Study finds methane leaks from 30% of abandoned wells – but emissions average less than a single cow

Crawberry Hill 131115  Decomissioning

A study of decommissioned onshore oil and gas wells in the UK found that 30% were leaking methane. But the average leak produced lower emissions than a breeding dairy cow.

The research, published today in the journal Science of The Total Environment, concluded that the leaks were caused by well integrity failure and that wells were most likely to leak within 10 years of being abandoned.

The industry body, UK Onshore Oil and Gas, said the study should reassure people. But Greenpeace said it raised questions about the development of fracking in the UK.

The study was by the ReFINE research consortium on fracking, led by Newcastle and Durham Universities and funded primarily by Centrica and INEOS.


Researchers selected 102 wells from four onshore UK oil and gas basins in the Weald, North Yorkshire, the East Midlands and Wessex.

The wells were chosen to give a range of conditions and they varied in age from eight to 79 years. They had all been decommissioned in line with best practice in the UK. They had been cut off, sealed and buried in soil to 2m. Another well, drilled in 1917, was included because it had not been decommissioned properly.

The study analysed soil gas above each well and compared it with a nearby control site of similar land use and soil type.

  • In 31 out of 102 wells (30%) the soil gas methane was significantly higher than control sites
  • In the most extreme example, the methane was 147% greater than the control
  • In 39 out of 102 (39%) wells the soil gas methane was significantly lower than controls.
  • Leaks from the well that had not been decommissioned properly were more than 10 times higher than the average

In the wells that were leaking, the researchers said:

“The estimated fugitive emissions from decommissioned wells are less than that for the agricultural activities that would take place on the reconstituted land.”

However, the researchers acknowledged that they looked only at vertical emissions from well integrity failure and not at the potential for diffuse leakage into surrounding groundwater or over a broad area.

They estimated emissions to be on average 364+/-677kg CO2 equivalent per well per year. The paper compares this with emissions for dairy cows and ewes.

“For dairy breeding herd the CH4 emissions factor (enteric and manure sources) is 128 kg CH4/head/year (2944 kg CO2eq/head/year) while for a breeding ewe the value is 8.9 kg CH4/head/year (205 kg CO2eq/head/year)”.

A DrillOrDrop reader has calculated that based on the figures in the paper the average leaking well could produce emissions just over 1/10th that of a single cow.

The researchers said wells did not appear to leak more as they got older:

“The relative CH4 [methane] concentration above wells did not significantly increase with the age of the well since drilling and 40% of the most recent wells surveyed showed leaks implying that leaks develop early in the post-production life of a decommissioned well.”

They said lower soil gas methane levels than the control indicated that soils on some decommissioned sites acted as a net methane sink.

Well integrity failure

The industry stresses the importance of well integrity to prevent contamination. At a meeting in North Yorkshire last Friday, Ken Cronin, chief executive of the industry organisation, UK Onshore Oil and Gas, told local councillors:

“The most fundamental and important thing about any oil or gas operation is the integrity of the well. If you get the design and creation of that well correct from the start then you reduce the environmental impact of fracking.”

Well integrity failure happens when barriers of cement or steel casings fail, allowing pathways for fluids and gases to groundwater, surface water and the atmosphere.

In today’s study, the researchers said:

“We interpret elevated soil gas CH4 concentrations to be the result of well integrity failure but do not know the source of the gas nor the route to the surface.”

They added:

“Oil and gas wells are typically constructed with multiple barriers to maintain well integrity and prevent leaks, thus well integrity failure is a consequence of complete barrier failure.”

“A loss of well integrity is important because it represents an uncontrolled release of fluids – whether liquid or gas – which could pose a risk to groundwater supplies and air quality.”

The importance of monitoring

Leaks of methane can have important consequences for climate change because the gas has a warming potential 28-36 greater than carbon dioxide over 100 years.

Another ReFine study in 2014 found only two confirmed cases of well integrity failure in the UK in 143 active onshore wells but it revealed that there was no monitoring of abandoned wells. Of these 65% were not visible, while 35% had some evidence at the surface of previous drilling activity.

One of the authors of today’s study, Professor Fred Worrall, told the BBC:

“The point is that even with proper decommissioning you will still have those wells that leak as cement cracks and steel corrodes and so monitoring is important,”.

“Overwhelmingly wells are properly decommissioned and our study shows that when methane does leak the levels are low, for example when compared to methane produced by the agricultural use of the land”.


Ken Cronin, of UKOOG, said:

“What ReFINE has shown is that the public should have no health or environmental concerns about emissions from properly decommissioned wells adhering to current industry standards.”

“Indeed the research has found that in the minority of cases where they have recorded some methane emissions from decommissioned wells, these emissions are typically less than one would get from just a handful of livestock grazing in the same fields.”

But Doug Parr, chief scientist of Greenpeace, said:

“If even an industry-funded study suggests that 30% of conventional wells appear to be leaking, it raises serious questions over the long-term impact of the extensive development of unconventional gas in the UK which is clearly the government’s plan.”

Updated 29/1/16 to include figures for methane emissions and comparison with livestock.

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19 replies »

  1. The reality is 30% were found to be leaking, which is a high proportion. Imagine the cumulative leakage from thousands and thousands of unconventional gas wells.

    The sample size was small, what will be the impact, cost and legacy of having to monitor thousands of unconventional gas wells for decades/ Plus this study cannot comment on what may or may not be leaking below ground.

    The reference to agriculture is not really relevant either, it is well documented that we have to find new ways of reducing methane emissions from agriculture. It is a bit like saying that because we are already omitting too much methane into the atmosphere from one source some more from another source won’t matter. It absolutely does matter.

    I found Ken Cronin’s comments particularly disingenuous because this study has proved abandoned wells leak and ALL fugitive emissions of methane are unacceptable and will have a devastating impact on climate change.

    This information is not reassuring – and particularly for the unconventional gas industry.

    • This study does not go far enough. It shows that wells are leaking and that this was proved by detecting methane at the surface. What the study does not show is that IF the integrity of these wells has been compromised, in that methane is detectable at surface, then it can be assumed the wells are leaking in many other ways too. And of these wells that have been proved to be leaking at surface, how many wells had further checks below surface to ensure the leaks were not contaminating aquifers? How many of the leaking wells have been fixed or attempts made to fix them?

  2. The EA should be very concerned about these findings. They have to consider source, pathway,and receptor. They acknowledge the source and receptors associated with fracking, but distant themselves from potential pathways. This industry funded report proves pathways exist.

  3. This study selected 103 wells from across the 4 onshore UK oil and gas basins with proven oil and gas accumulations where there was more than one productive well.
    I wonder why the study did not report on Preese Hall. It is decommissioned and abandoned and is the only hydraulically fractured shale well in the country.

  4. Anyone who has done a research course would know it is often how results are interpreted that sway the analysis whither way those sponsoring it want to prove or disprove. The results need closer scrutiny for checking veracity of reporting.

    The fact abandoned wells are now being tested at last, is cause for celebration. The fact this test has happened nearly 100 years after the first one was left behind and ignored, says much about the cavalier approach to thorough observance of deviations past ignored and not applied to innovations of new technology, which similarly will be the next scandal in 100 years time.

    The red herring in all this is the fact offshore wells, much older, are not tested at all once abandoned, nor are there any stats regarding the impact on marine environs.

    The fact that soil is now heavily polluted says reams about the lack of due diligence of our EPA and DEFRA regulations, which clearly are nowhere near the best in the world nor trustworthy, and yet we are expected to believe that fracking, already known to be highly hazardous, will be ”safe” in sleight of hands already known to favour industry profits over human health.

    The fact that water will be badly polluted if fracking is allowed is greater cause for concern. I notice no mention of groundwater pollution, nor riverway/waterway pollution in this study.

    There are no stats publically available about the highly hazardous chemical content tested for by the EA in freshwater on surface and groundwater channel. Drinking Water Industry analysis does not include the most dangerous chemicals only the EA are allowed to test for away from drinking water feeds and courses. This implies there may have been heavy methane or even ethane or metals found already in ground and underground waterways, which would add to the toxic chemical mix but not be included in the research presented in this study.

    Hydrologists haven’t a map for water courses below two miles underground therefore heavier pollution than detected in this survey may be even greater and potentially more harmful at groundwater level where ”safe” fracking is supposed to be delivered. Laterally drilling for up to two miles across potentially very heavily polluted groundwater, porous rocks and shale channels would serve only to loosen up high hazardous compounds that need leaving underground.

    Methane is one major life threatening hazard, it is those pollutants not tested for or reported upon in this survey, such as ethane mercury, lead or radon that need better study.

    The EA and DEFRA need to come clean about high hazardous finds across the country, on agri and grazing land AND IN ALL OUR WATER, not just drinking water supplies, even if it means the rest of us can see how much damage has been done, not by farmers, but by industrial roll outs, poor or competent disposal of dangerous pollutants, as well as chemical washes farmers have been ordered to use on cattle and crops that are now high pollutants in soil and air.

    It took the angling community six years to bring a court case they won, about the right to full public accountability of the water industry, and now the agencies need to come clean about sharing all stats about marine, land and underground waterways.

  5. Just had a quick tour of the science and here are a few flaws—quite normal to be honest given science is always a constantly variable change of perspective once new fields of study get added, so not being too critical, just realistic.

    There is now (conveniently) no way to to set up a comparative study of methane from wells and from cattle and from cattle in abandoned well areas, to isolate how much methane supposedly from cattle may or not actually have been from abandoned wells? The report clearly evidences this flaw ”There is currently no emissions factor for CH4 from grassland or arable soils in the UK — the emissions are assumed to be from the housing of livestock, storage of manures, manure application, and fertiliser but not from the soil and vegetation itself” and that statement renders the following one illogical ” If the decommissioning of the wells considered in this study had brought 1 ha of land back into livestock production then the increase in herd size would considerably dominate over the emissions from the decommissioned well in that field.”

    Cattle have been practically eliminated in most rural agricultural areas, so testing the same analytical ”fields” for methane isn’t possible to see if in fact former cattle methane emmissions have erroneously been attributed to livestock instead of soil absorption, vegetation and exposed mini faults, none bore wells and other deep clefts and crags.

    In addition, there is very little if any ”a priori’ testing of migrating methane properties to see distance methane travels over clearly defined time limits, also factoring in seismic sifts and natural climatic impacts, as the statement about ”meteorological variants of sampling’ clearly conveys…..

    Terrible once you start analysing, just how many variables there are and how difficult it is to be certain, which is why we should not force through a new technology before understanding better the ones we are only just finding out about….

  6. “To recover 15% of shale gas in Lancashire would need 33,000 wells on 5,500 pads. To be independent of gas imports, we need to continue drilling 1,000 wells every year.” Andy Aplin, Professor of Unconventional Petroleum at Durham University
    So, imagine in a hundred years’ time, there are tens of thousands of wells, and 30% of them leak methane. How would that affect the climate?
    This study completely demolishes the industry argument that we have gold-standard regulations and that none of the wells will ever leak. On the contrary, it shows that however many layers of steel and concrete there are, leaks will occur over time. The fact that few wells are even monitored is even more worrying. And I agree that Mr Cronin’s arguments about methane from cows. The amount of greenhouse gases the agricultural industry is of course another big issue, but to say that just because another industry produces methane that leaks from wells don’t matter is really scraping the barrel.

  7. The lease agreements between land owners and shale gas companies that we have obtained are for 30 years. The HSE have stated that abandoned wells are not places of work and therefore not monitored or inspected after decommissioning. Although generally “polluter pays”, legal advice suggests that land owners would ultimately be legally responsible. As we have seen some of the figures paid to landowners for these leases it seems unlikely they would have enough funds to pay out for any environmental damage when the wells fail. This report also highlights that the reservoirs remain pressurized years after abandonment.This problem exists in both conventional and unconventional reservoirs as gas constantly leaks into natural or induced voids in the formations long after the wells are deemed financially viable. We would be leaving future generations with unsolvable environmental problems.

    • Operators have compulsory purchase powers which includes land for well pads, road ways, gathering pipelines, glycol dehydrators and compressor stations or any other processes related to oil and gas exploration, extraction, capture, processing and distribution.
      Where operators become insolvent landowners are no longer liable to third parties from pollution related to oil and gas extraction on their land following a provision added to the Infrastructure Act. That liability now accrues to the state supported by the tax payer.

  8. Perhaps the report should also have noted the significant quantities of methane going into the atmosphere from natural sources and anthropogenic sources other than coal mining and oil and gas so that comparisons / scale of emissions can be noted.

    Have a look at the IPCC report table 7.2 (an entity not known for its love of the extractive industries):

    Interesting to note that all studies show cows creating more methane than O & G as noted by others commenting above, and also rice agriculture in most of the studies.


    The IPCC table does not include geological sources of methane.

    The offshore fishing industry (deep trawling) has done far more damage to the seabed / bentha in the North Sea. When you look at the seabed with an ROV when undertaking a site survey to establish baseline conditions prior to starting drilling, pretty much everywhere in the NS, all you find is a destroyed seabed carved up (ploughed) with trawl boards.

    Getting all this into perspective is important. That said, abandoned O & G wells should not leak. New wells have significantly improved casing and cementing guidelines and verification to adhere to, including shale wells in the UK. These include improved annulli isolation, cementing to surface, more casing etc.

  9. Actually, its not really possible to conclude from this study that any of the abandoned wells are leaking methane. That’s because the researchers didn’t conduct any isotopic laboratory analysis to determine whether the methane they found was thermogenic (i.e. of hydrocarbon origin) or biogenic methane that results from the natural delay of organic matter much nearer the surface and that’s often found in soil and groundwater.

    But even if the wells are releasing some methane, the study tells us that the overwhelming majority (70%) are not emitting methane at all, and the 30% that may be are not doing so at much above background levels, which suggests these wells were decommissioned to a high standard.

    The upper quartile concentration for both the control and the well sites is reported as 1.7 mg CH4/l. This represents a concentration of 2,400 ppm. For comparison the Environment Agency use 1% (10,000 ppm) methane above background as a compliance limit for biogenic landfill gas migration from landfills (i.e. no action is taken if the measured concentration is less than 1%).

    So, overall, not a worrying finding.

      • “LA: I got into this toward the end of my career. I started in logistics and then moved into marketing and refining. I was in Japan and Singapore for a total of 12 years, ended up running Mobil’s operations in Japan, which was their biggest [marketing and refining] operation outside the US. And then I came back to headquarters in the US to head up the logistics area ”

        Personally, I don’t think he knows much about geology or geochemistry or geophysics or seismology or geomechanics or well engineering which are pretty much what you need to know a lot about to make the judgement that he seems to have made.

        He wasnt even in Mobil when fracking was commenced. It even says so in the article:
        “[But] about the time we bought this house and started restoration, people that knew I had been in the oil business started saying, what do you think about fracking? I had not been following it at all, and said, ‘What do you mean?'”

        I think he knows about logistics and he knows about being a nimby. So much for an expert witness.

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