Landmark shale gas study shows no groundwater problems

One of the difficulties in the current shale gas debate is that good data is hard to come by. Operators collect lots of data from around their sites, including water sampling to test for pollution, and geophysical monitoring to track where the fractures went during stimulation. However, this data is often considered commercially sensitive, so it rarely sees the light of day.

A government-sponsored project would be very useful, because it would provide a test-bed for an extensive monitoring program. All data could then be made public, and the claims of all those involved in the shale gas debate openly tested.

This is exactly what has been happened in the USA, with the final report released this week. The US National Energy Technology Lab (NETL) sponsored a monitoring program at a hydraulic fracking operation in Greene County, Pennsylvania. The monitoring program consisted of 2 parts: microseismic monitoring to track the fractures created by the stimulation, and geochemical sampling in overlying layers to test whether any contamination has occurred. Most importantly, because the data is publicly available, it's a great opportunity to talk through the anatomy of hydraulic stimulation.

The first stage of shale gas extraction is to drill horizontal wells through which the fracking will be done. The figure below shows a map of the lateral wells drilled. Those in the yellow box were the 6 wells that made up the NETL study.

Another day, another shale gas report

Update (23.7.2014): It transpires that Gwen Harrison, the report's lead author, was recently an election candidate for the Green Party, which has explicitly stated its opposition to fracking in all circumstance. Moreover, judging by recent tweets it seemed she was involved blockading trucks at IGas's Barton Moss site.

Of course, there's nothing wrong with joining political parties nor joining protests. However, it makes a mockery of the claim that the report is "impartial" and "evidence-based", and goes a long way to explaining the report's contents.


Original Article:
Another day, another shale gas report to dissect. Today's offering comes to you courtesy of Scientists for Global Responsibility and the Chartered Institute of Environmental Health. The report claims to take an "impartial, evidence based approach". It does anything but, so once again it falls to me to point out the more egregious errors.

The best place to start is on the very first page, which shows two schematic images of the fracking process. In both cases the scale of images is such that the depth of the well is smaller than the height of the drilling rig, implying that fracking is taking place at a depth of less than 100m, rather than the actual depth, typically 2 - 3km.

Similar images are provided on page 4, and nowhere are images with the correct scales shown. The images are so out of scale that the "impartial, evidence based" claim immediately cannot be taken seriously. The moment you see an image like this, you know what to expect.

To the non-expert, the degree of the error in these images might not be immediately apparent, so I did a little photoshopping to demonstrate. Imagine if you were reading a report on whether it was safe for commercial airliners to overfly cities at altitude, and on the first page of the report was the following image, I don't think it would be taken that seriously by air safety experts:

New paper: Estimates of error in micro-earthquake magnitude estimation

With excellent timing, on the same day as the new BGS report into the shale oil potential of the Weald Basin, a new paper, written by two co-workers at Bristol Uni and myself, has been released in Geophysical Prospecting. In it, we examine the uncertainties in estimates of event magnitude made on small earthquakes.

This paper is significant for shale gas extraction in the wake of DECC's traffic light system (TLS) proposal for fracking operations. Under the TLS, operational decisions during the fracking process must be taken on events as small as magnitude 0.0 (the amber level), with complete cessation of activities for events larger than magnitude 0.5.

As most people are aware, a magnitude 0 event is very small, at the limit of what can be detected using conventional seismographs (see our efforts at Balcombe, for example). Expensive downhole microseismic monitoring systems are required to robustly detect smaller magnitudes.

The TLS pre-supposes that earthquake magnitudes at this low level can be accurately determined. The purpose of the TLS was to provide a simple-to-understand system to re-assure the public. Uncertainties in event magnitude estimation could undermine this, generating more controversy, not less.

We show in our paper that event magnitude estimations at these low levels can be very uncertain: you can get different answers depending on what methods you use and assumptions you make. It doesn't take too much imagination to think of a scenario where one group reporting on a fracking operation concludes that an induced earthquake was just below the TLS threshold, but another group using a different method finds that the earthquake did exceed it. The current debate over shale gas extraction is febrile enough as it is, can you imagine the recrimination and the confusion that such an eventuality would generate?

Image of the day: Comparing a train to a fracking-induced earthquake

This image compares the vibrations from a passing train, measured at a distance of 150m, to a simulated earthquake occurring 2km below Cuadrilla's Balcombe drilling site (from the Bristol University Balcombe baseline study). We found that the train vibrations had similar amplitude to a magnitude 1.5 earthquake, equivalent to the second quake that lead to the shut down Cuadrilla's operations in Blackpool in 2011 (and a two-year moratorium).

Recent Earthquakes in Ohio

The Associated Press reports several earthquakes in eastern Ohio that have been linked to shale gas extraction. If true, this represents the 4th time that hydraulic stimulation in shales has been associated with seismic activity. This follows Preese Hall, Lancashire, the Horn River Basin, Canada, and Garvin County Oklahoma.

Note that it is important to differentiate between earthquakes triggered by hydraulic stimulation (i.e. fracking) and those triggered by underground disposal of large volumes of waste fluids, which is not being considered in the UK. It is the underground waste disposal wells that have been attributed to the increase in mid-continental seismicity seen in the USA.

Attributing cause and affect with respect to earthquake triggering is a difficult challenge. Frohlich and Davis (1993) came up with a series of 7 questions that are still commonly used to attribute "induced" earthquakes. These are:

1. Are these events the first known earthquakes of this character in the region?
2. Is there a clear temporal correlation between injection and seismicity?
3. Are epicentres near wells (within 5km)?
4. Do some earthquakes occur at or near injection depths?
5. If not, are there geologic structures that may channel flow to earthquake sites?
6. Are changes in fluid pressure at the well toe sufficient to induce seismic activity?
7. Are changes in fluid pressure at hypo central locations sufficient to encourage seismicity? 

However, without good quality seismic data, these questions can be difficult to answer.

Image of the day: Induced seismicity in energy technologies

They say a picture paints a thousand words. Which can only be good news if you're a time-pressed academic such as myself. This post introduces a new feature - image of the day (or week or month, depending on how often I'm able to post.) Each time, I'll post a single image that will, hopefully, say a thousand words about unconventional gas extraction in the UK.

First up, an image from the 2013 Davies et al. paper on induced seismicity. The bar chart shows the magnitudes of earthquakes triggered by human activity in the subsurface. Many human activities can trigger earthquakes, including hydroelectric dam impoundment, geothermal energy, coal and mineral mining, waste fluid re-injection, conventional oil and gas reservoirs, and of course, hydraulic stimulation. These activities are represented by the different coloured blocks - hydraulic stimulation is the thin black boxes at M = 2 - 3 (2 earthquakes) and M = 3 - 4 (1 earthquake). You can see how this compares with other activities. In the words of Professor Davies himself at the Unconventional Gas Aberdeen conference this week, "in terms of earthquakes, shale gas doesn't even make it into the premier league".

Seismometer Deployments at Balcombe: Final Report

Cuadrilla's drilling at Balcombe attracted a lot of headlines. In a previous post I described (mainly by way of lots of holiday snaps) the deployment of seismometers by Bristol colleagues and I.

We have now completed our data analysis, and our results are available for you to read!

Hydraulic stimulation was not planned for this phase of Cuadrilla's operations. Therefore, we did not expect to see any induced seismic events. Nevertheless, we saw this as a good opportunity to attempt several objectives:

The first objective was simply about public perception. The average member of the public does not know much about earthquakes or about seismometers. They don't really understand magnitude scales, and they are not aware of the detection capabilities of modern seismometers. We hoped that the high levels of publicity surrounding Balcombe would give us a chance to help educate the public in these regards.

However, we had two main technical objectives as well. These relate to DECC's proposed traffic light scheme, whereby operators are required to stop if they trigger events above magnitude 0.0. Traffic light schemes are common for such operations - the Swiss in particular seem to like them. However, the minimum threshold here is far lower than anything used by the Swiss. Our aim is not to say whether this is appropriate or not, but its operation does pose some additional challenges, which our work seeks to address.

The first issue stems from the Gutenberg-Richter law, which states that the number of earthquakes (N) that occur which are larger than a given magnitude (M) is given by
                             log(N) = a - bM.
where a and b are measurable constants. The BGS gives values for a and b in the UK of 3.82 and 1.03, respectively. Using a magnitude of 0.0 (the lowest cutoff for the traffic lights), this relationship tells us that over 5,000 such events occur every year. The existing BGS seismic network is not capable of detecting these low magnitude events.

In order for the traffic light scheme to work effectively, we need to be able to distinguish between the 5,000 naturally occurring magnitude 0.0 and greater quakes that occur each year, and those induced by hydraulic stimulation. This requires us to have data about the naturally occurring events, which we do not currently have. Therefore, one purpose of our array was to begin to establish baseline measurements around a potential drilling site so that we can characterise any pre-existing, natural seismicity. This is but a small start, with only 1 month of background data. In an ideal scenario we'd want to have at least a year of baseline data.

The second purpose of our array was to measure typical levels of seismic noise and detectability thresholds for small, temporary arrays such as ours. The traffic light threshold of magnitude 0.0 is often at the threshold of detectability for surface seismometers. The detectability is controlled in part by the levels of noise on the seismometers. Although you might think the British countryside is a quiet place, there are many potential sources of noise, such as trains, roads, farm machinery, rivers. We wanted to see whether a small, relatively cheap array like ours would be helpful in administering the traffic light scheme, or whether more expensive microseismic monitoring methods are likely to be needed.

So, what did we find?
Well, the most obvious thing we saw was the train, made famous by local concerns about seismic impacts on the viaduct. We saw the train on all 4 seismic stations that we deployed. Here is an example:

You can see that the train is coming from the north. It is seen on station BA02 first, which is the northernmost, and on BA04 last, which is the southernmost. BA04 is only 150m from the rail line, so you can see the biggest signal on this station.

We wanted to compare the vibration from the train with typical earthquake magnitudes. To do this we used the UK magnitude scale, which is defined as
                             Ml = log(A) + 0.95log(R) + 0.00183R - 1.76,
where A is the amplitude of the signal at the station, and R is the distance between earthquake and seismometer. We modelled earthquakes occurring directly below the drilling site, and found that a quake with magnitude of 1.5 (the same as the 2nd Preese Hall quake) produced a similar amount of vibration to the train going past at 150m.

We used an automated trigger algorithm to search our data for potential local seismic events. Sadly, we didn't see anything that looked like a local earthquake, either before or during drilling.

The seismometers that we used are actually designed to detect earthquakes from around the globe. We did spot a number of such events (called "teleseismic arrivals"). Here's an example from a magnitude 7.7 event in Pakistan:

This map shows all 25 such events that we spotted:

One of our stations was only 300m from the drilling site. We did notice that things got slightly noisier on this station when drilling started. This figure compares the background noise before and during drilling. A simulated M0.5 event is shown - this shows up above the noise for both cases.

We didn't see any events during our monitoring period. However, we wanted to work out what we could have seen, had something happened. We simulated earthquakes occurring below the drill site, with a variety of magnitudes, and ran the simulated data through our automated detection algorithm, to see what was the smallest that could be reliably identified, given our recorded noise levels

We found that magnitude -0.2 was the smallest we could see. This simulated event is shown below:

As you can see, it just peaks up above the noise. This is the smallest event we can expect to see. This is just below what is required for the traffic light scheme, so a small array like this could work. However, I'd want to see a larger number of stations to really push the detection limits below the magnitude 0.0 cutoff.

Discussion - Accurate event magnitudes?
We finish with a number of recommendations for the implementation of the traffic light scheme (TLS). A fact unbeknownst to most non-seismologists is that there are in fact a number of different magnitude scales, depending on how magnitude is measured. They are all designed to be close to each other, however they are not always exactly the same.

The most common magnitude scale is known as "local magnitude", or ML. This is basically the good ol'fashioned Richter scale, and is fairly simple to compute. You simply measure the maximum amplitude of the seismic trace, you take the distance from source to receiver, and you put it into a local magnitude equation as I outlined above.

An alternative magnitude scale is the "Moment magnitude", or Mw. This directly relates to the moment (read 'force' or 'energy' in layman's terms) released by the earthquake, and in turn to both the size of the fault and the amount that the fault slipped. Mw is slightly harder to compute - you have to look at the frequency content of the earthquake signals - but probably a better representation of the physical process occurring in an earthquake (as opposed to an empirical approximation, as provided by ML).

Small, local arrays such as ours will typically report ML. However, the dense coverage provided by microseismic arrays (as now installed at Preese Hall) often report Mw. It needs to be made absolutely clear how these different types of measurements will be factored into the TLS, because they may not be exactly the same - indeed at small magnitudes they can be different by half a magnitude unit or more. So, for example, what happens if a quake is measured with ML = -0.1 but Mw = +0.1?

Similarly, all measurements of magnitude are subject to an error. This is rarely reported for the large earthquakes you see on TV - the relative signal to noise ratios for a large event are so large that you can be sure that it is magnitude 6.5 (or whatever) ± a very small amount. However, as you enter the world of micro-seismic events, the signal to noise ratio deteriorates (as you can see in image #6 above). As this happens, the error in the calculation gets larger. Again, the incorporation of errors into the TLS needs to be clarified - what happens if an event has magnitude -0.1 ± 0.2?

These issues do not invalidate the traffic light scheme. However, given that operational decisions, and therefore potentially millions of pounds, hang on the accurate characterisation of event magnitudes, it would be helpful to iron out any potential inconsistencies now, rather than in the wake of another induced event.




In closing, I would like to thank the co-authors of this work, who don't yet have blogs of their own.

My first media hack job: "The Truth Behind the Dash for Gas"

The Truth Behind "The Truth Behind the Dash for Gas"

Talk to media people enough, and something like this was inevitable, but it seems that I am the star in a new anti-fracking documentary entitled "The truth behind the dash for gas" (my part starts from about 20 minutes in).

Back in November last year I received an email from a young guy who said he was looking to make his way as a film-maker just out from film-school. His email to me is quoted below:

I am putting together a short film about fracking in Somerset. The aim is to present a fair and informative assessment of the potential for fracking in Somerset, the risks and dangers associated with it, and the views of local people. The film and those working on it are independent of both the anti-fracking campaign groups and those who stand to gain from the fracking industry.

I think just by watching the first few minutes of the film you can see that their  claimed intent "to present a fair and informative assessment of the potential for fracking in Somerset" is barefaced lie. Even more barefaced is their claim that "the film and those working on it are independent of [...] the anti-fracking campaign groups". However, the film has a facebook page, in which it clearly states that the film is facilitated by Frack Free Somerset. The FrackFreeSomerset and FrackOff websites appear prominently in the credits at the end of the film.

Given that the very first contact between myself and the film makers was a lie, one can hardly expect the remainder of the film to do any better. I find it especially ironic that the 2nd word in the film title is "truth", while their very first contact with me was an obvious, barefaced and outright lie. It's not worth my time to address the content of the film as a whole, but I do want to comment on the parts in which my comments have been used.

Comment #1: that debate over hydraulic fracturing has descended into a media slanging match, and I don't think anyone could disagree with that. However, the film moves straight to the same science denialism more usually seen in the anti-climate-change world - if you can't trust the Royal Society for advice on scientific matters, the British Geological Survey, or the Geological Society, for matters geological, or Public Health England for public health matters, then I'm not sure where is left for you to turn, and the term conspiracy theorist begins to apply (see my final comment for more in this vein).  

As for my own 'close ties', I spent 3 months in the BP Institute in Cambridge as a 20-year-old M.Sci student. While BP provided the funds to set up the lab, the students who do projects there are  university students, and have no connection to BP (I certainly spoke to noone from BP while I was there, and in fact the majority of research being done when I was there was on developing energy efficient buildings). I also spent a few months in Rijswijk in Shell's research facility during my Ph.D. During my Ph.D I developed geophysical techniques to ensure safe storage of CO2 in geological reservoirs - so-called CCS, a potential method to mitigate climate change. During this time Shell asked my to come over and help apply some of these methods to their test site at Ketzin, Germany. All of this is made abundantly clear on my website.

Comment #2: I say that in many cases the impacts have been exaggerated. The Scranton Times-Tribune investigated claims made by residents about shale developments in Pennsylvania, finding that 77% of accusations were without substantiation. Surely an example of impacts exaggerated? Equally, even in cases where regulatory breaches by companies have lead to issues - the example of Dimock springs to mind - the impacts of this have been regularly exaggerated. At Dimock, while methane was found to have contaminated groundwater, there was no evidence of fracking fluids in the water. It's not good to have methane in groundwater, and this should be prevented from occurring at all times. However, methane is not toxic or harmful to human health, barring the risk of explosion if it allowed to accumulate in significant amounts. After the company had been cited and forced to repair its wells, levels of methane dropped, returning below the minimum safety levels set by the EPA (a fact never mentioned by activists, who will tell you that once contaminated, an aquifer can never be restored).

Comment #3: The most famous flaming tap in Gasland, the Markham well, had nothing to do with oil and gas drilling. This has been made abundantly clear by the Colorado State regulator (COGCC), which felt the need to release a comment to "correct several errors" in the film. The flaming tap is the headline image of Gasland, it appears in all the trailers and promotional material. That the gas is of biogenic origin, from shallow layers well above those targeted for drilling, implying that gas drilling is not the cause. This film attempts to argue that poor well casing still allowed shallow biogenic methane to migrate. However, the COGCC report makes clear that "there is little or no temporal relationship" between gas drilling in the area and the complaints made about the Markham and McClure wells. This is a fairly massive oversight to be made, one that I think that is worthy of comment. Clearly the film-makers find it easy to relate to other films that are economical with the truth in order to tell a story.

The regulators did rule that a drilling company was at fault in the case of the Ellsworth well. This company reached a settlement with the claimant (again, a fact that the film neglects to mention). The COGCC conducted sampling over a 170 sq mile area, and the Ellsworth well was the only one where any impact was detected. Strangely, we don't get to see Josh Fox setting the Ellsworth taps on fire - one can only guess at why?

The next sleight of hand is either quite clever, or monumentally dumb, I'm really not sure which. They move on to discuss the Duke methane studies, which I have discussed in previous posts here and here. Of course, there are a number of studies performed along along these lines, all of which come to very different conclusions to the Duke study. For some reason the film makers don't mention these (one wonders why). However, these film-makers can't even get the Duke PNAS study facts right! A screen-grab of the PNAS abstract is shown, highlighting an apparent claim that methane was found in 82% of drinking water within 1km of a gas well.

 How about we look at that section of the abstract in full:

In fact, you can clearly see that the 82% figure refers to all the water sampled, not just the ones near gas drilling sites. Methane was found in 82% of water samples, REGARDLESS OF WHETHER THEY ARE NEAR GAS WELLS OR NOT! Incidentally, this is a similar percentage to that found by Molofsky et al., who sampled a much larger dataset (1,700 samples vs 140 samples), finding that 78% of samples contained methane, regardless of proximity of gas wells. In fact this is why establishing whether shale development has caused problems is so difficult in Pennsylvania - there is already a lot of methane in the groundwater. Where studies have been conducted in areas where natural methane is not present in shallow water, they have not seen an impact from drilling.

I honestly find it hard to believe that this accidental highlighting of parts of two sentences, conveniently removing the context to make a scarier quote, is accidental. Either way it is particularly dumb to hope that people familiar with the source material won't spot the attempted trick.

Comment #4 is about well integrity. The astute among you will notice a cut in the editing between the start and end of my answer. Clearly, other things I've said have been edited out. Sadly, this interview was conducted a year ago, so I can't remember exactly what I said, and back then I was too naive to make my own recordings (not a mistake I'll make again), but presumably it was something that didn't fit with the narrative being portrayed.

The films then cuts to the SLB Oilfield Review from 2003. Always a good litmus test of a shale gas commentator is how they treat this report. Firstly this report covers data from deep offshore in the Gulf of Mexico. This is a very challenging drilling environment, so it's not surprising to have more problems offshore than onshore. The only statistics relevant to onshore UK shale drilling are stats from other onshore wells.

More importantly, the film describes the stats as showing either "leakage" or "failure". In fact, they depict incidents of Sustained Casing Pressure. SCP isn't a good thing, and again it should be avoided, but it doesn't equate to the mass leakage of hydrocarbons into shallow layers. Categorically, these stats have no bearing on the rate at which well integrity issues are causing contamination, which is what, misleadingly, the film tries to claim.

The most obvious place to look for wellbore integrity-related contamination issues from onshore wells drilled under a UK regulatory system, is of course to look onshore in the UK, where we have drilled 2,000 wells already, many of them in the 1960s, 1970s and 1980s (making most of them 30 years old at least). One of the few things this film gets right is that whether a well is fracked or not has no bearing on wellbore integrity issues. Therefore, if the statistical claims made in this film were true, there would be 1,000 onshore contamination incidents already. If the bold claim that follows ("all wells leak eventually") were true, we'd surely have 2,000 incidents by now. Clearly the claims made in the film do not add up, because I'm not aware of any problems associated with onshore wells in the UK.

Similarly, after the Piper Alpha disaster, regulations were significantly tightened to prevent such an event ever happening again. Again, the North Sea has not been turned into an environmental wasteland - we're still so keen to eat North Sea cod that there's almost none left!

We can also look to the US, which has hundreds of thousands of onshore wells, and actually examine statistics relating to actual incidents of groundwater contamination, as opposed to SCP. Luckily, the US Groundwater Protection Council has done exactly this, in a study released in 2011. They find that of 187,000 wells drilled in Texas, and 33,000 wells drilled in Ohio, only 21 and 12 wells respectively had seen casing issues leading to contamination, rates of 0.01% and 0.04%.

Comment #5 regards regulatory differences between US and UK, and resulting differences in operating practices. The above statistics show that contamination is not endemic to shale drilling. However, even the handful of cases that have occurred is a handful too many. These few incidences are inevitably the result of poor practice, and/or the contravention of regulations.

While I'm speaking, they cut to some shots of flowback waste pits. What they fail to point out is that these are not allowed in the UK - any waste flowing back from the wells must be stored in double-lined steel tanks. This is with good reason: in the GWPC report I mention above, the majority of drilling-related contamination incidents (172 in Ohio, 190 in Texas) have come from surface activities, not from processes happening under the ground. In the US it is common to store the waste fluid in open, plastic-lined pits. These have been known to overflow during heavy rain, or for the liners to tear, allowing the contents to leak. I think the endless shots of waste-fluid pits that activists like to show indicates either that they are not aware that these are banned in the UK, or that they do know this but don't like to let facts get in the way of the story.

For example, in one well-publicised case XTO opened the valve on one of their tanks, allowing the fluid to flow out into the ground, while in another case a trucker dumped his load into a nearby storm drain, rather than taking it to the treatment plant. This sort of illegal activity should absolutely be prevented, and it is important that regulators keep a sharp eye on operators to ensure that this doesn't happen. But it doesn't show that shale gas development is inherently problematic. Again, we can look the the UK example for dealing with produced water. The existing UK onshore industry handles 70 millions barrels of produced water a year, with no apparent contamination problems.

The next interviewee, Laurence Rankin, is presented a "Former Environment Agency manager", with the obvious intention of making us think that he is an impartial commentator. Since my 3 months as a 20-year-old M.Sci student at the BP Institute is worthy of mention, maybe the film should have also pointed out that he is also a coordinator of the Sefton Green Party and member of Friends of the Earth, so perhaps slightly less impartial than first appearances might suggest. While the Green Party man seems to have a problem with Cuadrilla's activities, the Environment Agency itself doesn't, and hasn't claimed that Cuadrilla have broken any of their regulations. The fact that the Green Party man isn't familiar with fracking, doesn't mean it hasn't happened. For example, horizontal wells have been fracked at Wytch Farm in Dorset. Update - this comment reflected media reports regarding Wytch Farm. Water is injected into the Wytch Farm reservoir, but this is to increase the reservoir pressure and drive oil towards production wells (a common practice in conventional fields), not to fracture the rock.

The use of the term 'slick-water' is another slight of hand, somehow implying that slick-water is somehow worse that what has gone before. In fact, in the good old days it was common to use a mix of gelled gasoline and napalm as the frack fluid. Given the choice of water with 1% chemical additives, or gasoline and napalm as the frack fluid, the use of slick-water represents an improvement. And the fact that there were no specific references to fracking in exploration licenses is that it was considered such a normal part of oilfield and drilling activities (with 10% of existing onshore wells being hydraulically stimulated). The main difference between now and what has gone before is one of scale, with modern treatments using higher volumes, rather than any major differences in the technique itself.

The film moves on to the Cuadrilla-induced earthquake near Blackpool. The next mistake made comes with the claim that the increase in earthquakes seen in US is directly attributable to hydraulic stimulation. In fact, the increase in seismicity is caused by an increase in the volumes of waste fluids, from both conventional and unconventional operations, being disposed of by deep injection into saline aquifers. I know this because I have worked in depth on these events, including writing a report for parliament, because they have implications for CCS. There are no proposals in the UK to dispose of fracking fluids through injection into deep aquifers. As far as I am aware, we do not have suitable deep saline aquifers onshore (although we are targeting such aquifers offshore in the North Sea for CCS). Again, one is left wondering whether the film makers know this and are lying, or simply do not understand the science that is being done in this area?

There is only one case in the US where fracking has triggered seismicity - in the Eola field, Oklahoma, which occurred in January 2011, 3 months before Preese Hall event, but was not reported as such until August 2011, after Preese Hall, and one case in Canada (British Columbia), where events occurred between 2009 and 2012, although they were not reported until August 2012, a long time after Preese Hall. So Preese Hall was the first reported incident of induced seismicity triggered by hydraulic stimulation for shale gas.

With respect to reporting of the earthquake and resulting casing deformation to the Energy Minister, there was no regulatory requirement to report casing deformation to him - this is the role of the HSE. Moreover, I think the actions taken were entirely appropriate - they ceased operations to allow a 6-month scientific study to be conducted, after which the results were reported for DECC, HSE and the rest of the world to read. While we're on the point, all of the casing deformation was within the production casing string, within the target zone of production - it was actually below the depths of the frack stages that triggered the seismicity. It poses no risk whatsoever to the integrity of the well. The figure below shows the well design - the deformation is the little yellow bar right at the bottom.

I think that's it in terms of my contribution to this piece of work. I'll comment briefly on the accusation of "mission-creep" in terms of chemical use - every chemical used in the UK must be permitted by the Environment Agency, and fully disclosed to the public.

One final point in closing: the go-to 'expert' for this film appears to be Ian R. Crane, an ex-oilfield-executive, who gets the final word as far as this film is concerned. I don't usually like to stoop to ad-hom arguments, but as Mr Crane seems to appear on an increasing number of anti-fracking pieces, it'll be worth your time having a look at his profile on RationalWiki, a website dedicated to uncovering cranks, conspiracy theorists, and pseudoscience. If this is the best figure-head that the anti-fracking movement can come up with, I would suggest they need to try a little harder.

UPDATE: I checked out the FrackFreeSomerset website to look for more information. According them, the film is not just "facilitated" by FFS, but in fact "produced" by them.

UPDATE (21/11/2013): The film maker himself has left a comment for me. He is correct to point out that I failed to address my comments of water use. In the film, I describe how much water is used for a single stimulation. Of course, the issue is cumulative effects over time if many wells need to be stimulated. The water use for an individual well (~10,000 - 50,000 cubic metres) sounds like a lot, but it must be placed in context. Between the 3 largest water utilities (Severn Trent, United and Thames), 1.7 billion liters of water are lost to leaks PER DAY. If water companies were able to improve on this by just 1%, we would have available an extra 17,000 cubic metres of water, that's enough water to frack a well every day. If water consumption is your concern, don't blame frackers, get the water utilities to fix their leaks (or at least 1% of their leaks).

Professor David Smythe's critique of Cuadrilla's drilling plans: A comment

Update (1.8.2014): It seems that the Geological Society are very unhappy about Prof. Smythe claiming to be a chartered geologist. The Geol Soc state that this title requires "proof of continuous professional development", with the clear implication that they do not believe Prof. Smythe meets this requirement.

Glasgow University are also unhappy about being associated with the professor. Paul Younger, Professor of Energy Engineering at Glasgow stated:

"He has published nothing on [shale gas] in any proper scientific forum — no doubt because he knows he would never get past peer review with his pseudo-scientific scaremongering. He falsely claims to be a chartered geologist. That’s fraudulent. It’s wilful untruth. I am concerned about the damage to the reputation of the university by someone who never fails to use his university affiliation.”

Original Article:
This post is a comment on the critique of Cuadrilla's Balcombe drilling plans made by David Smythe, Emeritus Professor of Geophysics at Glasgow University. The key points of this critique are as follows:

• Cuadrilla's interpretation of faults in the Weald basin differs from a potentially more parsimonious interpretation.
• Cuadrilla's interpretation omits smaller faults near to the well site, some of which might intersect a horizontal well.
• Seismic data is restricted to 2D seismic profiles of 1990s vintage, making it challenging to keep the horizontal well within the target micrite layer.
• If the well does stray out of zone, it may contact Kimmeridge Clay an important potential shale resource. It is suggested that the proposed micrite target is in fact a "cover story" for the targeting of Kimmeridge shales.
• Concerns are raised that if faults are intersected, they may act as "fast-track conduits" for surface water contamination, and/or lead to the triggering of seismic activity.

My comments are as follows:

There are indeed differences between the fault interpretations made by Cuadrilla and by Prof. Smythe. Without access to more data it is probably difficult to determine whose interpretation is the more accurate. This is a fact appreciated by all geology students who have ever done a mapping project: with limited data multiple interpretations are always possible. However, disagreements between fault locations are limited to the areas south of the Bolney well, which are not in Cuadrilla's license area. Within Cuadrilla's license area, the principal area of interest, both sets of fault interpretations are closely matched.

It is argued that the lack of 3D seismic data means that it will not be possible to keep the horizontal drill within the target micrite formation, and that it will not be possible to identify if/when small faults are intersected. This criticism ignores one of the key technological developments of the last 20 years, which is closely associated with the development of horizontal drilling. That technology is called "Geosteering" (also known as "Logging While Drilling"). For more detailed info on these techniques I'll have to hand you over to google for now, but this article provides a decent explanation.

Essentially, geophysical measurements are taken continuously at the drill tip. This data tells drilling engineers what rocks they are in. They use this to guide where the drill goes, allowing them to stay within the target formation. If you read the linked article, you'll note that it even allows engineers to see when they've intersected faults. Geosteering is common practice when drilling horizontal wells in the Barnett and the Marcellus, the two most significant shale plays in the US.

I'll include here some comments on a couple of issues raised on Prof. Smythe's website, which don't appear in the linked slides but form a key part of the conclusions outlined above. In the comments on faulting in US and European basins, he argues that "faulting is almost non-existent in the US basins". This isn't the first time I've heard this suggestion, and I don't know where this meme has come from. The eagle-eyed among you will have spotted this comment in the linked Geosteering article:

"In some areas in Pennsylvania, the geology is very complex across some of our leases," Collins noted. "There are very large thrust faults"

I've even had the pleasure of seeing them myself - they tend to show up in microseismic data. You can see an example in this paper, and below is another microseismic dataset clearly showing the interaction of the stimulated stages with a fault:

(image courtesy of Microseismic Inc)

Faults are clearly not "almost non-existent in the US basins". Prof. Smythe criticises the well-known Warpinski-Fisher paper that looked at hydraulic fracture height growth for its failure to include fault data. However, the Warpinski-Fisher paper explicitly includes data from examples when hydraulic fractures have intersected faults (see slides 7 and 11 in this presentation, for example), providing clear evidence that stimulation does not create pathways from deep-lying reservoirs to shallow potable aquifers, even when faults are present.

I would also like to address the comment that "faults do not normally act as seals". This is a misleading comment. It is true that when risking a potential reservoir trap identified on seismic data, the observation of faulting on the top of an anticline would present a risk, because with seismic surveys alone it is difficult to tell whether a fault might be sealing or not, and so whether there might be hydrocarbons present, of if they might have all leaked away over geological time.

However, it is not true to claim that "faults do not normally act as seals". Fault traps - where the geometry of faults and reservoir units serve to form a trap, instead of the traditional anticline domes - are a common method of trapping oil and gas. If that last sentence didn't make sense, there are plenty of pictures on google. Fault compartmentalisation - where sealing faults break up a reservoir and prevent fluids from flowing to the well - is a common problem in conventional reservoirs. You can read about a case example here. A particularly pertinent quote is "clay-rich lithologies (i.e. shales) are likely to reduce fault zone permeability (i.e. provide better fault sealing) more than clay-poor lithologies". We know from Conoco's drilling in the 1980s that oil is present in the micrite beds underneath Balcombe. This oil has been trapped there for hundreds of millions of years. This would suggest that, even if the Paddockhurst Park Fault does intersect the target micrite formation, it is not providing a transmissive pathway to flow.

Finally on the issue of induced seismicity. It is a misconception that if a hydraulic stimulation intersects a fault, it will inevitably create a "larger" earthquake (i.e. one that might be felt by humans at the surface, such as at Blackpool). Again, this is not the case, as documented in the microseismic examples above. It is not uncommon for stimulations to intersect small faults, yet incidences of felt seismic events are extremely rare amongst hundreds of thousands of stimulations. Although in some cases event magnitudes have increased slightly upon intersection with a fault, they remain well below the threshold that could be felt at surface. For hydraulic stimulation to trigger detectable seismic events, the stress state on the triggered fault must already have optimal orientation and magnitude - that is to say the fault must already be close to it's failure state. The majority of faults likely to be intersected during stimulation will not meet these criteria, hence the lack of detected seismicity during operations in the USA, and hence the conclusion by the expert report into the Blackpool earthquakes that they represent "exceptional" circumstances.

That said, as with pretty much any subsurface activity, there is a small risk of triggering small seismic events that should be considered. DECC have already put into place strict seismic monitoring guidelines to ensure that there is no repeat of events near Blackpool. Bristol University already has seismic monitoring stations deployed around Balcombe.

I agree with some of the more general suggestions made by Prof. Smythe: more geophysical surveys will enable us to better understand the subsurface geology. This is beneficial all around - enabling operators to maximise their production efficiency while regulators can minimise any environmental risk. I expect that as potential shale gas developments move through exploration into preliminary production phases, we will see more and more geophysical data being collected (as we have already seen a new 3D seismic survey collected on the Fylde). However, I strongly disagree with Prof. Smythe with respect to current operations at Balcombe - they are not likely to pose a significant risk in terms of fluid migration from depth or from induced seismicity.

Update (04/09/2013): Another example of hydraulic stimulation interacting with faults without adverse impact is the NETL hydraulic fracturing study, which received a lot of coverage last month. In this study, researchers injected tracer chemicals along with the fracking fluid. The shale layers were at 8,000ft depth, and an overlying layer at 5,000ft depth was monitored, looking to see if the tracers appeared in this overlying formation. The microseismic data from this operation has not yet been published, but reports seem to indicate that the stimulation intersected a fault. Even so, there was no evidence for the tracers in the overlying formation, nor were any larger-magnitude seismic events triggered.

Update (05/09/2013): Of course, I've missed perhaps the best example of stimulation intersecting a fault, in fact probably the best known one: the operations near Blackpool that triggered seismic events in 2011. This is the worst-case scenario - a stimulation intersecting a fault that is optimally oriented in the present day stress field, and close enough to failure that the stimulation is capable of triggering some of the largest seismic events ever seen during hydraulic fracturing in shales. Yet even for this worst-case example, the operators were able to produce gas from the reservoir, without any suggestion of shallow groundwater contamination from this fault.

Seismometer deployment to monitor drilling at Balcombe

If you follow me on twitter as well as reading my blog will know that I go by the name @TheFracDoctor. This choice of name was influenced in part by the fact that I had recently finished my PhD, and as anyone who has experienced the flush of post-viva success, there is the temptation to put the word ‘Doctor’ in front of everything. 

But also it is the role of the doctor to monitor the health of his patient, and that is how I see seismic and micro-seismic monitoring – a tool to monitor the health of a fracture stimulation.

In the last few weeks I’ve had the opportunity to do this for real in the UK for the first time: deploying seismometers around Cuadrilla’s planned Balcombe well. I’ll note right now that the current Cuadrilla plan is to drill into limestone for conventional oil, with no intention of hydraulic fracturing at this stage, but we wanted to get some experience deploying seismometers for this sort of situation.

However, Balcombe is the site of the now-infamous ‘Battle of Balcombe’ and has been at the center of much debate of unconventional gas extraction (these stations were put in a month ago, well before the events of last week). Of particular focus has been the risk of seismic activity to the Balcombe Viaduct.

This spectacular bridge, built in 1841, still carries the main London-to-Brighton rail line:

After the seismic events during stimulation at the Preese Hall well, Blackpool, concerns were raised about the possibility of similar seismic activity affecting this bridge. So we decided to deploy seismometers while they drill their Balcombe well. There are no plans for fracking at the moment, so we’re not expecting any seismic activity. Our main aims were (1) to get some experience deploying seismic stations in rural England, and (2) to record baseline activity prior to drilling.

Baseline data will help us understand the noise levels in the area, which will determine the size of the smallest earthquake we can detect – obviously the lower the noise level, the smaller event you can detect. The current traffic light scheme for seismicity proposed by DECC requires events as small as M0.0 to be detected. We want to see if this will be possible with a small array of 4 surface seismometers (we will compute the expected shaking from an M0.0 event, and see if it emerges above the noise).

Baseline data will also enable to see what changes (if any) drilling activities produce.

I will post updates as and when we collect and analyse the data. For now, this seems like a good time to share some holiday snaps, so you get to learn about what we do when we deploy seismometer arrays, and what they look like.

Firstly, here’s the piece of kit that we use: a Trillium 120 seismometer:

This is a fairly standard piece of kit in earthquake seismology, capable of measuring the vibration of the earth across a wide frequency, from long periods (up to 60 seconds) up to the sampling rate of 250Hz.

To reduce the noise from things like wind and rain, they need to be buried 50cm or so under ground. Which means you have to dig a hole. I used to work on building sites during my A-levels, and I was delighted when I got my degree, knowing that my days of manual labour were over (because digging holes all day is TOUGH work). Yet, a masters degree and PhD later, and here I am digging holes all day!

Once the pit is ready, the seismometer is carefully placed into the hole:

The batteries and data logger go in the steel box next to the pit. We run cables, insulated inside fire hose, from the instrument into the box:

 

Initial covering for the instrument, to further minimise surface noise, is provided by its ‘lid’, the black dome you can see below:

Once we are happy that the instrument is working properly, we fill the hole (being careful not to dislodge the insulating cover from the instrument. We lay a waterproof sheet just below the surface, and pile turf on top as a final covering:

Finally, we put a small chicken-wire fence around the station. This is more of a deterrent than anything else: it’s not likely to stop a marauding cow, nor is it really capable of keeping out a determined rodent (animals chewing on loose cables is a real problem in many seismic deployments):

And after all that (a couple of hours work at least), you have your seismic station:

We placed 4 stations in total, including one a few hundred yards from the viaduct:

As we set this station up, we could see the vibrations from the trains going past every 5 minutes recorded on our seismometer. It will be interesting to see what caused more vibration – the Preese Hall earthquakes or the train going past at a distance of a couple of hundred yards. After all, the initial concern at Balcombe was that seismicity would trouble the bridge – even though this is a bridge that is being shaken by an express train every 5 minutes.

We enjoyed our two days in the picturesque British countryside, and we were very glad we missed all the protestors. Fortunately, the stations are all a couple of km at least from the London Road protest site, and accessible from other roads, so that’s a gauntlet we won’t have to run. The only disturbance we saw was from these guys:

So there’s our seismic deployment in Balcombe. More to follow once we’ve analysed the data.

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?