Frickin' Fracking...

Our intense and escalating addiction to sweet, sweet hydrocarbons combined with our collective paranoia about dependency on foreign oil (damn you Canada!) has driven some pretty clever advances in the petroleum geosciences.  Whether in terms of important scientific concepts (like chronostratigraphic approaches to understanding the rock record, or facies model approaches to understanding paleoenvironmental characteristics) or in terms of applied engineering (i.e., all the different ways we now have to acquire and understand subsurface data sets), the need to exploit more and more of the Earth's hydrocarbons have led us into heady intellectual territory. 

Some of the schemes utilized to find and recover hydrocarbons from the subsurface are downright Strangelovian.  While THE goofiest has to be the Wagnerian boondoggle of CO2 sequestration, a close second in terms of seeming craziness is fracking.  Hydrofracking, or simply "fracking" if you're "hip" and "with-it", is the process by which humans enhance the connectivity of an existing oil or gas field.  Briefly, let's say you've got an gas field sitting out in the middle of nowhere.  You know there's hydrocarbons in them there interstitial pores, but your wells aren't producing at the rate or capacity that you had hoped.  What you do then is what every red-blooded human has done since we knapped our first flint; you IMPROVE on nature!  In this case, you pump a slurry of quartz and who-knows-what chemicals under high pressure into the reservoir in question.  The high pressure fluids initiate and build-up a series of new fractures, while the quartz grains prop open the newly anthropogenic fractures, allowing your hydrocarbon fluids to flow more freely.

Fracking has been done for quite a while; commercial use of hydrofracture techniques began in 1949, although people were apparently sending water/nitroglycerine mixtures into wells to do the same thing as early as the 1860s.  A pretty good historiography of hydrofracking techniques can be found here.

Despite this long-term history, Fracking has been in the news recently, on account of Oil Companies expanding interests in shale gas reservoirs.  Shales, of course, are noted for their very poor porosity and permeability; fine-grained muds undergo some pretty impressive compaction in the subsurface, resulting in "tight" rock that really restricts the fluid flow paths.  Since the universe is largely ruled by Irony, however, mudrocks and shales are also often extremely rich in organic material. Organics, when subjected to the right conditions, are what we pump out of the ground in the form of oil and gas.  So, these mud-rich reservoirs are often very high in organic content, but actually REMOVING the fluids-of-interest from those sopping shales can be tricky!  What nature fails to provide, human ingenuity must produce; thus, frack the shit out of some shales, and viola!  You've got a productive field where once was only a tight, uneconomical subsurface lithosome. 

However, some spoilsports don't seem to be willing to embrace the Inevitable March of Progress, and have voiced some concern regarding hydrofracking.  One of the things that seems to have really caught a lot of people's attention is the supposed link between fracking and seismicity.  People are worried that, by producing new fracture networks in the subsurface, hydrofracking might be causing earthquakes.  The idea of human-induced seismicity is one of those sort of Doomsday type things that freak folks out, and there have been a number of reports and anecdotes from folks in and around fracking sites claiming that there has been a noticable increase is earthquakes.  But is there any evidence for such a link?

A company in the UK, Cuadrilla Resources, recently published a report that does, for perhaps the first time, actually seem to support the idea that hydrofracking can be linked to seismic events.  The company was in the Bowland Basin in Lancashire, trying to exploit a shale gas play through hydrofracking.  Their press release can be found here, while the pertinent (and actually fairly interesting) technical report is available as well, titled "Geotechnical Study of Bowland Basin Seismicity". 

Briefly, the company had been monitoring seismic activity during their fracking proceedures, generally through the use of down-hole geophones.  In the past, these had recorded seismic events well below the "0" magnitude threshold that were apparently closely associated with active hydrofracking.  However, there were some larger events, including a 2.3 Magnitude event and a 1.5 Magnitude event that the company believes are highly likely to have been caused by their fracking.  Importantly, neither of these events had any sort of structural effect at the surface, and didn't actually cause any sort of damage.

What is interesting is the fact that the company's study has identified a few contingent geological factors that seem to have been part of the reason for the fracking-induced seismic activity.  These include structurally complicated stratigraphies with locally variable dips as well as pre-existing faults in the succession, which interacted in a sort of "perfect storm" with the hydrofracking to induce slip and result in a series of small earthquakes, including the two "big" ones mentioned above (2.3 and 1.5).  The companies conclusion is that, yes Virginia, fracking DID (most likely) cause these specific earthquakes, but a) they weren't that big and didn't do any damage to structures or the the surface and b) the seismic activity was a result of fracking AND the presence of pre-existing structure.  The company points out that these local conditions imply that fracking induced seismicity can be the result of very specific conditions that have to be met.  Regardless, the report advocates continued monitoring in this and other settings, which would allow us to better understand both the mechanisms and processes that produce fracking seismicity, as well as predict those conditions in other fields in the future.

It's a pretty interesting report, and freely available online, which is nice.  And while it does show that fracking CAN cause seismicity, for the reasons stated above it also shows that this seismicity is not that big a deal and actually probably really rare.  And, to be honest, I never really FELT like there was much danger of fracking being a big deal in terms of causing earthquakes or destroying towns.  Still, it's nice to have some actually science on the subject.

Of course, the REAL worry regarding fracking doesn't have anything to with earthquakes, in my opinion.  That's just the sort of sexy catastrophe-mongering peddled by the popular press, and, at the risk of sounding conspiratorial, just the sort of low-risk/high-publicity kind of thing big Industrial/Business concerns like people worrying about.  As Pynchon wrote in Gravity's Rainbow, "if they can get you asking the wrong questions, they don't have to worry about the answers". 

The Earthquake worry is the wrong question to ask about fracking; what should be eliciting some raised eyebrows is the fact that companies are pumping huge volumes of unknown, proprietary fluids into the ground, with the expressed purpose of making it easier for fluids of ALL kinds to move more easily in the subsurface.  Don't worry about earthquakes destroying central Pennsylvania; worry about ground water contamination!  And not just from the mystery fluids used in fracking.  There's all sorts of unpleasant things in the brines that lurk in the subsurface.  I'd like to see a little more transperancy, and a LOT more science, on the question of what impacts, if any, fracking is actually having on groundwater and the environment. 

And, as pointed out by the Cuadrilla report, it's often a question of local contingencies that matter.  What might be perfectly safe in upstate New York COULD be disastrous in North Dakota, or in Wyoming, or in Romania.  The question of fracking needs some serious study, particularly in light of the complicated natural systems that we geologists know characterize the actual Earth.

Drilling for Oil...in the Everglades?

The insane Republican mantra of "DRILL EVERYWHERE!" has been one-up'd recently by everyone's favorite fugue-state maniac, Michelle Bachmann!  Whereas the previous crop of knuckle-heads had merely ignored environmental or economic reasons for not tearing the Earth asunder, ol' Bachmann has gone the final step, and is completely ignoring REALITY in here fervent rush to drill the hell out of the US (for Jesus).  Her latest scheme for Energy Independence?  Drill the Everglades.

Now, most folks would hear about that plan, and decide that, EVEN if there was oil lurking below the peaty vastness of Everglades National Park, perhaps completely destroying one of the most delicate ecosystem in the continental US might not be such a good idea.  Hell, the everglades are already stressed by horrendous water issues and terrible invasive organism problems; in the immortal words of the internet, "Leave the Everglades alone!"

But let's say you're some libertarian asshole that doesn't give a piss for the environment.  Let's say you couldn't care less about a swath of incredibly beautiful, biologically rich, and ecologically amazing piece of real estate that represents a triumph of the egalitarian spirit of the National Parks System; is there any reason that we SHOULDN'T be drilling in the Everglades for the vast hydrocarbon reserves of southern Florida!?!

Well, one VERY good reason for NOT drilling in the Everglades is that, as it turns out, there ain't any goddamn oil or gas there.  And, unless BP has recently initiated an ambitious peat-cutting scheme as a response to their deep water woes, I don't think there's much of a chance of anybody actually wanting to drill into the Everglades any time soon.

Albert Hine, a University of South Florida Geologist, pointed this out to some reporters, who took Hine's observation to Bachmann for comment.  Bachmann's response?  "The radical environmentalists put up one road block after another to prevent accessing American energy".  Intense, huh?  AND, despite the fact that she was completely ignorant and wrong about the everglades AND has had it pointed out to her, Bachmann is STILL endorsing a plan to open-up south Florida to oil and gas exploration.  That level of madness, pure and blinding as a the sun, is the sort of can-do attitude that the Tea Party brings to America!  Facts?  Fuck em!  We don't need no stinkin' liberal-commie facts!

History of Oil podcasts

I recently came across another earth science-flavored podcast out there on the interwebs that folks might enjoy: A History of Oil. A strict adherent to truth in advertising, the podcast author/presenter is going through the history of everyone's favorite hydrocarbon in nice, digestible 10-15 minute segments. I've only listened to the first few episodes, but so far, so good! You can subscribe on that there iTunes! Enjoy!

Oil Shale Will Set Us Free! (right?)

Recently, NPR had a story about the role of oil shale in the American petro-economy complex (I made that phrase up, but I think it sounds kind of neat), likening the Pieance Basin to an "American Saudi Arabia" rich in oil shale. It was an interesting story, particularly in the context of the recent reversal of an old Bush policy that made it easier for Companies to lease and explore oil shale production schemes. Now, I work in rocks of similar age to the Pieance (specifically, the clastic phase of the Wilkins Peak Member of the Green River Fm, famous for it's own oil shale), so I was a little familar with the crazy development schemes some folks have come up for these oil shale deposits. One of the things that always strikes me is the fact that very few discussions about oil shale actually tell you what the stuff is, which is kind of important, as prospecting and (potentially) developing oil shale economically is pretty different from the more traditional hydrocarbon methods. The picture below is a bit of organic-rich oil shale in Outcrop from the Laney Member of the Green River Fm. The richest oil shales are always that blueish-purple in outcrop.



So, what exactly is "Oil Shale"? Well, to paraphrase a geologist who has worked extensively in these deposits, oil shales are neither Oil nor Shale. Actually, they are organic rich micrites, relatively common in some lacustrine deposits (such as those formed by Eocene Lake Gosiute in SW Wyoming). The organic matter is mostly derived from algae living in the lake, and total organic content can range considerably; in the Mahogany Zone, one of the major oil shale intervals of the Uinta Fm in the Pieance Basin, total organic carbon is 40%!



The picture above shows just how rich these rocks are in organics; pretty black stuff, huh? This picture is from oil shales in the Tipton Member of the Green River Fm, SW Wyoming.



This picture above is an interval of Oil Shale from the Wilkins Peak Mbr in core. Again, organic rich, huh?



YET ANOTHER picture, also from the Tipton; these rocks actually smell like petroleum, and sure enough you can set them on fire and they'll burn. Of course, they smell like a tire fire, but that's the price of Energy Independence, I guess.



And there are a LOT of these THICK intervals in the Green River Fm, too; the picture above is from the Tipton, again, showing a thick (whitish) interval of rich oil shale. Start thinking about this in 3-D, and you quickly realize that there is a considerable volume of these oil shales throughout SW Wyoming (in the Green River) and down into the Uinta Fm in the Pieance Basin, in Colorado.

Now, some folks start thinking about all that hydrocarbon, and can't help but get droolin' a little. But how would you get these at these hydrocarbons? Well, as you can see in the Green River (and the Uinta Fm), these intervals are fairly shallowly buried (if not directly exposed). You could mine them directly, and then cook the oil out in some sort of processing, I reckon. Of course, then you're left with a huge, ugly-as-hell open pit hole sitting there.

Other schemes are plentiful, of course, and include in situ heating, hyrdo-fracing, and all sorts of Strangelovian schemes that generally require a substantial input of energy, which changes the ol' equation a bit, you know? I sort of wonder what kind of efficiency you could hope to get out of subsurface extraction?

Oh, and remember how I said that these things smell terrible when burned? Well, turns out there are probably several good reasons for this; oil shales are dirty. Like, filthy. Like, Larry Flynt filthy, man. This study, done on an Estonian power plant that burns Oil Shale for energy, shows that these things have ridiculously high concentrations of heavy metals in them, much higher than even low-grade coals. Kinda grim, really.

All in all, I think I have to applaude Obama's "Hold-on-a-minute-there-pardner!" policy reversal in regards to Oil Shale development. It's fine to push technical and geological innovation, and I certainly think oil shales warrant further study. I can tell you, there are some VERY interesting stratigraphic relationships between these organic rich intervals, clastic phases, and evaporite phases in the Green River Basin (check HERE if you don't believe me!), and careful study of the stratigraphy and depositional processes associated will probably help us understand all sorts of source-rock issues (at least). BUT, I think that there are substantial economic, social, and environmental issues at stake here that really do need careful, considered, and multidisciplinary study before we dig up all of SW Wyoming in some mad bid to become "Energy Independent".

Trace Fossils and Hydrocarbons

The utility of trace fossils in exploration geology is fairly obvious, such as constraining depositional environments or identifying chronostratigraphically important surfaces. Their impact on the production side of things, however, tends to be viewed as a purely negative effect; the critters are churning up all the lovely sandbeds, bringing mud into the system, and generally screwing-up all the nicely sorted sands. A relatively recent paper (Pemberton and Gingras 2005) shows how this assumption may be incorrect.

The authors point out that the view of bioturbation as a simple sediment-churning activity is a gross oversimplification. The nature of the activity defines what the trace morphology and characteristics will be. For instance, some critters may excavate extensive dwelling burrows, penetrating meters into the sediment; depending on the density and interconnectedness of the animals and their burrows, some of these dwelling structures may be quite extensive.

As an example, the authors point to the Jurassic Arab-D, Ghawar Field, Saudi Arabia, which is the largest oil field on earth, with estimated reserves of 75 and 83 billion bbl. The reservoir interval had been interpreted previously as being dominated by fracture porosity. In this paper, however, Pemberton and Gingras (2005) reinterpret the unit as an expression of the Glossifungites ichnofacies, developed on a regional ravinement surface. The traces were made in a micritic substrate, and have a sucrosic dolomite infill (interpreted to be detrital in origin). The differences in porosity and permeability between these two contrasting lithologies is striking, resulting in what the authors term a “biogenic plumbing system”.


This paper has some very nice figures in it; I suggest you print it in color, if it’s available, just to take advantage of some of the nice core photos. It also has some artwork quality images, painted by T.D.A. Saunders. The figure above is Fig. 6 of Pemberton and Gingras (2005), found on page 1500, and shows the conceptual model for the development of the Ghawar field plumbing.

The paper goes on to identify five separate kinds of biogenically-enhanced permeability, and presents several case studies in producing reservoirs where these different processes seem to play an important role. These processes range across a variety of depositional environments and facies, and include both clastic and carbonate systems.

The impact that these burrow systems have on the reservoir potential of some of these units is staggering, as is the potential for vastly under- or over-estimating the potential reserves by not taking these networks into account. All in all, it’s a pretty nifty paper, and one I would strongly recommend for the petroleum-focused among us.

Pemberton, S.G., and Gingras, M.K., 2005, Classification and characterizations of biogenically
enhanced permeability: AAPG Bulletin, v. 89, n. 11, p. 1493-1517.