Practical Application of WTEM Transient Electromagnetic Method in Coal Mine Geological Survey

Practical Application of WTEM Transient Electromagnetic Method in Coal Mine Geological Survey

Background

The Gold Company has used the WTEM transient electromagnetic method system to survey the geological conditions of the coal mine. Based on the current geological exploration data and contour lines of the coal seam floor, the propagation values of the apparent resistivity at various exploration points in each area are calculated and deduced. The calculated values and the depths previously measured are then annotated on the surveyed points. Subsequently, a comprehensive, reliable, and effective plan view is drawn based on multiple data sources. With the transient electromagnetic method, a complete geological exploration plan view can be obtained, effectively reflecting the areas of anomalous geological structures within the surveyed area and showing the apparent resistivity. With the help of the transient electromagnetic method, exploration personnel can effectively understand the geological conditions of the surveyed area in geological exploration technology and take precautionary measures against potential geological disasters and risks, providing safety assurance for coal miners.

Survey

When using transient electromagnetic methods for mine detection, the preferred equipment is the WTEM Multi-Function Electromagnetic Workstation with the center return device. Measurement points should align with recording points to minimize the volume effect and observe a uniform field in the transmitting wireframe center. Parameters include a power supply current of 7.5A, receiving antenna magnetic torque of 1000 square meters, and 512 superimposed times with a turn-off delay of 120 μs. Measurements focus on the z-component with 25 channels. The surveyor sets up 1350 lines in the mine collapse area and uses area-type measurement methods within a 1.6km×1.4km range with 200m×40-20m grid spacing. Interference points are eliminated, induced electric potential pre-processed, and true resistivity generated through two-dimensional inversion for geological analysis and interpretation. Data at different depths are extracted, leading to a comprehensive planar map reflecting mining zone characteristics accurately.

Equipment Used

• WTEM-2J TEM Receiver

• WTEM-2D/60 15KW TEM Transmiiter

Results

After validation, it was observed that the reflections of other survey lines in the mine are consistent with line 1350. Height anomaly layers were used to determine mining area extent and open area extension. Starting from the southern end at 1450m elevation, line 1350 extends northward, aligning with mining levels and reaching the seventh level return air shaft at 1350m elevation. Comparison with ZKJ103 drill hole data and coal mining information helped clarify mining conditions, ensuring data validity for future mining operations. This analysis guides exploration field development effectively.

Geological sketch copper deposit

The transient electromagnetic resistivity section