Hi Junzhi, I was compiling a world wide database of permeabilities in crystalline rock (metamorphic and igneous) including some hundred lugeon/WD tests. At least in terms of the distribution of permeability the results of a statistical analysis suggest that there is no difference between vertical, inclined and horizontal measurements. This is somehow counter intuitive as one would expect that the orientation relative to the fracture orientations is important. However, transfering results from one borehole to another will be misleading as the rock properties (like permeability) exhibit a wide scatter. Maybe this helps you a bit.

Cheers Peter

Dear Peter,

Thanks for the kind response. I definitely believed that your database indicate the general statistical trend. But in my study area, we drilled two boreholes, one vertical and one inclined at the same location. Then we conducted Lugeon tests for these two boreholes. We found that for some sections, the Lugeon value for the vertical is larger than the inclined, while for other sections is smaller. To explain this phenomenon, we just use the simple relationship of apparent and true fracture spacing. But it is hard to expand this technique into 3 D.

The reason for "no difference between vertical, inclined and horizontal" , I think, maybe due to the fact that their ratios mostly vary in one-order.

Best regards, Junzhi

Hi Junzhi,

assuming the boreholes are not directly aside each other, I think you mostly deal with natural heterogeneity. You are right apperent fracture spacing is difficult to use in 3D. If you want some information about the fracture system you could use a pressure tomography. But this of course needs a lot more time and data...

Bests Peter