Hydraulic conceptualization of a single fracture using hydraulic interference tests at a deep underground condition

Abstract

In this study, we evaluated the conceptualization approaches to represent heterogeneous hydraulic property of a single fracture using geostatistics and stochastic method. Interference tests at the single fracture, which was identified at the depth of about 250 m from the ground surface in the Olkiluoto island, Finland, were simulated. The transmissivity data from the test boreholes were geostatistically analyzed, and the analysis results were used to reproduce the transmissivity field of the single fracture by the ordinary krigging and conditional random generation approaches. The groundwater flow models were calibrated by comparing the observed flow rates at the boreholes during the interference tests to the simulated ones. The simulation results show that the discrepancies between the simulated and observed flow rates became larger as the observed flow rates were large, which indicates that the ordinary krigging and conditional random generation approaches for conceptualization of the single fracture were not be able to sufficiently reflect the real hydraulic property. Nevertheless, the observed flow rates were included in the ranges of simulated ones when using the conditional random generation approach, which shows that the conditional random generation approach is applicable although the number of observations is too small to reenact the real hydraulic property of a single fracture.