Tuesday, 3 September 2013

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.


  1. Smythe's assertion that a 33m bed of micrite would be almost impossible to follow with a horizontal or sub horizontal well is very outdated.
    Current directional equipment give survay accuracy far greater than that and combined with modern rotary steerable tools, a 33m corridor is a simple proposition. Modern LWD tools add the information needed to fill the gaps between 2D seismic during geosteering.

    Smythe's main push seemed to be obliquely suggesting that Cuadrilla were only drilling Balcombe 2 in order to test the surrounding Kimmeridge Clay Formation Claystones for shale potential. Given the expansion of shale gas and oil elsewhere in the world, that may probably be said for any conventional exploration well, anywhere, nowadays.

  2. I reviewed this article by Smythe a week or so ago when asked by a friend. The statement "faults do not normally act as seals" would mean a very large (majority?) of producing oil and gas fields could not exist if it were true.

    Smythe's article is full of holes and your critique is excellent and, based on my experience in the business, factually accurate.

    On a further point, does Smythe think that mapping work by the BGS should be taken as gospel and written in stone? Whilst seismic interpeters in an area will be familiar with the BGS interpretation, they are often working on proprietary seismic data which the BGS has not interpreted yet (or may never interpret). Operating companies are quite free to put their own interpretation on the data. The BGS maps may be wrong. They are also based on interpretation of data after all, there is subjectivity.


    1. Thanks 'ThinkinScientist'. I agree completely with your point about fault maps. I've got a lot of field mapping experience, and I've been down to Balcombe a few times now. There's really not a lot of outcrop, it's all fields. So unless the BGS faults are based on seismic, I wouldn't want to hang too much on their locations.

      You mention that you have also reviewed Smythe's article. Did this review make it online anywhere? I'd be interested to read a second opinion (even if it's similar too mine - sometimes it's nice to be reassured that you're not going crazy).

    2. I'm a geologist and I live in Balcombe. The BGS map puts a fault through my front garden, its beyond me how they could have mapped it. As you say with the lack of outcrop the mapping of faults is not to be taken too seriously. The 2D seismic line available on UKOGL that runs north south past the well site even suggests a fairly major fault 500m to the south may not actually exist

    3. Thanks anonymous, your expertise is welcome. Having spent a little time in the area deploying our seismometers, it became apparent that any fault map based on surface mapping alone is going to be very approximate.

  3. It doesn't add up...30 September 2013 at 13:26

    I'm sure you've seen the results are in.

    Cuadrilla is pleased to announce that the Balcombe exploration drilling operations have been successfully completed. We have commenced the removal of our drilling equipment from the site and expect to have removed all equipment by 28th September.

    On-site operations involved the drilling of a vertical exploration well to an approximate depth of 2,700ft, collecting 294ft of rock samples (“core”) on the way. We also carried out a set of advanced petrophysical logs which provide valuable data about the characteristics of the underground rock and the fluids contained in those rocks.

    As per UK requirements, cores from the vertical well have already been divided between Cuadrilla and the British Geological Survey, who maintain a record of all UK drilling.

    In addition to the vertical well a horizontal well was drilled through the middle Kimmeridge Micrite which is a band of limestone rock within the Kimmeridge Clay Formation. A total distance of some 1700ft of horizontal drilling was achieved, drilling in a direction of just south of due west under the Balcombe estate. Using geo-steering technology, the entire 1700ft was successfully drilled within the target limestone.

    Along with the operational drilling success achieved at Balcombe the well also confirmed the presence of hydrocarbons. Whilst further testing will be required to determine flow rates, Andrew Quarles, Cuadrilla’s Exploration Director said that “the well was a success and we are very encouraged by the findings so far.”


    Looks like the Prof was wrong.

    1. I think the phrase is "I hate to say I told you so". And I really do - this was one blog post that I never should have had to write, unfortunately.

  4. Great post. It is important to follow a plan while drilling for oil and gas.

    First Liberty Energy

  5. Blackpool Resident12 June 2014 at 08:31

    Can I ask, other than the information critiqued here, what is the basis of Professor Smythe's continued opposition to frac'ing?

  6. From one geologist to another Professor Smythe is bugging me now. He seems to be on a crusade rather than acting as a scientist.

    I have drilled something like 120 wells over the past decade working as a geologist at the wellsite. Yes, there are many faults. But well after well I have seen no evidence of hydrocarbon transmission above the main reservoirs. Drill down and there is zero gas, until you change formation and then bam! up it comes. Every well is like this. No hydrocarbons until you get through the cap rock into the reservoir or until you drill through a source. Directly above either there is nothing or a source with low hydrocarbons. I have seen numerous wells in the UK and not once have I seen any evidence of these faults allowing hydrocarbons to naturally rise up the strata. Log after log after log shows the complete opposite - these hydrocarbons are confined by the above formations. There is not the evidence to suggest that faults are acting as transmission paths. I honestly do not know where Professor Smythe pulls that from. It is something we just do not see in the field actually drilling the wells.

    I should correct the idea that LWD is at the bit. The bit is at the bit. LWD tools are tools that must fit in the string somewhere and they are behind the bit, stabilisers, non magnetic collars etc. What this means is that there is a bit of a lag - the tools are behind where the bit is, so your data is behind. You can drill an extra 10m to get the tool there, but then the bit is 10m ahead. On deviated wells trying to keep in a formation it gives you a bit more to think about. The answer your description is missing with regard to directional drilling is the good old geologist sitting there looking at the rocks as they come up to surface who very often (unless you are drilling quicker than it takes to get the rocks circulated to surface, in which case, slow down..) will see formation changes before LWD does. If the LWD is itself directional (eg capable of measuring changing resistivity etc around the tool, not just taking a single reading that could be coming from any direction), then it is good for indicating whether the formation change approaching is above you or below you, in which case you know whether to steer the bit down, or up, etc.

    1. Thanks for your comment Mr Anonymous Geologist.

      I agree with your comments as regards Prof Smythe's crusade. The more usual method for scientific communication is to publish peer-reviewed papers and technical reports. Prof Smythe doesn't seem at all interested in validating his claims by doing this.

      However, there should also be a certain onus on professional geologists in the UK to challenge and refute his wilder claims. For example, your observations regarding faulted caprocks and the lack of HC migration in the UK need to be put before the wider public for consumption. You might wish consider writing this information into a short report written in a way that the general public can understand. I appreciate that much of the necessary information might be confidential, but if you can find a way (and the time) to do this it might make for an influential report.

      Thanks for the extra info on LWD. I'll admit that while I'm aware of the basics, it is not my particular speciality. Though anyone remotely familiar with drilling will know that hitting a 30m thick unit is hardly a challenge for modern drilling methods. I should have been more precise about my comment of "at the drill tip", where "near the drill tip" would be more accurate.

  7. I’ve stumbled upon Prof. Smythe’s website only recently, and I highly appreciate his concern toward environmental risk management. What happened to Blackpool is really a remarkable one, so I guess that must be the reason why most people believe that stimulation can trigger an earthquake. Well, it really makes sense, since the vibrations that come from the drill tip, and the hole that's left afterwards, could trigger up those rock faults. However, additional studies should be done with regard to the issue, so that there will be undeniable proof of it, once it is presented to the public and the officials concerned.

    Jermaine Ryan @ Loadcraft Industries, Ltd.

    1. Hi Jermaine,
      I think you've misunderstood how hydraulic fracturing can trigger seismicity. It is nothing to do with the vibrations from the drill tip. The drilling part of the shale gas process is no different from any other kind of drilling operation.

      In hydraulic fracturing, once the well is drilled, water is pumped down at high pressure in order to crack the rock, with the resulting fractures providing a pathway for gas to flow from the shale rock into the well bore more easily. If the high pressure fluid reaches a geological fault, the effect of the high pressure is to lubricate the fault slightly, making it easier to slide.

      The best analogy I can come up with is if you press your hands together and try to slide them past each other. If you press your hands tightly together, it is hard to slide them. If you only press them together gently, you can slide them more easily. The effect of the high pressure fluid is that the two sides of the fault are pressed together less strongly, so they slide slightly easier.

      The key point here is that this is a relatively small effect, and that it requires a fault that is close to failure anyway. So it is not creating an earthquake "from scratch": a fault must be pretty close to having an earthquake anyway, the hydraulic stimulation makes it happen a bit sooner.

      Because most faults are not near to this critical stress, most of the time when hydraulic stimulation occurs near a fault, no earthquakes occur. Of hundreds of thousands of frac stimulations that have been done in the world, I am aware of only 4 cases that have triggered seismicity: Blackpool in 2011, Garvin County Oklahoma in 2011, the Horn River Basin, B.C., Canada, and a case in Mahonig County Ohio this year, which is still under investigation.

      Also, the hydraulic fracturing process typically takes place over a couple of hundred meters or so. This means it can't really impact and trigger the larger faults, only faults that are themselves of a similar length scale. The size of an earthquake is determined by the length of the fault triggered.

      This is why the sizes of earthquakes triggered by hydraulic fracturing have been relatively small - usually less than magnitude 3. The Royal Society report concluded that magnitude 3 was probably the largest earthquake that could be triggered by fracking in the UK. A magnitude 3 quake is unlikely to cause any damage to buildings or property - we have many of these size events occurring naturally every year.

      I hope that helps you understand the process a little better.


  8. Hi JV

    "..and a case in Mahonig (sic) County Ohio this year, which is still under investigation."

    The paper, "Earthquakes Induced by Hydraulic fracturing in Poland Township, Ohio," will be published online Jan. 6, 2015 and in print in the February/March issue of BSSA.


  9. Great details. Thanks intended for providing us all a real useful details. Continue the excellent work and also proceed providing us all far more high quality details on occasion.Geomentary on Geo News

  10. The biggest fast track conduit for contamination results from a lack of well integrity, primarily caused by inadequate cement jobs, or over time by casing degradation.
    The failure of seals within a well is by no means uncommon,especially after abandonment. For some reason the literature on fracking, both positive and negative, for the most part ignores this fact. A literature review worldwide would show the percentage of wells that are defective, both on and offshore, is uncomfortably high.