The Inclusion of Faults in Conventional Flow Simulation Models: A Consideration of Representational Assumptions and Geological Uncertainties

Tom Manzocchi¹, John J. Walsh¹, Andrew E. Heath², Bala Palananthakumar¹, and Conrad Childs^1
1Fault Analysis Group, University College Dublin, Dublin, Ireland
²Fault Analysis Group, University of Liverpool, Liverpool, United Kingdom

Even in circumstances when geologically-based methods are used to determine fault rock thicknesses and permeabilities for input into flow simulators, a wide range of simplifying assumptions regarding fault structure and content are still present. We examine many of these assumptions by defining quantitative and flexible methods for realistic parameterisation of fault-related uncertainties, and by defining automated methods for including these effects routinely in full-field flow simulation modelling. Fault effects considered include the two-phase properties of fault rocks, spatial distributions of naturally variable or uncertain single-phase fault rock properties and fault throws, and the frequencies and properties of sub-resolution fault system or fault zone complexities including sub-seismic faults, normal drag and damage zones, paired slip surfaces and fault relay zones. Innovative two-phase or geometrical up-scaling approaches implemented in a reservoir simulator pre-processor provide transmissibility solutions incorporating the effect, but represented within the geometrical framework of the full-field flow simulation model. The solutions and flexible workflows are applied and discussed within the context of a sensitivity study on two faulted versions of the same full-field flow simulation model and reveal significant influence of some of these generally-neglected fault-related assumptions and uncertainties.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas