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Thread: Earthquakes Triggered by Injection

  1. #1 Earthquakes Triggered by Injection 
    Universal Mind John Galt's Avatar
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    This is interesting, not because of a convenient way of knocking the oil industry*, but as a suggestion of how we might seek to control major quakes in earthquake zones.

    Two-year survey comparing earthquake activity and injection-well locations in the Barnett Shale, Texas

    Abstract
    Between November 2009 and September 2011, temporary seismographs deployed under the EarthScope USArray program were situated on a 70-km grid covering the Barnett Shale in Texas, recording data that allowed sensing and locating regional earthquakes with magnitudes 1.5 and larger. I analyzed these data and located 67 earthquakes, more than eight times as many as reported by the National Earthquake Information Center. All 24 of the most reliably located epicenters occurred in eight groups within 3.2 km of one or more injection wells. These included wells near Dallas–Fort Worth and Cleburne, Texas, where earthquakes near injection wells were reported by the media in 2008 and 2009, as well as wells in six other locations, including several where no earthquakes have been reported previously. This suggests injection-triggered earthquakes are more common than is generally recognized. All the wells nearest to the earthquake groups reported maximum monthly injection rates exceeding 150,000 barrels of water per month (24,000 m3/mo) since October 2006. However, while 9 of 27 such wells in Johnson County were near earthquakes, elsewhere no earthquakes occurred near wells with similar injection rates. A plausible hypothesis to explain these observations is that injection only triggers earthquakes if injected fluids reach and relieve friction on a suitably oriented, nearby fault that is experiencing regional tectonic stress. Testing this hypothesis would require identifying geographic regions where there is interpreted subsurface structure information available to determine whether there are faults near seismically active and seismically quiescent injection wells.

    From: Published online before print August 6, 2012, doi: 10.1073/pnas.1207728109. Link

    *If you want to knock the oil industry just stop buying their products, including gasoline, electricity, textiles, plastics, etc. If we stop using all those the nasty oil industry will go away.


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    Forum Masters Degree MrMojo1's Avatar
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    You have forgotten I posted this information in Fracking Histeria and Science Thread.


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  4. #3  
    Universal Mind John Galt's Avatar
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    Indeed. Still it demostrates that my short term memory and long term memory are equally effective.
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    without reading the article I would say earth quakes with this we could PREVENT! powerful earth quakes because the triggered earth quakes are less powerful because the power cannot bottle up
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  6. #5  
    Universal Mind John Galt's Avatar
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    Quote Originally Posted by The Geographer View Post
    without reading the article I would say earth quakes with this we could PREVENT! powerful earth quakes because the triggered earth quakes are less powerful because the power cannot bottle up
    That was exactly my point - "This is interesting....as a suggestion of how we might seek to control major quakes in earthquake zones." I used control to indicate reduction of the magnitude of any quakes: allow the same total fault plane movement, but spread over many small incidents, rather than one catastrophic event.
    Last edited by John Galt; September 11th, 2012 at 08:10 AM. Reason: correct typos
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    I wasn't aware of this negative effect of mining the earths oil.

    Surely we have other was of producing electricity? other ways of powering vehicals? other ways of producing textiles? plastic... do we need it?

    I think it's fine to knock the oil company whilst still ignorantly or otherwise using consumables driven by oil. The evil oil companies probably own the other companies which advertise and subliminaly get us to consume their products... it's not our fault, we'r only human.

    It's like when your friend knows you want to diet, yet they offer you a chocolate muffin when your hungry, you might not have the will power to resist the chocolate muffin but you can still tell your friend that you are not happy they put temptation in your way.
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  8. #7  
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    This is natural gas mining, not oil.

    It's cheap (my heating bill shows that) and plentiful, and causes less pollution than oil, or especially, coal.
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  9. #8  
    Universal Mind John Galt's Avatar
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    Nomenclature point. We don't generally talk about mining for oil and gas. Mining implies the digging of large holes in or under the ground. This is wholly different, in almost every regard, from drilling for oil and gas.
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    Quote Originally Posted by John Galt View Post
    Nomenclature point. We don't generally talk about mining for oil and gas. Mining implies the digging of large holes in or under the ground. This is wholly different, in almost every regard, from drilling for oil and gas.
    Ok ty. Though drilling also certainly implies creating a large hole... Earthquaks from drilling also implies some major ground disturbance to me.

    Does anybody know how the gas and oil is found underground... I mean, is is great big natural caves of the stuff? or is it contained in among minerals that it needs extracting from?
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  11. #10  
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    Quote Originally Posted by question for you View Post
    Quote Originally Posted by John Galt View Post
    Nomenclature point. We don't generally talk about mining for oil and gas. Mining implies the digging of large holes in or under the ground. This is wholly different, in almost every regard, from drilling for oil and gas.
    Ok ty. Though drilling also certainly implies creating a large hole... Earthquaks from drilling also implies some major ground disturbance to me.

    Does anybody know how the gas and oil is found underground... I mean, is is great big natural caves of the stuff? or is it contained in among minerals that it needs extracting from?
    conventional oil and gas is found in porous layers of sandstone
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  12. #11  
    Universal Mind John Galt's Avatar
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    I was using terms qualitatively. In this context "large hole" meant large enough to accomodate people, or machinery.

    I recall going down the Outokoumpo copper mine in Finland before it closed. They had huge bulldozers and other earth-moving equpment moving around in the excavated galleries. On another occassion I visited a salt mine to the north of Bogota, in Columbia. The miners had carved out an abandoned portion of the mine to create a cathedral. Quite magnificent, with high soaring columns and eerie lighting. In contrast the lead mine at Wankockhead in the southern Uplands of Scotland, now part of a mining museum, has narrow passageways barely wide enough to pass through. However, these are examples of what I mean by large.

    The boreholes drilled to extract oil and gas are much smaller. The hole size is decreased progressively with increasing depth. In the North Sea a typical sequence would be 26", 17 1/2", 12 1/4", 8 1/2". In West Texas it might be 12 1/4", 8 3/4", 6". In Algeria 16", 12 1/4", 8 1/2", 5 7/8".


    Oil and gas are found in porous formations. A network of interconnected pore spaces (holes) are present in most sedimentary rocks. These will contain oil, gas, water, or more likely a mix of all three. These pore spaces are small: typically less than 1mm diameter. Sandstones and limestones are the most common reservoirs, since not only are they porous , but they may also be permeable i.e. the hydrocarbons can flow through them easily.
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    Very interesting.

    With the drill size sequence, I wonder what depths each diameter of drill can reach too?

    So all the natural caves I have seen are made from water? and none of the oil or gas hotspots contain any large cavities which could collapse after extraction?

    The collapsing and earthquaks caused by drilling are because of many tiny pours simultaneously collapsing?

    One final question... is 'gas' found and extracted from the earth in liquid form?
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  14. #13  
    Universal Mind John Galt's Avatar
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    Quote Originally Posted by question for you View Post
    With the drill size sequence, I wonder what depths each diameter of drill can reach too?
    It does vary from region to region, basin to basin. You also need to specify whether you are talking about mesured depth (MD) or true vertical depth (TVD). Many (most) well drilled today are directional - they are drilled at angle, often following quite complex paths. Many of them run horizontally through the reservoir rock. The MD is the length measured along the borehole. The TVD is the depth from surface (or sea level, or seabed) to the measurement point.

    To expand on the North Sea example, 26" hole would typically be only a few hundred feet, though it could be as much as 4,000'. 17 1/2" hole would be a few thousand feet long. 12 1/4" hole again a few thousand feet and the same for 8 1/2". Total well length would be, perhaps 10,000', but in some cases could exceed 30,000' MD, though TVD might be only 5.000'.

    So all the natural caves I have seen are made from water? and none of the oil or gas hotspots contain any large cavities which could collapse after extraction?
    Yes. Most caves are produced by solution of carbonate rocks (limestones for the most part).

    There are some instances where limestone reservoirs may contain large solution cavities that are very much larger thant the normal small pore spaces, but these are a rare exception.


    The collapsing and earthquaks caused by drilling are because of many tiny pours simultaneously collapsing?
    There are two quite different processes at work. When we produce oil and gas from a reservoir, the pressure of the remaining fluid in the reservoir decreases. this allows the overburden of rock to cause further compaction of the rock - in a sense the pores do partially collapse. This may lead to subsidence at the surface.

    That mass movement may cause minor activity along minor fault plains. This would produce tremors (low intensity) rather than earthquakes. However the issue discussed here is about the increased movement along large fault planes essentially because they have been lubricated by fluids injected into wells to enhance productivity.
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