Dual permeability modeling of solute transport in discrete fracture systems
The flow and transport properties of a dual permeability model have been evaluated in a form which allows discrete simulation of the complete range of fracture size in a series of successively larger models up to reservoir scale. In matrix dual permeability modeling, the flow and transport processes occur in both matrix cells and the superimposed discrete fractures. The matrix cell models use Darcian flow and Fickian transport relationships to represent processes occurring in the numerous small channels which make up the micro-structure of the rock. The macro-fractures are modeled discretely up to the size of the multi-cell model. If the overall properties of the multi-cell model can be determined they can be used to represent this model as a single cell in a larger model along with the next larger set of fractures. Since its cells represent the rock matrix *and* the distributed effect of small fractures, the larger model is termed a distributed or representative element dual permeability model. Successively larger models then allow simulation up to the scale of the reservoir. An initial step in this development has been achieved by numerically determining the non-Darcian, non-Fickian properties of a two-dimensional model composed of Darcian and Fickian matrix cells and a discrete fracture system. The porous matrix properties were assumed to be those measured in a visibly unfractured core. The discrete fracture system was a realization of the smaller fractures in a stochastic system. The FRACSL code was used to determine flow coefficients and residence time distributions for the porous matrix combined with each of five different realizations of the stochastic fracture system. Reservoir scale simulation could be achieved with reasonable computer resources and with fidelity to the fractured media by incorporating this type of results in successively larger models.
- Research Organization:
- Idaho National Engineering Laboratory, Idaho Falls, ID
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AS07-84ID12529
- OSTI ID:
- 887294
- Report Number(s):
- SGP-TR-113-39
- Country of Publication:
- United States
- Language:
- English
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