swenson

linpwei, Modeling a reservoir is both a technical challenge and an art. I am not a geothermal engineer, so I am limited in my response to your question. It is essential that the modeler use realistic values for material properties and have in mind a plausible geologic model. Once you have that, you can start your simulation process. The first step is to come to an initial state solution. I have attached a very simple model that illustrates some of the components you might want to use. However, I would encourage you to gather specific information for your site. My model includes the following: 1. A bedrock layer with low permeability. This layer has a uniform heat generation. 2. A porous media material that is used for most of the model. This represent most of the reservoir. 3. A surface layer with low permeability and a fixed temperature and pressure. Note that it was necessary to change the weighting of the permeability calculation to harmonic in order to have the low permeability of the surface affect the flow. 4. A fault with high permeability. Fluid is injected into the bottom of the fault. 5. A flow region with relatively high permeability. The cells at the outer boundary of this region are fixed so that they provide an exit flow for the fluid. I have attached a steady state plot of the temperature and the fluid flow vectors. Please send an email to me: support@thunderheadeng.com and I will send the PetraSim model. This forum does not allow me to attach the file. Hope this helps, this is as much as I can contribute to this discussion. Daniel Swenson Thunderhead Engineering

Jaeshik Chung, That is the way TOUGH2 names cells. Five characters are used, the first three are characters (A-Z) and the last two are numbers (0-9). You can export a file with a mapping of the Cell Number and Cell ID. On the File menu click Write Mesh Data. See the attached files. Daniel Swenson Thunderhead Engineering names.zip

The best way is to make a large single element model at the desired injection state (P, T, etc.), then produce from the element at a very small rate. In the TOUGH2 output you will see the enthalpy. See the attached files. enthalpy.zip

Mette, Because you mention that the pressure is doing funny things, it would be worthwhile to make sure the flow solution is valid without any reactions. On the Global Properties dialog of PetraSim, unselect Enable Reactive Transport. Now run the problem and make sure the pressure solution is ok. Warnings and error messages from the reaction solution are output in the runlog.out file. Looking there might provide additional guidance. Best wishes, Daniel Swenson

Ethan, The temperature at the injection block is a good clue. One way to verify the enthalpy is to just run a single cell problem at your injection conditions and produce at a small rate from the cell. The production enthalpy will then be printed out. If you still have questions, please send your PetraSim file to support@thunderheadeng.com and we will take a look. Thanks, Dan Swenson

Aku, The problem is related to the weighting options used at the grid block interfaces. See pages 135-136 of the TOUGH2 user manual for a discussion. In the Solution Controls dialog, select the Weighting tab. Change the Mobility at Interface to "Harmonic Weighted", The Permeability at Interface to "Harmonic Weighted", the Density at Interface to "Average of Adjacent Elements", and the Diffusive Flux at Interface to "Coupled Harmonic Weighting". Your problem will then run quickly and the solution appears reasonable. However, it would be helpful to have a deeper discussion on the numerical solution that makes these changes in weighting necessary. Perhaps inviting Karsten Pruess to discuss this would be useful. You could send your model (the saturation.dat file) to him and ask. Daniel Swenson, Thunderhead Engineering

Mitra, Without more details, it is difficult to answer your question. Would you be willing to send your model and instructions on how to duplicate your problem to support@thunderheadeng.com? We will look at your model and try to identify the problem. Thanks, Daniel Swenson Thunderhead Engineering

If anyone would like to try this feature, Thunderhead Engineering can supply an special executable. Please contact support@thunderheadeng.com.

Please allow me to add some suggestions. In any PetraSim/TOUGH2 analysis it is important to always be as realistic as possible. The physics in a simulation are always complex, and keeping the analysis realistic helps ensure convergence of the solution. Also, always start with a simple 1D or 2D model before proceeding to a more complex model. I would suggest that you follow the basic procedures as described in the VOC Contamination Problem, Chapter 7 in the PetraSim Example Manual. Assuming we start with a 1D model: 1. The top two layers of cells can be of a very porous material used to the atmosphere and the water "pool". Turn off capillary pressure in this material and give it a high permeability. 2. The first step in the analysis should be to come to an initial gravity/capillary equilibrium state. The VOC Contamination Problem uses "extra cells" that will be available in the next release, but the same goals can be accomplished using thin cells at the to and bottom. 3. Restart from the equilibrium solution, and fix the top and bottom cell boundary conditions. 4. Add the rain as a source in the second layer (you can use a table so the source is only active for part of the analysis). This will increase the water in the cell and act as a "pool" to the cells below. 5. You will then need to examine the results to make sure that it makes physical sense. Good luck.