Abstract
Abstract. The flow dimensions of fractured media were usually predefined before the determination of the hydraulic parameters from the analysis of field data in the past. However, it would be improper to make assumption about the flow geometry of fractured media before site characterization because the hydraulic structures and flow paths are complex in the fractured media. An appropriate way to investigate the hydrodynamic behavior of a fracture system is to determine the flow dimension and aquifer parameters simultaneously. The objective of this study is to analyze a set of field data obtained from four observation wells during an 11-day hydraulic test at Chingshui geothermal field (CGF) in Taiwan in determining the hydrogeologic properties of the fractured formation. Based on the generalized radial flow (GRF) model and the optimization scheme, simulated annealing, an approach is therefore developed for the data analyses. The GRF model allows the flow dimension to be integer or fractional. We found that the fractional flow dimension of CGF increases near linearly with the distance between the pumping well and observation well, i.e. the flow dimension of CGF exhibits scale-dependent phenomenon. This study provides insights into interpretation of fracture flow at CGF and gives a reference for characterizing the hydrogeologic properties of fractured media.
Highlights
For the determination of the hydrogeologic parameters, the traditional methods usually assume that the flow dimensions are predefined along with assumptions of homogeneity and isotropy before analyzing hydraulic test data
The results show that there is no correlation between flow dimensions and fractal dimensions of dolomites and the flow dimensions are lower than the corresponding fractal dimensions in Slovenia
The measured drawdowns obtained from four observation wells during an 11-day long hydraulic test performed at Chingshui geothermal field (CGF) in Taiwan are chosen for the data analysis using the present approach
Summary
For the determination of the hydrogeologic parameters, the traditional methods usually assume that the flow dimensions are predefined along with assumptions of homogeneity and isotropy before analyzing hydraulic test data. When analyzing data from the hydraulic test, it is difficult to choose an appropriate flow dimension in a fractured formation system. A one-dimensional (1-D) or two-dimensional (2-D) flow model would probably be preferred (Barker, 1988) if the fracture density is low and its distribution is anisotropic. Barker (1988) developed a generalized radial flow (GRF) model for hydraulic tests in fractured formations by regarding the dimension of the flow as a parameter. Both integer and non-integer dimensions are possible in the GRF model. Both integer and non-integer dimensions are possible in the GRF model. Walker and Roberts (2003) indicated that the flow dimension is not necessarily a simple
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