Closed Boundary Conditions (No Flow Boundaries)
Erinç Barış Koç
I am working on the gas condensate reservoir simulation. Initially, there exist constant water (0.2) and gas saturation (0.8) in all 6 layers of reservoir.
All 6 layers are open to flow.
I did not add any boundary condition into schedule section. As I know from MRST scripts, no specified boundary corresponds to no flow boundary condition. However,simulation schedule goes on, there is water flow into reservoir from bottom layers especially. I added some picture of water saturation in the reservoir.
Is there any possible way to define closed boundary into reservoir in MRST? How can I prevent water flux into reservoir from outer layers?I also added my schedule section.
Olav Møyner
Hello,
By default, all boundaries are assumed to be no-flow. Your schedule does not contain any boundary conditions, so I suspect that the model uses no-flow boundary conditions.
So why does the water saturation increase? Without knowing your fluid model, recall that the water saturation is the amount of pore-volume filled by water. If you have compressibility in the water, the volume occupied by the same amount (mass) of water, can change. Another possibility is that you have gravity in your model, but the initial state is not at equilibrium. In this case, the water will move towards the bottom of the model during the simulation. You can run a schedule with no wells for a long time (100+ years) to verify this. In your case, I think this is what happens: You will have more water at the bottom, and less at the top. The total amount in mass remains constant.
Best regards,
Olav
Sent: Thursday, September 7, 2017 2:28:49 PM
To: MRST-users: The Matlab Reservoir Simulation Toolbox User Group
Subject: [MRST Users] Closed Boundary Conditions (No Flow Boundaries)
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Erinç Barış Koç
Hello Olav,
Thank you very much for your answer. I applied our suggestion that model is run without any production or injection for 110 years. The water saturation is increased toward the bottom of the reservoir and vice versa for gas saturation. It is in the following picture.
You are right that system probably is not in equilibrium because of both gravity and capillary forces so water flow throughout bottom layer. However, I have also question,
1) If I used the ‘Fluxside’ function, I add zero flux to all boundaries of the reservoir. Can I say that the following reservoir will behave as closed boundary reservoir?
7 Eylül 2017 Perşembe 16:00:47 UTC+3 tarihinde Olav Møyner yazdı:
Olav Møyner
Hello,
Setting zero flux boundary conditions using fluxside is possible. However, it is also extra work for the simulator that is not needed, as faces without BC will be assumed to be no-flow. I do not think that water is actually entering your model, though. What you are seeing is actually the re-distribution of the existing mobile water due to gravity (less water on top, more at the bottom). The total amount of water is fixed.
Best regards,
Olav
To: MRST-users: The Matlab Reservoir Simulation Toolbox User Group
Jhabriel Varela
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