This post represents two milestones for WUWT.
1. It is the first post where a detailed examination of fracking has been offered to the readers.
2. It is the first post I’ve authored from an airplane cruising about 35,000 feet enroute from Atlanta to Phoenix. I’m connected to Southwest’s new inflight WiFI service. Mr. McClenney sent me this post just as I was about to board and I emailed back that I wouldn’t be able to get to it for hours. And then I discovered this new miracle of technology. Here’s my view just before posting:
Guest post by William F. McClenney
I had occasion recently to watch several presentations on environmental aspects of hydraulic fracturing at the world’s largest oil and gas industry conference. To this day I remain dumbfounded as to why the argument I am about to present here has never been mentioned before (at least to my knowledge).
It is fundamental to all arguments which attempt to deal with the effects of oil and gas development to consider the initial discoveries of petroleum: seeps. Seeps are natural leaks from traps where migration of hydrocarbons have accumulated predominantly in reservoir rocks in the subsurface. These seeps represent leakage of these trapped hydrocarbons along predominantly fractures and faults, and to a lesser extent other pathways (such as unconformities etc.). (For a basic video see: http://wn.com/oil_trap)
Until the past decade or so, the search for these traps has been the focus of the O&G industry since its inception. Reservoir rocks are those rocks which have facilitated this migration through the provision of porosity and permeability necessary to allow the movement of fluids and gases derived primarily from the maturation of hydrocarbons most commonly derived from source rocks such as shales and mudstones which lie beneath them stratigraphically. Perhaps the most common reservoirs are sandstones.
Let me repeat that, the source rocks almost always lie beneath the reservoir rocks.
The other necessity for a reservoir rock to be a reservoir rock is a top seal or rock of low to minimal porosity and permeability (often also shales), sometimes in association with a structural discontinuity, such as a fault or anticline, which prevent the majority of the migrated hydrocarbons to keep migrating towards the surface. Stratigraphic traps, which also require a top seal rock, are also targets, such as conversion of limestone to dolomite through the addition of magnesium rich fluids which ideally can result in creation of up to 11% porosity in the dolostone. Where the updip limit of this conversion occurs defines the limits of the stratigraphic traps.
So traps, however they were formed, are the key to comprehending not only how economic accumulations of hydrocarbons occur, but also the how and why you literally cannot get here from there with hydraulic fracturing.
Let’s start with hydraulic fracturing itself. This only recently impinged on the popular consciousness and is therefore “new”. To the petroleum or gas geologist, these
arewere new techniques to increase porosity and permeability beginning in the 1960s, with their initial use in the reservoir rocks in mostly vertical wells. Read reservoir rocks, not top seal or much lower source rocks. “New” must therefore encompass the massive use of this technique for over half a century in strata which overlie the source rocks, and in just about every known oil or gas field in the world.
Combine source, reservoir and top seal and you have what we call a “petroleum system”.
Oddly, use of hydraulic fracturing for the last half-century in the reservoir rocks has not caused a groundwater problem anywhere I am aware of. Those of you that can provide examples of where this half-century of intense reservoir hydraulic fracturing has caused drinking water aquifer impacts please chime in.
But the game changed ever so slowly with the development and evolution of directional drilling into steerable horizontal drilling now all the rage. The horizontal evolution spanning mostly just the last decade or so.
What this means is that for the most part, we are now targeting for the first time the source rocks themselves. What that means is we are now going after the much lower, stratigraphically, tight organic source shales etc. This could be the end game for petroleum and gas exploration, for once we have exhausted the source rocks……………..
So here is what has been missing entirely (from what I can tell) from the present “hot” discussion on fracking. So think “source rock”. Lying beneath the reservoir rocks, where fracking has been going on extensively for decades. Now add in horizontal drilling, sometimes for miles away from the drillpad in several directions. As they are “fracked”, enormous lift, on the order of maybe millimeters to maybe inches or possibly a few feet occurs to open up pathways for migration of the hydrocarbon load towards the horizontal well(s).
Do you realize what this means? It means that there is a definite possibility that such radical lifting and fracturing of the source rocks has a very slight possibility of increasing what for tens to hundreds of millions of years was already the natural seeping of hydrocarbons from the source rocks into the reservoir rocks!
Do you realize what that means? That means that meager induced releases of new hydrocarbons from the surfaces of the source rocks could actually “get on the freeway” of the reservoir rocks where they could mischievously, eventually, make their way into the structural and stratigraphic traps where they could literally be “stuck” under the top seals or structural seals, at least until removed by say existing oil field wells in the reservoir rocks, or egregiously eke their way through the labyrinthine natural plumbing of the natural seeps to say drinking water aquifers.
Imagine even a few feet lifting from hydraulic fracturing in the source rocks propagating all the way through the reservoir rocks, literally blasting past all the hydraulic fracturing maybe occurring there for decades before, and even more powerfully fracturing not only the top seal rocks but the miles of sediments and beds above. Very, very impressive, if we could only do it…….. A nuclear test might, repeat might, crack the entire stratigraphic section to1 the surface a mile or two above it, but not much else is likely to.
For oil and gas, the migration process could be considered “fast” geologically, perhaps taking from tens of thousands to tens of millions of years to occur due to the density drive which allows crude and gas to “rapidly” migrate into the reservoirs above the formation water. You know, oil floats on water, and so on.
Seismic section image off the coast of California showing sedimentary layering, faults, and other geologic features. Some of the features, especially in the deeper and lower parts, are artifacts of the imaging technique, and it is helpful to be trained in the interpretation of seismic sections. This type of data is crucial and common in oil exploration. Note the vertical scale of depth. Image source: http://walrus.wr.usgs.gov/mapping/csmp/data_collection.html
But the fate of the myriad chemicals being employed in today’s hydro-fracturing regimes is not so sublime. What would drive these chemicals even into the culminations of the structural or stratigraphic traps? Most are water based solutions, with water starting out with a slight density advantage to say salt water (most connate waters are salty, surface seawater today ~1.025 specific gravity), that is until you dissolve said myriad chemicals into them, when the density drive case gets rather murky at best for water-based chemical fracking fluids, if not strongly negative (specific gravities being greater than 1.0).
Shoot these out into the connate water parts of the oil/column/reservoir rocks and voila, there you have it! They might be denser than even the connate waters, but unlike oil, they will dissolve and disperse. Whereas we have natural oil seeps above many known oil finds, we don’t often find brine springs. Why? Well oil is generally lighter than water (gas dramatically lighter) so it floats. If fresh water can “float” atop the denser warm Gulf Stream waters of the Atlantic, and shut down its circulation (according to many), how is this denser, salty or chemically laden, probably denser formation and frack water supposed to rise up, undispersed, through the top seal and structural traps, cascading and being refracted along countless bedding planes and unconformities to arrive, and still be detectable in near-surface (say less than 1,000 foot deep, and that’s being generous) aquifers thousands of feet to miles higher in a geologic instant?
Such that the USEPA can claim that they have found its signature in 3 places, only to later recant that they bungled that badly in each case.
With one exception, the ONLY way to get these “dangerous chemicals” into an aquifer quicksmart is if they
Possess a density less than crude oils yet greater than methane (assuming they remain water-based solutions and do not spontaneously become a gas at deep formation pressures (ludicrous just to cogitate)
Have an yet unreported ability to jet through the labyrinth of bedding planes, other shales etc. in order to reach the surface often miles above in no time flat, where we can sample them.
The exception being transmission up the annulus of the exploratory boring/well itself. Now this can be a rather egregious problem as Macondo informs us. Are we not yet to learn the dirty details of Halliburton’s slipshod cementing of Macondo’s annulus? And this is an all too common problem for the O&G industry, driven as it is by economics, often offering bonuses to drilling contractors for completing the well ahead of schedule. Newly drilled wells are all too frequently subjected to anthropogenic pressures “before their time”, i.e. before the cement has been allowed to properly setup. Assuming it is proper cement in the first place.
This egregious problem can readily be addressed with some skillful regulations on concrete formulations (with allowances for evolution of these formulations by rigorous engineering standards which they must achieve), and a permit-specified curing time etc.? At least at the minimum.
That is literally about all it would take. This would not be egregiously expensive to the O&G industry, at least not when compared to blow-outs, extensive baseline groundwater monitoring ahead of and during drilling/production, cleanup costs etc. Environmental considerations, frankly, should be everyone’s first move these days. Would better up-front due diligence have prevented Macondo, Elgin or Frade? It’s just risk management, which Macondo informs us, can be a pretty big part of exploration management, and cost.
Just as “A stern chase after a lie is a long one” so is the trip for natural oil and gas seeps, which have had tens to hundreds of millions of years to do it, and a much more robust density drive than water based, and therefore easily further dissolved/dispersed chemical fracking solutions are likely to ever have. The “hole” in this theory is the exploration/production borehole itself, a relatively trivial and inexpensive problem to solve.
William F. McClenney