Hvordan skifergass egentlig fører til jordskjelv


Produksjon av skifergass kan utløse små jordskjelv, men avfallet fra produksjonen gir langt større problemer

Det siste tiåret har sett en stor økning i produksjon av gass, og delvis olje, fra skiferformasjoner. Teknologien har redusert gasspriser dramatisk, særlig i USA der bruken er mest utbredt. Samtidig hører vi stadig om problemer med skifergass: I tillegg til rapporter om forurensing av drikkevann, er det frykt for at produksjonen kan utløse jordskjelv. Forskning de siste årene har vist en klar sammenheng mellom produksjon av gass fra skifer og jordskjelv, men at sammenhengen er mer komplisert enn en først kunne tenke seg.

Selv om skifer tilsynelatende er massiv, kan en stor andel av steinen være hulrom; porøsiteten er ofte høyere enn i sandstein, som utgjør de klassiske olje-reservoarene. Forskjellen mellom skifer og sandstein er at de enkelte porene i skifer er langt mindre. Dette gjør at selv om totalvolumet av porene i skifer er høyere, er det vanskeligere for væske å strømme gjennom skiferen, den har lavere permeabilitet. Dette var i lang tid et hinder for produksjon av gass og olje fra skifer.

Moderne skifergass-produksjon har en enkel, om enn noe brutal, løsning på dette: Ved å injisere vann med svært høyt trykk fra horisontale brønner, knekker skiferen enkelt sagt opp over store områder. For å hjelpe prosessen, og for å holde sprekkene som dannes åpne, blandes injeksjonsvannet med kjemikalier. Etter vanninjeksjon har skiferen langt høyere permeabilitet, og når strømmen snus slik at væske tappes ut av brønnen, kommer det en blanding av vann og gass.

Når vann injiseres i bakken, øker dette spenninger som alltid finnes i jordskorpen. Dersom produksjonen av skifergass skjer nær en eksisterende svakhet, en forkastning, kan denne forskyve seg og utløse jordskjelv. Det er påvist en klar sammenheng mellom vanninjeksjon for produksjon av skifergass og jordskjelv, men med svært få unntak er skjelvene så svake at mennesker knapt merker dem. Tilsynelatende kan skifergass dermed sies å gi kun ubetydelige jordskjelv, men historien slutter ikke der.

Vannet som produseres sammen med gassen har med seg  blant annet kjemikalier som ble brukt til å effektivisere oppsprekkingen. Et biprodukt av gassproduksjonen er dermed store mengder forurenset vann som må renses eller deponeres: Vi snakker fort millioner av liter per brønn, og det bores tusenvis av brønner i året i USA. Deponering gjøres ved å injisere vannet i bakken igjen, gjort i riktig formasjon vil dette ikke føre til forurensing av drikkevann. Imidlertid vil injeksjonen igjen gi økte spenninger i jordskorpen, og siden avfallsbrønner ofte tar seg av vann fra mange produksjonsbrønner, er volumene og de økte spenningene langt større. Dette er tilstrekkelig til å gi merkbare jordskjelv: Eksempelvis har Oklahoma på få år gått fra et fåtall til flere hundre merkbare jordskjelv i året, av styrke over 3, og det er påvist at dette skyldes injeksjon av forurenset vann fra skifergassbrønner.

Jordskjelvproblematikken skyldes dermed ikke direkte produksjon av skifergass, men at undergrunnen brukes som avfallsplass for biprodukter av produksjonen.

35 thoughts on “Hvordan skifergass egentlig fører til jordskjelv

    1. Author ImageHarald Bjerring

      Skremmende at Statoil som et statlig selskap driver denne virksomheten og er noen tvil se trailer over.

      1. Author ImageOle Sandal

        Alle statlige oljeselskaper over hele verden er sterkt inne i skifergass. Det er framtidens ressurser og må bare utnyttes på en riktig måte. Gasland videoen er gammelt nytt, noe er riktig, annet uriktig

    2. Author ImageOle Sandal

      Vi har fracket i Nordsjøen i 20 år. Hva tror dere Norge er rik for? Selv om man ikke ser det til dagen, må man ikke tro at oljeselskaper er forskjellige, ei heller Statoil

        1. Author ImageOle Sandal

          Du må begynne å lese deg opp.
          Der finnes pt ikke et eneste grunnvann i hele verden som er forgiftet av fracking, og der er boret mer enn 300.000 brønner. Youtube, Gasland og Walt Disney funker ikke. Anbefaler de statlige forskningsinstitusjoner (PTIL, doe.gov, epa.gov)

          1. Author ImageRazzbender

            “This past week, with little to no mention in the conservative media, the California State water Resources Board issued a report to the EPA confirming that yes, at least nine of the eleven fracking sites were deliberately dumping poisoned waste water directly into central California aquifers.”

            http://www.politicususa.com/2014/10/11/report-confirms-fracking-poisoning-californias-dwindling-aquifers.html

            In April 2011, Democratic members of the House Committee on Energy and Commerce released a report detailing the range of chemicals used in fracking. According to the report, the most widely used chemical in fracking fluids, methanol, is a hazardous air pollutant and is on the candidate list for potential regulation under the Safe Drinking Water Act. Isopropyl alcohol, 2-butoxyethanol, and ethylene glycol were the other most widely used chemicals. The study noted that in some cases benzene (a known carcinogen), toluene, xylene, and ethylbenzene are used. Many of the hydraulic fracturing fluids contain chemical components that are listed as “proprietary” or “trade secret.”[19]

            Of the 300-odd compounds that private researchers and the Bureau of Land Management suspect are being used in fracking, 65 are listed as hazardous by the federal government. The New York State Department of Environmental Conservation was tasked with going through a public review of its new rules on hydraulic fracturing, and looked into reports that “gas companies use at least 260 types of chemicals, many of them toxic, like benzene.” The chemicals tend to remain in the ground once the fracturing has been completed, raising fears about long-term contamination.”[20]

            Radiation

            A February 2011 study in the NY Times, based upon thousands of internal documents obtained by The Times from the Environmental Protection Agency, state regulators, and drillers, found never-reported studies by the EPA and a confidential study by the drilling industry that both concluded that radioactivity in drilling waste cannot be fully diluted in rivers and other waterways. The Times found that of more than 179 wells producing wastewater with high levels of radiation, at least 116 reported levels of radium or other radioactive materials 100 times as high as the levels set by federal drinking-water standards. At least 15 wells produced wastewater carrying more than 1,000 times the amount of radioactive elements considered acceptable.[21]

            A November 2010 study of fracking’s effect on radioactive material in the Marcellus Shale by Tracy Bank, a geologist at the State University of New York in Buffalo, found that the process that released the gas also releases uranium trapped in the shale. She said additional study is needed to understand and predict the reaction in the shale to fracking.[22]

            Methane

            Methane in itself is not considered toxic by U.S. regulations, but concentrations of it in enclosed spaces raise the risk of explosions.[23]

            The 2011 peer-reviewed study, “Methane contamination of drinking water accompanying gas-well drilling and hydraulic fracturing,” found “systematic evidence for methane contamination” of drinking water associated with shale gas extraction.” Water wells half a mile from drilling operations were contaminated by methane at 17 times the rate of those farther from gas developments.[24]

            A 2013 PNAS study analyzed 141 drinking water wells across northeastern Pennsylvania, and detected methane in 82% of drinking water samples, with average concentrations six times higher for homes less than 1 km from natural gas wells.[25]

            According to Cornell University engineer Anthony Ingraffea, oil/gas industry studies show that five to seven per cent of all new oil and gas wells leak methane. As wells age, the percentage of methane leaks can increase to 30 or 50 per cent. The worst leaks are “deviated” or horizontal wells commonly used for hydraulic fracturing.[26]

            Benzene

            Data released in February 2015 from a report on California fracking found that there was 700 times the federal standard amount of Benzene in fracking waste fluids. The raw data showed that 98% of wastewater samples taken from 329 fracking sites in the state had dangerous levels of benzene, which is a known carcinogen. The data was gathered over a one year period by the Center for Biological Diversity.[27]

            Potential for contaminants to migrate into aquifers

            A 2012 study published in GroundWater, “Potential Contaminant Pathways from Hydraulically Fractured Shale to Aquifers,” used computer modeling and concluded that natural faults and fractures in the Marcellus Shale, exacerbated by the effects of fracking itself, could allow fracking fluids and its chemicals to reach the surface in as little as “tens of years” — challenging the argument that impermeable layers of rock would keep fracking fluid, which contains benzene and other dangerous chemicals, safely locked nearly a mile below water supplies.[28] According to Barbara Arrindell, Director of Damascus Citizens for Sustainability (DCS): “hydraulic fracturing technique permanently shatters the underground geology and can connect gas bearing layers with water bearing layers.”[29]

            In June 2012, the U.S. Department of Energy said it will be testing whether hydraulic fracturing fluids can travel thousands of feet via geologic faults into drinking water aquifers close to the surface, as a fault from the Marcellus Shale could provide “a quick pathway for fracking fluids to migrate upwards.” The experiment is being carried out at a site in Greene County in southwestern Pennsylvania and should be completed within a month.[30]

            There is also the potential for water contamination through well casing failures. There are documented cases by the oil and gas industry of cement and steel casing problems with drilling wells. Some geologists argue the casings have relatively short life spans (maximum 100 years, before needing reinforcement) compared with the million year life span of the aquifers they are supposed to protect. In addition to the quality of the casing eroding over time, the fracturing process itself can result in cracking of the cement sheath.[31]

            http://www.sourcewatch.org/index.php/Fracking_and_water_pollution

          2. Author ImageRazzbender

            og det du hevder kan sammenlignes med å si at eksplosjonen har ingenting med dynamiten å gjøre. Eller at det er røyken, og ikke selve cigaretten som er farlig, men å samtidig velge å ikke se sammenhengen. Latterlig

            At fracking industien har forgiftet grunnvann er 100% utvilsomt. De sidene ,og studiene jeg leser er uavhengige. EPA har forsøkt å gjemme fakta, og gjøre studiene utilgjengelige for folk, men det er avslørt i rettsaker at de tidlige studiene deres fra 10 år siden bevist så vekk ifra at fracking industrien var skyldig å forgifte grunnvann.

          3. Author ImageOle Sandal

            Fint. Der står mange advokater i USA og venter på deg og bevisene dine, så kan vi andre bedrive ordentlig forskning. Lykke til

          4. Author ImageRazzbender

            Høyesteretten i New York så bevisene, og dømte i favør motstanderne. Det er andre staten som gjør dette, og mer regnes å følge. Colorado ser ut til å bli neste. Dette var ikke et halvt år siden engang. Bra du følger med.

            Faced with such mounting evidence Zucker recommended a ban:

            “The overall weight of the evidence from the cumulative body of information demonstrates that there are significant uncertainties about the kinds of adverse health outcomes that may be associated with high volume hydraulic fracturing (HVHF), the likelihood of the occurrence of adverse health outcomes, and the effectiveness of some of the mitigation measures in reducing or preventing environmental impacts which could adversely affect public health. Until the science provides sufficient information to determine the level of risk to public health from high volume hydraulic fracking… the department of health recommends that HVHF should not proceed.”

            http://www.theguardian.com/environment/blog/2015/jan/19/what-the-uk-could-learn-from-new-yorks-fracking-ban

          5. Author ImageHenrikknutsen

            Again, merely wishful thinking from the illogical left without any scientific evidence or proof. What is evident though, is that the energy exploration sector is clearly the brightest spot in the US economy providing high wages and employment security. As for the New York ban on fracking, fact is unemployed people in northern NY will remain that way. A second is the move of NY residents to states with a better business climate. Third will be a loss of taxes to the state government followed by liberal cries to tax the rich more as they aren’t paying their fair share. This movies been seen before. And libs wonder why there is a hollowing out of the middle class – go figure.

          6. Author ImageRazzbender

            Yes. People on the left are “wishing” that a possible new energy source will poison the water and cause cancer in children. They want it so bad….

          7. Author ImageHenrikknutsen

            The problem with the left is their anti-growth, anti-progress and anti-free enterprise agenda. Economic growth sure can be a nuisance. The fracking boom in other US states has led to overbooked hotels, restaurants where you can’t get a table, and the quandary of how to spend disposable income from rapidly rising wages. Life is tough when people have more money. Fracking first took place in the US as early as 1947 with millions of wells drilled since then, is regulated both at the state and federal level yet no adverse health effects have so far been evidenced. But that clearly does not stop the left from believing otherwise.

          8. Author ImageHenrikknutsen

            Why don’t you produce any scientific evidence supporting such irresponsible accusations. Or better yet, have you ever been near a fracking / horizontal drilling platform in your life seeing what goes into such an operation and the safety precautions taken to both crew and the environment. Well, son, I have many times and I can tell you that you and your crowd are only blowing hot air without a clue of actual knowledge (and that holds true for this newspaper and the untrue headline to this article)

          9. Author ImageRazzbender

            The highest court in New York state saw all the evidence. Even EPA reports which has not been released to the public. They ruled against the fracking. You can keep imagining that these court cases never happened, and that the evidence does not exist. Just don’t expect the rest of us to live in your dream world.

          10. Author ImageHenrikknutsen

            Wrong again, The Governor of New York State made his decision based on recommendations from the acting state Health Commissioner and the state Dept. of Environmental Conservation not the state Supreme Court, The recommendations could not site specific evidence but based their recommendations on possible future unspecified health hazards. As for the EPA studies, you are also wrong as both studies, prepared jointly by the EPA and the Ground Water Protection Council was released to the public and are available online. As for the fracking process itself, you are clearly uninformed as 98% of the fracking fluid is water and sand and only 2% are high-viscosity chemical additives designed to maximize the effectiveness of the process, most of them common household compounds. So in your little world, you are accusing the US Federal Government and 48 states to be completely wrong in permitting fracking. Seen your psychologist lately ?

          11. Author ImageRazzbender

            aahhh personal attacks now. Clear evidence of failure.

            No, not completely wrong. Just deliberately misinformed by the industry . The new information the courts heard before ruling in December 2014 had not been released to the public. Thats why it took a court case to access the information.

            I don´t go to a psychologist.

          12. Author ImageHenrikknutsen

            Well, perhaps you should consider it. But I always enjoy the exchange of thoughts and ideas for which I thank you.

    3. Author ImageHenrikknutsen

      Fracking and horizontal drilling, despite the shouting from the “green” radical nuts are completely safe and of huge benefit to economic growth. Two studies conducted by the US Environmental Protection Agency (EPA) and the Ground Water Protection Council (GWPC)—the national association of state ground water and underground injection agencies whose mission is to promote the protection and conservation of ground water—found that there have been no confirmed incidents of groundwater contamination from hydraulic fracturing. This is particularly noteworthy in consideration of the fact that approximately one million wells have been hydraulically fractured in the United States. Furthermore, according to the Interstate Oil and Gas Compact Commission (IOGCC)—the multi-state governmental agency representing states’ oil and gas interests—each IOGCC member state has confirmed that there has not been a case of groundwater contamination where hydraulic fracturing was attributed to be the cause. Furthermore, worth noting that after a fracturing job has been completed, the majority of fracturing fluids are recovered from the well and recycled in a closed system for future use. Surface disposals of fracturing fluid are subject to the federal Clean Water Act, requiring treatment for any potentially harmful substances prior to discharge, or the federal Safe Drinking Water Act if disposed in an oil and gas injection well.

        1. Author ImageHenrikknutsen

          Recently reelected, Governor Cuomo succumbed to the pressure from his liberal base. The Governor’s men couldn’t find conclusive evidence that fracking presents a significant risk to public health or the environment. So they’re going to ban fracking until they do. New York thus follows Vermont as the only other U.S. state to ban fracking, joining such economic “superpowers” as France and Bulgaria. This illogical decision no doubt is the reason why several upstate New York counties now wants to secede from the state joining Pennsylvania instead where fracking is permitted and brought prosperity to the people of the state.

  1. Author ImageJon Inge Teigland

    Jeg registrerer at det blir sagt at det er “kjemikalier” som blir injisert.
    Hvilke kjemikalier er det snakk om?
    Jeg har hørt at det er SAND som blir injisert sammen med vannet, og at disse sandkornene kommer seg inn i sprekkene og holder disse åpne.
    Så hva er det egentlig som blir injisert?

    1. Author ImageOle Sandal

      Artikkelen er god, men ikke helt korrekt. Når man injiserer vann og sand (fracker), vasker man rørene først med en liten dæsh syre. men grunnen til at vannet som kommer ut igjen er “toxic”, er enkelt fordi det har vært på besøk i et reservoar på 2-3 km dyp med giftig olje og gass, og noen ganger naturlig radioaktivitet.

      1. Author ImageJon Inge Teigland

        Det du skriver er kanskje fullstendig riktig. Men ettersom kronikkforfatteren kaster rundt seg med masse fine ord, så høres det ut som om han faktisk har en relevant utdannelse i forhold til dette, og dermed vet hva han snakker om.
        Så derfor vil jeg gjerne at kronikkforfatteren skal svare meg på hvilke kjemikalier det er som blir brukt i fracking, hvordan disse kjemikaliene gjør frackingen mer effektiv, og hvor giftige disse kjemikaliene er.

        Ut fra det han skriver i kronikken, er det åpenbart at han må vite dette. Hvis han ikke vet dette, så er det jo like åpenbart at hele kronikken er basert på synsing og rykter, og dermed ikke er verd papiret den er skrevet på.

        1. Author ImageOle Sandal

          Det jeg sier er fullstendig riktig, jeg er Geofysiker, har jobbet som Geolog, og har 15 års erfaring fra 200 skifergass brønner. Jeg vet nøyaktig hva som går inn og kommer ut av en brønn. Det er den eneste faktafeilen kronikkforfatteren har. Artikkelen er veldig god, den.

  2. Author ImageHenrikknutsen

    Nonsense. Accusations that fracking can cause small earthquakes and / or pollute drinking water is just that, accusations from the “green” radicals without basis or any kind of reliable evidence. That fracking can pollute drinking water is a mere impossibility as the mix of water and a small part of chemicals used in fracking is pumped into the fissures through the borehole well below the drinking water aquifers. Fracking is such a great example of human innovation in a free-market, pro-growth environment that Europe would do good to copy.

    1. Author ImageElisabeth Guldbrandsen

      Din argumentasjonsteknikk framstår som saklig, argumentene er veloverveide, og du viser stor respekt for meningsmotstandere .

      Spesielt tydelig er dette i innledningen av innlegget ditt.

      1. Author ImageHenrikknutsen

        Thank you. I thought it important to have said it. As for the fracking revolution in the US, in addition to keeping prices low for American consumers—who get 24 percent of their electricity from natural gas—increased domestic production also creates jobs and generates royalties for residents, cities, and school districts. For example, a recent study estimates that just in 2009, the development of the Marcellus Shale created 44,000 new jobs in Pennsylvania, and added $389 million in state and local revenue, over $1 billion in federal tax revenue, and almost $4 billion in value added to the state’s economy. Food for thought in a Europe sorely in need of economic growth.

        1. Author ImageElisabeth Guldbrandsen

          I was being sarcastic.

          Sorry that that didn’t come clearly through to you

          1. Author ImageHenrikknutsen

            Thank you again. I clearly got your sarcasm but chose to ignore it. There is a lot of misinformation in the Norwegian media about fracking and horizontal drilling and I thought it more important to inform rather than respond to sarcasm. However, I am glad you can be sarcastic as I always suspected that it is a good Norwegian quality (except among the “green” radicals who appears to have lost that quality)

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