Predicting transmissibilities of carbonate-hosted fault zones
It is common practice to incorporate deterministic transmissibility multipliers into simulation models of siliciclastic reservoirs to take into account the impact of faults on fluid flow, but this is not common practice in carbonate reservoirs due to the lack of data on fault permeability. Calculation of fault transmissibilities in carbonates is also complicated by the variety of mechanisms active during faulting, associated with their high heterogeneity and increased tendency to react with fluids. Analysis of the main controls on fault-rock formation and permeability from several carbonate-hosted fault zones is used to enhance our ability to predict fault transmissibility. Lithological heterogeneity in a faulted carbonate succession leads to a variety of deformation and/or diagenetic mechanisms, generating several fault-rock types. Although each fault-rock type has widely varying permeabilities, trends can be observed dependent on host lithofacies, juxtaposition and displacement. These trends can be used as preliminary predictive tools when considering fluid flow across carbonate fault zones. Fewer mechanisms occur at lower displacements (<30 m), creating limited fault-rock types with a narrow range of low permeabilities regardless of lithofacies juxtaposition. At increased displacements, more fault-rock types are produced at juxtaposition of different lithofacies, with a wide range of permeabilities.