How to model a leakage around existing well annulus in TOUGH
We are trying to model gas leakage around exisiting well annulus (The space between wellbore and casing, where fluid flow can occur). However, the aperture is relative large and I wonder whether this will violate Darcy's law and/or this error is acceptable? Can I use TOUGH for this type of representation?
8 replies
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Hi Qian,
I'm working on something similar. What aperture are you referring to (e.g., the mesh size around the well)?
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Hi, the aperture I am referring is the void space between casing and tubing, where fluid flow can occur. This is the potential leakage pathway for gas. Right now, I am still in the preliminary developing phase, so I don't have a mesh size yet.
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Hi Amy,
I just wonder whether you happen to find a way to deal with leakage pathways?
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Hi Qian,
I am just a lowly grad student, not one of the gurus around here, which is why I didn't comment further before. That said, in my experience, TOUGH can handle most of what you throw at it, including adjacent regions with very different permeabilities. Does this answer your question? I'd have to know more about your conceptual model to answer in detail. For more advice on choosing a model, I'd recommend the LinkedIn groundwater modeling forum. Also, this paper is great example of using TOUGH to model gas well leakage: http://onlinelibrary.wiley.com/doi/10.1002/2014WR016086/full
I hope this helps!
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Hi Amy,
Thanks for your reply, the paper you shared is definitely helpful. I think what I am trying to figure out is whether I can still use TOUGH under a really high-porosity (>0.9) and high permeability condition, which might violate darcy flow. Or in another word, the flow in the well annulus (which is continuous voids). In the paper you shared, it seems that TOUGH+ code should be able to handle this. I will need more research on that.
Qian
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Hi Amy,
Just a few quick thoughts:
(1) Yes, check whether laminar flow applies for your conditions.
(2) Consider, whether your flow rates change significantly during the simulation period. If not, it may be sufficient to assign an effective permeability to the annulus, Yes, you would make a mistake, but it may be acceptable given all the other uncertainties you have.
(3) T2Well could properly simulate two-phase flow in an annulus under non-Darcy flow conditions. Not sure whether this is in the standard version, though - contact Lehua Pan.
(4) Both TOUGH+ and iTOUGH2 can simulate non-Darcy flow using the Forchheimer equation.
I would start with (2).
Stefan
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Hi Amy,
Just a few quick thoughts:
(1) Yes, check whether laminar flow applies for your conditions.
(2) Consider, whether your flow rates change significantly during the simulation period. If not, it may be sufficient to assign an effective permeability to the annulus, Yes, you would make a mistake, but it may be acceptable given all the other uncertainties you have.
(3) T2Well could properly simulate two-phase flow in an annulus under non-Darcy flow conditions. Not sure whether this is in the standard version, though - contact Lehua Pan.
(4) Both TOUGH+ and iTOUGH2 can simulate non-Darcy flow using the Forchheimer equation.
I would start with (2).
Stefan
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Hi Stefan,
Thank you very much for confirming my doubts and your valuable suggestions. I think I will start with (2) to see whether the results are acceptable before I move forward with TOGUH+.
Qian