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A new day and a new soil column

Submitted by Austin Hudson on August 23, 2012 - 9:26am

After making a new soil column I continued with measuring xanthan viscosities as a function of shear rate. The experiment is proceeding much smoother now. Although the results do not exactly match those of the capillary tube, they are very close. 

The figure below illustrates the differences between how a 400mg/L xanthan solution behaves in the capillary (green) and in the soil column (blue). While flowing through the sand the solution appears to have a much higher infinite shear viscosity. This has serious implications for the use of xanthan to stabilize subsurface reactants- larger viscosities at high shear rates require significantly higher injection pressures during reactant emplacement. Now that the 400 mg/L solution has been tested I will move to larger concentrations of xanthan.


 
While the experiments run, I concurrently work on a model that uses the Thiem equation to calculate the radial distribution of pressure from an injection well. The equation is a simple approximation of how the pressure is distributed when a shear thinning fluid is pumped through the subsurface. It assumes the soil is homogenous and isotropic, the flow acts only in the radial direction, and the aquifer is confined. Using the results from the soil and capillary experiments I can assign different viscosities within the radial flow field that are a function of specific discharge at any point in space.
 

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