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Marcellus Shale: An Environmental Disaster In The Making

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  • #16
    In another life I worked as the production/operations manager for a good sized independent oil producer. We operated about 425 wells, and during my time there, drilled 100 + wells, of which about 35 were hydraulically fractured. This is intended to give a simplified backdrop to evaluate the cited article. You can decide for yourself if there is anything hysterical about it.

    A little geology is necessary to understand some of the process. Generally, an oil producer is looking for an underground structure to form a trap to collect oil or gas underground. Visualize a producing stratum as an undulating layer of rock underground. There are a number of different types of traps, but basically you are looking for a place where the particular underground stratum or strata creates a place for oil or gas to collect, within the rock itself. Bear in mind we are talking about processes that occurred over geologic time, hundreds of millions of years. One type is an anticline, where the stratum forms an underground hill. Seismic analysis can locate some traps, but precise mapping is usually done by well logging, running various instruments down a wellbore to take readings. There are many different types of instruments used, but one of the first and frequently used for mapping structures is a natural gamma ray tool. These are instruments that are run down along the well on a cable and take various measurements of the sides of the wellbore. All strata/soils have some degree of natural radioactivity. Shales, because of their chemical composition are more radioactive than most productive strata, which are generally limestone/dolomite or sandstones. Shales are relatively impermeable, so they tend to create an impermeable cap over most structures. Basically, the gamma ray log will produce a graphical output strip of radioactivity vs depth and because the shales create spikes on the graph, you can use them as geologic “markers,” and map and determine the depth to a particular horizon from well to well, sometimes over hundreds of miles, and see where they rise and fall, forming hills and valleys. The radiation they are talking about is actually the naturally occurring radiation in some of the elements that have a small percentage of radioisotopes that compose the clays that compose the shales.

    The second thing a geologist looks for in a productive stratum, besides the presence of hydrocarbons, is the porosity and the permeability of the material. There is no “pool” down there. The oil or gas exists within the pore space within the rock. Look at a piece of chalk or limestone, they are probably about 3-6% porous, the hydrocarbons are located within those miniscule pores. Once you find porosity, a place for fluid to collect within the rock, you then have to see if it is permeable, or just how well those pore spaces are connected up, to allow the gas or fluid to flow through the rock. Shales are much less porous and much less permeable, probably by an order of magnitude, but I do not have any hard numbers to quantify how much as there was no shale production where I worked. The oil and gas are under pressure, sometimes considerable. There are several mechanisms that move oil and gas thru the rock. One is called solution gas drive, much like letting the fizz out of a bottled drink, the wellbore allows the gas to expand, driving it to the well. Usually oil and gas exist with brine, generally many times more saline than seawater. The oil and gas generally separate to some degree to the top of the structure. The brine, despite being a fluid can be compressible slightly, and the expansion of the brine when a well is drilled at the top of the structure can also drive the oil and gas to a wellbore. It can be a combination of both. Produced brines in an oilfield are disposed of re-injecting into disposal wells or into other areas of the producing formation, thousands of feet below any potable water.

    When we drilled a well, we were required to “case” the well. The well would be started with a “native” drilling mud, that is fresh water and the fine particulates ground up in the drilling process. The mud is pumped down through the drill pipe and bit and circulated back up the outside to the surface, cooling the bit and carrying with it the drill cuttings which were allowed to settle out in pits or tanks. The mud was continuously re-circulated. We were required to drill down, several hundred feet, to well below any strata known to have potable water. We would then set the surface casing, usually, in our area, 8-5/8” pipe, within a 13-14 inch well bore. The pipe would then be cemented in place, by pumping cement down the inside of the pipe, until it circulated clean cement up to the surface. This was usually plain Portland cement, no aggregate, basically a grout. It sets within seconds once it stops moving. It is given time to cure and develop strength. The purpose of the surface casing is to isolate each of the strata and to protect any fresh water bearing strata. Then a smaller bit would go back into the well, inside the casing, out the bottom, and the well would be drilled to its final depth. This drilling is done with native mud until they get near the producing zone, when they “mud up,” adding generally natural materials such as corn starch and bentonite ( a kind of clay) to increase the viscosity of the mud and to help it carry the drill cuttings from that depth. If they are in an area where the formation pressure is substantial, then “weighting” compounds are added to the mud, generally materials like ground walnut shells or barite (a natural, but heavy, material), to add to the weight of the column of fluid to counteract/balance the formation pressure. Mechanical blow out preventers are installed where needed to give them the capability to seal off the well bore at the surface. Once at total depth, the wells would then be “logged.” There might be intermediate casing strings that could be needed depending on the depth of the well and the conditions, but generally, the “production” casing would then be set and similarly cemented, to several hundred feet above any producing strata. Generally, the next step is to locate the productive zones within a well and then to perforate those sections of the casing. This is done by wireline tools which carry an array of small explosive "shaped" charges that cut a hole, about 3/8” in diameter, through the casing, the cement and into the producing formation, probably to about 20” or so in depth. A better explanation of logging, tools and perforation process could probably be found at the Schlumberger website, they are probably the leader in this field.

    Hydraulic fracturing is used to compensate for low permeability of the rock and to thereby increase production. Basically, the object is to create a vertical fracture (picture a knife blade) through the producing rock and propping it open, exposing the face of the producing rock to what will become a high permeability channel, allowing more face of the rock to drain to the crack and then to the wellbore. The rock will fracture along the plane of the rocks least compressive strength. In a well deeper than 2500 feet, the overburden, the weight of the soil and strata above the producing zone, will prevent a horizontal fracture. There is considerable engineering that goes into designing a “frac job.” There are other ways of doing it, some techniques involve using nitrogen-based foams instead of gelled water because they clean up easier.

    The process involves pumping a fluid into the well, through the perforations and into the formation at enough pressure to generate a fracture in the rock, followed by a tapered mixture of “proppant” generally sand, but in exotic wells involving extreme depths, pressures and temperatures, might be small spheres of sintered bauxite or other materials. The height of the fracture is regarded as being a function of the rate the fluid is pumped into the well. The overall length is determine by the amount of fluid, but is also influenced by the rock properties and how fast the fluid pressure bleeds off into the rock face. The fluid we used was water gelled with guar gum, the same stuff we use to thicken salad dressings. There are catalysts that cause it to “crosslink” and become about the consistency of the green Slime we used to play with as kids. The initial 20-30% of the fluid is pumped into the well as a “pad,” just gel, to initially generate the crack, this is followed as a continuous process, by adding proppant to the gel, e.g.,1# per gallon, for so many gallons of gel, then 2# per gallon, on up, starting with a fine sand and then usually shifting to a coarser sand. The sand we used was called Brady sand, SiO2, like beach sand, but each grain was almost spherical. The sand would carry down the crack until the gel bled off into the face of the rock, the fracture would stop growing and the sand would be packed, propping the crack apart enough to create a high permeability channel. There are chemicals added to reverse the gel and the fluid is eventually swabbed back out of the well. Then the production equipment is then installed, usually through a third string of pipe, typically 2-3/8” steel tubing to bring the production to the surface.

    Well density and spacing, or the acreage for each drilling unit, and the pattern for drilling, is usually set by whatever regulatory body is involved, based upon the nature of the producing zone and intended to efficiently drain the reservoir. Oil wells can be spaced as close as 5-10-20-40 acres where I worked. Gas wells are generally spaced less densely, one well each160-320-640 acres is common. A “section” is a square mile, 640 acres. Operating companies will “pool” acreage from several owners, to form a drilling unit, but may also be constrained by what acreage they can include in a unit by the pattern established by the spacing rules. The owners of the acreage usually agree to share their interest in the production in the proportion to their acreage in the unit, but this can be a subject of negotiation.

    I’d be curious to know the circumstances of a drilling rig burning down, that is generally avoidable by good engineering and pressure control practices. I’d be surprised to hear about a blowout in shale production, because if you had the kind of pressures and flow rates required for a blow out, you would not need to fracture a well. On the other hand, if the rig was a workover rig, repairing an already producing well, and they weren’t careful controlling the pressures, I could see a rig fire. The difference between the kinds of rigs is not always appreciated by someone not in the business. Having flammable water from a drinking water well caused by a gas well doesn’t make much sense, I’d start looking for a nearby gas station with leaking tanks first. There would be about a mile of vertical separation in addition to the cementing. I’d like to know the dates of the anecdotal stories because while there are historical accounts from the earliest days of drilling, a century ago and longer, where wells were allowed to leak and overflow into streams, when there were no environmental concerns and fires burned on the surface, but there is absolutely no reason for it today.
    Last edited by Paradox6; 11-16-2009, 10:31 PM. Reason: added

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    • #17
      Thanks for the drilling information.

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      • #18
        Originally posted by chairrock View Post
        Does anyone know the amount of $$$$ that are paid to the landowners for the mineral rights/drilling contract?
        Even small landowners are eligible for a piece of the pie.
        The drilling companies take a"section", say a hundred acres, then divide the royalties by the acre, so the more acres you own in a section, the larger your cut.

        But with hydro fracturing I wonder about the water well problems for small towns and rural folks and farms.
        On November 30 Cornell Cooperative Extension is running symposium in Owego.
        See ya there....
        I know of one group of landowners here near Binghamton that are close to signing a deal at $5,500 an acre with 20% royalties.

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        • #19
          Paradox6, thanks for the drilling information! I'm currently taking a geology class so I can understand some of what you are saying. I work for a water treatment company and deliver many products to drillers but did not know the drilling practices. Seems like there are similarities in drilling water wells and gas or oil wells, but drilling for oil or gas sounds a little more complex. Again your info is informative and appreciated.

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          • #20
            Originally posted by Paradox6 View Post
            ...Having flammable water from a drinking water well caused by a gas well doesn’t make much sense, I’d start looking for a nearby gas station with leaking tanks first. There would be about a mile of vertical separation in addition to the cementing. I’d like to know the dates of the anecdotal stories because while there are historical accounts from the earliest days of drilling, a century ago and longer, where wells were allowed to leak and overflow into streams, when there were no environmental concerns and fires burned on the surface, but there is absolutely no reason for it today.
            From Candor, NY
            http://www.youtube.com/watch?v=TEtgvwllNpg

            I am not saying what caused it to happen - just pointing out the video.

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            • #21
              Originally posted by sp_nyp View Post
              From Candor, NY
              http://www.youtube.com/watch?v=TEtgvwllNpg

              I am not saying what caused it to happen - just pointing out the video.
              At one family member's place in central NY, you can ignite the first bit of air that comes out of the garden hose when you turn the faucet on, and at other family member's places in the area the water stinks like sulfur and leaves you with a slimy feeling after you get out of the shower. None of these places are near gas wells, but that isn't to say drilling wouldn't aggravate the problem.

              My guess is that gas production will end up being - like most things - neither a disaster nor a panacea. As far as fossil fuels go, natural gas is the most environmentally friendly, and ultimately I think it would be best for it to be produced in our own backyard where we have plenty of people keeping a very close and skeptical eye on production and its consequences.

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              • #22
                SP NYP - Thanks for the link. Anybody see any info on whether or not he had any kind of analysis of the water for the type of contamination?

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                • #23
                  Originally posted by Paradox6 View Post
                  SP NYP - Thanks for the link. Anybody see any info on whether or not he had any kind of analysis of the water for the type of contamination?
                  The guy's address is in the video - you could probably call him up and find out if you really wanted to know.

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                  • #24
                    Well, for a little perspective, even these admittedly left wing environmental groups aren't saying "no drilling at all". They just want proper regulation, full disclosure, and some basic research and fact finding before we let these companies punch holes every square mile and start pumping stuff down there, some of which is going to come back up and require disposal. It's hard to be encouraged when the contents of this fluid are a secret.

                    the fact is, we don't know what they're pumping down there, and we don't know what's coming back up, and we don't know how to dispose of it. And no offense (really), but a guy on a forum saying "it's just guar gum, like in salad dressing, plus some other stuff", doesn't count as full disclosure. It's when industrial interests resist regulation and disclosure that I start to wonder what they're hiding. Got nothing to hide? Good, then open your books and let us monitor the process.

                    Heres what I think the relevant quote is:
                    The state took its 13 samples -- 11 of which significantly exceeded legal limits [of radiation]-- between October 2008 and April 2009. The DEC did not respond to questions about whether additional sampling has begun or whether the state would begin issuing drilling permits before the radioactivity issues are resolved. The DEC told ProPublica it did not know where the wastewater would be treated.
                    the fact that DEC reports aren't even addressing issues of radioactivity in wastewater before issuing permits is very troubling to me. What point is testing the water if the data isn't actually used in the decision making process?
                    Last edited by Hobbitling; 11-18-2009, 12:52 PM.
                    He found himself wondering at times, especially in the autumn, about the wild lands, and strange visions of mountains that he had never seen came into his dreams.

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                    • #25
                      Originally posted by hobbitling View Post
                      well, for a little perspective, even these admittedly left wing environmental groups aren't saying "no drilling at all". They just want proper regulation, full disclosure, and some degree of accountability before we punch holes every square mile and start pumping stuff down there. It's hard to be encouraged when the contents of this fluid are a secret. And no offense (really), but a guy on a forum saying "it's just guar gum, like in salad dressing, plus some other stuff", doesn't count as full disclosure.

                      It's when industrial interests resist regulation and disclosure that I start to wonder what they're hiding. Got nothing to hide? Good, then open your books and let us monitor the process.
                      Or to put it in simpler terms, "No Once-lers!"
                      “Death is the only wise advisor that we have. Whenever you feel, as you always do, that everything is going wrong and you're about to be annihilated, turn to your death and ask if that is so. Your death will tell you, 'I haven't touched you yet.” Carlos Castenada

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                      • #26
                        huh?
                        He found himself wondering at times, especially in the autumn, about the wild lands, and strange visions of mountains that he had never seen came into his dreams.

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                        • #27
                          Hobbitling - Could have saved myself a lot of time if I had just tagged these.:http://en.wikipedia.org/wiki/Hydraulic_fracturing
                          http://en.wikipedia.org/wiki/Complet..._and_gas_wells)
                          This is not new technology, my experiences were in the late 70's and early 80's, much of the info was in petroleum engineering texts, including the chemistry. There are a number of contractors who do this work: BJ Services, Schlumberger had a division that did this, there were others. They compete for the work and are a little reluctant to just give up their design and proprietary info to their competitors. It's been too long for me to remember details as far as the additives. Some of their marketing materials talked about the products used and they sure listed everything they sold on their bills. Oil companies in areas newly developed don't immediately share a lot of the info and their contractors respect that, they take all of the risk to make the investment to drill the wells, could be a a few million on some wells, and the info will help them determine where they will lease or drill next. There are a lot of oil companies competing for the acreage and where to drill next and you don't give that up, any more than Macy's told Gimbels.

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                          • #28
                            Originally posted by Paradox6 View Post
                            They compete for the work and are a little reluctant to just give up their design and proprietary info to their competitors.
                            A-ha! I too was wondering why there wasn't "full disclosure" - competitive reasons seems like a very reasonable explanation. Thanks.

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                            • #29
                              Food manufacturers are required to list all the ingredients in their products, yet there still seems to be plenty of competition in that industry... and just like the food industry, surely there's more to creating these concoctions than just an ingredients list? Relative quantities, preparation, method of use, etc?

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                              • #30
                                Originally posted by colden46 View Post
                                Food manufacturers are required to list all the ingredients in their products, yet there still seems to be plenty of competition in that industry... and just like the food industry, surely there's more to creating these concoctions than just an ingredients list? Relative quantities, preparation, method of use, etc?
                                True, too! That seems like a reasonable requirement. I don't think anyone would appreciate some sort of 'secret sauce' getting pumped down into their aquifer.

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