Sunday, 30 June 2013

Methane found around gas wells in PA. Methane also found not around PA gas wells....

Two more studies looking at the connection between shale gas extraction and water contamination have been released. One from the USGS, looking at water quality in areas of Pennsylvania that haven't yet been drilled, and one from the same Duke team that has in the past found evidence for drilling-related methane in groundwater in Pennsylvania, but did not find evidence for any contamination above the Fayetteville shale (in Arkansas).

The USGS study examined water quality in Sullivan County, Pennsylvania. Crucially, this study focussed on areas that have yet to be drilled for shale gas. So far in the USA such baseline studies have been rare, which means that it can be difficult to establish whether water has been contaminated by shale gas drilling, or whether it was already of poor quality to begin with.

As I have discussed in a prior post, it is wrong to assume that all groundwater was of Evian-quality prior to drilling: there are many potential sources of groundwater contamination, both natural and man made, that could have caused problems well before shale gas drilling began.

Therefore, although this USGS study hasn't received the press attention given to the Duke study, it could come to be seen as really important, because it provides a baseline against which changes caused by drilling can be assessed.

So what does the Sullivan County baseline look like? Well 85% of the 20 water samples taken contained at least some radon-222 above the US maximum level of 300 picocuries per liter (pCi/L), while 10% exceeded the alternate maximum level (I have no idea why the USEPA has a maximum level and then an alternate maximum level - what does that mean?) of 4,000 pCi/L. 35% of the wells had some methane in them, although only 2 samples (10%) had levels to get excited about: 4.1 and 51.1mg/L (the US maximum level is 10-28mg/L).

Importantly, the USGS carried out isotopic fingerprinting of the methane in these wells. It is possible to tell the difference between methane that has been created in the shallow surface by bacterial activity (so-called 'biogenic' methane) and that created at depth by heat and pressure (so-called 'thermogenic' methane), and it has been suggested that, where thermogenic gas is found, shale gas drilling is the likely culprit.

Unfortunately, the isotopic fingerprinting of the Sullivan County gas showed that is WAS thermogenic, in an area WTHOUT any gas drilling. Does this mean that the thermogenic/biogenic testing can no longer be used as the determining factor in the debate over whether methane is caused by shale gas extraction? I think at the least more caution might be required.

The main take-home point from the USGS study is that water quality in the region is highly variable. This means that, whether you believe that shale gas drilling has or has not caused contamination, proving your case either way will be very difficult, especially without baseline studies.

Moving on to the Duke study, which examined the water quality in gas-producing areas of Pennsylvania. Rather than bore you with statistical analyses about P<0.0007 for this and P=0.0001 for that (necessary for science, less interesting for blogs), I think the story would be better told with a couple of pictures. Firstly, where the groundwater was sampled (along with the locations of shale gas drilling):

and then the results - methane concentration plotted versus distance from shale gas wells:
There appears to be a clear correlation with increased methane concentrations near to gas wells.

The Duke researchers also looked at the isotopic composition of the methane gas, finding it to be thermogenic, and they also found ethane (a slightly heavier form of natural gas, not produced biogenically), implying that the gas must have originated at depth, and therefore be caused by shale gas drilling. I think that this part of their conclusions is slightly shakier - we've seen from the USGS study above that it is possible to have thermogenic methane, and smaller amounts of ethane, in areas that haven't seen drilling.

I also have some doubts about how the wells were chosen for analysis. You can see from the first plot that the wells sampled occur in clusters - they're very non-random. Above I pretended to chose not to discuss the statistics in the Duke paper to save the poor reader from a load of boring numbers. In fact, my concern is that such statistical analyses usually assume a certain degree of uniformity in a sampling process, and that doesn't seem to be the case here, so I'm not sure as to their validity.

In the methods section of their paper, the Duke team mention that they got their samples via Homeowner Associations. Although which homeowner associations these might be are not described, it seems likely that these are homeowner associations would be those opposed to natural gas drilling. In turn, such associations are presumably likely to have (a) elevated methane concentrations in the water and (b) gas drilling in the near vicinity. So, if your sampling is biased by choosing to select water from sites that match both descriptions, it's not particularly surprising to find homes near gas wells with elevated methane - because that's how your samples were chosen in the first place.

You can see this by looking at the distribution of sampling points in the above figure, which are clustered in certain places on the map, rather than spread evenly. To really robustly establish a link between drilling and methane contamination, a much more uniform sampling and testing program would be required. It's a shame that the Duke researchers did not do this, because they've left what could have been a really fundamental study open to criticism.

To summarise my thoughts - I think that it is likely that at least some of the incidences of methane contamination in the Duke study HAVE been caused by drilling. The example of Dimock shows a pretty clear case where of shoddy drilling practices leading to methane contamination. However, based on the sampling methods used, I'm not sure that this study, despite the media fanfare, actually adds anything to this. The real question we want to know is - are methane issues ubiquitous and inevitable, or do they represent a handful of 'bad apple' cases of poor drilling practice, the number of which can be minimised with good practice, strong regulation and good oversight? A more rigorous attempt to sample PA wells more uniformly is required (for example, many of the Duke samples do not have much/any methane in them).

Finally, keep in mind that methane, while a nuisance, is not toxic, and most private drinking wells should have filters to remove methane prior to the water entering the house. The Duke researchers also looked for other chemicals that might be associated with drilling. Opponents of shale gas often point to a smorgasbord of nasty-sounding chemicals associated with fracking fluids that they claim are polluting groundwater.

Much like their previous studies both in PA and elsewhere, the Duke researchers found no evidence for any of these chemicals. Nor would we expect them to: methane, being buoyant, has the potential to move up through the annular gaps and/or cracks left in a poorly-cemented well. Drilling and/or fracking fluids are not buoyant (i.e., they have similar densities to the brines that saturate the rocks at the depths of the shale reservoirs), so there is no force available to push them back to the surface - you may as well try to suggest that dumping sewage/pollution in London is going to contaminate the headwaters of the Thames in the Cotswolds. The water is simply flowing in the wrong direction.

So, because it's been another long and rambling post, a summary:
  • lots of the water in PA is of poor quality to begin with,
  • it is possible (likely) that there have been some instances of methane contamination,
  • whether these cases represent a few outliers, or are more ubiquitous, is not established by the Duke study,
  • and there is absolutely no evidence that any of the various chemicals associated with fracking fluids are getting into groundwater.

Thursday, 27 June 2013

BGS Finally Reveal Their New Bowland Shale Gas Estimates

It's finally here. We've been expecting it since January (date originally planned for publication), and the BGS have finally delivered. The definitive report on the amount of shale gas underlying Lancashire and Yorkshire in the Bowland Shale.

The headline figures: somewhere between 822 - 2,281 tcf (trillion cubic feet) of shale gas, with 1,300 tcf being the best estimate.

This map shows the area covered by the report:
The geographically astute amongst you will realise that this report only covers part of the UK. There is potential for shale gas in other parts of the UK as well, in particular the Southeast (centered on Sussex and Hampshire), South Wales, and parts of Scotland. Understandably, at present the media are treating this new number as a UK-wide number, but there could well be even more.

In case you are wondering what the green and red dots are on the map above, these represent existing oil and/or gas wells in the region. So onshore drilling isn't new to the area. The two maps below show the seismic lines and well logs used to create the report. You can see that there is a lot of data available - much of the wells and seismic will be legacy data from past exploration for the conventional fields shown above.

If you are a bit of a geo-geek, I really recommend you check out the UK Onshore Geophysical Library, where you can actually see all the wells and seismic data for yourself. They have a slick little interactive map viewer where you can plot all sorts of information.

So, what does 1,300tcf mean for the UK? The key thing to think about is recovery factors - how much of the gas can we actually get out of the ground. It has become conventional to assume a recovery factor of 10%. I'm not sure why, when US experience points to more like 20-30%, but lets be conservative and stick to 10%.

10% of 1,300tcf is 130tcf of produceable gas. Keep in mind that the UK's annual consumption is 2-3tcf. So 130 divided by 2.5 is 52 years of total UK gas consumption.

A different and perhaps more illuminating comparison is with the largest conventional gas fields in the world, which you can see here. 130 tcf of recoverable resource would place the Bowland shale as the 4th largest field in the world, behind only the Qatari Pars Dome and Russia's two largest fields.

If money, rather than volumes, is of more interest to you then consider: 130tcf is approximately 130 billion MMBTU. The current European gas price is something like $8 per MMBTU, so the total value of recoverable gas in the Bowland shale is something like 130 billion x $8 = $1,000,000,000,000, or $1 trillion dollars (cue much of this). Of course, that money will be shared out amongst the companies involved (and the many UK workers they will employ) and the UK government, which will take its cut via the taxman. It remains to be seen exactly how the government tax the shale gas industry - I hope they set up something similar to the Norwegian Sovereign Wealth Fund.

Of more immediate interest is the decision by the government to ensure that, as well as the taxman, local communities benefit from shale gas development. For every well pad, £100,000 will go to local communities, plus 1% of production revenues.

Let's examine those figures in more detail. A typical well pad might have 10 lateral wells diverging from a single pad. A typical total recovered volume for a single well in US is 3 bcf (billion cubic feet) per well (estimate from the recent IoD shale gas report). So a single wellpad might produce 30 bcf, or 30 million MMBTU, which at $8 per MMBTU is $240 million (or about £156 million). 1% of £156 million is £1.5 million. Add in the additional £100,000 fee and we're up to £1.6 million going to the local community, for a site covering a couple of hectares and looking something like this:

How does this compare in terms of electricity generation? 30 bcf of gas will generate 5,000 GWh of electricity. If a single well pad is operational for 30 years, that's an average of 166 GWh per year (in reality, more will be produced in the earlier years, with a decline through time). This compares with the average output of 150GWh that we get from from the UK's largest onshore wind farm, Scout Moor:
Many people assume that because I am broadly in favour of shale gas, I must be anti-wind. I am not: I think we should be doing all we can to develop and improve renewable energy technologies. Long term, all of our energy will have to come from renewables and/or nuclear technology. But the above two images show the challenge that this poses at present: we can get more energy from a single well pad covering a couple of hectares (a football pitch) than we can by plastering an entire mountain with 150m high turbines (and that's before we even get into intermittency issues etc).

Perhaps the UK government can spend some of its $1 trillion windfall on research on improving renewables, nuclear fission, or finally working out how to get fusion working...

Monday, 24 June 2013

Horizon: Fracking, a new energy rush by Professor Iain Stewart - a review

Shale gas and fracking got the big time BBC treatment this week with the airing of Prof Iain Stewart's Horizon special. Link is here, although be quick, because the BBC don't tend to keep them up (also, you probably can't see it unless you are in the UK).

<colossal name drop> I've been fortunate enough to chat to Britain's favourite geo-celebrity before on this topic </colossal name drop>, so I knew that this was in the works, although I wasn't expecting it to hit our screens so soon.

I'm also pretty sure, unlike the author of this blog, that the views expressed genuinely represent how Iain sees the subject. I don't think, to quote, that
that Prof. Stewart was ready to burst, he was holding back so much. It was the uncomfortable way he spoke to camera, I could almost sense the person behind the camera giving him a stern look. Be balanced, be careful, this is dangerous stuff. Hang on, let’s cut to you saying nothing and driving, that’s safer.
To be fair, there WERE a lot of driving shots. It seems to be the done thing for documentaries these days. Perhaps it is assumed that unless we see shots of the presenter travelling between locations we might get confused and think they're still in the same place.

However, I don't quite understand the surprise felt by many commentators over Iain's take on the topic. The view of pretty much every professional organisation that has addressed the topic, be it the British Geological Survey, the Royal Society, the Royal Academy of Engineers, is that shale gas extraction can be conducted safely, and that risks posed are not much different to conventional hydrocarbon extraction. That's not to say that there are no risks (everything we do carries a risk), but that those risks can be managed within the UK's already robust oil and gas regulatory regime. I'm not sure why Prof Stewart, a professional geologist, would be desperate to (and I quote again)
blown his top and started ranting at the camera. ‘For pities sake, wake up, this isn’t the solution, this is shortsighted madness! We drill and pump and waste billions of gallons of fresh water extracting this stuff, we burn it, we increase carbon in the atmosphere and then it runs out. Remember ‘North Sea Gas?’ Yes it’s easy and a stopgap and a final, last ditch frenzied attempt at keeping the crumbling edifice of the fossil fuel corporations going, but it’s insane.’
I think if you only read, say, the Guardian, on shale gas, you'd be fairly convinced that fracking is completely awful, and that no-one in their right mind could support it, unless you are a greedy Texan oil baron. It must then come as a bit of shock when someone like Iain Stewart, supposedly one of the good guys, the cuddly face of geology,  takes the view (as the majority of geologists do) that the risks of shale gas extraction should be entirely manageable. Hence the rather nasty comments suggesting that either Iain, or the producers, must surely have been in the pockets of big oil to commit such an outrage.

In all I feel it was a very balanced program. The best evidence for this is that after the show, @ProfIainStewart's twitter feed was bombarded with angry commentators from both sides of the debate castigating him for making such a biased program. If you're pissing off both sides, you're probably doing a reasonable job.

The first half of the show was dedicated to the benefits of shale gas extraction.  This included a visit to a Louisiana 'shale-ionaire', a man who received a $430,000 one-off payment, plus regular monthly royalties, for drilling rights on his farmland. It also showed the scale of shale gas extraction in the US: it's not limited to Pennsylvania and Texas (although these are two hotspots). There are over 1 million wells in over 30 states. Some people believe that there is more gas in the US than there is oil in Saudi Arabia. The effects the shale gas revolution on the economy, and in particular the attraction of cheap energy to manufacturing and chemical industries that are 're-shoring' to the US was mentioned.

Particularly interesting was the visit to the National Grid control center, during the Strictly Come Dancing finale. As the show ends and everyone in the UK makes a cup of tea, the demand spikes and the Grid brings on extra power to meet this demand. I'd heard of the so-called 'TV Pickup' effect before, but it was still fascinating to see it in action. We are all so accustomed to receiving electricity quite literally at the flick of a switch, and we so rarely think about the sheer complexity of infrastructure needed to deliver it too us! It really is mind-blowing when you step back to look at it.

The scale of this infrastructure was further demonstrated by the visit to the Isle of Grain LNG terminal, where gas from Qatar is landed. The scale of the holding tanks and the size of the tankers were quite astounding - quite literally like a wall of steel as Iain describes it. The tanker is 1/4 of a mile long, and carries enough gas to power 70,000 homes for a year. Which is just as well, because 40% of our electricity comes from gas, and more than 50% of our gas is imported. This highlights the often underestimated issue of energy security - gas tankers are highly flexible, so if the Qataris ever decide to sell their gas to someone else, or someone else decides to pay a higher price for it, we'd begin to run out of gas pretty quickly. Hence the geo-political importance of 'home-grown' energy to buffer us from these consequences.

Having looked at the potential benefits, the second half of the program heads to Pennsylvania to examine some of the potential issues. Iain meets with a family, the McIntyres, who list a series of health problems that they associate with contaminated water caused by nearby gas drilling. It seems the whole community is scared of their water, and now only drink from delivered bottles. The McIntyres admit that it has been difficult to prove this link scientifically, and this comes across in the program: lots of complaints, not a lot science to back them up.

The confidential make up of drilling fluids was also mentioned. There's little doubt that drilling companies made a strategic blunder in trying to keep this information secret. There reason for doing so - the desire to keep commercial secrets from their competitors - is technically a valid one, but only if you are thinking mainly of your competitors, not the general public. Because if the public see you are keeping secrets, they will assume you have something to hide. The industry is starting to come around to this fact, and more and more wells are registered on FracFocus, but from a PR point of view this horse (and trust in the industry) has long bolted.

One of the few scientific studies that has found any kind of link between methane contamination and drilling is the famous Duke study, which receives some air time at the end of the show. It's worth bearing in mind that this study hasn't gone without substantial criticism (see here, here and here (last link is industry funded and not peer reviewed, but worth including)). This included Iain performing the now famous lighting of the water due to methane content, and the debate continues as to what extend groundwater methane is naturally occurring, and to what extent it has been exacerbated by drilling.

Overall, I think the final point is right on the money: UK shale gas operations will likely look very different to the US shale gas experience - the operating culture, the regulatory system, and the mineral rights systems are all completely different. However, it is up to British scientists and engineers to prove that they know the risks, and that they can manage the risks safely.

The thing that impressed me most about the program however, wasn't any information about shale gas. Having been involved in the topic for some time now, there wasn't a lot to surprise me. What I really enjoyed was that, perhaps unintentionally, it showcased real geoscientists doing what real geoscientists actually do.

We're not short of popular outreach in the geosciences (especially thanks to the work of Prof Stewart et al.). However, geoscience in the media tends to revolve around dinosaurs and disasters. Super-volcanoes and Stegosaurus. Tsunamis and T-Rex. In fact, only a small portion of geoscientists are palaeontologists or vulcanologists, especially in the commercial world outside of academia. This is leading to public misunderstanding of the work geoscientists do, perhaps exemplified by the incident of Iain Duncan Smith, the geologists and the shelf-stacker.

During this program, we got to see drilling engineers alongside the incredibly complex surface operations - that spaghetti-like tangle of hydraulic lines - needed to conduct a well stimulation. Such incredibly complex engineering that we rely on completely just to go about our daily lives!

We saw a geophysicist using 3D seismic data to work out where the shale rocks were, 3 to 4km beneath us, and using microseismic event locations - pops and cracks that carry no more energy than a dropped bottle of milk, detected and located with pin-point accuracy on arrays of geophones kilometers away - to map exactly how far and in what directions the stimulated fractures went. The geophysicist points out that, as the first person to look at the 3D seismic data, he really is the first living thing to 'see' these rocks since those dying organisms, whose organic matter eventually transformed into methane, were buried 350 million years ago. Astounding!

We saw Iain himself go in for a bit of palaeofacies reconstruction in some Peak District caves, using information from sedimentary structures and fossilised corals and plant matter to reconstruct the enivronmental conditions hundreds of millions of years ago, to work out where the coastline would once have been, and therefore where the best places to drill might be. What to the untrained eye might be a boring-looking grey rock, actually contains a wealth of information about what the world was like 350 million years ago!

We saw inside the BGS core store, where 250km of core samples from across the UK, logging the depths beneath our feet, are stored. We saw how electron microscopes are used to see the tiny, tiny pores within shale rocks, which may only be 5 nanometers across. These tiny pores may be pretty-much invisible to the naked eye, yet in sufficient number they allow apparently rock solid, dense shales to trap trillions of cubic meters of natural gas!

Finally, we saw hydrologists conducting water sampling across Pennsylvania. Not glamorous, perhaps, but vital work to guarantee the health and livelihoods of people who rely on that water! 

There's so much more to geoscience than the big box-office sellers: dinosaurs and natural disasters. I'm glad that, perhaps unintentionally, this program was able to show that.

Saturday, 8 June 2013

Heard it on the radio

Update (9.6.13) I think first my attempt to attached audio via blogger failed. Hopefully they should be working ok now (so long as your browser supports html5).

Things often occur in twos. This week I've done two radio interviews out of the blue, both on 5Live.

The first interview (below) on 5Live Drive was in response to the new IGas announcement of their resource estimate of 100tcf of gas in their licence area. I'm not particularly happy with my own interview, because I wanted to get across, and was unable to, was the sheer uncertainty in this estimate. The media have focussed on the upper bound figure of 170tcf of resource (for reference, UK gas use is something like 2-3 tcf per year), but in fact the estimate range was from 15 to 170 tcf, with 100tcf being the most likely number. Add in uncertain recovery rates (anywhere between 5 - 50%) and you can see how uncertain the numbers really are. At the low end, 15tcf at a 5% recovery rate gives 0.75tcf, less than half a year of the UK's annual use, at the upper end, 170tcf at 50% recovery gives 85tcf, enough to completely cover the UK's gas use for the next 40 years.

Keep in mind of course that this estimate is for the IGas license block, with has an area of 300 square miles, or an area 17 miles by 17 miles, so although the estimate is very uncertain, it only accounts for a very small part of the country.

Also on the show was Phelim McAleer, director of FrackNation, which could be described as a response to Gasland - well worth watching if you can get hold of a copy - who is strongly in favour of shale gas development based on what he has seen in the US.

Having been on 5Live Drive, my name and number have clearly been put on the 5Live database of frackers, because I got a late night call to take part in a post-BBC-Question-Time phone-in debate, a part of which was given over to fracking, after a question on the topic during the main show. The question during the debate was very incoherent, and sadly the lady in question came of looking a little mad, but the 3 interviewees during the phone in were all broadly pro-shale gas. Again, though, I personally think I might need a little more media training to learn how to put myself across more effectively, without so much umm-ing and err-ing. But maybe that's just me, we all hate the way we sound when played back, right?

Tuesday, 4 June 2013

Two new studies on US shale gas and water contamination

There are many potential issues that have been associated with shale gas extraction. I think that by far the most emotive is that of water contamination. The idea that fracking could render groundwater supplies permanently contaminated and unusable is indeed a potent rallying point, making up the majority of the charge sheet in films such as Gasland.

Gasland shows a small handful of cases where gas drilling is imputed to have impinged on groundwater. There are now hundreds of thousands of shale gas wells in the US. Pointing to a handful of accusations can hardly be considered science (although it does make for good movies).

Heretofore this has been something of an issue, because there doesn't seem to have been a large amount of data available with which to go about addressing this issue. So, in this post I will explore two recent reports (one a scientific paper, one a newspaper article) that attempt to answer the question - will shale gas lead to water contamination?

The first report comes from the Scranton (Pennsylvania) Times-Tribune, via a freedom of information request to the Department of Environmental Protection to release its record pertaining to water contamination incidents. The original article can be found here.

The two statistics that initially leap out at me are that of 969 complaints drilling impacts on water quality, 77% were in fact unrelated to drilling. Perhaps this is not surprising when 40% of water wells tested by Penn State in 2011 failed at least one federal drinking water standard.

Almost everyone in the UK gets their water from a utility, almost noone maintains their own well. The utilities filter and treat the water for us, so we know we can take a glass right from the tap. Because the distances and infrastructure needed to reach rural parts of the US, it is much more common for people to have their own wells. Essentially, you go out into you back garden, drill a hole approximately 20-100m down, and drink whatever comes up, sometimes with minimal treatment or filtering. I don't know about you, but I wouldn't be prepared to drink what comes up, even in my parent's fairly rural, pleasant Hampshire pile, let alone in my own rather grubby back garden in Bristol.

There are many potential sources of contamination, both naturally occurring and manmade. Groundwater can contain naturally occurring salts and heavy metals leached from surrounding rocks, and naturally occurring hydrocarbons (methane, benzene etc) from both bacterial activity and from natural oil and gas seeps. Further human activity can add to contamination from, for example, prior industrial activity in a region, coal mining (which can be especially bad for water contamination, and there has been a LOT of coal mining in Pennsylvania, and run-off of agricultural products (fertiliser, pesticides etc).

We seem to have made the mistaken assumption that all groundwater, prior to drilling, is pure, virgin Evian-quality drinking water, meaning of course that any contamination must be due to drilling. I think this is a concept that must be addressed. In an area where 40% of the water already fails drinking water standards, differentiating a new source of contamination from the old and/or naturally occurring can be extremely challenging.

Moreover, drinking water quality may change over time: the amount and rate of water taken out of an aquifer, and the rate/amount supplied via rainfall, will affect the water composition. Bearing this in mind it's pretty easy to see how misconceptions can quickly arise: a local person notes a change in the water quality from his well. They look around, and see that gas drilling has been going on in the nearby area, and of course that is going to be the first and only thing that they blame, regardless of what any subsequent scientific tests show. This is not to in anyway accuse the 77% of unsubstantiated complainants as blaggers. However, equally it shows that we cannot simply take every complaint and assume that the little guy is right and that gas companies are nasty corporate bastards and that fracking is inherently evil. Rigorous scientific testing is necessary before blame (if any) can be ascribed.

What about the remaining cases? The vast majority are associated with stray methane leakage, although their are a couple of more mundane examples - sediment increases from road and pipeline construction, for example. It's worth keeping in context though that over 12,000 shale gas wells have been drilled in the area between 2008-2012, so these examples represent a small percentage of the wells drilled.

Moreover, the timing of the incidents is also interesting. The majority of incidents were in 2008 and 2009, when fewer wells were drilled, while in 2011-2012, when more wells were drilled, saw fewer cases. This almost certainly is associated with changes in regulations, and changes made by drillers, to ensure adequate cement casing for wells. The drop from 2008-09 to 2011-12 shows to me that shale gas extraction can be regulated.

The second report is an academic paper published in 'Applied Geochemistry' which examines water quality above the Fayetteville shale in Arkansas. This paper examined major ion chemistry, trace metals, methane content, and methane isotopic signature, in 127 drinking water wells, and compared them with flowback water from Fayetteville shale wells. 

They found small amounts of methane in many of the wells. However, there was no relationship between cases near to and far from shale gas wells, both had equal amounts of methane. Isotopic testing confirms that the gas has a shallow, biogenic (i.e. produced by bacterial activity) source. Again, these results serve to show that small amounts on methane in groundwater is a common and naturally occurring, so cannot immediately be blamed on gas drilling. The chemical analyses did not reveal any other evidence for frack fluid chemicals in the sampled water wells.

I would describe the Pennsylvania report as encouraging, but showing room for improvement - there have been a small number of genuine contamination incidents that need to be addressed. Especially encouraging is the reduction in incidents seen from 2008 to 2012 - showing the need for effective regulation in order to ensure that there is no methane migration. The Arkansas report is even more encouraging, comprehensive testing showing no evidence for either methane or frack fluid contamination across the Fayetteville shale