Mapping the Preferential Flow Paths Within a Fractured Reservoir

Abstract

In a fractured reservoir, three dimensional (3-D) preferential flow paths are likely to be formed (i.e. 3-D channeling flow) due to the heterogeneous aperture distributions of individual fractures. However, to date there is no practical modeling method that precisely represents the 3-D channeling flow. In this study, we developed a novel method to analyze and predict channeling flow in an actual fractured reservoir, where a novel discrete fracture network (DFN) model simulator, GeoFlow, is used. In GeoFlow, heterogeneous aperture distributions are given for individual rock fractures depending on their scale and shear displacement. Realistic DFN models are created for an actual fractured reservoir (i.e. the Yufutsu oil/gas field) and fluid flows in the reservoir are simulated. Through a series of the fluid flow simulations, it is clarified there are some possibilities that three orders of magnitude difference in the productivities between the neighboring two wells is marked in fractured reservoirs due to the occurrence of 3-D channeling flow. Specifically, the impact of 3-D channeling flow is significant in the domain where the degree of fracture connectivity is relatively limited. These findings are revealed for the first time by mapping the 3-D preferential flow paths within a fractured reservoir, which means the following; we may come to the wrong conclusions for development or utilization of a fractured reservoir, if the occurrence of 3-D channeling flow within the reservoirs is ignored. As long as highly-reliable DFNs are created for a fractured reservoir on the basis of 3-D seismic data, crustal stress data, and so on, we can now map the realistic flow path distribution (i.e. 3-D channeling flow) with GeoFlow.