Abstract - Single phase horizontal bulk permeabilities for 3km
x 3km volumes of varying thickness of a typical Brent permeability sequence
have been calculated, both before and after faulting by a range of sub-seismic
fault arrays, with fault maximum displacements of 20m-2m. The models incorporate
realistic juxtaposition geometries across fault surfaces. Results are expressed
in terms of fractional bulk permeabilities (Kf) i.e. ratio of bulk
permeability of faulted model and of pre-faulting model. Fault and fault
array variables modelled and tested were fault density, spatial distribution,
orientation distribution and fault zone permeability relative to the host
rocks, expressed as transmissibility Factor (Tf). Realistic fault
zone thicknesses were incorporated by use of a scaling factor. Low, moderate
and high fault densities have significant and markedly different effects
on Kf whereas the effects of spatial and orientation distribution
variations are slight except at very low Tf values (Tf<0.001).
The relative insignificance of fault spatial distributions is due to closer
fault spacing resulting in locally high hydraulic gradients which increase
flow through fault surfaces unless these surfaces have very low Tf
values. Prediction of fault zone hydraulic properties remains the most
important factor contributing to modelling uncertainties.
In: Structural geology in reservoir characterization. (Eds.
Coward, M. P., Johnson, H. & Daltaban, T. S.). Geological Society of
London, Special Publication 127, 99-114, 1998.