Residual hydraulic fracturing water not a risk to groundwater, study says .........
In case you missed this on Jack's Picks, this research is notable in explaining away some of the unfounded groundwater concerns.
Source: http://phys.org/news/2014-09-residual-hydraulic-fracturing-groundwa...
Residual hydraulic fracturing water not a risk to groundwater, study says
13 hours ago
Read more at: http://phys.org/news/2014-09-residual-hydraulic-fracturing-groundwa...
Sixty-one minutes of imbibition and evaporation of a 154 microliter bead of tap water on a 2.3 gram chip of the Union Springs Member of the Marcellus Formation. The drop disappeared in approximately 100 minutes. The photograph labeled 0 min was taken about 10 seconds after the bead was dropped on the Marcellus chip. Counter-current imbibition is indicated by methane bubbles floating up into the water bead from the Marcellus chip, starting on the left side of the bead at time = 0 min. This experiment was started 5 days after receiving fresh cuttings of the Union Springs from a horizontal well in PA. Credit: Engelder, Penn State
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Hydraulic fracturing—fracking or hydrofracturing—raises many concerns about potential environmental impacts, especially water contamination. Currently, data show that the majority of water injected into wells stays underground, triggering fears that it might find its way into groundwater. New research by a team of scientists should help allay those fears.
In a paper published in the current issue of the Journal of Unconventional Oil and Gas Resources, Terry Engelder, professor of geosciences, Penn State; Lawrence Cathles, professor of earth and atmospheric sciences, Cornell University; and Taras Bryndzia, geologist, Shell International Exploration and Production Inc., report that injected waterthat remains underground is sequestered in the rock formation and therefore does not pose a serious risk to water supplies.
Hydraulic fracturing is a drilling technique commonly used to extract gas from previously inaccessible "tight" gas reserves, including gas trapped in shale formations such as the Marcellus. During this technique between 1.2 and 5 million gallons of water mixed with sand and chemical additives are injected at high pressure into each well to fracture the rock and release the gas.
Typically less than half of the injected water returns to the surface as "flowback" or, later, production brine, and in many cases recovery is less than 30 percent. In addition to the chemical additives, flowback water contains natural components of the gas shale including salt, some metals, and radionuclides and could impair water quality if released without proper treatment. While flowback water can be managed and treated at the surface, the fate of the water left in place, called residual treatment water or RTW, was previously uncertain.
Some have suggested that RTW may be able to flow upward along natural pathways, mainly fractures and faults, and contaminate overlying groundwater. Others have proposed that natural leakage of the Marcellus is occurring without human assistance through high-permeability fractures connecting the Marcellus directly to the water table and that hydraulic fracturing could worsen this situation.
The researchers report that ground water contamination is not likely because contaminant delivery rate would be too small even if leakage were possible, but more importantly, upward migration of RTW is not plausible due to capillary and osmotic forces that propel RTW into, not out of, the shale. Their study indicates that RTW will be stably retained within the shale formation due to multiphase capillary phenomena.
"Capillary forces and coupled diffusion–osmosis processes are the reasons the brines and the RTW are not free to escape from gas shale," said Engelder. "The most direct evidence of these forces is the observation that more than half the treatment waters are not recovered. Introducing treatment water causes gas shale to act like a sponge based on the principles of imbibition.
"Imbibition into gas shale is made possible by the high capillary suction that a fine-grained, water-wet shale matrix can exert on water. As water is wicked into gas shale, the natural gas in the shale is pushed out. The capillary forces that suck the RTW into the gas shale keep it there."
Estimating imbibition is complicated, but simple experiments conducted by the researchers show that water can be readily imbibed into gas shale in quantities fully capable of sequestering RTW. The researchers demonstrated this process in a series of experiments on cuttings recovered from the Union Springs Member of the Marcellus gas shale in Pennsylvania and on core plugs of Haynesville gas shale from NW Louisiana.
"The hydraulic fracturing fluid consists mostly of very low-salinity surface water, while the shale contains high concentrations of water soluble inorganic cations and anions," said Engelder. "During hydraulic fracturing water is lost to the formation while inorganic cations and anions are transferred from the formation to the hydraulic fracture. Diffusion osmosis assists the rapid imbibition of water by the shale and diffusion of ions into the treatment water causing the high salinities observed in flowback fluids. The point to be emphasized here is that this osmotic pressure pushes the hydraulic fracture fluids into the shale matrix, expelling gas and cations to make high-salinity flowback in the process."
The researchers believe that in addition to there not being enough water in the shale to contaminate groundwater, the most important point of their work is that multiphase capillary phenomena must be considered in cases where a non-aqueous fluid is present in the subsurface pore space. The vadose zone—the area from the surface to the groundwater—and oil and gas migration cannot be understood using single-phase, porous-media flow methods, and any policy insights or prescriptions based on single-phase considerations will be fatally flawed, they argue.
"The practical implication is that hydrofracture fluids will be locked into the same 'permeability jail' that sequestered overpressured gas for over 200 million years," said Engelder. "If one wants to dispose of fracking waters, one could probably not choose a safer way to do so than to inject them into a gas shale."
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Replies to This Discussion
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Permalink Reply by Barry D on
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JS,
A great read, thanks for posting.
In fact I'm saving to my computer.
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Permalink Reply by David Perotto on
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Yet another anti-fracing talking point debunked...
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Permalink Reply by Barry D on
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David,
Not so fast.(just kidding)
The antis will claim it is a bogus study because someone from Shell was a part of it.
They will completely overlook the science.
But as pointed out in a thread you posted it's ok for their anti shale studies to be funded by virulent leftist environmental organizations.
Hypocrites.
This a great read if people take the time; very informative.
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Permalink Reply by Jack Straw on
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What the Engelder, el al study demonstrates is that the Marcellus Shale is hydrophilic (from the Greek, meaning 'loving water').
It would appear that the combination of capillary action and hydrophilic clays (as constituents of the Marcellus Shale) are holding a large portion of the frac fluids,
RE: "As water is wicked into gas shale, the natural gas in the shale is pushed out."
As an added benefit to sequestering the spent frac fluid, that 'trapped' frac fluid displaces and helps push out the Natural Gas (and any NGLs); assisting in recovery.
When it comes to the fracing of the Marcellus, the story gets better and better.
As every day passes, the arguments of the anti-fracers are shown to be ever more spurious.
All IMHO,
JS
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Permalink Reply by Barry D on
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JS,
having read about the composition of the shale I always wondered how the water in a frac job reacted with the shale. I was curious as to if it had some detrimental effect that had to be compensated for.Your post actually shows how it helps move hydrocarbons out of the shale.
Great stuff, thanks for sharing.
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Permalink Reply by Rodney T Hytonen on
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A "chip" doesn't have the vertical and/or oblique fissures naturally found, intentinally opened and propped, and even created by millins of gallons (per frack per well-not per pad, which can have 12, 12 2-mile bores each, wells, each fracked repeatedly)wit 5-8 millin gallons of 20,000 psi pressurized, permanently poisoned water/chemical mix.
Do you have any idea what 20,000 (20 thousand) psi is like?
Air at 'only' 400 (4 hundred) psi, will puncture your skin and inflate your hand.
The problem with this nightmare is its brutal SCALE - and as the profitable life is abut 18 months, they HAVE to keep proliferating like a giant cancer until nothing is left unpoisoned- and it's all permanently abandoned - a toxic, barren wasteland with no habitable (nor arable - NOTHING will ever grow or live there again) space in between.
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Permalink Reply by Frank Walker on
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Permalink Reply by David Perotto on
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Rodney,
First take a deep breath. Second, when you make wild claims such as your last paragraph you need to back up your claims with some real world examples. Only problem is, they dont exist. Quit living in a make believe world. With all of this said, I would suggest you keep focused on real world analysis of the oil and gas industries. We all need and want energy and we all need to extract fuels in the safest manner possible. Everyone can win, these are not mutually exclusive goals.
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Permalink Reply by Jack Straw on
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At a depth of 12,000’, the Lithostatic Pressure (the pressure on the rock matrix exerted by the rock overburden) approximates 12,127 psi (the hydrostatic pressure alone exceed 5000 psi).
Fracing with fluid pressures of the order of 20,000 psi are required to open small fracture; which can be propped open with clean sand (or little ceramic balls). 20,000 psi, at 12,000’ …. No big deal …. Move along, nothing to see here.
The good news is that what happens at 20,000’ essentially stays at 20,000’.
More good news is in that modern frac fluids are made up of rather innocuous materials … much worse is sitting in the cabinet beneath your kitchen sink.
Frac fluids contain such things as:
Table Salt (to more closely match the salinity of the in situ formation fluids),
Beach Sand (as a proppant),
Surfactants (a fancy term for dish washing liquid),
Anti-bacterials (make that Dawn Anti-bacterial dish washing liquid),
Thickeners (such as Guar Gum; like what is found in Ice Cream or Salad Dressing),
and …. Water.
…. No big deal …. Move along, nothing to see here.
Rodney, no need to foam at the mouth …. or are you in some sort of competition with Paul H. to be declared the unofficial ‘GoMarcellusShale Village Idi*t’?
As David suggested, take a deep breath, you seem to be hyperventilating over nothing.
JS
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Permalink Reply by Jack Straw on
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OBTW Rodney, for $599.99, you can get a nice 4200psi Pressure Washer to clean your driveway, wash your car or clean your aluminum siding.
JS
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