Validation of Clustering of Fractures in Discrete Fracture Network Model by Using Fracture Density Distributions Along Boreholes

摘要

This study reports a procedure for validating a reliability of alocation distribution of fractures in highly populated portions(clusters) of a constructed discrete fracture network (DFN)model. In the procedure, we focus on a relationship between afracture density distribution along boreholes and spatialextents of clusters of fractures in a DFN model. The numericalexperiments show that a shape of a fracture densitydistribution function evaluated using fractures crossingboreholes mainly depends on a location distribution offractures, and is less affected by a size distribution and anorientation distribution of fractures.The DFN model is constructed by the procedure we hadproposed previously. At the procedure, geostatistics method isused for predicting extents of clusters of fractures. However, itis pointed out that the extents of clusters have uncertainty dueto the prediction by using only the observed locations offractures along boreholes. This uncertainty reduces areliability of a constructed DFN model.To meet the issue, the fracture density distributions alongboreholes are calculated for constructed DFN models withdifferent extents of clusters and compared with theobservations. Through the studies, it is confirmed that thefracture density distributions along boreholes are useful toconstrain the uncertainty of the extents of the clusters and thatthe optimum extent of the cluster can be extracted by focusingthe fracture density distribution along boreholes. Additionally,fluid flow behaviors of the constructed DFN model with theoptimum extents of clusters is verified by flow simulations.