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Politics : Formerly About Advanced Micro Devices -- Ignore unavailable to you. Want to Upgrade?

To: Brumar89 who wrote (619088)	7/12/2011 5:13:12 PM
From: tejek	Read Replies (1) \| Respond to of 1580544

Water laden with chemicals will flow down until it finds a bottom.........and that's where the ground water is located. Well water usually comes from a few hundred feet down. Natural gas is normally found thousands of feet farther down. Thanks for pointing that out. I keep forgetting the shale is below the ground water in most spots. However, there are some spots where the shale is very close to the surface and the ground water could be in jeopardy from toxic chemicals. Nonetheless, the real issue is the pressure created by the hydrofracking that could lead to contamination of the groundwater: What to really worry about: secondary effects of pressure Pressure bulb above a hydrofracking zone. Illustration: Sandusky Bay Journal While it is true that the fracking fluid will most likely not reach the groundwater, what we need to examine are the secondary effects on drinking water wells, caused by a fracking induced “pressure bulb”. When you apply pressure to soil or rock, the pressure doesn’t just stop at the surface you are pushing on; the pressure spreads and dissipates through the surrounding soil or rock. In hydro-fracking, the pressure applied is enormous. In order to crack the rock down deep, the injected pressure has to be in the same ballpark as the weight of the soil and rock overhead. For a rough rule of thumb, we can estimate that the pressure due to the weight of overlying strata is about 1 pound per square inch (psi), for every foot of depth. By this estimate, the pressure a mile down (5,280 feet down) would be about 5,280 psi. Due to internal friction within soil or rock, the sideways pressure is only about 1/3 of the vertical pressure, so one might only have to push outward at 1500 to 2000 psi in order to get shale to fracture a mile down. That 1500 to 2000 psi will dissipate through the rock and soil above the shale. Pressure is also called “stress,” and the movement that occurs in response to stress is called “strain.” So, imagine throughout the stress bulb above the hydrofracking zone, there is a corresponding strain bulb. Imagine that all of the rock and soil above the frack moves, just a little bit. This little bit of movement can be measured at the ground surface, by a sensitive device called an inclinometer. Let’s consider an example from salt mining. In 1993, the Ohio Department of Natural Resources (ODNR) issued a report entitled “Investigation of Active and Abandoned Class III Salt Solution Mining Projects in Ohio.” ODNR documented a solution-mining operation near Barberton, Ohio, that began in 1899 and continued until the 1980s. At this facility, 36 solution mining wells were drilled into the salt-bearing Salina formation, which was tapped at depths ranging from 2721-3208 feet below the land surface (BLS). Pressure was induced into the subsurface, both to bring brine to the surface, and in some low-pressure attempts at hydrofracking. ODNR made two observations that are key to understanding the effects of fracking: 1.“…faults are conduits for migration, and the migration of petroleum, gas, or water in a fault plane can take place, up or down … 2.Numerous oil and gas wells surrounding the Barberton solution salt mines had fluid flowback at the surface. Now, let’s put the entire picture together for hydrofracking. High pressure is injected at a depth of a mile or more. This creates a pressure bulb above the injection location, which slightly lifts all of the strata above the injection location. In the immediate vicinity of the injection, cracks open in the shale layer, and a sand “proppant” is injected to keep the cracks open and allow the gas to flow. Further up in the profile, there are tiny shifts along existing fractures, and permeability of the overlying rocks is increased. The existing fluids in the overlying rocks are pushed up by the injected fracking fluids. We never expect the fracking fluids themselves to enter shallow groundwater aquifers, nearly a mile above the shale. However, the fracking fluids may be expected to push naturally salty water up into the freshwater zone near the surface. eriewire.org