Did You Know That High-density Electrical Method And Transient Electromagnetic Method Can Be Used Together?

                   Did You Know That High-density Electrical Method And Transient Electromagnetic Method 

                                                                            Can Be Used Together?

yes! Our two geophysical methods can also be jointly applied, today the main thing is to share with you a combination of two methods to find water in the Gobi application!

The role of geophysical exploration in predicting the amount of water is crucial in the hydrologic drilling preparation process. Each geophysical method has its own conditions and limitations, making the use of a single method somewhat limited. Therefore, using integrated geophysical approaches to locate water sources allows for a more thorough analysis of subsurface rock characteristics and water availability, and to verify the validity of the methods. The DC resistivity method and the excitation polarization method are often used in the traditional groundwater exploration work.

The pilot area is located in the south of the mining area of Hami City, Xinjiang Province. The natural geographical conditions are extremely dry, the atmospheric precipitation is rare, no surface runoff and water body, and the groundwater is mainly replenished by the melting of snow and ice. In the northern mountains. The main rock types in this area are quaternary, Neogene and Jurassic sedimentary clastic rocks, and the main target aquifer is the pore-fissure aquifer of Neogene clastic rocks.

The experiment began:

In order to observe the impact of mining activities on groundwater and reduce the high-density resistance, the geophysical survey line is laid near a coal-fired power plant complex in the working area, and the riverbed is flat and dry (Figure 1). The surface soil of the riverbed is all compacted and cracked, and some vegetation grows. After digging out the compacted soil block, the electrode is inserted, with low resistance. The bank of the riverbed is covered with barren desert vegetation, with extremely high resistance compared with the riverbed, which is not suitable for high-density power survey. Therefore, two measuring lines, WT 1 and WT 2, were laid on the dry riverbed for high-density electrical and transient electromagnetic measurements.

Analytical methods for two different geophysical exploration equipment:

1. High-density electrical method analysis:

Figure 2 (a) and Figure 3 (a) show high-density resistivity imaging profiles for WT 1 and WT 2 lines with horizontal lengths of 500 m and 700 m, and vertical depth ranging from 0 to-150 m. These profiles exhibit consistent patterns of horizontal stratification across electrical information, with a characteristic trend of resistivity from low to high to low with increasing depth.

 2. Analysis of the transient electromagnetic method:

Figure 2 (b) and Figure 3 (b) show the inversion profiles of the WT 1 and WT 2 lines, respectively. The horizontal section length is 500 m and 700 m, respectively. Due to the blind zone in the shallow part of the transient EM method, the longitudinal depth range is-50~ -200 m. The overall electrical information of the section is distributed horizontally, and the resistivity from shallow to deep shows the law of "high resistance-low resistance-high resistance".

Considering the interpretation of high-density electric method and transient electromagnetic method, the resistivity change of the two exploration methods is basically the same, showing the law of alternating high and low. The high density electric method provides more detailed information on the shallow layer, which can effectively identify the relatively low resistance areas in the shallow and high resistance areas, and may indicate the water filling cracks of the bedrock. On the other hand, the transient EM method lacks shallow information, with low resistivity in-100 to-150 m, which corresponds to the results of the high-density method. It indicates the existence of a weak water-permeable layer, which provides important support for the aquifer localization.

It has been proved that the aquifer exposed by the borehole is a recent weak aquifer, and according to the pumping experiment, the water inflow is 82.512 m 3 / d. The results demonstrate the effectiveness of high density electric and transient electromagnetic combined detection.