This paper presents a new leak detection system for a long-distance pipeline using soil-gas techniques. The new leak detection system runs underground along the nearby pipeline and consists of intermittent porous tubes connected in series with impermeable polyethylene tubes. Applying the new detection system to long-distance pipelines for leak detection minimizes the large number of soil-gas samples and analyses that are required when conventional soil-gas probes are employed. A mathematical model was developed for designing the distribution of airflow in the new detection system. Field leak tests were conducted using both conventional soil-gas probes and the new system. Results indicated that the effective detection distance of the new system was at least 30 m, while the effective detection radius from the conventional soil-gas probes is only~5 m.
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.
In fractured media, the flow dimension was usually predefined before the determination of the hydraulic parameters in the past. However, it would be improper to make assumption about the flow geometry 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 hydrogeologic properties such as 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 for 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 increases near linearly with the distance between the pumping well and observation well, i.e., the flow dimension in the 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
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