FSP calculations in TransGen Version 3

The TGFSP keyword in the TGDATA runfile can be followed by up to 5 Fault Seal Potential definitions including for example any of the following:- basic Shale Gouge Ratio, Clay Smear Potential (Yielding et al. 1997), Clay Smear Potential (Fulljames et al. 1997), Vshale weighted Clay Smear Potential, Shale Smear Factor (Lindsay et al. 1993), Shale Smear Factor for multiple shale beds, Distance-weighted variants on SGR. The instructions for each FSP measure in the TGFSP keyword string are based on the general equation:-

The introduction of shale faces in the FSP calculations is a significant conceptual difference between the Shale Gouge Ratio (SGR) in TransGen Version 2 and the FSP calculation in Version 3. In Version 2, SGR is calculated as a function of the faulted faces of all the cells in the model that have slipped past the vertex of the connection being processed. In Version 3, a subset of these faces (which can include none or all of them) are designated shale faces (i.e. EffectiveVshale) and only these shale faces are used in the FSP calculation.

The Figure below shows a cartoon of a simple 2D model with dipping COORD lines. Cells that have been designated shales are shown in brown, while non-shales which are not therefore included in the FSP calculation are shown in yellow. For each of the four shale faces (1 to 4), the figure shows the definition of Throw (D), Thickness (t) and Effective Vshale (eVs) included in the FSP equation. Figure (b) shows the the three possible definitions of the Distance term for a calculation on the vertex highlighted with a red dot.  

NOTE:-The Throw term is not necessarily the same for the 4 shale faces - for example if there is stratigraphic growth across the fault and these Throws can differ from the fault displacement of the vertex, calculated from the Throw in the hangingwall and the the Throw in the footwall. These displacements are functions of the vertex being processed, rather than of the shale layers that have passed this vertex.

By default, TransGen reports the FSP measures in 3D, by measuring all distances, thicknesses and throws parallel to the COORD lines bounding the faulted connection faces as shown in Figures (a) and (b) above. TransGen assumes implicitly, therefore, that the displacement vector of the fault is parallel to the COORD lines used to construct the 3D model geometry.

By changing the Plunge correction option to Strike projection, the FSP measures can be reported on a vertical projection of the fault. The definition of throw (D), thickness (t) and distance (d) terms in the FSP calculation using this option are shown in Figure (c) above. However this option is NOT available for Fault displacement which is always reported in 3D. If desired, the vertical component of fault displacement can be calculated in a thickness plugin.