Hooke's oolite

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52 Things You Should Know About Rock Physics came out last week. For the first, and possibly the last, time a Fellow of the Royal Society — the most exclusive science club in the UK — drew the picture on the cover. The 353-year-old drawing was made by none other than Robert Hooke. 

The title page from Micrographia, and part of the dedication to Charles II. You can browse the entire book at archive.org.

The title page from Micrographia, and part of the dedication to Charles II. You can browse the entire book at archive.org.

The drawing, or rather the engraving that was made from it, appears on page 92 of Micrographia, Hooke's groundbreaking 1665 work on microscopy. In between discovering and publishing his eponymous law of elasticity (which Evan wrote about in connection with Lamé's \(\lambda\)), he drew and wrote about his observations of a huge range of natural specimens under the microscope. It was the first time anyone had recorded such things, and it was years before its accuracy and detail were surpassed. The book established the science of microscopy, and also coined the word cell, in its biological context.

Sadly, the original drawing, along with every other drawing but one from the volume, was lost in the Great Fire of London, 350 years ago almost to the day. 

Ketton stone

The drawing on the cover of the new book is of the fractured surface of Ketton stone, a Middle Jurassic oolite from central England. Hooke's own description of the rock, which he mistakenly called Kettering Stone, is rather wonderful:

I wonder if anyone else has ever described oolite as looking like the ovary of a herring?

These thoughtful descriptions, revealing a profundly learned scientist, hint at why Hooke has been called 'England's Leonardo'. It seems likely that he came by the stone via his interest in architecture, and especially through his friendsip with Christopher Wren. By 1663, when it's likely Hooke made his observations, Wren had used the stone in the façades of several Cambridge colleges, including the chapels of Pembroke and Emmanuel, and the Wren Library at Trinity (shown here). Masons call porous, isotropic rock like Ketton stone 'freestone', because they can carve it freely to make ornate designs. Rock physics in action!

You can read more about Hooke's oolite, and the geological significance of his observations, in an excellent short paper by material scientist Derek Hull (1997). It includes these images of Ketton stone, for comparison with Hooke's drawing:

Reflected light photomicrograph (left) and backscatter scanning electron microscope image (right) of Ketton Stone. Adapted from figures 2 and 3 of Hull (1997). Images are © Royal Society and used in accordance with their terms.

Reflected light photomicrograph (left) and backscatter scanning electron microscope image (right) of Ketton Stone. Adapted from figures 2 and 3 of Hull (1997). Images are © Royal Society and used in accordance with their terms.

I love that this book, which is mostly about the elastic behaviour of rocks, bears an illustration by the man that first described elasticity. Better still, the illustration is of a fractured rock — making it the perfect preface. 

References

Hall, M & E Bianco (eds.) (2016). 52 Things You Should Know About Rock Physics. Nova Scotia: Agile Libre, 134 pp.

Hooke, R (1665). Micrographia: or some Physiological Descriptions of Minute Bodies made by Magnifying Glasses, pp. 93–100. The Royal Society, London, 1665.

Hull, D (1997). Robert Hooke: A fractographic study of Kettering-stone. Notes and Records of the Royal Society of London 51, p 45-55. DOI: 10.1098/rsnr.1997.0005.

52 Things... Rock Physics

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There's a new book in the 52 Things family! 

52 Things You Should Know About Rock Physics is out today, and available for purchase at Amazon.com. It will appear in their European stores in the next day or two, and in Canada... well, soon. If you can't wait for that, you can buy the book immediately direct from the printer by following this link.

The book mines the same vein as the previous volumes. In some ways, it's a volume 2 of the original 52 Things... Geophysics book, just a little bit more quantitative. It features a few of the same authors — Sven Treitel, Brian Russell, Rachel Newrick, Per Avseth, and Rob Simm — but most of the 46 authors are new to the project. Here are some of the first-timers' essays:

  • Ludmilla Adam, Why echoes fade.
  • Arthur Cheng, How to catch a shear wave.
  • Peter Duncan, Mapping fractures.
  • Paul Johnson, The astonishing case of non-linear elasticity.
  • Chris Liner, Negative Q.
  • Chris Skelt, Five questions to ask the petrophysicist.

It's our best collection of essays yet. We're very proud of the authors and the collection they've created. It stretches from childhood stories to linear algebra, and from the microscope to seismic data. There's no technical book like it. 

Supporting Geoscientists Without Borders

Purchasing the book will not only bring you profund insights into rock physics — there's more! Every sale sends $2 to Geoscientists Without Borders, the SEG charity that supports the humanitarian application of geoscience in places that need it. Read more about their important work.

It's been an extra big effort to get this book out. The project was completely derailed in 2015, as we — like everyone else — struggled with some existential questions. But we jumped back into it earlier this year, and Kara (the managing editor, and my wife) worked her magic. She loves working with the authors on proofs and so on, but she doesn't want to see any more equations for a while.

If you choose to buy the book, I hope you enjoy it. If you enjoy it, I hope you share it. If you want to share it with a lot of people, get in touch — we can help. Like the other books, the content is open access — so you are free to share and re-use it as you wish. 

Q is for Q

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Quality factor, or \(Q\), is one of the more mysterious quantities of seismology. It's right up there with Lamé's \(\lambda\) and Thomsen's \(\gamma\). For one thing, it's wrapped up with the idea of attenuation, and sometimes the terms \(Q\) and 'attenuation' are bandied about seemingly interchangeably. For another thing, people talk about it like it's really important, but it often seems to be completely ignored.

A quick aside. There's another quality factor: the rock quality factor, popular among geomechnicists (geomechanics?). That \(Q\) describes the degree and roughness of jointing in rocks, and is probably related — coincidentally if not theoretically — to seismic \(Q\) in various nonlinear and probably profound ways. I'm not going to say any more about it, but if this interests you, read Nick Barton's book, Rock Quality, Seismic Velocity, Attenuation and Anistropy (2006; CRC Press) if you can afford it. 

So what is Q exactly?

We know intuitively that seismic waves lose energy as they travel through the earth. There are three loss mechanisms: scattering (elastic losses resulting from reflections and diffractions), geometrical spreading, and intrinsic attenuation. This last one, anelastic energy loss due to absorption — essentially the deviation from perfect elasticity — is what I'm trying to describe here.

I'm not going to get very far, by the way. For the full story, start at the seminal review paper entitled \(Q\) by Leon Knopoff (1964), which surely has the shortest title of any paper in geophysics. (Knopoff also liked short abstracts, as you see here.)

The dimensionless seismic quality factor \(Q\) is defined in terms of the energy \(E\) stored in one cycle, and the change in energy — the energy dissipated in various ways, such as fluid movement (AKA 'sloshing', according to Carl Reine's essay in 52 Things... Geophysics) and intergranular frictional heat ('jostling') — over that cycle:

$$ Q \stackrel{\mathrm{def}}{=} 2 \pi \frac{E}{\Delta E} $$

Remarkably, this same definition holds for any resonator, including pendulums and electronics. Physics is awesome!

Because the right-hand side of that relationship is sort of upside down — the loss is in the denominator — it's often easier to talk about \(Q^{-1}\) which is, more or less, the percentage loss of energy in a single wavelength. This inverse of \(Q\) is proportional to the attenuation coefficient. For more details on that relationship, check out Carl Reine's essay.

This connection with wavelengths means that we have to think about frequency. Because high frequencies have shorter cycles (by definition), they attenuate faster than low frequencies. You know this intuitively from hearing the beat, but not the melody, of distant music for example. This effect does not imply that \(Q\) depends on frequency... that's a whole other can of worms. (Confused yet?)

The frequency dependence of \(Q\)

It's thought that \(Q\) is roughly constant with respect to frequency below about 1 Hz, then increases with \(f^\alpha\), where \(\alpha\) is about 0.7, up to at least 25 Hz (I'm reading this in Mirko van der Baan's 2002 paper), and probably beyond. Most people, however, seem to throw their hands up and assume a constant \(Q\) even in the seismic bandwidth... mainly to make life easier when it comes to seismic processing. Attempting to measure, let alone compensate for, \(Q\) in seismic data is, I think it's fair to say, an unsolved problem in exploration geophysics.

Why is it worth solving? I think the main point is that, if we could model and measure it better, it could be a semi-independent measure of some rock properties we care about, especially velocity. Actually, I think it's even a stretch to call velocity a rock property — most people know that velocity depends on frequency, at least across the gulf of frequencies between seismic and acoustic logging tools, but did you know that velocity also depends on amplitude? Paul Johnson tells about this effect in his essay in the forthcoming 52 Things... Rock Physics book — stay tuned for more on that.

For a really wacky story about negative values of \(Q\) — which imply transmission coefficients greater than 1 (think about that) — check out Chris Liner's essay in the same book (or his 2014 paper in The Leading Edge). It's not going to help \(Q\) get any less mysterious, but it's a good story. Here's the punchline from a Jupyter Notebook I made a while back; it follows along with Chris's lovely paper:

Top: Velocity and the Backus average velocity in the E-38 well offshore Nova Scotia. Bottom: Layering-induced attenuation, or 1/Q, in the same well. Note the negative numbers! Reproduction of Liner's 2014 results in a Jupyter Notebook.

Top: Velocity and the Backus average velocity in the E-38 well offshore Nova Scotia. Bottom: Layering-induced attenuation, or 1/Q, in the same well. Note the negative numbers! Reproduction of Liner's 2014 results in a Jupyter Notebook.

Hm, I had hoped to shed some light on \(Q\) in this post, but I seem to have come full circle. Maybe explaining \(Q\) is another unsolved problem.

References

Barton, N (2006). Rock Quality, Seismic Velocity, Attenuation and Anisotropy. Florida, USA: CRC Press. 756 pages. ISBN 9780415394413.

Johnson, P (in press). The astonishing case of non-linear elasticity.  In: Hall, M & E Bianco (eds), 52 Things You Should Know About Rock Physics. Nova Scotia: Agile Libre, 2016, 132 pp.

Knopoff, L (1964). Q. Reviews of Geophysics 2 (4), 625–660. DOI: 10.1029/RG002i004p00625.

Reine, C (2012). Don't ignore seismic attenuation. In: Hall, M & E Bianco (eds), 52 Things You Should Know About Geophysics. Nova Scotia: Agile Libre, 2012, 132 pp.

Liner, C (2014). Long-wave elastic attenuation produced by horizontal layering. The Leading Edge 33 (6), 634–638. DOI: 10.1190/tle33060634.1. Chris also blogged about this article.

Liner, C (in press). Negative Q. In: Hall, M & E Bianco (eds), 52 Things You Should Know About Rock Physics. Nova Scotia: Agile Libre, 2016, 132 pp.

van der Bann, M (2002). Constant Q and a fractal, stratified Earth. Pure and Applied Geophysics 159 (7–8), 1707–1718. DOI: 10.1007/s00024-002-8704-0.

The sound of the Software Underground

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If you are a geoscientist or subsurface engineer, and you like computery things — in other words, if you read this blog — I have a treat for you. In fact, I have two! Don't eat them all at once.

Software Underground

Sometimes (usually) we need more diversity in our lives. Other times we just want a soul mate. Or at least someone friendly to ask about that weird new seismic attribute, where to find a Python library for seismic imaging, or how to spell Kirchhoff. Chat rooms are great for those occasions, Slack is where all the cool kids go to chat, and the Software Underground is the Slack chat room for you. 

It's free to join, and everyone is welcome. There are over 130 of us in there right now — you probably know some of us already (apart from me, obvsly). Just go to http://swung.rocks/ to sign up, and we will welcome you at the door with your choice of beverage.

To give you a flavour of what goes on in there, here's a listing of the active channels:

  • #python — for people developing in Python
  • #sharp-rocks — for people developing in C# or .NET
  • #open-geoscience — for chat about open access content, open data, and open source software
  • #machinelearning — for those who are into artificial intelligence
  • #busdev — collaboration, subcontracting, and other business opportunities 
  • #general — chat about anything to do with geoscience and/or computers
  • #random — everything else

Undersampled Radio

If you have a long commute, or occasionally enjoy being trapped in an aeroplane while it flies around, you might have discovered the joy of audiobooks and podcasts. You've probably wished many times for a geosciencey sort of podcast, the kind where two ill-qualified buffoons interview hyper-intelligent mega-geoscientists about their exploits. I know I have.

Well, wish no more because Undersampled Radio is here! Well, here:

The show is hosted by New Orleans-based geophysicist Graham Ganssle and me. Don't worry, it's usually not just us — we talk to awesome guests like geophysicists Mika McKinnon and Maitri Erwin, geologist Chris Jackson, and geopressure guy Mark Tingay. The podcast is recorded live every week or three in Google Hangouts on Air — the link to that, and to show notes and everything else — is posted by Gram in the #undersampled Software Underground channel. You see? All these things are connected, albeit in a nonlinear, organic, highly improbable way. Pseudoconnection: the best kind of connection.

Indeed, there is another podcast pseudoconnected to Software Underground: the wonderful Don't Panic Geocast — hosted by John Leeman and Shannon Dulin — also has a channel: #dontpanic. Give their show a listen too! In fact, here's a show we recorded together!

Don't have an hour right now? OK, you asked for it, here's a clip from that show to get you started. It starts with John Leeman explaining what Fun Paper Friday is, and moves on to one of my regular rants about conferences...

In case you're wondering, neither of these projects is explicitly connected to Agile — I am just involved in both of them. I just wanted to clear up any confusion. Agile is not a podcast company, for the time being anyway.

In search of the Kennetcook Thrust

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Behind every geologic map, is a much more complex geologic truth. Most of the time it's hidden under soil and vegetation, forcing geologists into a detective game in order to fill gaps between hopelessly sparse spatterings of evidence.

Two weeks ago, I joined up with an assortment of geologists on the side of the highway an hour north of Halifax for John Waldron to guide us along some spectacular stratigraphy exposed in the coastline cliffs on the southern side of the Minas Basin (below). John has visited these sites repeatedly over his career, and he's supervised more than a handful of graduate students probing a variety of geologic processes on display here. He's published numerous papers teasing out the complex evolution of the Windsor-Kennetcook Basin: one of three small basins onshore Nova Scotia with the potential to contain economic quantities of hydrocarbons.

John retold the history of mappers past and present riddled by the massively deformed, often duplicated Carboniferous evaporites in the Windsor Group which are underlain by sub-horizontal seismic reflectors at depth. Local geologists agree that this relationship reflects thrusting of the near-surface package, but there is disagreement on where this thrust is located, and whether and where it intersects the surface. On this field trip, John showed us symptoms of this Kennetcook thrust system, at three sites. We started in the footwall. The second and third sites were long stretches spectacularly deformed exposures in the hangingwall.  

Footwall: Cheverie Point

SEE GALLERY BELOW FOR ENLARGEMENT

SEE GALLERY BELOW FOR ENLARGEMENT

The first stop was Cheverie Point and is interpreted to be well in the footwall of the Kennetcook thrust. Small thrust faults (right) cut through the type section of the Macumber Formation and match the general direction of the main thrust system. The Macumber Formation is a shallow marine microbial limestone that would have fooled anyone as a mudstone, except it fizzed violently under a drop of HCl. Just to the right of this photo, we stood on the unconformity between the petroliferous and prospective Horton Group and the overlying Windsor Group. It's a pick that turns out to be one of the most reliably mappable seismic events on seismic sections so it was neat to stand on that interface.

Further down section we studied the Mississippian Cheverie Formation: stacked cycles of point-bar deposits ranging from accretionary lag conglomerates to caliche paleosols with upright tree trunks. Trees more than a metre or more in diameter were around from the mid Devonian, but Cheverie forests are still early and good examples of trees within point-bars and levees.  

Hangingwall: Red Head / Johnson Beach / Split Rock

SEE GALLERY BELOW FOR ENLARGEMENT

SEE GALLERY BELOW FOR ENLARGEMENT

The second site featured some spectacularly folded black shales from the Horton Bluff Formation, as well as protruding sills up to two metres thick that occasionally jumped across bedding (right). We were clumsily contemplating the curious occurrence of these intrusions for quite some time until hard-rock guru Trevor McHattie halted the chatter, struck off a clean piece rock with a few blows of his hammer, wetted it with a slobbering lick, and inspected it with his hand lens. We all watched him in silence and waited for his description. I felt a little schooled. He could have said anything. It was my favourite part of the day.

Hangingwall continued: Rainy Cove

The patterns in the rocks at Rainy Cove are a wonderland for any structural geologist. It's a popular site for geology labs from Atlantic Universities, but it would be an absolute nightmare to try to actually measure the section here. 

SEE GALLERY BELOW FOR ENLARGEMENT

SEE GALLERY BELOW FOR ENLARGEMENT

John stands next to a small system of duplicated thrusts in the main hangingwall that have been subsequently folded (left). I tried tracing out the fault planes by following the offsets in the red sandstone bed amidst black shales whose fabric has been deformed into an accordion effect. Your picks might very well be different from mine.

A short distance away we were pointed to an upside-down view of load structures in folded beds. "This antiform is a syncline", John paused while we processed. "This synform over here is an anticline". Features telling of such intense deformation are hard to fathom. Especially in plain sight.

The rock lessons ended in the early evening at the far end of Rainy Cove where the Triassic Wolfville formation sits unconformably on top of ridiculously folded, sometimes doubly overturned Carboniferous Horton Rocks. John said it has to be one of the most spectacularly exposed unconformities in the world. 

I often take for granted the vast stretches of geology hiding beneath soil and vegetation, and the preciousness of finding quality outcrop. Check out the gallery below for pictures from our day.  

I was quite enamoured with John's format. His field trip technologies. The maps and sections: canvases for communication and works in progress. His white boarding, his map-folding techniques: a practised impresario.

What are some of the key elements from the best field trips you've been on? Let us know in the comments.

The 5%

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We recently published our 500th post on this blog. I made the first post on 11 November 2010, a week after quitting my job in Calgary (yes, there was a time when people used to quit jobs). So, 500 posts in a little over 2000 days — about a post every 4 days. About 300,000 words (still only about half of War and Peace). And I probably shouldn't think about this, but let's call it at least 1000 hours (it's probably double that). 

To celebrate the milestone, however arbitrary, I thought I'd spend an evening rounding up some of our favourite and most popular posts. If nothing else, it might serve as place to start for any new readers.

Geoscience

Uncertainty (broadly speaking)

Tech and coding

Our culture

I did say this post was about the top 5%, so strictly I owe you one more post. If you'll indugle me, I'll hark right back to the start — this post on The integration gap from 5 January 2011 was one of my early favourites. It was one of those ideas I'd been carrying around for a while. Not profound or interesting enough for a talk or an article. Just a little idea. I doubt it's even original. I just thought it was interesting. It's exactly what blogs were made for.

It only remains to say Thank You for the support and attention over the years. We appreciate it hugely, and look forward to crafting the next 500 posts for lining the bottom of your digital cat litter box.

PRESS START

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The dust has settled from the Subsurface Hackathon 2016 in Vienna, which coincided with EAGE's 78th Conference and Exhibition (some highlights). This post builds on last week's quick summary with more detailed descriptions of the teams and what they worked on. If you want to contact any of the teams, you should be able to track them down via the links to Twitter and/or GitHub.

A word before I launch into the projects. None of the participants had built a game before. Many were relatively new to programming — completely new in one or two cases. Most of the teams were made up of people who had never worked together on a project before; indeed, several team mates had never met before. So get ready to be impressed, maybe even amazed, at what members of our professional community can do in 2 days with only mild provocation and a few snacks.

Traptris

An 8-bit-style video game, complete with music, combining Tetris with basin modeling.

Team: Chris Hamer, Emma Blott, Natt Turner (all MSc students at the University of Leeds), Jesper Dramsch (PhD student, Technical University of Denmark, Copenhagen). GitHub repo.

Tech: Python, with PyGame.

Details: The game is just like Tetris, except that the blocks have lithologies: source, reservoir, and seal. As you complete a row, it disappears, as usual. But in this game, the row reappears on a geological cross-section beside the main game. By completing further rows with just-right combinations of lithologies, you build an earth model. When it's deep enough, and if you've placed sources rocks in the model, the kitchen starts to produce hydrocarbons. These migrate if they can, and are eventually trapped — if you've managed to build a trap, that is. The team impressed the judges with their solid gamplay and boisterous team spirit. Just installing PyGame and building some working code was an impressive feat for the least experienced team of the hackathon.

Prize: We rewarded this rambunctious team for their creative idea, which it's hard to imagine any other set of human beings coming up with. They won Samsung Gear VR headsets, so I'm looking forward to the AR version of the game.

Flappy Trace

A ridiculously addictive seismic interpretation game. "So seismic, much geology".

Team: Håvard Bjerke (Roxar, Oslo), Dario Bendeck (MSc student, Leeds), and Lukas Mosser (PhD student, Imperial College London).

Tech: Python, with PyGame. GitHub repo.

Details: You start with a trace on the left of the screen. More traces arrive, slowly at first, from the right. The controls move the approaching trace up and down, and the pick point is set as it moves across the current trace and off the screen. Gradually, an interpretation is built up. It's like trying to fly along a seismic horizon, one trace at a time. The catch is that the better you get, the faster it goes. All the while, encouragements and admonishments flash up, with images of the doge meme. Just watching someone else play is weirdly mesmerizing.

Prize: The judges wanted to recognize this team for creating such a dynamic, addictive game with real personality. They won DIY Gamer kits and an awesome book on programming Minecraft with Python.

Guess What!

Human seismic inversion. The player must guess the geology that produces a given trace.

Team: Henrique Bueno dos Santos, Carlos Andre (both UNICAMP, Sao Paolo), and Steve Purves (Euclidity, Spain)

Tech: Python web application, on Flask. It even used Agile's nascent geo-plotting library, g3.js, which I am pretty excited about. GitHub repo. You can even play the game online!

Details: This project was on a list of ideas we crowdsourced from the Software Underground Slack, and I really hoped someone would give it a try. The team consisted of a postdoc, a PhD student, and a professional developer, so it's no surprise that they managed a nice implementation. The player is presented with a synthetic seismic trace and must place reflection coefficients that will, she hopes, forward model to match the trace. She may see how she's progressing only a limited number of times before submitting her final answer, which receives a score. There are so many ways to control the game play here, I think there's a lot of scope for this one.

Prize: This team impressed everyone with the far-reaching implications of the game — and the rich possibilities for the future. They were rewarded with SparkFun Digital Sandboxes and a copy of The Thrilling Adventures of Lovelace and Babbage.

DiamondChaser

aka DiamonChaser (sic). A time- and budget-constrained drilling simulator aimed at younger players.

Team: Paul Gabriel, Björn Wieczoreck, Daniel Buse, Georg Semmler, and Jan Gietzel (all at GiGa infosystems, Freiberg)

Tech: TypeScript, which compiles to JS. BitBucket repo. You can play the game online too!

Details: This tight-knit group of colleagues — all professional developers, but using unfamiliar technology — produced an incredibly polished app for the demo. The player is presented with a blank cross section, and some money. After choosing what kind of drill bit to start with, the drilling begins and the subsurface is gradually revealed. The game is then a race against the clock and the ever-diminishing funds, as diamonds and other bonuses are picked up along the way. The team used geological models from various German geological surveys for the subsurface, adding a bit of realism.

Prize: Everyone was impressed with the careful design and polish of the app this team created, and the quiet industry they brought to the event. They each won a CellAssist OBD2 device and a copy of Charles Petzold's Code.

Some of the participants waiting for the judges to finish their deliberations. Standing, from left: Håvard Bjerke, Henrique Bueno dos Santos, Steve Purves. Seated: Jesper Dramsch, Lukas Mosser, Natt Turner, Emma Blott, Dario Bendeck, Carlos André, B…

Some of the participants waiting for the judges to finish their deliberations. Standing, from left: Håvard Bjerke, Henrique Bueno dos Santos, Steve Purves. Seated: Jesper Dramsch, Lukas Mosser, Natt Turner, Emma Blott, Dario Bendeck, Carlos André, Björn Wieczoreck, Paul Gabriel.

Credits and acknowledgments

Thank you to all the hackers for stepping into the unknown and coming along to the event. I think it was everyone's first hackathon. It was an honour to meet everyone. Special thanks to Jesper Dramsch for all the help on the organizational side, and to Dragan Brankovic for taking care of the photography.

The Impact HUB Vienna was a terrific venue, providing us with multiple event spaces and plenty of room to spread out. HUB hosts Steliana and Laschandre were a great help. Der Mann produced the breakfasts. Il Mare pizzeria provided lunch on Saturday, and Maschu Maschu on Sunday.

Thank you to Kristofer Tingdahl, CEO of dGB Earth Sciences and a highly technical, as well as thoughtful, geoscientist. He graciously agreed to act as a judge for the demos, and I think he was most impressed with the quality of the teams' projects.

Last but far from least, a huge Thank You to the sponsor of the event, EMC, the cloud computing firm that was acquired by Dell late last year. David Holmes, the company's CTO (Energy) was also a judge, making an amazing opportunity for the hackers to show off their skills, and sense of humour, to a progressive company with big plans for our industry.

Automated interpretation highlights

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As you probably know by know, I've been at the EAGE conference in Vienna this week. I skipped out yesterday and flew over to the UK for a few days. I have already written plenty about the open source workshop, and I will write more soon about the hackathon. But I thought I'd pass on my highlights from the the Automated Interpretation session on Tuesday. In light of Monday's discussion, I made a little bit of a nuisance of myself by asking the same post-paper question every time I got the chance:

Can I use your code, either commercially or for free?

I'll tell you what the authors responded.

The universal character of salt

I especially enjoyed the presentation by Anders Waldeland and Anne Solberg (University of Oslo) on automatically detecting salt in 3D seismic. (We've reported on Anne Solberg's work before.) Anders described training eight different classifiers, from a simple nearest mean to a neural network, a supprt vector model, and a mixture of Gaussians classifier. Interestingly, but not surprisingly, the simplest model turned out to be the most effective at discrimination. He also tried a great many seismic attributes, letting the model choose the best ones. Three attributes consistently proved most useful: coherency, Haralick energy (a GLCM-based texture attribute), and the variance of the kurtosis of the amplitude distribution (how's that for meta?). What was especially interesting about his approach was that he was training the models on one dataset, and predicting on an entirely different 3D. The idea is that this might reveal the universal seismic characteristics of salt. When I asked the golden question, he said "Come and talk to me", which isn't a "yes", but it isn't a "no" either.

Waldeland and Solberg 2016. Salt probability in a North Sea dataset (left) and the fully tracked volume (right). The prediction model was trained on a Gulf of Mexico dataset. Copyright of the authors and EAGE, and used under a Fair Use claim.

Waldeland and Solberg 2016. Salt probability in a North Sea dataset (left) and the fully tracked volume (right). The prediction model was trained on a Gulf of Mexico dataset. Copyright of the authors and EAGE, and used under a Fair Use claim.

Secret horizon tracker

Horizons tracked with Figueiredo et al's machine learning algorithm. The horizons correctly capture the discontinuities. Copyright of the authors and EAGE. Used under a Fair Use claim.

Horizons tracked with Figueiredo et al's machine learning algorithm. The horizons correctly capture the discontinuities. Copyright of the authors and EAGE. Used under a Fair Use claim.

The most substantial piece of machine learning I saw was Eduardo Figueiredo from Pontifical Catholic University in Rio, in the same session as Waldeland. He's using a neural net called Growing Neural Gas to classify (aka or 'label') the input data in a number of different ways. This training step takes a little time. The label sets can now be compared to decide on the similarity between two samples, based on the number of labels the samples have in common but also including a comparison to the original seed, which essentially acts as a sort of brake to stop things running away. This progresses the pick. If a decision can't be reached, a new global seed is selected randomly. If that doesn't work, picking stops. Unfortunately he did not show a comparison to an ordinary autotracker, either in terms of time or quality, but the results did look quite good. The work was done 'in cooperation with Petrobras', so it's not surprising the code is not available. I was a bit surprised that Figueiredo was even unable to share any details of the implementation.

More on interpretation

The other two interesting talks in the session were two from Paul de Groot (dGB Earth Sciences) and Gaynor Paton (GeoTeric). Paul introduced the new Thalweg Tracker in OpendTect — the only piece of software from the session that you can actually run, albeit for a fee — which is a sort of conservative voxel tracker. Unsurprisingly, Paul was also very thorough with his examples, and his talk served as a tutorial in how to make use of, and give attribution to, open data. (I'm nearly done with the grumbling about openness for now, I promise, but I can't help mentioning that I find it a bit ironic that those scientists unwilling to share their work are also often a bit lax with giving credit to others whose work they depend on.)

Gaynor's talk was about colour, which you may know we enjoy thinking about. She had gathered 24 seismic interpreters, five of whom had some form of colour deficiency. She gave the group some interpretation tasks, and tried to gauge their performance in the tasks. It seemed interesting enough, and I immediately wondered if we could help out with Pick This, especially to help grow the sample size, and by blinding the study. But the conclusion seemed to be that, if there are ways in which colour blind interpreters are less capable at image interpretation, for example where hue is important, they compensate for it by interpreting other aspects, such as contrast and shape. 

Paton's research into how colour deficient people interpret attributes. There were 5 colour deficient subjects and 19 colour normal. The colour deficient subjects were more senstive to subtle changes in saturation and to feature shapes. Image c…

Paton's research into how colour deficient people interpret attributes. There were 5 colour deficient subjects and 19 colour normal. The colour deficient subjects were more senstive to subtle changes in saturation and to feature shapes. Image copyright Paton and EAGE, and used here under a fair use claim.

That's it for now. I have a few other highlights to share; I'll try to get to them next week. There was a bit of buzz around the Seismic Apparition talks from ETHZ and Statoil, for example. If you were at the conference, I'd love to hear your highlights too, please share them in the comments.

References

A.U. Waldeland* (University of Oslo) & A.H.S. Solberg (University of Oslo). 3D Attributes and Classification of Salt Bodies on Unlabelled Datasets. 78th EAGE Conference & Exhibition 2016. DOI 10.3997/2214-4609.201600880. Available in EarthDoc.

M. Pelissier (Dagang Zhaodong Oil Company), C. Yu (Dagang Zhaodong Oil Company), R. Singh (dGB Earth Sciences), F. Qayyum (dGB Earth Sciences), P. de Groot* (dGB Earth Sciences) & V. Romanova (dGB Earth Sciences). Thalweg Tracker - A Voxel-based Auto-tracker to Map Channels and Associated Margins. 78th EAGE Conference & Exhibition 2016. DOI 10.3997/2214-4609.201600879. Available in EarthDoc. 

G. Paton* (GeoTeric). The Effect of Colour Blindness on Seismic Interpretation. 78th EAGE Conference & Exhibition 2016. DOI 10.3997/2214-4609.201600883. Available in EarthDoc.

A.M. Figueiredo* (Tecgraf / PUC-Rio), J.P. Peçanha (Tecgraf / PUC-Rio), G.M. Faustino (Tecgraf / PUC-Rio), P.M. Silva (Tecgraf / PUC-Rio) & M. Gattass (Tecgraf / PUC-Rio). High Quality Horizon Mapping Using Clustering Algorithms. 78th EAGE Conference & Exhibition 2016. DOI 10.3997/2214-4609.201600878. Available in EarthDoc.

Open source geoscience is _________________

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As I wrote yesterday, I was at the Open Source Geoscience workshop at EAGE Vienna 2016 on Monday. Happily, the organizers made time for discussion. However, what passes for discussion in the traditional conference setting is, as I've written before, stilted.

What follows is not an objective account of the proceedings. It's more of a poorly organized collection of soundbites and opinions with no real conclusion... so it's a bit like the actual discussion itself.

TL;DR The main take home of the discussion was that our community does not really know what to do with open source software. We find it difficult to see how we can give stuff away and still make loads of money. 

I'm not giving away my stuff

Paraphrasing a Schlumberger scientist:

Schlumberger sponsors a lot of consortiums, but the consortiums that will deliver closed source software are our favourites.

I suppose this is a way to grab competitive advantage, but of course there are always the other consortium members so it's hardly an exclusive. A cynic might see this position as a sort of reverse advantage — soak up the brightest academics you can find for 3 years, and make sure their work never sees the light of day. If you patent it, you can even make sure no-one else gets to use the ideas for 20 years. You don't even have to use the work! I really hope this is not what is going on.

I loved the quote Sergey Fomel shared; paraphrasing Matthias Schwab, his former advisor at Stanford: 

Never build things you can't take with you.

My feeling is that if a consortium only churns out closed source code, then it's not too far from being a consulting shop. Apart from the cheap labour, cheap resources, and no corporation tax.

Yesterday, in the talks in the main stream, I asked most of the presenters how people in the audience could go and reproduce, or simply use, their work. The only thing that was available was a commerical OpendTect plugin of dGB's, and one free-as-in-beer MATLAB utility. Everything else was unavailble for any kind of inspection, and in one case the individual would not even reveal the technology framework they were using.

Support and maintenance

Paraphrasing a Saudi Aramco scientist:

There are too many bugs in open source, and no support. 

The first point is, I think, a fallacy. It's like saying that Wikipedia contains inaccuracies. I'd suggest that open source code has about the same number of bugs as proprietary software. Software has bugs. Some people think open source is less buggy; as Linus Torvalds said: "Given enough eyeballs, all bugs are shallow." Kristofer Tingdahl (dGB) pointed out that the perceived lack of support is a business opportunity for open source community. Another participant mentioned the importance of having really good documentation. That costs money of course, which means finding ways for industry to support open source software development.

The same person also said something like:

[Open source software] changes too quickly, with new versions all the time.

...which says a lot about the state of application management in many corporations and, again, may represent opportunity rather than a threat to open source movement.

Only in this industry (OK, maybe a couple of others) will you hear the impassioned cry, "Less change!" 

The fog of torpor

When a community is falling over itself to invent new ways to do things, create new value for people, and find new ways to get paid, few question the sharing and re-use of information. And by 'information' I mean code and data, not a few PowerPoint slides. Certainly not all information, but lots. I don't know which is the cause and which is the effect, but the correlation is there.

In a community where invention is slow, on the other hand, people are forced to be more circumspect, and what follows is a cynical suspicion of the motives of others. Here's my impression of the dynamic in the room during the discussion on Monday, and of course I'm generalizing horribly:

  • Operators won't say what they think in front of their competitors
  • Vendors won't say what they think in front of their customers and competitors
  • Academics won't say what they think in front of their consortium customers sponsors
  • Students won't say what they think in front of their advisors and potential employers

This all makes discussion a bit stilted. But it's not impossible to have group discussions in spite of these problems. I think we achieved a real, honest conversation in the two Unsessions we're done in Calgary, and I think the model we used would work perfectly in all manner of non-technical and in technical settings. We just have to start doing it. Why our convention organizers feel unable to try new things at conferences is beyond me.

I can't resist finishing on something a person at Chevron said at the workshop:

I'm from Chevron. I was going to say something earlier, but I thought maybe I shouldn't.

This just sums our industry up.

Open source FWI, I mean geoscience

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I'm being a little cheeky. Yesterday's Open Source Geoscience workshop at EAGE was not really only about full waveform inversion (FWI). True, it was mostly about geophysics, but there was quite a bit of new stuff too.

But there was quite a bit on FWI.

The session echoed previous EAGE sessions on the same subject in 2006 and 2012, and was chaired by Filippo Broggini (of ETH Zürich), Sergey Fomel (University of Texas), Thomas Günther (LIAG Hannover), and Russell Hewett (Total, unfortunately not present). It started with a look at core projects like Madagascar and OpendTect. There were some (for me) pretty hard core, mathematics-heavy contributions. And we got a tour of some new and newish projects that are seeking users and/or contributors. Rather than attempting to cover everything, I'm going to exercise my (biased and ill-gotten) judgment and focus on some highlights from the day.

Filippo Broggini started by reminding us of why Joe Dellinger (BP) started this recurrent workshop a decade ago. Here's how Joe framed the value of open source to our community:

The economic benefits of a collaborative open-source exploration and production processing and research software environment would be enormous. Skilled geophysicists could spend more of their time doing innovative geophysics instead of mediocre computer science. Technical advances could be quickly shared and reproduced instead of laboriously re-invented and reverse-engineered. Oil companies, contractors, academics, and individuals would all benefit.

Did I mention that he wrote that 10 years ago?

Lessons learned from the core projects

Kristofer Tingdahl (dGB) then gave the view from his role as CEO of dGB Earth Sciences, the company behind OpendTect, the free and open source geoscience interpretation tool. He did a great job of balancing the good (their thousands of users, and their SEG Distinguished Achievement Award 2016) with the less good (the difficulty of building a developer community, and the struggle to get beyond only hundreds of paying users). His great optimism and natural business instinct filled us all with hope.

The irrepressible Sergey Fomel summed up 10 years of Madagascar's rise. In the journey from v0.9 to v2.0, the projects has moved from SourceForge to GitHub, gone from 6 to 72 developers, jumped from 30 to 260 reproducible papers, and been downloaded over 40 000 times. He also shared the story of his graduate experience at Stanford, where he was involved in building the first 'reproducible science' system with Jon Claerbout in the early 1990s. Un/fortunately, it turned out to be unreproducible, so he had to build Madagascar.

It's not (yet?) a core project, but John Stockwell (Colorado School of Mines) talked about OpenSeaSeis and barely mentioned SeismicUnix. This excellent little seismic processing project is now owned by CSM, after its creator, Bjoern Olofsson, had to give it up when he went to work for a corporation (makes sense, right? o_O ). The tool includes SeaView, a standalone SEGY viewer, as well as a graphical processing flow composer called XSeaSeis. IT prides itself on its uber-simple architecture (below). Want a gain step? Write gain.so and you're done. Perfect for beginners.

Jeffrey Shragge (UWA), Bob Clapp (SEP), and Bill Symes (Rice) provided some perspective from groups solving big math problems with big computers. Jeff talked about coaxing Madgascar — or M8R as the cool kids apparently refer to it — into the cloud, where it can chomp through 100 million core hours without setting tings on fire. This is a way for small enterprises and small (underfunded) research teams to get big things done. Bob told us about a nifty-looking HTML5 viewer for subsurface data... which I can't find anywhere. And Bill talked about 'mathematical fidelty'. and its application to solving large, expensive problems without creating a lot of intermediate data. His message: the mathematics should provide the API.

New open source tools in geoscience

The standout of the afternoon for me was University of Vienna post-doc Eun Young Lee's talk about BasinVis. The only MATLAB code we saw — so not truly open source, though it might be adapted to GNU Octave — and the only strictly geological package of the day. To support her research, Eun Young has built a MATLAB application for basin analysis, complete with a GUI and some nice visuals. This one shows a geological surface, gridded in the tool, with a thickness map projected onto the 'floor' of the scene:

I'm poorly equipped to write much about the other projects we heard about. For the record and to save you a click, here's the list [with notes] from my 'look ahead' post:

  • SES3D [presented by Alexey Gokhberg], a package from ETHZ for seismic modeling and inversion.
  • OpenFOAM [Gérald Debenest], a new open source toolbox for fluid mechanics.
  • PyGIMLi [Carsten Rücker], a geophysical modeling and inversion package.
  • PySIT [Laurent Demanet], the Python seismic imaging toolbox that Russell Hewett started while at MIT.
  • Seismic.jl [Nasser Kazemi] and jInv [Eldad Haber], two [modeling and inversion] Julia packages.

My perception is that there is a substantial amount of overlap between all of these packages except OpenFOAM. If you're into FWI you're spoilt for choice. Several of these projects are at the heart of industry consortiums, so it's a way for corporations to sponsor open source projects, which is awesome. However, most of them said they have closed-source components which only the consortium members get access to, so clearly the messaging around open source — the point being to accelerate innovation, reduce bugs, and increase value for everyone — is missing somewhere. There's still this idea that secrecy begets advantage begets profit, but this idea is wrong. Hopefully the other stuff, which may or may not be awesome, gets out eventually.

I gave a talk at the end of the day, about ways I think we can get better at this 'openness' thing, whatever it is. I will write about that some time soon, but in the meantime you're welcome to see my slides here.

Finally, a little time — two half-hour slots — was set aside for discussion. I'll have a go at summing that up in another post. Stay tuned!

BasinVis image © 2016 Eun Young Lee, used with permission. OpenSeaSeis image © 2016 Center for Wave Phenomena