Science outreach is becoming a big deal - there's a huge appetite for it from the general public. There can be little doubt - science is now cool!
This week I had the privilege to attend the 3rd Bristol Science Show-Off - an opportunity for science-lovers to gather in a boat (well, a boat masquerading as a pub but which does excellent beers) and listen to 10 brave scientists spout off about their favourite sciencey-tidbit.
Notably, well before kick-off the place was pretty much full to the rafters (probably too full for the HSE's liking one imagines), I wouldn't have had a seat had I not been acccidentally roped in to do tech support (by virtue of being tall enough to hang the projector screen up, and happening to have a laptop with me).
The night began with Bonnie Buckley explaining how one tells alligators and crocodiles apart, and what not to do when in the presence of a wild one - mainly, don't feed them, or them may decide that your kids also represent food. In fact, don't feed them with your own body parts either seems like sensible advice. This was followed by Matt Tosh, who showed us the science (pyromania really) behind firework displays, and the importance of not blowing everything up at once. Ceri Wyn-Thomas then brought
up a traumatic maternal childhood prank (her mother convinced her that
when she was 7 she'd shed her skin like a snake) to talk about ecdysis -
how and why crabs, lobsters, spiders etc shed their skins, with much
'stripping-off' innuendo. Karl Byrne talked us through the longest-running science experiments in history, including some fields in Rothamsted and the Queensland Pitch Drop. As fascinating as watching paint drip and/or watching grass grow. The first half finished off with Mark Lewney using an electric guitar to play us through a typical Horizon show - a one stop guide to structuring a science show.
After the break, Emily Coyte and Audrey
Nailor explained how cute lolcatz pictures are in fact science because they are memes, while Becky Holmes showed a slightly unhealthy fascination with all things firemen (so we had one talk starting fires, and one putting them out), including proving definitively that a randomly selected audience member looked hotter after donning a fireman's uniform. Things got a little sticky when Joe Wright gave a 'seminal' talk using his microscope to image certain human cells, before Neil Jerome reminded us all of the tricky business of statistics, and the importance remaining scrupulously impartial when we conduct experiments, rather than trying to bend statistics to our will. This included several examples of scientific papers when authors have failed to heed the above advice, seeing what they want to see rather than what the data actually show. An important reminder for us all! Finally, the night closed with Ross Exton building a composite mega-animal (for the record, body of a cheetah, ears of an owl, nose of a mole, eyes of a mantis shrimp, punching forelimbs of a mantis shrimp, and jaw of a crocodile). A word also for the compere Steve Cross who did a great job, witty throughout.
Nothing about shale gas in this post, but I really felt the need to comment on what was a really enjoyable evening. It's really encouraging that so many members of the public are keen to engage with science, and I hope that such events become a regular fixture. It's up to us scientists to get out there and talk science!!
Sunday, 26 May 2013
Friday, 24 May 2013
IoD Report on UK Shale Gas
Big news for UK shale gas this week, as the Institute of Directors has released their report into the economic impacts of UK shale. This report focuses on how shale gas development will affect the UK economy, rather than safety aspects, which is a welcome change because it seems we spend a lot of time talking about potential negative impacts of shale gas, without remembering that there are significant gains to be made.
Here are the key headlines from the report:
The report finishes by highlighting the likely barriers to UK shale gas development. They recommend that some of the economic benefits of production are funneled directly to local communities, and that more is done to engage local people. Some of the above headlines will help I'm sure.
Here are the key headlines from the report:
The IoD’s previous report, published last year, looked at the number of jobs that shale gas production could potentially create. We now believe that it could be higher still. According to the detailed scenarios presented in this report of a potential production phase, investment could peak at £3.7 billion a year, supporting 74,000 jobs – not just for geologists and drilling specialists, but for construction workers, truck drivers, cement manufacturers, water treatment experts, and people working in local retail and service industries.
Jobs could be created in parts of the country that need them most – over the last decade, the proportion of working-age people receiving at least one out-of-work benefit has averaged more than 15% in the North West, compared to less than 9% in the South East.
Shale gas production, with tax rates of up to 62%, could generate significant tax revenue, helping to offset a predicted future tax gap of 1.25% of GDP from lower Fuel Duty and North Sea receipts.
Far from a “dash for gas”, the Department for Energy and Climate Change expects overall gas demand, for heating and industry as well as electricity, to remain roughly flat over the next two decades. This is consistent with carbon reduction of 45% by 2025. But 76% of the UK’s gas is likely to be imported by 2030, costing £15.6 billion. In our central scenario, shale gas production could reduce gas imports to 37% in 2030, and the cost of imports could fall to £7.5 billion.I think this is a key point to keep in mind. At least some proportion of shale gas opposition derives from a concern that shale gas will displace renewable energy on the grid. In fact, the ideal for shale gas is that it replaces gas that we currently import from the middle east. As an example, renewable energy installation has boomed in the US in the last 5 years, despite (or even in tandem with) the shale gas boom. Producing gas domestically rather than importing is beneficial for many reasons: it boosts our economy, rather than that of Qatar; it improves our energy security; and potentially the shorter transport distances mean that this gas has a lower carbon footprint than imported LNG (which has to be compressed and shipped). The IoD estimate that shale gas could replace half of our imports, saving £15billion, and as noted in the report, could reduce our greenhouse gas footprint.
According to the Committee on Climate Change, if production is well regulated, shale gas can have lower emissions than imported gas. If shale gas supports the production of chemicals and other goods in the UK, global emissions will also be lower, as UK industry is very energy-efficient.
Natural gas has great potential as a transport fuel, particularly for lorries and buses. In the US, 19% of municipal buses run on natural gas.An abundance of gas could also encourage an increase in gas-fuelled buses and lorries, which have lower CO2 emissions than diesel.
Only a small amount of land is needed for shale gas development. One 2-hectare site could potentially support 40 horizontal wells and supply enough gas to power 747,000 homes at peak production. 100 such sites would take up just two square kilometres of land, and could supply around one third of our gas needs at peak.This is a very interesting conclusion. One of the principal concerns about shale gas is the surface footprint - that huge swathes of the UK countryside will be covered by wellheads. The UK Bowland shale is remarkably thick, much thicker than most of the US shale formations. This means that a greater volume of rock can be accessed from single well points. Operators are envisaging so called 'stacked laterals' (shown below), where multiple lateral wells are drilled on top of each other. This will substantially reduce the surface footprint of developments for a given volume of gas produced, because rather than 6 wells per pad, suddenly you are looking at 12, 18, 24 wells per pad.
Water use could peak at just 0.05% of the UK’s total consumption of 11,000 million cubic metres a year.As often mentioned on this blog, water use is a non-issue for the UK: water companies lose more water every day in pipeline leakages than needed for fracking.
The report finishes by highlighting the likely barriers to UK shale gas development. They recommend that some of the economic benefits of production are funneled directly to local communities, and that more is done to engage local people. Some of the above headlines will help I'm sure.
Wednesday, 8 May 2013
Open access is here
This is a quick post to comment on Bristol University's open access policy in the wake of new guidelines from RCUK. In essence, any RCUK-funded research must now be open access, either green or gold (green is where the paper is archived in a repository of some kind, gold is where an article processing charge (APC) is paid to the publisher so that they make the paper openly available).
For now I will reserve comment on whether open access is overall a good or bad thing - it is happening regardless. For any UK researcher it is vital that their papers are considered to be REF-eligible, and this means that they must be open access.
However, as anticipated, I think that the costs have been hugely underestimated. Bristol Uni has put aside a block grant of £500,000 to fund APCs of gold open access articles. However, a quick perusal of the University publications database reveals that, in 2012, the Faculty of Science produced 1,100 academic journal papers. The university as a whole produced more than 3,000. Assuming an average APC of £1,000, that means that the cost of the output from the Science Faculty alone is more than £1million, and from the whole university is more than £3million.
So I'm not sure how they worked out that £500,000 would be sufficient to cover this. Of course, it presumably means that there will be competition for this money, and is it likely that I, as a young researcher without a lot of clout compared to the senior professors and staff at the uni, will get a piece of it? In turn, does this mean that if I want my papers to be REF-eligible, will they have to be published in journals other than the ones of my choice? I suspect so, and I am concerned at the impact that this will have on my career (the career of any young scientist is controlled disproportionately by which journals he/she is able to get papers published in).
For now I will reserve comment on whether open access is overall a good or bad thing - it is happening regardless. For any UK researcher it is vital that their papers are considered to be REF-eligible, and this means that they must be open access.
However, as anticipated, I think that the costs have been hugely underestimated. Bristol Uni has put aside a block grant of £500,000 to fund APCs of gold open access articles. However, a quick perusal of the University publications database reveals that, in 2012, the Faculty of Science produced 1,100 academic journal papers. The university as a whole produced more than 3,000. Assuming an average APC of £1,000, that means that the cost of the output from the Science Faculty alone is more than £1million, and from the whole university is more than £3million.
So I'm not sure how they worked out that £500,000 would be sufficient to cover this. Of course, it presumably means that there will be competition for this money, and is it likely that I, as a young researcher without a lot of clout compared to the senior professors and staff at the uni, will get a piece of it? In turn, does this mean that if I want my papers to be REF-eligible, will they have to be published in journals other than the ones of my choice? I suspect so, and I am concerned at the impact that this will have on my career (the career of any young scientist is controlled disproportionately by which journals he/she is able to get papers published in).
Sunday, 28 April 2013
Shale gas and Cash-for-Locals?
This week the Parliamentary Select Committee for Energy and Climate Change released its assessment of 'The Impact of Shale Gas on Energy Markets'.
I particularly enjoyed conclusion 5:
More interesting, in my view at least, is conclusion 6:
In the US, mineral rights are generally owned by the person that owns the land. This means that if your farm sits on top of some shale gas, you stand to benefit directly from royalties from the gas development (try sticking the default numbers into this calculation engine). As a result, shale gas is generally wildly popular among rural American communities.
However, in the UK, in most cases the mineral rights being to the Crown Estate (i.e. 'er maj, gawd bless 'er), meaning that royalties from gas production goes straight to central government, rather than via local people.
Of course, that's not to say that shale gas development will not benefit a local community. While many of the jobs involved are high tech, and as such cannot be easily accessed by local people, there are plenty of roles for relatively unskilled workers, particularly in construction and haulage. Moreover, however the influx of skilled workers need places to stay, to eat and to drink, to do their laundry. They need to buy petrol, buy stuff from convenience stores, the list goes on. In Pennsylvania you hear of companies block-booking whole hotels for 6 month stretches to house the workers, restaurants full to bursting every lunchtime and bars full in the evenings.
However, UK public opinion continues to waver in regards to shale gas development. So, is it right to consider setting up community benefit schemes, whereby some of the profits from gas development are injected directly back into the local community? Or is this all a bribe to get people to accept something that they'd otherwise not be comfortable with?
In all honesty, I'm not sure I know the answer to this. On the one hand, shale gas development will involve some local disruption. Not the scare stories of exploding taps, blighted aquifers and general geological disruption - the so-called 'geological dread factor' - but increases in traffic, construction sites, laying new pipeline etc. Therefore it does seem reasonable that a community should receive some recompense for that. On the other hand, offering what could easily look like little more than a bung could make it look like shale gas has something to hide, when so long as the government ensures that there is 'a robust factual response by government to scare stories' it shouldn't have to.
It is worth noting at this juncture that such schemes seem to be common for wind farms (see here and here for two randomly selected examples) and nuclear power stations. I have enjoyed seeing how the language changes depending on your preferred form of energy, particularly wind farm proponents who have touted these community wind farm benefits as a great example of how wind can benefit a community, while if shale gas companies suggest the same thing then it is little more than a bribe.
So I'm still not sure whether this is a good idea or not. Regardless, in the meantime, IGas have drilled two exploration wells in Lancashire.
I particularly enjoyed conclusion 5:
One key to community acceptance will be a robust factual response by government to scare storiesI wonder who/what they could be referring to there....
More interesting, in my view at least, is conclusion 6:
Communities who are affected by shale gas development should expect to receive, and share in, some of the benefits of the developmentor, as the Guardian would put it: Fracking firms should offer sweeteners to locals. It's an interesting idea, but I'm still torn between whether it is a good one or not.
In the US, mineral rights are generally owned by the person that owns the land. This means that if your farm sits on top of some shale gas, you stand to benefit directly from royalties from the gas development (try sticking the default numbers into this calculation engine). As a result, shale gas is generally wildly popular among rural American communities.
However, in the UK, in most cases the mineral rights being to the Crown Estate (i.e. 'er maj, gawd bless 'er), meaning that royalties from gas production goes straight to central government, rather than via local people.
Of course, that's not to say that shale gas development will not benefit a local community. While many of the jobs involved are high tech, and as such cannot be easily accessed by local people, there are plenty of roles for relatively unskilled workers, particularly in construction and haulage. Moreover, however the influx of skilled workers need places to stay, to eat and to drink, to do their laundry. They need to buy petrol, buy stuff from convenience stores, the list goes on. In Pennsylvania you hear of companies block-booking whole hotels for 6 month stretches to house the workers, restaurants full to bursting every lunchtime and bars full in the evenings.
However, UK public opinion continues to waver in regards to shale gas development. So, is it right to consider setting up community benefit schemes, whereby some of the profits from gas development are injected directly back into the local community? Or is this all a bribe to get people to accept something that they'd otherwise not be comfortable with?
In all honesty, I'm not sure I know the answer to this. On the one hand, shale gas development will involve some local disruption. Not the scare stories of exploding taps, blighted aquifers and general geological disruption - the so-called 'geological dread factor' - but increases in traffic, construction sites, laying new pipeline etc. Therefore it does seem reasonable that a community should receive some recompense for that. On the other hand, offering what could easily look like little more than a bung could make it look like shale gas has something to hide, when so long as the government ensures that there is 'a robust factual response by government to scare stories' it shouldn't have to.
It is worth noting at this juncture that such schemes seem to be common for wind farms (see here and here for two randomly selected examples) and nuclear power stations. I have enjoyed seeing how the language changes depending on your preferred form of energy, particularly wind farm proponents who have touted these community wind farm benefits as a great example of how wind can benefit a community, while if shale gas companies suggest the same thing then it is little more than a bribe.
So I'm still not sure whether this is a good idea or not. Regardless, in the meantime, IGas have drilled two exploration wells in Lancashire.
Tuesday, 23 April 2013
Bristol's shake table
Shake tables are used to simulate the effects of earthquakes on structures. Engineers use them to simulate the effects of earthquakes on structures, so that they can design buildings to withstand shaking.
You can program in the earthquake of your choice, put your structure on the table, and see how well it does. Today I got to visit the Bristol Engineering Dept shake table. Here's some video:
You can program in the earthquake of your choice, put your structure on the table, and see how well it does. Today I got to visit the Bristol Engineering Dept shake table. Here's some video:
Thursday, 11 April 2013
The Maximum Magnitude Conundrum
I talked in my last post about seismicity (i.e. earthquakes) induced by subsurface fluid injection. In fact, there are many human activities that have the potential to cause earthquakes, including:
Which in turn begs a really important question - for a given operation, what (if anything) will determine the maximum possible earthquake magnitude that your activity will produce? This is a really important question both for human activities, as well as seismologists who work on natural seismicity: what is the largest earthquake possible in a given setting?
Before I get into this, a word on earthquake magnitudes (skip this if you already know about magnitudes). Most people are familiar with the Richter magnitude scale running from 0 (i.e. very very small, basically undetectable) to about 9 for the biggest quakes we've ever had. Most people are also aware that it is a logarithmic scale, meaning that an M2 event is 10 times as large as an M1 event, not twice the size. In fact, the Richter scale, which was essentially an arbitrary scaling function, has largely been supplanted by the Moment Magnitude scale, which relates more directly to earthquake physical processes. More specifically, Moment Magnitude is calculated from the seismic moment (Mo), according to:
Magnitude = (2/3) log(Mo) - 16.1,
This equation was deliberately scaled so that it followed the Richter scale, so that seismologists (and the public) could still understand magnitudes in the same way. In turn, the seismic moment is defined by the size of the rupture during the earthquake, according to:
Mo = G A D,
where G is the shear modulus of the rock, A is the cross-sectional area of the earthquake rupture, and D is the average dislacement that one side of the fault moves relative to the other. So you can see that, if there is no limit to the size of a fault (which controls the rupture area), there is no limit to the maximum magnitude that an earthquake can be. In reality, however, the the thickness of the earth's crust probably imposes an upper limit on the size that an earthquake can be, which is why even the largest earthquakes (on Earth at least - who knows, a planet with a thicker crust could probably have larger earthquakes) don't ever seem to get much bigger than M9.
Now, back to human activities triggering earthquakes. It's unlikely that any of the activities listed above could trigger a crustal-scale fault capable of triggering an M9 earthquake. So what controls the maximum magnitude that could be triggered by mankind's operations? In my last plot I showed the graph used by Art McGarr to explain induced seismicity in the USA and around the world:
BUK is the famous fracking-induced Blackpool earthquake. RMA is the Rocky Mountain Arsenal. YOH is Youngstown Ohio. PBN is Paradox Basin, Colorado. GAK is Guy, Arkansas. BAS is Basel, Switzerland. GAR is Garvin County, Oklahoma. STZ is Soultz, France. RAT is the Raton Basin, Colorado.
McGarr adapted the long established McGarr equation, which originally stated that the total seismic moment released is proportional to the volume of rock extracted during mining (multiplied by G):
TotalMoment = G x VolRockMined.
This equation was soon adapted to cover seismicity induced by fluid removal and/or injection, with VolRockMined being replaced by dV: the volume of fluid injected. The physical basis for doing so has always been slightly dubious, but empirically it seems to do a reasonable job. After the recent induced seismicity incidences, the McGarr equation has been modified again: now G dV gives not the total seismic moment released, but the magnitude of the largest event alone. This modification should only be strictly true in situations where the single largest event completely dominates the total seismic moment released. So we end up with the modified McGarr equation for injection-induced seismicity:
MaxMo = G dV.
This is the equation plotted in the above figure, and you can see that it does a good job of fitting the data. But the key thing to note with the McGarr equation is that it is empirical, it does not have any real physical basis - i.e. it is something that is observed, but it doesn't really explain WHY the maximum magnitude should be controlled by the volume of fluid injected (instead of, say, the rate of injection or the change in pore fluid pressure).
A new model for Mmax has been developed by Serge Shapiro of the Freie University, Berlin, which I find very interesting. The Shapiro model suggests that Mmax should be controlled by the size of the fluid-affected zone.
A large earthquake can't just happen anywhere - a pre-existing fault plane must be present on which the quake happens. As an approximate scaling, the maximum earthquake magnitude created by a circular shaped fault with radius r can be approximated as:
Mmax = 2 log(2r).
So an M3 quake needs a fault of radius 15m, and an M6 quake needs a fault of radius 500m. So, could the size of the area stimulated by fluid injection control the size of the earthquake? Lets consider fluid injection into a completely homogeneous porous rock. The fluid-saturated zone will spread as a sphere (assuming it has similar density to the in situ fluid). The radius of this sphere can be easily calculated from the volume injected. Shapiro argues that the size of the largest fault that can be triggered must scale with the radius of the injected fluid volume.
If a fault is significantly larger than the radius of the injection zone, only a small portion of this will be influenced by it, and this will not be sufficient to trigger rupture. Failure will only occur on faults where the majority of the fault is influenced by injection. As a result, we have a reason to scale Mmax with injection volume. Do the maths and you end up with:
RADIUS = (3/4)*VOLUME^(1/3)
so
Mmax = 2 log((3/4)*VOLUME^(1/3)).
In the plot below, the green circles show Mmax for the McGarr data, which I have calculated using the Shapiro model. You can see that, much like the McGarr model, they fit pretty well. So do we now have a better model to explain Mmax?
Unfortunately, I don't think we do. When you look in more detail at the induced events, you can see that some of the key assumptions of the Shapiro model are not met. The Shapiro model requires that events occur within the immediate radius of the injection zone. The figures below show induced seismic events from Arkansas, Oklahoma and Colorado, with the injection wells marked.
A common theme is that the majority of events occur well below the injection point. Perhaps some of the initial seismicity is triggered in the injection interval, but the majority of the triggered faults lie outside the zone that is directly influenced by injection. The Shapiro model explicitly assumes that the triggered faults lie almost completely within the injection-influenced interval. I think that the Shapiro model is a great attempt to simplify a difficult problem, but to me it seems that more complicated effects involving stress transfer through many layers of rock are acting, and need to be taken into account, to understand the triggering of these faults.
This takes us back to the title of this post: predicting Mmax is still a conundrum. The McGarr model seems to fit the data, but it is only empirical, there is no real physics behind it. The Shapiro model also fits the data well, and has a physical mechanism of control. However, the suggested controlling mechanism doesn't stack up when the events are studied in more detail.
A physically realistic, empirically verified model to predict Mmax still eludes us. We are usually able to explain post hoc why a particular operation triggered an event. However, we are still not very good at predicting in advance whether a project will induce larger seismic events. If you can come up with a better method, then do get in touch, because a solution will be extremely valuable in a range of industries as discussed above.
In the meantime, we are left with the empirical McGarr equation as our main guide. It should of course be remembered that the McGarr equation does not tell you the maximum magnitude you will get in an operation. The maximum magnitude produced during most operations fall well below the McGarr line. The McGarr line tells you the maximum magnitude you could get if you are very unlucky.
- mining
- waste fluid injection
- carbon capture and storage
- fracking
- nuclear waste storage (potentially at least)
- reservoir impoundment (for hydro-electricity and/or pumped storage)
- geothermal energy
- conventional hydrocarbon production
Which in turn begs a really important question - for a given operation, what (if anything) will determine the maximum possible earthquake magnitude that your activity will produce? This is a really important question both for human activities, as well as seismologists who work on natural seismicity: what is the largest earthquake possible in a given setting?
Before I get into this, a word on earthquake magnitudes (skip this if you already know about magnitudes). Most people are familiar with the Richter magnitude scale running from 0 (i.e. very very small, basically undetectable) to about 9 for the biggest quakes we've ever had. Most people are also aware that it is a logarithmic scale, meaning that an M2 event is 10 times as large as an M1 event, not twice the size. In fact, the Richter scale, which was essentially an arbitrary scaling function, has largely been supplanted by the Moment Magnitude scale, which relates more directly to earthquake physical processes. More specifically, Moment Magnitude is calculated from the seismic moment (Mo), according to:
Magnitude = (2/3) log(Mo) - 16.1,
This equation was deliberately scaled so that it followed the Richter scale, so that seismologists (and the public) could still understand magnitudes in the same way. In turn, the seismic moment is defined by the size of the rupture during the earthquake, according to:
Mo = G A D,
where G is the shear modulus of the rock, A is the cross-sectional area of the earthquake rupture, and D is the average dislacement that one side of the fault moves relative to the other. So you can see that, if there is no limit to the size of a fault (which controls the rupture area), there is no limit to the maximum magnitude that an earthquake can be. In reality, however, the the thickness of the earth's crust probably imposes an upper limit on the size that an earthquake can be, which is why even the largest earthquakes (on Earth at least - who knows, a planet with a thicker crust could probably have larger earthquakes) don't ever seem to get much bigger than M9.
Now, back to human activities triggering earthquakes. It's unlikely that any of the activities listed above could trigger a crustal-scale fault capable of triggering an M9 earthquake. So what controls the maximum magnitude that could be triggered by mankind's operations? In my last plot I showed the graph used by Art McGarr to explain induced seismicity in the USA and around the world:
McGarr adapted the long established McGarr equation, which originally stated that the total seismic moment released is proportional to the volume of rock extracted during mining (multiplied by G):
TotalMoment = G x VolRockMined.
This equation was soon adapted to cover seismicity induced by fluid removal and/or injection, with VolRockMined being replaced by dV: the volume of fluid injected. The physical basis for doing so has always been slightly dubious, but empirically it seems to do a reasonable job. After the recent induced seismicity incidences, the McGarr equation has been modified again: now G dV gives not the total seismic moment released, but the magnitude of the largest event alone. This modification should only be strictly true in situations where the single largest event completely dominates the total seismic moment released. So we end up with the modified McGarr equation for injection-induced seismicity:
MaxMo = G dV.
This is the equation plotted in the above figure, and you can see that it does a good job of fitting the data. But the key thing to note with the McGarr equation is that it is empirical, it does not have any real physical basis - i.e. it is something that is observed, but it doesn't really explain WHY the maximum magnitude should be controlled by the volume of fluid injected (instead of, say, the rate of injection or the change in pore fluid pressure).
A new model for Mmax has been developed by Serge Shapiro of the Freie University, Berlin, which I find very interesting. The Shapiro model suggests that Mmax should be controlled by the size of the fluid-affected zone.
A large earthquake can't just happen anywhere - a pre-existing fault plane must be present on which the quake happens. As an approximate scaling, the maximum earthquake magnitude created by a circular shaped fault with radius r can be approximated as:
Mmax = 2 log(2r).
So an M3 quake needs a fault of radius 15m, and an M6 quake needs a fault of radius 500m. So, could the size of the area stimulated by fluid injection control the size of the earthquake? Lets consider fluid injection into a completely homogeneous porous rock. The fluid-saturated zone will spread as a sphere (assuming it has similar density to the in situ fluid). The radius of this sphere can be easily calculated from the volume injected. Shapiro argues that the size of the largest fault that can be triggered must scale with the radius of the injected fluid volume.
If a fault is significantly larger than the radius of the injection zone, only a small portion of this will be influenced by it, and this will not be sufficient to trigger rupture. Failure will only occur on faults where the majority of the fault is influenced by injection. As a result, we have a reason to scale Mmax with injection volume. Do the maths and you end up with:
RADIUS = (3/4)*VOLUME^(1/3)
so
Mmax = 2 log((3/4)*VOLUME^(1/3)).
In the plot below, the green circles show Mmax for the McGarr data, which I have calculated using the Shapiro model. You can see that, much like the McGarr model, they fit pretty well. So do we now have a better model to explain Mmax?
Unfortunately, I don't think we do. When you look in more detail at the induced events, you can see that some of the key assumptions of the Shapiro model are not met. The Shapiro model requires that events occur within the immediate radius of the injection zone. The figures below show induced seismic events from Arkansas, Oklahoma and Colorado, with the injection wells marked.
A common theme is that the majority of events occur well below the injection point. Perhaps some of the initial seismicity is triggered in the injection interval, but the majority of the triggered faults lie outside the zone that is directly influenced by injection. The Shapiro model explicitly assumes that the triggered faults lie almost completely within the injection-influenced interval. I think that the Shapiro model is a great attempt to simplify a difficult problem, but to me it seems that more complicated effects involving stress transfer through many layers of rock are acting, and need to be taken into account, to understand the triggering of these faults.
This takes us back to the title of this post: predicting Mmax is still a conundrum. The McGarr model seems to fit the data, but it is only empirical, there is no real physics behind it. The Shapiro model also fits the data well, and has a physical mechanism of control. However, the suggested controlling mechanism doesn't stack up when the events are studied in more detail.
A physically realistic, empirically verified model to predict Mmax still eludes us. We are usually able to explain post hoc why a particular operation triggered an event. However, we are still not very good at predicting in advance whether a project will induce larger seismic events. If you can come up with a better method, then do get in touch, because a solution will be extremely valuable in a range of industries as discussed above.
In the meantime, we are left with the empirical McGarr equation as our main guide. It should of course be remembered that the McGarr equation does not tell you the maximum magnitude you will get in an operation. The maximum magnitude produced during most operations fall well below the McGarr line. The McGarr line tells you the maximum magnitude you could get if you are very unlucky.
Monday, 1 April 2013
Induced Earthquakes in the USA, and some implications for CCS
Here's a recent BBC report on earthquakes induced by oil and gas activities in the USA. As can be expected, the twitter/blogo-sphere has been lighting up over this in the last few days. For me the biggest surprise is that this has only come up in the wider media in last few days: induced earthquakes have been a key topic of discussion among geophysicists for a couple of years now. The USGS has noted an increase in medium-sized earthquakes in the last decade:
The black line shows the total number of earthquakes in the midcontinent USA (excluding the very active San Andreas fault and other active parts on the west coast) greater than M3 since 1970: you can see the increases as the line gets steeper.
The oil industry likes to dispose of waste-water by injecting it into deep-lying saline aquifers. However, it has been well known since the Rocky Mountain Arsenal in the 1960s that deep fluid injection can trigger earthquakes. It is argued that the increase in oil industry injection activities in the last decade has been the cause of the increase in the numbers of earthquakes.
This remains under debate - could the increase be simply that, as more (and better) seismic monitoring networks are installed, we are detecting more earthquakes than we did in the past. The latest news story is a case in point. The paper in Geology attributes an M5.7 earthquake in Oklahoma to injection of waste-water. The Oklahoma Geological Survey has subsequently released a rebuttal stating that as far as it is concerned, there is not enough evidence to tie the quake to injection activities (strangely enough, the OGS rebuttal hasn't been given much of a look-in from the media).
Nevertheless, I think that it inarguable that, in certain cases at least, fluid injection has triggered earthquakes with magnitudes from about M3 to M6.
This brings me to a couple of asides. Firstly, following on from my last post about bad media reporting of these issues, many reports attributed the quake to injection of waste-water from fracking. This is not the case - the waste water in this case came from conventional oil production. This harks back to an older post I made about the relative risk profiles from fracking in comparison to conventional oil and gas. The need to dispose of large quantities of contaminated waste water is not a new, fracking-related problem in the oil industry. If you are opposed to fracking, you must presumably be opposed to all oil and gas related activity.
Secondly, M5.7 is a large earthquake. It is about 100,000 times larger than the quake induced in Blackpool by fracking. It is larger than any earthquake ever recorded in the UK. Perhaps only a few historical earthquakes in the UK have been of a similar size. An M5.7 triggered earthquake here would be serious news.
So, can we get an estimate of what earthquake magnitude might be triggered by our various activities? Art McGarr, a venerable (and venerated) and highly experienced geophysicist with the USGS has made an effort to do this. McGarr cut his teeth in the 1970s looking at mining induced seismicity, where he noticed a correlation between the total energy released during rock extraction and the volume of rock extracted. He developed the so-called McGarr equation:
Sum(Moment) = G dV
The sum of the released seismic moment equals the volume change (dV) multiplied by the shear modulus (G). It should be noted that this equation is based on empirical observation only. It has subsequently been applied to fluid injection (or mis-applied, some would say, as there is no obvious basis for arguing that physical processes during fluid injection should match those during rock removal (mining)), where dV becomes the volume of fluid injected.
More recently, McGarr has been looking at earthquakes attributed to fluid injection. This includes waste-water injection as discussed above, as well as geothermal activities and, of course, fracking. He has developed the following plot:
Each + represents an injection-induced seismic event. Unfortunately for any non-geophysicist readers, McGarr has given the earthquake sizes in moment, rather than magnitude, but 10^12 is about M2, 10^15 is about M4, 10^18 is M6. I've not found out what all of McGarr's abbreviations are, but
So how does this apply to the UK? The first thing to note is that deep injection of waste fluids is not allowed in this country, so we can strike this risk off immediately. What about fracking? A typical frack stimulation uses about 1000 - 5000 metres cubed of water - that's ~10^3. This leaves us with a maximum induce-able moment of ~10^13 (or a magnitude of about M3). We get 30 or so M3 events in the UK every year, so inducing a few more due to fracking isn't going to make much difference.
What about CCS? Carbon capture and storage is a key plank in the UK's CO2 emissions reductions plan. All well and good, but CCS involves the injection of very large volumes of fluid into subsurface aquifers. Could this trigger earthquakes?
I've modified McGarr's plot to add the injection volumes of Sleipner and In Salah, two of the foremost CCS projects currently in operation (as well as changing the scale from moment to magnitude to make life a little easier for non-geophysicists):
You can see that, following the McGarr plot, Sleipner and In Salah have the potential to trigger earthquakes of M5 or larger! Of course, they haven't: Sleipner has barely done anything, while In Salah has triggered at most an M1 event (so small you can't feel it without the aid of sensitive seismometers). The McGarr plot tells you the maximum possible magnitude, not what magnitude you will get. Hence why I have shaded in the area under the line: you could get an event on the line, or anywhere under the line.
Still, I find the potential for induced earthquakes from CCS to be worrying. I think this has been under-appreciated by the UK CCS community. There is a clear need for further study on why most injection sites do not produce seismicity, but a few do? What is it that is different about these sites, and how can we identify this in advance, and only select sites that won't trigger events during CO2 injection. At the same time, we can quickly see that the earthquake risk from fracking has been hugely overplayed in comparison to the risks posed by other activites (geothermal, CCS, waste-water injection, mining, and even hydroelectric energy).
The oil industry likes to dispose of waste-water by injecting it into deep-lying saline aquifers. However, it has been well known since the Rocky Mountain Arsenal in the 1960s that deep fluid injection can trigger earthquakes. It is argued that the increase in oil industry injection activities in the last decade has been the cause of the increase in the numbers of earthquakes.
This remains under debate - could the increase be simply that, as more (and better) seismic monitoring networks are installed, we are detecting more earthquakes than we did in the past. The latest news story is a case in point. The paper in Geology attributes an M5.7 earthquake in Oklahoma to injection of waste-water. The Oklahoma Geological Survey has subsequently released a rebuttal stating that as far as it is concerned, there is not enough evidence to tie the quake to injection activities (strangely enough, the OGS rebuttal hasn't been given much of a look-in from the media).
Nevertheless, I think that it inarguable that, in certain cases at least, fluid injection has triggered earthquakes with magnitudes from about M3 to M6.
This brings me to a couple of asides. Firstly, following on from my last post about bad media reporting of these issues, many reports attributed the quake to injection of waste-water from fracking. This is not the case - the waste water in this case came from conventional oil production. This harks back to an older post I made about the relative risk profiles from fracking in comparison to conventional oil and gas. The need to dispose of large quantities of contaminated waste water is not a new, fracking-related problem in the oil industry. If you are opposed to fracking, you must presumably be opposed to all oil and gas related activity.
Secondly, M5.7 is a large earthquake. It is about 100,000 times larger than the quake induced in Blackpool by fracking. It is larger than any earthquake ever recorded in the UK. Perhaps only a few historical earthquakes in the UK have been of a similar size. An M5.7 triggered earthquake here would be serious news.
So, can we get an estimate of what earthquake magnitude might be triggered by our various activities? Art McGarr, a venerable (and venerated) and highly experienced geophysicist with the USGS has made an effort to do this. McGarr cut his teeth in the 1970s looking at mining induced seismicity, where he noticed a correlation between the total energy released during rock extraction and the volume of rock extracted. He developed the so-called McGarr equation:
Sum(Moment) = G dV
The sum of the released seismic moment equals the volume change (dV) multiplied by the shear modulus (G). It should be noted that this equation is based on empirical observation only. It has subsequently been applied to fluid injection (or mis-applied, some would say, as there is no obvious basis for arguing that physical processes during fluid injection should match those during rock removal (mining)), where dV becomes the volume of fluid injected.
More recently, McGarr has been looking at earthquakes attributed to fluid injection. This includes waste-water injection as discussed above, as well as geothermal activities and, of course, fracking. He has developed the following plot:
- BUK is the Blackpool earthquake
- RMA is the quake induced by fluid disposal at the Rocky Mountain Arsenal
- BAS is the Basel (Switzerland) earthquake caused by geothermal activity
- STZ is an earthquake caused by geothermal activity at Soultz, France
- RAT (several of them) are earthquakes in the Raton Basin (Colorado) associated with waste water injection
- POK is the Oklahoma earthquake discussed in this blog
So how does this apply to the UK? The first thing to note is that deep injection of waste fluids is not allowed in this country, so we can strike this risk off immediately. What about fracking? A typical frack stimulation uses about 1000 - 5000 metres cubed of water - that's ~10^3. This leaves us with a maximum induce-able moment of ~10^13 (or a magnitude of about M3). We get 30 or so M3 events in the UK every year, so inducing a few more due to fracking isn't going to make much difference.
What about CCS? Carbon capture and storage is a key plank in the UK's CO2 emissions reductions plan. All well and good, but CCS involves the injection of very large volumes of fluid into subsurface aquifers. Could this trigger earthquakes?
I've modified McGarr's plot to add the injection volumes of Sleipner and In Salah, two of the foremost CCS projects currently in operation (as well as changing the scale from moment to magnitude to make life a little easier for non-geophysicists):
You can see that, following the McGarr plot, Sleipner and In Salah have the potential to trigger earthquakes of M5 or larger! Of course, they haven't: Sleipner has barely done anything, while In Salah has triggered at most an M1 event (so small you can't feel it without the aid of sensitive seismometers). The McGarr plot tells you the maximum possible magnitude, not what magnitude you will get. Hence why I have shaded in the area under the line: you could get an event on the line, or anywhere under the line.
Still, I find the potential for induced earthquakes from CCS to be worrying. I think this has been under-appreciated by the UK CCS community. There is a clear need for further study on why most injection sites do not produce seismicity, but a few do? What is it that is different about these sites, and how can we identify this in advance, and only select sites that won't trigger events during CO2 injection. At the same time, we can quickly see that the earthquake risk from fracking has been hugely overplayed in comparison to the risks posed by other activites (geothermal, CCS, waste-water injection, mining, and even hydroelectric energy).
Friday, 29 March 2013
My visit to Glastonbury: Part II - The reaction
I discussed in my previous post my visit to the councillors of Glastonbury to talk to them about unconventional gas extraction, and the potential impact it could have on the area. In that post I gave a summary of what I said in my talk. In this post, I'd like to talk about the reaction.
It should be noted that I didn't go there with the intention of changing anyone's mind. Given that the council had already voted to ban fracking, I hardly thought a 45 minute presentation by a gravitas-lacking 29 year old (even if he does have a good number of letters after his name) would be enough to change their minds (I was more worried about getting out of there without being tarred-and-feathered to be honest).
However, the councilman who had asked me to come give the talk sent me a very kind email afterwards, saying he saw the evening as a total success, at that some members 'had come to confessions and said the presentation had changed their minds'. I wasn't aware that councillors had 'confessions', but I'm very glad that I appear to have had some small effect at least.
Furthermore, there was a reporter from the local paper in attendance, who placed a story on my talk in the Somerset Gazette, which has granted me my first experience of being completely misrepresented by the media (I guess we all get to experience this eventually.
It ran under the headline: 'Expert warns fracking leaks are the result of cutting corners'. Which is true. What is completely missing is the context - the fact that leaks from fracking are not inevitable side effects of the process, but that they can be prevented by a stronger regulatory regime. Also, missing is the context that the majority of companies are not cutting corners, which is why the percentage rate of leakage instances remains very very low.
In my view (perhaps unfairly, I'd love to hear your comments), you could be mistaken for thinking that I am opposed to fracking, based on that article. For instance, the line:
The final and most important item left out in the story is that I summarised my talk by stating that, while it is not my decision to take, I believe that unconventional gas extraction can be done safely in the South West, and that it will have a beneficial impact on the area. It would have been nice if that could have been reported as well.
It should be noted that I didn't go there with the intention of changing anyone's mind. Given that the council had already voted to ban fracking, I hardly thought a 45 minute presentation by a gravitas-lacking 29 year old (even if he does have a good number of letters after his name) would be enough to change their minds (I was more worried about getting out of there without being tarred-and-feathered to be honest).
However, the councilman who had asked me to come give the talk sent me a very kind email afterwards, saying he saw the evening as a total success, at that some members 'had come to confessions and said the presentation had changed their minds'. I wasn't aware that councillors had 'confessions', but I'm very glad that I appear to have had some small effect at least.
Furthermore, there was a reporter from the local paper in attendance, who placed a story on my talk in the Somerset Gazette, which has granted me my first experience of being completely misrepresented by the media (I guess we all get to experience this eventually.
It ran under the headline: 'Expert warns fracking leaks are the result of cutting corners'. Which is true. What is completely missing is the context - the fact that leaks from fracking are not inevitable side effects of the process, but that they can be prevented by a stronger regulatory regime. Also, missing is the context that the majority of companies are not cutting corners, which is why the percentage rate of leakage instances remains very very low.
In my view (perhaps unfairly, I'd love to hear your comments), you could be mistaken for thinking that I am opposed to fracking, based on that article. For instance, the line:
I am here to tell you how the process works and the effects that science has shown that it has on the people nearby and the surrounding areas,placed without context, suggests that I am saying that science has shown lots of impacts. In fact, in my talk I went on to point out, for example with the Texas and Pennsylvania air quality surveys, that scientific evidence for negative impacts of fracking on water and/or air quality have been remarkably hard to come by, bar a small number of documented surface spill and well integrity cases.
The final and most important item left out in the story is that I summarised my talk by stating that, while it is not my decision to take, I believe that unconventional gas extraction can be done safely in the South West, and that it will have a beneficial impact on the area. It would have been nice if that could have been reported as well.
Wednesday, 27 March 2013
My visit to Glastonbury
Last week I had the pleasure of visiting Glastonbury, a small town in Somerset best known for its tor and its music festival. Glastonbury Town Council has preemptively declared itself to be 'frack-free'. Much like Frome's similar decision last year, this is more a symbolic gesture, because (a) it's not clear that there is any unconventional gas to be had from around Glastonbury, and (b) if there were, it is unlikely to be developed for many years.
The decision was not a unanimous one. Some councillors felt that the decision had been rushed, having heard only of the negative sides from Frack Free Somerset. Jim Barron, one of the dissenting councilmen, pleaded in the local paper for a more evidence based discussion before any decisions be taken.
As a result, I was asked to come down to Glastonbury one evening after work to give a presentation to the council. You can download the presentation that I ended up giving from here. You might as well read it in full, but here's a potted summary.
I began by explaining what shale gas is, why it is different to conventional gas, and why hydraulic fracturing is necessary. I followed this by explaining the process, including a time-lapse video of a well being drilled and fracked, and an animation showing how microseismic events are used to image where the stimulated fracture is going. I gave a short overview of existing UK onshore oil/gas operations, including the fact that fracking has been done over 200 times in the UK since the 1970s.
I then outlined what I see as the potential issues relating to unconventional gas extraction: water usage, earthquakes, water contamination, air pollution, and surface impacts. The first, water usage, can be quickly shown to be a red herring: the water lost by SouthWest Water through leakage every day would be enough to frack more than 30 wells. I talked about the Blackpool earthquake, discussing how event magnitudes work (and that the event in Blackpool is so small that most of my real-earthquake-studying colleagues wouldn't get out of bed for something 10 times the size), and looking at evidence for fracking-induced earthquakes elsewhere (of which there are a handful in Canada, but none in the US).
Water contamination is perhaps the major issue for fracking. It is clear that there have been some cases of methane contamination through wells, and of chemical spills at the surface. I listed some of the key incidents taken from this report. However, it is important to point out that where methane leakage has occurred, it is inevitably due to shoddy practice from the drillers: poor or incomplete casing and/or missing cement. Equally, it should be fairly easy not to spill chemicals on pads at the surface, while open tailings ponds (often the most common source of surface contamination) are not allowed in the UK. It is most important to consider the context of these incidents: for example, the Groundwater Protection Council estimate that less than 0.1% of wells have seen a problem.
With respect to air pollution, I showed a number of studies from both Pennsylvania and Texas, which do not show increases in benzene, ozone or volatile organic compounds (VOCs) before and after drilling. I then looked at a study of employee health statistics for the oil and gas industry in comparison to other sectors. If drill pads are unhealthy places to be, with dangerous chemicals being pumped into the air, then surely the employees should be getting the sickest, given that they might be on site 6 days a week for months on end. In fact, sickness rate in the gas industry is pretty consistent with national average rates, and a lot lower than many other industries.
To demonstrate the surface impacts of shale gas extraction, I showed some photos of what the rigs look like during drilling (on site for a month or two), and what the pads look like once the well is completed, and talked about pad spacing (minimum 2 - 6km as an approximation), as well as pointing out other impacts like new pipelines, and the truck journeys to and from the pads.
I then talked about the public debate around fracking in the US, pointing out that it has become highly polarised, with protest groups, but then anti-protest groups who protest the protest groups. I also showed the data from a Pittsburgh public opinion survey that showed that generally fracking does have more support than opposition (although perhaps the opposition is more vociferous).
Finally, as I like to do, I compared the risks from fracking to the risks from conventional gas extraction. To me at least, if you are opposed to fracking, you should be opposed to all hydrocarbon extraction, so I posed the question to Glastonbury's councilmen: take the scary boogey-word 'fracking' out of the question, and ask what would you do if there was a large conventional gas field discovered under Glastonbury. What would you do?
The decision was not a unanimous one. Some councillors felt that the decision had been rushed, having heard only of the negative sides from Frack Free Somerset. Jim Barron, one of the dissenting councilmen, pleaded in the local paper for a more evidence based discussion before any decisions be taken.
As a result, I was asked to come down to Glastonbury one evening after work to give a presentation to the council. You can download the presentation that I ended up giving from here. You might as well read it in full, but here's a potted summary.
I began by explaining what shale gas is, why it is different to conventional gas, and why hydraulic fracturing is necessary. I followed this by explaining the process, including a time-lapse video of a well being drilled and fracked, and an animation showing how microseismic events are used to image where the stimulated fracture is going. I gave a short overview of existing UK onshore oil/gas operations, including the fact that fracking has been done over 200 times in the UK since the 1970s.
I then outlined what I see as the potential issues relating to unconventional gas extraction: water usage, earthquakes, water contamination, air pollution, and surface impacts. The first, water usage, can be quickly shown to be a red herring: the water lost by SouthWest Water through leakage every day would be enough to frack more than 30 wells. I talked about the Blackpool earthquake, discussing how event magnitudes work (and that the event in Blackpool is so small that most of my real-earthquake-studying colleagues wouldn't get out of bed for something 10 times the size), and looking at evidence for fracking-induced earthquakes elsewhere (of which there are a handful in Canada, but none in the US).
Water contamination is perhaps the major issue for fracking. It is clear that there have been some cases of methane contamination through wells, and of chemical spills at the surface. I listed some of the key incidents taken from this report. However, it is important to point out that where methane leakage has occurred, it is inevitably due to shoddy practice from the drillers: poor or incomplete casing and/or missing cement. Equally, it should be fairly easy not to spill chemicals on pads at the surface, while open tailings ponds (often the most common source of surface contamination) are not allowed in the UK. It is most important to consider the context of these incidents: for example, the Groundwater Protection Council estimate that less than 0.1% of wells have seen a problem.
With respect to air pollution, I showed a number of studies from both Pennsylvania and Texas, which do not show increases in benzene, ozone or volatile organic compounds (VOCs) before and after drilling. I then looked at a study of employee health statistics for the oil and gas industry in comparison to other sectors. If drill pads are unhealthy places to be, with dangerous chemicals being pumped into the air, then surely the employees should be getting the sickest, given that they might be on site 6 days a week for months on end. In fact, sickness rate in the gas industry is pretty consistent with national average rates, and a lot lower than many other industries.
To demonstrate the surface impacts of shale gas extraction, I showed some photos of what the rigs look like during drilling (on site for a month or two), and what the pads look like once the well is completed, and talked about pad spacing (minimum 2 - 6km as an approximation), as well as pointing out other impacts like new pipelines, and the truck journeys to and from the pads.
I then talked about the public debate around fracking in the US, pointing out that it has become highly polarised, with protest groups, but then anti-protest groups who protest the protest groups. I also showed the data from a Pittsburgh public opinion survey that showed that generally fracking does have more support than opposition (although perhaps the opposition is more vociferous).
Finally, as I like to do, I compared the risks from fracking to the risks from conventional gas extraction. To me at least, if you are opposed to fracking, you should be opposed to all hydrocarbon extraction, so I posed the question to Glastonbury's councilmen: take the scary boogey-word 'fracking' out of the question, and ask what would you do if there was a large conventional gas field discovered under Glastonbury. What would you do?
Thursday, 14 March 2013
Coal bed methane in Falkirk
There's been a fair bit of activity down in the SW over UK Methane's plans for coal bed methane extraction around Keynsham. Coal bed methane, like shale gas, uses fracking to extract gas, only from deep coal seams rather than shale beds.
Coal bed methane has already been in operation in Scotland for several years (I wasn't aware of this, and am indebted to Frack-Off for pointing this out).
So, how has CBM extraction affected Falkirk? Has it become an environmental wasteland? Here's the local MP (Eric Joyce) on the issue, writing in the Guardian:
As an aside, it is interesting that Eric Joyce draws parallels with the anti-scientific approach of those who oppose unconventional gas with those who opposed GM food a decade ago. He's not the first to make this comparison (nor the second)...
Coal bed methane has already been in operation in Scotland for several years (I wasn't aware of this, and am indebted to Frack-Off for pointing this out).
So, how has CBM extraction affected Falkirk? Has it become an environmental wasteland? Here's the local MP (Eric Joyce) on the issue, writing in the Guardian:
My constituency of Falkirk is home to one of the UK's most advanced coalbed methane extraction projects. As Lord Browne says, the extraction of coalbed methane is a low carbon bridge to future technologies, is unobtrusive and is environmentally safe. I have received a handful of local objections to the project, all from the same campaign group and all reminiscent of the disastrous anti-science, anti-GM lobby of a decade ago. On the other hand, I have received many messages of support from constituents who accept the potentially valuable contribution unconventional gas extraction has to make to the UK's energy mix.It surprises me how much these onshore unconventional gas developments seem to have slipped under that radar, on both sides of the argument. Councillors and locals with worries about CBM developments in Somerset should be making a bee-line to find out more about how it has impacted Falkirk? Surely that might help improve the quality of the debate somewhat.
As an aside, it is interesting that Eric Joyce draws parallels with the anti-scientific approach of those who oppose unconventional gas with those who opposed GM food a decade ago. He's not the first to make this comparison (nor the second)...
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