The detection method and the application of several aspects are used for comprehensive evaluation.
First, the principle and method of geophysical instrument determine the accuracy of its water and well
At present, the most long-time users are the electrical instruments of the artificial field source time domain (including resistivity method).
Instrument, high-density resistivity method, excitation polarization method), because it is limited by the depth of the earth feeding, the geographical environment of the cable, the high-resistance and low-resistance of the underground, and so on, combined with the labor and long time The well location is selected only by the sounding data of several points detected in one day. It can only be speculated whether there is a fault structure, the depth of the aquifer, and the location of the detected points, but for the underground faults and fissures. The location and orientation of the structure, the distribution of the aquifer, etc. are not known. Just like a scorpion touching an elephant, just touching a few points, it is hard to imagine the appearance of an elephant.
Second, the performance indicators of geophysical instrument hardware determine the accuracy of picking up underground lithology information.
Although the principles and implementation methods of many geophysical methods are different, the purpose is to pick up as much as possible.
Take useful information about underground lithology. First, the probe of the primary pick-up signal is sensitive, and it can pick up the weak electromagnetic signal of the microvolt level. Second, the amplification factor and linearity of the signal are high, so that the precision amplification is not distortion; the third is strong anti-interference ability. Various filtering methods remove high frequency and high frequency interference; Fourth, the accuracy of the analog-to-digital conversion and control devices used is high enough to be accurate to 0.01 or 0.001 microvolts.
Third, the resolution of the detectable underground depth layer determines the accuracy of finding water and fixing wells.
Just as the higher the resolution of the TV is, the more clearly it is, the more the depth depth layer that can be detected, the more layered
The finer the resolution, the more the detected underground lithology information becomes clearer, and the accuracy of the well is definitely higher. The detection depth of the electric instrument depends on the length of the two-wire cable feeding to the earth. The data measured by the 100-meter cable of the cable contains comprehensive information within 100 meters of the underground. The length measured by one length is the depth layer of the point. Data, in theory, can be infinitely layered to increase resolution, but time is not allowed. Generally, it is detected in the shallow part by 10 meters/layer, and the distance between the layers is gradually increased by 100 meters. Even if such a detection point is tossed for about 2 hours, it is good to do the sounding of four or five points a day. It is very important to find more water and to rely on hydrogeological knowledge and analysis and judgment of limited detection data.
For the natural field source geophysical instrument, the most common manufacturer on the market is the natural electric field frequency selector.
There are 3 frequency points for detection, and there are also 5 frequency points. According to the principle of convergence depth effect, each frequency point corresponds to one depth layer. Only three or five depth layers should reflect the geological conditions of 300 meters underground. The accuracy is definitely not enough. Even the imported geophysical instrument EH-4, which sells for up to 670,000, can only detect 20 depth layers above 800 meters, and the detection accuracy is limited.
Fourth, the geophysical data analysis method determines the accuracy of its water and well drilling
Generally, there are two methods for the geophysical instrument to directly display the detection data for analysis. One is a single point deep.
The connection diagram of the degree data, the electric instrument can only perform single point sounding analysis because of the small number of detection points; the other is the connection diagram of the data of each detection point of a certain depth layer, the tri-frequency point frequency selector can A connection diagram of 3 depth layers is made to observe the changes in the lithology of the 3 deep depth layers on the detection line. All instruments, including imported instruments such as V8, GDP32, and EH4, can indirectly input the detection data into the Surfer drawing software to draw a color two-dimensional contour map of the detection line. The only difference is that the more valid data is input. The more realistic the image reflects the underground situation, some of the graphics masters can use the Surfer software to draw a nice color equivalent color map with only three or four points of sounding data.
5. Field exploration work and experience have a great influence on the accuracy of finding water and wells.
Even if you use the same kind of geophysical instrument, the method of spot detection in the field, the understanding of geology,
The accuracy of the actual well-fixing is directly determined by the analysis and judgment experience of the detected data.
Many occupations have been looking for water for several decades. The resistivity meter and the electro-opometer are used to find the artificial field source.
Water wells work, and there are also many experts, the accuracy of wells is also high. Sometimes, using high-grade imported geophysical equipment to find water and wells in water-deficient areas, like anti-aircraft guns to fight mosquitoes, the accuracy of well fixing is also not high.