A dual representation of multiscale fracture network modelling: application to a giant UAE carbonate field

Abstract

The network of faults and fracture corridors assumed to act as preferential fluid pathways between reservoir units in a Type III Lower Cretaceous reservoir in Abu Dhabi is evident on 3D seismic data, but its elements are too numerous to be efficiently picked by hand. Alternative modelling techniques with increased levels of complexity and accuracy were tested for incorporation into the 3D model: deterministic fault patches, geobodies, and multipoint statistics, the latter to correct for the difference in corridor location observed between seismic and well data. Seismic and matrix properties guided the modelled distribution of unit-bound fractures outside the corridors. The new dual-scale approach to fracture network modelling applied in this study uses discrete fracture networks to represent the large fractures that provide connectivity between the grid cells, and describes statistically, with an implicit fracture model, the small fractures that probably enhance matrix permeability and anisotropy. A model comprising only discrete fractures would have taken hours to run, and the smallest fractures would have been neglected for computational limitations; whereas creation and upscaling of the hybrid model was performed in few minutes, enabling future implementation of iterative workflows for more rigorous statistics and calibration of intermediate and final results.