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Reservoir Simulator InterfacesReservoir Simulator Interfaces

FracMan links directly the discrete feature network approach to conventional reservoir simulators such as Eclipse by deriving effective continuum properties (FracLips). FracMan also provides links to reservoir structural models (StrataFrac) and visualization tools such as Intergraph (FracView).

Linking between DFN models and conventional reservoir simulators requires that DFN models be adapted to provide the parameters needed for reservoir simulation, on a cell by cell basis. The following table illustrates the approach to map between ECLIPSE parameters and DFN models.

 

ECLIPSE Parameter DFN Approach Comments
cell size compute block size distribution determines the probability that a cell of a specific size contains sufficient fracture connectivity to be modeled as a continuum
active cell compute block size distribution determines the probability that a cell of a specific size contains insufficient fracture connectivity (inactive cell), gives spatial distribution of inactive cell
fracture porosities compute fracture volume based on fracture aperture distribution
directional absolute permeabilities create DFN, run MAFIC on appropriate block size steady state flow through two sides of a cube initiated by constant head boundaries, other four sides are no flow boundaries, ka is calculated from the resulting flow rate
directional relative permeabilities create DFN, run MPMAFIC on appropriate block size steady state flow through two sides of a cube initiated by constant head boundaries, other four sides are no flow boundaries, function of kr vs saturation is calculated from the resulting flow rates for different saturations
matrix-fracture coupling compute typical x,y,z dimension of a matrix block, calculate s based on KAZEMI, (SPEJ(Dec 1976) 317-326)
well kh run Oxfilet based on fracture intensity distribution and transmissivity distribution
well productivity/ injectivity index create DFN, run well test in MAFIC based on connected fracture network distribution (tributary drainage volume)

NOTE: Transferring DFN data into ECLIPSE input only makes sense, if the rock mass can be treated as a continuum. This is mainly a function of scale. The block/cell size analysis shows whether this is the case or not. The DFN approach does NOT need any upscaling or downscaling because it uses the actual cell size to compute permeabilities.