Although the ability to predict the sealing potential and transmissibility of carbonate-hosted fault zones has received significant interest, there is surprisingly little published data on the petrophysical properties of variable fault rock types within carbonate reservoirs. Intact and deformed carbonates have a high heterogeneity and propensity to react with fluids; however patterns to this heterogeneity can be observed and used as predictive tools when considering fluid flow across carbonate fault zones. Several carbonate-hosted fault zones have been examined to determine the type and distribution of fault rocks and their influence on fluid flow. Analysis of these fault zones has revealed that fault rock type, and corresponding porosity and permeability, is mainly controlled by lithofacies variation, lithofacies juxtaposition and displacement. Varying textures in different lithofacies control whether the strain is localised, causing grain crushing, or dispersed creating fractures that can hydraulically brecciate to produce a variety of breccia types. Each fault rock type has different porosity and permeability values, creating a large range to both porosity (1.6-34.7%) and permeability (0.0001-1000 mD). However, trends to these petrophysical properties are observed, depending on the three main controlling factors stated above, and can be used to predict a fault's transmissibility.


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