Inflows pose a serious concern to potash mining operations and often increase operating costs and production slow-downs. The mapping and understanding of water-bearing geohazards is vital in the potash mining industry. Critical to this effort is the development of geophysical tools to quantify the type and magnitude of these geohazards. In this paper, we propose using in-mine time-domain electromagnetics (TDEM) as a viable tool for investigating porous, water-bearing anomalies in geological layers more distant than has been done with electrical methods in the past. This work includes a TDEM survey to better delineate and quantify the properties of a suspected geohazard near a potash mine in southern Saskatchewan. Our investigations had two objectives: one was to confirm and define the extent of the conductive brine in the overlying lithology. The second was to determine the effectiveness of deploying TDEM in-mine where full-space effects and nearby machinery pose significant noise challenges to operation. Our results found a strong conductive EM signature to the suspected anomaly, suggesting there is high value in deploying TDEM underground. In addition, full-space EM computer modeling was performed in COMSOL Multiphysics using 2D-axisymmetric geometry to account for lithological changes both above and below our survey. We invert the survey data using a pair of different strategies. The results of which demonstrate that the anomalous EM response is caused by a conductive high in the Dawson Bay carbonate layers above the mine workings.
The first step in processing the determination of near-surface velocity structures is critical. In addition to improper static adjustments, a poor near-surface velocity model causes the rays predicted by the model to deviate from their actual ray paths. Due to the cumulative nature of this ray path deviation, even a small error in the near-surface velocity model can result in momentous errors in calculating the ray path and travel time. Furthermore, the deviation can notably degrade the seismic image at depth, particularly in regions with significant lateral velocity variations. A seismic model with significant lateral velocity variations and bare bedrock was built to perform theoretical calculations. The concept of first arrival tomographic static correction was also examined. Numerical simulation techniques were used to study the conditions and application consequences of the first arrival tomographic static correction, providing a reference for the static correction of challenging surface coal bed methane (CBM) seismic data. The findings demonstrate that tomographic static correction is better suited for processing complicated surface CBM seismic data and can effectively handle the problems of surface undulation and lateral velocity fluctuation, which are critical for improving the accuracy of CBM exploration.
Waterborne Ground Penetrating Radar (GPR) can be a powerful method for surveying bathymetry, water, and sedimentation volumes within water impoundments like Faylor Lake in Snyder County, Pennsylvania. Current methods for measuring sediment volume in water impoundments often involve invasive techniques, such as collecting cores, which lead to rough estimates due to limited available physical data. This study aims to utilize a custom-made GPR apparatus, which includes a 100 MHz transceiver, a GPR controller, and a GPS device, all mounted on a small 2-person crewed inflatable watercraft. Over 40,000 data points of depth locations spanning the entire lake were collected. The data has been used to generate contour maps and 3D models of the current bathymetry, as well as the original topography of the basin before the dam's construction in 1983. During this study, the lacustrine deposit's dielectric permittivity (<<) was directly measured using a laboratory bench experiment with a 1600 MHz GPR transceiver. The measured << = 51.69 has enabled the determination of accurate depth values and, subsequently, the sediment volume. The sediment volume represented 20% of the entire lake, with a volume of 139,281 m3. The water volume was also determined with << = 80, amounting to 663,659 m3. The 3D bathymetry map also shows the outlines of the old Middle Creek channel. The deepest part of the lake was identified on the southeast side, near the drop inlet of the dam, along the old Middle Creek channel, with an average depth of 1.63 m.
