have you had a look in to Moeck et al (2009)?

It gives you a slip tendency T_{s} along the lines of what I am dealing with in CO2 sequestration. The slip tendency is the ratio of the resolved shear to resolved normal stress on the fault surface which has to exceed the frictional sliding resistance (given by the sliding friction coefficient \mu_{s}).

So what you want is to compute the traction vector (which is the force acting on a surface element whereas stress acts on the volume element) for given stress tensor field on each single element in CSMP which represents the fault. Given the traction vector, you can resolve the shear and normal component on the element and compare it against the failure criterion as outlined in Pollard and Fletcher (2005). Maybe it is not necessarly to use the traction vector to compute the normal and shear component and use the farfield stress tensor field directly.

Stephan used this approach for calculation on stress dependent permeability changes for a fracture network using Cruikshank et al (1991). However, the stress field is held constant and does not include fluid pressure coupling.

I am not sure whether a stress redistribution calculation is possible without including displacement. Haven't seen any mehtods on this so far, but will have a thorough look into this. A reference as a starting point would be helpful, you have one?

Cheers,

Robert

Reference

- Moeck, Inga, Grzegorz Kwiatek, and Günter Zimmermann. 2009. Slip tendency analysis, fault reactivation potential and induced seismicity in a deep geothermal reservoir. Journal of Structural Geology 31, no. 10 (October): 1174-1182. doi:10.1016/j.jsg.2009.06.012.
- Pollard, David D., and Raymond C. Fletcher. 2005. Fundamentals of structural geology. Cambridge University Press.
- Cruikshank, Kenneth M., Guozhu Zhao, and Arvid M. Johnson. 1991. Analysis of minor fractures associated with joints and faulted joints. Journal of Structural Geology 13, no. 8: 865-886. doi:10.1016/0191-8141(91)90083-U.

Reason is that in geothermal reservoir stimulation models such things have been used and we wondered if we could include them as well.

]]>Computer code: more credit needed

Computer code: incentives needed

Computer code: a model journal

The idea would be to create a hybrid mesh 3D/2D of the phase diagram of H2O-NaCl. Phase boundaries would be represented by surfaces of, e.g., of triangles, the regions inbetween by volume elements like tetrahedra. I guess it'll be in the order of 10^5-10^6 elements to have sufficient resolution.

I'd need to pseudo-randomly access ANY xyz coordinate (BUT: for a given node in the simulation domain (not the lookup mesh) I'd probably have a good guess from the last time step in what region I should be).

As always, there is a trade-off to be considered: Currently, my 3D-lookup is a cartesian grid with variable resolution in certain regions. From given xyz (which are temperature-pressure-composition) I can jump to the correct position with one very quick operation and linearly interpolate in that rectangual cell.

This works fine, fast and cheap unless I am in a situation where a phase boundary (e.g. liquid/vapor) lies within that cell. Then there is a plethora of possible topologies how exactly that boundary lies in the cell (and whether there are one, two, or three boundaries). Figuring them out is possible but I'd like to avoid going through that pain. Up to now, I extrapolated across the boundary but this is probably not accurate enough for our upcoming strict transport CVFEM scheme (flow gets potentially unstable if fluid properties are even slightly inconsistent with each other).

So, creating an FE-based lookup table looked attractive as it (a) would give a very good geometric representation and (b) has intrisically consistent interpolation routines. The unattractive side would be the cost of finding the right element for interpolation.

One possibility I thought of is creating the mesh such that it'd essentially consist of a series of long prisms which have there long axis strictly parallel to one of the axes (in my case y) and are themselves then subdivided into smaller prism or tretrahedral elements. This would allow to quickly find the right "long" prism first and then loop within it to find the right spot along the y-axis. However, this is not well thought through yet.

]]>It was really nice to see everybody again!

]]>thanks again for your participation in the workshop. We are currently updating the workshop site such that you can download the talks from the programme site and a list of all email addresses as well. Please send me your pictures such that we can also include a collection of them. Some talks are still missing, we will contact the people individually.

Sebastian

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