T2Well (Error message)


I got the following error message in the output file while running T2Well case.

 Array size for connections is not enough:
 NCON=      243220 but MNCON=       57000
 Array sizes are not proper for your problem.
 The program will be terminated.
 Please modify the parameters in T2,
 and then recompile your program.


I would like to know if there is a maximum number grid cells/connections that I have to specify.

Thanks in advance

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  • Dear Refaat,

    According to the message, your grid has 243220 connections but the code is set to have maximum of 57000 connections.  In the T2 file, you need to find the parameter MNCON at set it to some number greater than or equal to 243220.  I recommend 243300.  Check your CONNE block and verify that it has 243220 lines.  Check your ELEM block and see how many lines it has.  There should be a parameter in T2 called MNELEM or something like that.  Make sure it is at least as big as the number of elements your grid has.  If not, set it to something slightly bigger than that.  Then save the file T2 and recompile the code.

    Good luck, Christine

    • Christine Doughty Dear Dr. Christine,


      Thank you for your clarification. I would like to know if T2Well can model coupled reservoir-wellbore problems (e.g. 3D reservoir model that contains injector and producer) so that I can see what happens in wellbores and reservoir during simulation. I find the examples illustrated in the manual mainly model fluid flow in wellbore. Do I need to couple T2Well and TOUGH3 by some means  to model this problem?

      Thanks in advance  

    • Christine Doughty Thank you for your reply. I can't find a file called "T2", however I have exe. file called "T2Well". I tried to open it and I find the following data including MNEL and MNCON. Is this the file that I have to change it manually? Can you please clarify how to compile the code after modifying it? 

    • Refaat G Hashish When you bought T2Well did you buy just the executable or the executable plus the source code?  If you just bought the executable, the instructions I gave you for changing the file T2 and recompiling will not work.  The file you show is the output file - it is telling you what your MNCON value is, but changing it there will not do anything.

    • Christine Doughty Thank you for your response. Actually, I am now working with a source code of T2Well and I have changed the maximum number of elements and connections in T2 file as shown below:


      C---  MNEL: Number of elements
            PARAMETER (MNEL = 22000)
      C---  MNCON: Number of connections
            PARAMETER (MNCON = 61300)


      compared with 20000 and 57000, respectively. I compiled the source codes and got the new executable code. The code is running without error messages but it does not output results. The OUTPUT file size is still showing 0 bytes after 30 minutes running. Any comments about this issue? Should the new maximum number of connections be compatible with the new maximum number of elements?




    • Refaat G Hashish Make sure your actual number of elements is no larger than 22000 and your actual number of connections is no larger than 61300.  That is the only requirement on MNEL and MNCON (The rule of thumb for a 3D rectangular grid is that there are about 3 times as many connections as elements).  When TOUGH starts to run, it first prints some general information (even before taking any time steps), so 0 bytes doesn't sound right.  Does your system allow you to look at the output file while the code is running?  I can do this on Ubuntu, and it is very convenient to check progress.  If you can't do that, try killing the job and then looking at the output file for clues as to why it is not working.  I usually set mop(1)=1 and mop(7)=1 and mop(5)=3 to get diagnostic information while the code is running.  Check the Users Guide for other MOPS you might want to set to see more output for debugging.

  • T2Well has TOUGH2 built into it, so it can model coupled reservoir-wellbore problems.  We do not currently have a "T3Well" where TOUGH3 is coupled to a wellbore simulator.  We do have long-term plans to create it, but I cannot predict when it will be available.  In the meantime, T2Well should work to model both reservoir and wellbore, but you will not be able to run in parallel.  Also, you should check the TOUGH3 User's Manual where it compares features that are different from TOUGH2, to make sure your input file does not use them.

    • Christine Doughty Thanks again for your reply. My last question is that Can the output results from T2Well be output in excel file format like (OUTPUT_ELEM in TOUGH3)?

  • I don't think so.  As I recall, providing output in excel format is a new feature with TOUGH3.  For TOUGH2, there is a free utility program called Ext (available for download, see Free Software Download web page) that takes TOUGH2 output and puts it in a format for the graphics package Tecplot.  The format should be usable by other graphics packages also.  However, I should warn you that Ext really just works for regular grids, and probably you have a customized grid including a wellbore, since you are using T2Well.  But it might be helpful for visualizing the reservoir part of your problem.

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