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I Can hydrocarbons in oil wells move to vacuum zones?

  1. Nov 28, 2016 #1
    if we have a vacuumed tube inserted into a reservoir of 10,000psi will the oil rise up in the vacuum tube of will it stay in place because there is no Δp?
     
  2. jcsd
  3. Nov 28, 2016 #2

    jbriggs444

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    What makes you say that there is no Δp?
     
  4. Nov 28, 2016 #3
    if the tube is vaccumed and then connected to the reservoir, won't that mean that there is no delta p inside the tube?
     
  5. Nov 28, 2016 #4

    jbriggs444

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    Yes, there is no pressure differential through the evacuated portion of the tube. So there is no net force on anything within the evacuated portion of the tube. But then there is nothing in the evacuated portion of the tube.

    There is a pressure differential between a point somewhere within the pressurized oil and somewhere within the evacuated tube. And there is oil in the region between. That oil will be under a net force.
     
  6. Nov 28, 2016 #5
    So even if the tube have zero pressure inside and oil have high pressure acting on it from overburden pressure, the oil will still flow in the vacuum tube right?
    I'd really appreciate it if you could explain more as this is really confusing me.
    Thank you :)
     
  7. Nov 28, 2016 #6

    jbriggs444

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    So now you have oil that has oozed (and is still oozing) out of the material and into the tube. This motion is sustained by a pressure gradient. High pressure in the bulk of the [nearly unmoving] oil deep within the material, lower pressure nearer the inlet to the tube and zero pressure at the surface of the oil within the tube.

    Every little bit of oil is under a pressure differential that accounts for its movement against viscous resistance (and against inertia in the case of higher flow rates).
     
  8. Nov 28, 2016 #7
    So oil will move to the inlet of the tube but not inside the tube itself?
    i'm sorry for asking too much but it's really confusing on what will happen if the production pipe is vacuumed and place in the reservoir while being sealed from above and no air is allowed in.
    thank you so much for your help :)
     
  9. Nov 28, 2016 #8

    jbriggs444

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    Every little bit of oil is under a pressure gradient that accounts for its motion. Once oil enters the tube, there is a pressure gradient (within the oil) within the tube.
     
  10. Nov 28, 2016 #9
    If I have a chamber under vacuum, and I poke a hole in the side of the chamber, will air (at absolute pressure of 1 atm) flow into the chamber?
     
  11. Nov 28, 2016 #10
    If the reservoir is under-pressured, the presence of a vacuum at the surface will probably still not be enough to get the oil to the surface. If the reservoir is over-pressured, a vacuum at the surface will not be necessary. Therefore, using a vacuum in the production string to try to get oil to the surface would not have much of an effect either way.
     
  12. Nov 28, 2016 #11
    10000 psi = 703000 mmH20 ~ 879000 mmpetroleum
    So, petroleum from a reservoir at 10000 psi will rise about 879 meters in an evacuated tube. It looks like the average oil well is 6000 feet deep, so, we wouldn't be able to get it at 10000 psi with vacuum alone.
     
  13. Nov 28, 2016 #12
    I disagree with this calculation. If the pressure at depth is 10000 psi, then this is 1440000 lb/ft^2. The density of oil is about 50 lb/ft^3. So the height that the oil could rise in the production string (above the depth of the well completion in the production formation) would be 1440000/50 = 28800 ft. So that pressure would be more than enough for the oil to exert substantial positive pressure at the surface (vacuum or no vacuum). A reservoir at 6000 ft and 10000 psi pressure would be considered highly over-pressured (i.e., above hydrostatic).
     
  14. Nov 28, 2016 #13
    Oops, I dropped a zero. 10000 psi = 7030000 mmH20 ~ 8790000 mmpetroleum
     
  15. Nov 28, 2016 #14
    thank you so much for your reply guys and sorry for replying late but one last thing.
    what i'm actually arguing with my classmates and trying to prove is that as long as there is no air allowed in the wellbore while drilling and drilling under vacuum conditions by sealing the top of the well before drilling that this will not allow a kick in the well as the pressure won't react with vacuum. there will be no influx if there is no air, so what im saying is that oil won't reach the top and blowout if we're drilling with vacuum?

    i know i'm asking alot but it has been an ongoing discussion in class and we still can't settle on the right answer
     
  16. Nov 28, 2016 #15

    jbriggs444

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    Your position is incorrect. Vacuum will not stop the influx of oil.

    Edit: By the same token, sucking on a garden hose will not stop the water from reaching your mouth.
     
  17. Nov 28, 2016 #16
    The flaw in your logic is that there can be a discontinuity in pressure at the interface between the production string and the formation. The two pressures must match, so a driving force will be present for the flow of fluid within the formation to (and through) the interface. Your classmates are correct, and, sorry to say, you are wrong.
     
  18. Nov 28, 2016 #17

    mfb

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    There is a relevant xkcd

    If you understand how oil can flow in with air (large pressure difference), and thinner air (slightly larger pressure difference), then extrapolating to negligible air density (slightly larger pressure difference) you should not expect a completely different result. Even if a perfect vacuum would exist (it does not), it wouldn't be different from very thin air. Oil flows in.
     
  19. Nov 28, 2016 #18
    Unless I'm missing something here, the last thing I would want if I was the wellsite geologist on this well, would be to introduce a vacuum anywhere between the formation and the surface. Instead, I'd want to switch to a very heavy drilling mud and have some faith in the blow-out preventers. A vacuum would just get the oil or gas up that much easier and a whole lot faster. It is, in effect, acting as a pump. 10K psi pressure at 6000 feet in an oil well would earn me a nice bonus if the well was completed properly. For that, I 'd rely on the drilling engineer.

     
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