feet could have migrated upward from the Marcellus over millions of years yet still have the isotopic signature of the Marcellus.

    It seems to me that they used a disproportionate number of wells from Dimock and that this is what led to their "17 times as likely" number. I'd like to see the wells from Dimock with a different symbol. Methane migration is definitely an issue that needs to be addressed squarely by the industry, but a more random data set would have more meaning. If we only sampled Fukushima we would say that all nuclear power plants have meltdowns. If we only sampled flights that crash we would say all flights crash.

    The news I have heard is not picking up the part of the story that said that no frack fluids or formation water was found in the wells. I suppose this is to be expected as well.

  6. Two words about water (and air) contamination.

    Stephanie Hallowich

    You know the truth.

  7. When I was with PADEP, I reviewed and provided interpretations of the molecular and isotopic results for samples collected for the Dimock investigation. The data revealed the stray gas found in the area water supplies was consistent with a thermally mature thermogenic gas consistent with gas that was likely source from a shale bed. To further interpret the gas was sourced from the Marcellus shale puts to fine a point on the interpretation as other gas bearing shale beds ith similar isotopic signatures occur above the Marcellus.

    With respect to the Duke publication, it is difficult to properly assess the work as the data for the conclusions offered by the authors is not provided in the publication. This is problematic and not consistent with the requirements of most peer reviewed journals.

    After reading the paper several times, it is not entirely clear to me if the Duke researchers are concluding that the thermogenic gases discovered in the groundwater near the gas well sites has migrated from the Marcellus shale into the aquifer systems as a result of drilling into the Marcellus, or if the thermogenic gas has migrated from more shallow formations as a result of Marcellus drilling activity. If the Duke researchers are concluding the former, then I would dispute that claim. If they are concluding that the origin of stray gas is thermogenic from the Catskill and Lock Haven, then we already knew that. As john pointed out, we also already knew that hydraulic fracturing is not a mechanism responsible for stray gas migration. I presented those findings to EPA in February.

    Thermogenic gases occur naturally in the shallow Catskill and Lock Haven formations. We’ve known this for some time. These formations serve as aquifer in some regions of NE PA. In addition, recent geochemistry for some of these shallow thermogenic gases reveal mixing, isotope reversals, and rollovers, and genetic similarities to deeper thermogenic gases (Marcellus, and deeper formations) that is still not well defined.

    - Fred Baldassare

  8. As a student of geology and engineering, I have to wonder if the high pressures associated with fracking can somehow encourage fluid migration (methane gas included)?
    If you pressurize any closed system to the point of failure, the failure will be at the weakest link, which in my opinion would be the cement in this scenario.
    If migrating gas has always been an issue, could fracking exacerbate the problem? Poorly cemented zones allow pressure from fracking to push methane from source formations up the outside of the wellbore and into aquifers?

  9. well John I must say your press releases at DEP seem to be pretty normal and to make sense. The explanation for Dimock gas issues seem to make sense too. How could Cabot screw this up? Was there evidence from the cement bond logs of a poor completion? or just finding of gas in wells. I see that there are a zillion gas wells around and in Dimock but can't get access to PA well records database to see how old they are and what depths they produced from. Are there a bunch of old shallow wells here and what is the shallowest producing horizon? I imagine some shallow water wells (say 100 to 300 feet) would encounter gas and may be converted to gas wells 100 years ago?? Any info n this? I mean the aquifers and gas occur in the same big package of rocks. AND why are PA geologists allowing Duke guys into their back yard. LOL

  10. Fred, makes total sense thanks for the clarity.

  11. Is the dataset acquired and used in the Duke study available anywhere? I'd like to map it, play with it, compare it to what other data I can get ahold of, just for fun. I'm a geologist, I like maps and spatial views of data.. but I can't find this data anywhere? Should be just a little spreadsheet of 68 rows with lat, long, measured values, and notes, right? Is it out there?

  12. OK, so I've tried to post this before, but somehow it didn't make it into the discussion.

    Frac fluids aside, casing and cementing has been a real issue for years; well integrity is the number one issue with gas migration, in my opinion.

    My question:
    Is it unreasonable to think that the pressures a well experiences during fracing could exacerbate a well integrity problem? If you are creating enough pressure to fracture rock 1000s of feet below the surface, then why wouldn't that pressure be great enough to make poor cement/casing jobs fail?

    As an engineer and geologist, this seems like a reasonable possibility. A system is only as strong as its weakest link. So in a way, fracing would be to blame for failed well integrity if the well was not constructed in a way that would withstand these pressures.

    Any thoughts? Would love some feedback.