Zhidi Wu

Hello, I encountered a convergence error (see screenshot below) while running a reactive transport model with two boundary fluids in X1t. The model was running fine with Fluid_1 but requires “suppress all” (disable new mineral to form) to be able to run. The convergence error occurred during Fluid_2, where a significant amount of CO2(aq) was added. I also attached the X1t model file and the thermo database for your information. I look forward to hearing your feedback. Thanks, Zhidi Test_1_04232024.x1t AGI_20e_4-11-2024_debug.tdat

Hello, I’m setting up a reactive transport model based on my flow-through experiment in X1t and keep getting two types of errors. First error states: Porosity of node 0 is too small: -0.670590. Second error states: Mineral volume in node 0 is greater than node volume. In my experiment, fluid is injected into a core sample with a bulk volume of 57 cm3, porosity of the core sample is 0.0885. The mass of each mineral composition of the core sample is known. Injection flow rate and the pressure drop across the sample is also known. Here are the questions I have that I think might be useful to trouble shoot those two errors I mentioned above. 1. Does X1t model consider the total injection fluid volume as an input parameter? I noticed that there is no fluid volume option, so is the fluid volume basically the pore volume when the domain is saturated, which can be calculated from domain volume and porosity? 2. If the injection fluid volume is not directly defined, but inferred by time and pressure drop, should I set 57 cm3 as the domain volume in Domain tab (from x, y, z)? In my batch model using React, I had to scale the bulk volume and mineral mass based on injection fluid volume (1000 ml H2O). 3. In Medium tab, is the porosity in X1t model the same as the porosity of my core sample (0.0885)? 4. In Reactants tab, when I define the mass for minerals, are they the mass within each nodal block, or for the entire domain? I set 10 nodal blocks in my model, which means I need to divide the total mass by 10 if it’s for each nodal block. Please let me know if you need to know more information to troubleshoot these errors. Thanks, Zhidi

Hi Brian, Of course. Here you go, thanks. Zhidi AGI_20e_7-24-2015.dat

Hi Brian, I attached the file here. Thank you for looking into this in advance, and I look forward to your insights. Zhidi Hd_batch_optimized_SuppressAll_1h.rea

Hello! I’m trying to calibrate the model parameters Sm (surface area) and k25 by matching fluid components (cation concentrations) up to lab measurements. But I found that the Ca2+ concentration neither changes much when increasing Sm and k25 of calcite, nor suppressing all minerals from precipitation. However, the saturation index of calcite in output is negative (unsaturated). To my understanding, this means Ca2+ should be below the solubility of calcite and is supposed to increase with Sm and k25. How to explain these opposing observations and increase the Ca2+ concentration (~153 ppm) to match up with lab measurements (~1143 ppm)? Similar observations were also seen when I tried to decrease Mg2+ by decreasing Sm and k25 of dolomite. Many thanks, Zhidi

Hi Jia, I still don't think I understand. In your example, there are vol. 5% quartz (mineral volume fraction) and 10% porosity (fluid volume fraction). Should the program automatically include vol. 85% inert mineral (non-reaction phase volume fraction) to sum the three components (fluid, mineral, and inert) up to 100%? Thanks, Zhidi

Hi Jia, That's helpful. I also looked into GWB Command Reference, and it answers most of my questions. However, I still have another question on how React calculates the mineral mass and volume. If I type wt% of the mineral in the Reactants tab and assign porosity and bulk volume in the Medium tab, the output file returns a mineral mass, a very small mineral volume, and a very large inert volume. I understand that the inert volume is ignored once porosity is defined according to Command Reference, but this results in an extremely large mineral density (~90 g/cm3), which is not realistic. I tried to use absolute mass unit instead of relative unit in the Reactant tab and the results are more realistic. My question is: how mineral and inert volumes are calculated in this case? Thanks, Zhidi

Hello! I'm trying to set up a batch reaction model on a shale sample in React. My shale core sample has a porosity of 8.85% and a bulk volume of 57.78 ml. Plus, the fluid volume in my batch experiment is 100 ml. Therefore, in the Medium tab, I set porosity to 0.0885, bulk volume to 57.78 ml, and permeability constants A=1 and B=-3.0885. The model has difficulty in convergence due to the porosity in node 0 being too small. I played around with the parameters in the Medium tab and found that the model runs when the bulk volume is higher than a certain value (~1400 ml). So, is the bulk volume in the Medium tab different from the bulk volume of my sample? Looking into the output file, the bulk volume seems to be the sum of fluid, mineral, and inert volumes. I realized that the bulk volume in the model is different from what I first assumed. How do I correctly set up the bulk volume to match the mineral, fluid, and pore volumes in my experiment? Many thanks, Zhidi