Static and dynamic connectivity in bed-scale models of faulted and unfaulted turbidites.



Manzocchi, T., Walsh, J.J., Tomasso, M.1, Strand, J., Childs, C., & Haughton, P.1
1 - Marine and Petroleum Geology Group, School of Geological Sciences, University College Dublin, Belfield, Dublin 4, Ireland.

Abstract - A range of unfaulted and faulted bed-scale models with sheet-like bed geometries have been built and analysed in terms of static bed connectivity and fractional permeability assuming permeable sands and impermeable shales. The models are built using a new method which allows amalgamation ratio to be included explicitly as model input and this property, rather than net:gross ratio, is found to be the dominant control on inter-bed connectivity. The connectivity of faulted sequences is much more complex and is dominated by interactions of variables. A comprehensive modelling suite illustrates these results and highlights the extremely rare combinations of circumstances in which faulted sequences have lower connectivities than their unfaulted sedimentological equivalents, irrespective of whether fault rock properties are included or not. In general, models containing stochastically placed shale smears associated with each faulted shale horizon are better connected than if deterministic Shale Gouge Ratio cut-offs are applied. Despite the complex interactions between geological input and bed-scale connectivity, the flow properties of a system are controlled by only three geometrical, rather than geological, variables describing connectivity, anisotropy and resolution. If two different faulted or unfaulted systems have identical values of these three variables they will have the same flow properties.


In: Structurally Complex Reservoirs. (Edited by Jolley, S.J., Barr, D., Walsh, J.J. & Knipe, R.J.). Geological Society of London, Special Publication 292, 309-336.