f Conceptual geological models and modelling tools for assessing fault-related uncertainties in flow from conventional clastic reservoirs

Attempts to consider fault-related parameters during convergence of a flow model towards a history-match will, at best, allow fault rock permeability to be altered systematically, often as a function of the local Shale Gouge Ratio (SGR). Several published examples now exist of history-matched field-specific SGR-to-permeability relationships, but all have one thing in common: they derive from Brent-province reservoirs. Why? Is there something characteristic about post-depositional faults in deltaic sequences (like the Brent province) that makes the SGR approach more likely to succeed in this setting than in others (e.g. deep marine sequences containing syn-depositional faults)? Empirical evidence and geomechanical models suggests that different aspects of faults are likely to be significant on reservoir-scale flow in different geological settings, and there may be good reason to expect, a priori, different fault characteristics (e.g. sub-seismic fault segmentation and discrete shale smears) to dominate uncertainty on flow in different reservoir types. New tools are required to handle these characteristics. One important conceptual difference between the existing fault property modelling tools and the future tools needed to handle a wider range of fault-related uncertainties, is the requirement to represent heterogeneity explicitly, rather than as an average property captured by an SGR-to-permeability relationship.