CN110018521A - A kind of natural electric field diurnal correction method - Google Patents

Abstract

A natural electric field diurnal variation correction method. This method uses a natural electric field measuring device to collect the natural electric field signal of a known geological point at a certain time interval. According to the acquisition time, frequency and other parameters of the natural _electric field, the _{formula n} ,f)‑U _O (T _n ,f))*L _O /U _O (T _n ,f)/L _n to correct the natural electric field data of other measuring points, so as to eliminate random changes and interference of natural electric field signals , more realistically reflect the geological conditions of the survey area, improve the quality of natural electric field data in the entire survey area, and improve the exploration effect.

Description

A Kind of Correction Method for Diurnal Variation of Natural Electric Field

technical field

The invention relates to a natural electric field diurnal variation correction method for improving the natural electric field exploration effect in the field of exploration geophysics.

Background technique

In electrical exploration, there is a frequency selection method that uses the measurement of natural electric fields for geological exploration. This method uses two grounded measuring electrodes to directly measure the electric field signal strength of different frequencies of the natural electric field of the earth, without measuring the natural magnetic field of the earth, and without arranging an artificial electric field, so the method has high working efficiency, low exploration cost, and resistance to Humanistic electromagnetic interference ability is strong, and it has obvious advantages in geological exploration. However, because the excitation source of the natural electric field signal that forms the earth is not stable, not only the signal strength of excitation sources of different frequencies is different, but even the signal strength of excitation sources of the same frequency will change with time, so the obtained data at different times The natural electric field signal strength of the same frequency is different; in addition, the human electric field interference also changes with time; if the natural electric field data obtained at different times are directly interpreted, the signal strength of the excitation source and the human electric field interference at different times will be different. , resulting in a decrease in the comparability of natural electric field data obtained at different times, thus affecting the exploration effect of this method. This is also the main reason why the frequency selection method is currently used more as a preliminary qualitative exploration. At present, the daily variation correction method of natural electric field data based on the frequency selection method is generally to use the measured data at the measuring point and the measured data of the daily variation station for direct ratio calculation. Although this method can correct the daily variation to a certain extent, but Since the natural electric field data obtained in the field measurement process contains random interference signals, the direct ratio method cannot reduce the influence of random interference, thus affecting the exploration accuracy.

Based on the above problems existing in the current natural electric field exploration, in order to improve the exploration effect of this method, it is worthwhile to carry out research on the correction method of natural electric field diurnal variation in order to reduce the influence of random interference on the measured data and improve the exploration accuracy of natural electric fields.

Invention content:

The purpose of the present invention is to propose a natural electric field daily variation correction method based on the problems of low comparability of natural electric field signals at different times and poor exploration effect existing in the existing frequency selection method to reduce the natural electric field at different times and frequencies due to the natural electric field. The excitation source signal and the influence of changes in the human electric field, thereby improving the exploration accuracy and effect of the natural electric field.

A natural electric field diurnal variation correction method, the specific steps are as follows:

a) Select a known point where the geological conditions are basically known and the human electric field interference is small, and an electrical equipment for measuring the natural electric field is arranged to measure the natural electric field signal and Record the acquisition time of each measurement of the natural electric field, form the natural electric field signal time series data U _O (t,f) of the known point, and record the natural electric field measurement pole distance L _O of the known point; where t represents the acquisition time, f represents the frequency of the natural electric field signal, and o is the number of the known point. The selection of known points can be based on the previous geological achievements, and try to choose electrical equipment with simple geological conditions, stable strata, and little interference to arrange known points; the measurement time interval can be based on the storage space of the instrument. , the number of field measurement points, the requirements of exploration accuracy, etc.; in order to improve the stability of the natural electric field signal at the known points, non-polarized electrodes are used as the measurement electrodes; the electrical equipment for measuring the natural electric field at the known points can be set to measure the natural electric field The total field signal or the natural electric field frequency domain signal; the working parameters of the electrical method equipment for measuring the natural electric field at the known point are the same as the electrical method equipment for measuring the natural electric field at the measuring point, but the time interval for data collection can be different; The measurement time range for measuring the natural electric field completely covers the measurement time range for measuring the natural electric field at the measuring point.

b) Use other electrical equipment for measuring natural electric field in the exploration area to measure the natural electric field data U _n (T _n , f) of the measuring points in the exploration area; where T _n is the data collection time; n is a natural number, representing different The number of the measurement point; f represents the frequency of the natural electric field signal and is the same as the frequency value in step a); and record the natural electric field measurement pole distance L _n of the corresponding measurement point. Multiple or one natural electric field electrical equipment can be used to measure the natural electric field data of all measuring points in the exploration area. The system is poor; the electrical equipment of the natural electric field on the measuring point uses copper electrodes as the measuring electrodes, so as to reduce the difficulty of field work and improve the work efficiency; The working parameters of the electrical equipment are the same; the measurement time range of the natural electric field at the measuring point is completely included in the measurement time range of the natural electric field at the known point.

c) according to the natural electric field data acquisition time T _n of the measuring point in step b); wherein n is a natural number, representing the number of different measuring points; the time series data U _O ( In t,f), the natural electric field signal U O (T n ,f) of the known point at the same acquisition time T _n and the same frequency as the natural electric field data of the corresponding measuring point in step b) is selected, and the natural electric field signal U _O (T _n ,f) obtained in step b) The natural electric field data U _n (T _n , f) of the same acquisition time T _n and the same frequency of the measuring point adopts the formula F _n (f)=(U _n (T _n ,f)-U _O (T _n ,f)) *L _O /(U _O (T _n ,f)*L _n ) is calculated to obtain F _n (f) data of corresponding measuring points and corresponding frequencies after daily variation correction. Since there is always some random interference in the natural electric field data measured in the field, and there is a certain degree of correlation between the random interference of the natural electric field data at the known point at the same moment and the natural electric field data on the measurement point, the use of (U _n (T _n , The method of calculating the difference between f)-U _O (T _n , f)) can reduce the influence of random interference signals in the difference, and then calculate the ratio with the daily variation data of the known points, which can further reduce the random interference Therefore, the obtained F _n (f) data more realistically reflect the actual geological situation. If there is a systematic difference in the electrical equipment of the natural electric field, the F _n (f) data should be systematically corrected to eliminate the systematic error between different instruments and further improve the exploration effect; the F _n ( f) The data eliminates the data changes caused by the different signal strength of the excitation source of the natural electric field and the interference of the human electric field at different times, and increases the comparability of the natural electric field data of the measuring points in the entire survey area, thereby improving the exploration effect and efficiency. Exploration accuracy.

d) Combined with the known geological conditions of the known points, map, analyze and interpret the F _n (f) data of all frequencies of all the measuring points, and judge the geological conditions of all the measuring points. Obtain the geological stratification and electrical characteristics of the known points, and draw the _geoelectric cross-section in combination with other achievements; The frequency value of , can qualitatively divide the geological layers, geological anomalies, etc. of all measuring points. When the F _n (f) of a certain frequency of a certain measuring point is equal to or close to 0, it means that the electrical characteristic reflected by the frequency of the measuring point is the same as the electrical characteristic reflected by the corresponding frequency of the known point or Similar; if the F _n (f) of a certain frequency of a certain measuring point is significantly greater than 0, it means that the electrical characteristics reflected by the frequency of the measuring point are different from those reflected by the corresponding frequencies of the known points. In other words, there is a high-resistance anomaly response, and the greater the difference, the greater the high-resistance anomaly trend; if the F _n (f) of a certain frequency of a certain measuring point is significantly less than 0, it indicates that the frequency of the measuring point reflects Compared with the electrical characteristics reflected by the corresponding frequencies of the known points, the electrical characteristics present a low-resistance anomaly response, and the greater the difference, the greater the low-resistance anomaly trend; The situation is comprehensively judged and interpreted based on the geological characteristics of the known points.

The natural electric field signals and data obtained from the known points and the measuring points in the above steps are normalized according to the measuring pole distance of the corresponding points. The purpose is to reduce the signal caused by the different lengths of the measuring electrodes at different measuring points. It can also arrange measurement electrodes that are more in line with the field site according to the actual situation of different measuring points in field work, reduce the difficulty of field work, and enhance the field adaptability and flexibility of the method.

The frequency selection method for measuring natural electric fields has high working efficiency and low exploration cost, but the exploration accuracy is low. After the daily variation correction carried out through the above methods, the exploration accuracy of the frequency selection method can be improved, thereby expanding the scope of application of this method and realizing Get higher exploration results with high exploration efficiency.

Description of drawings:

Fig. 1 is a kind of flow chart of the natural electric field diurnal variation correction method of the present invention;

Fig. 2 is the flow chart of the conventional exploration method of the existing natural electric field;

FIG. 3 is a schematic diagram of field layout of field measured data of a natural electric field diurnal variation correction method of the present invention.

In Figure 3, O is a known point with known geological conditions, 1 to 36 are the numbers of 36 measuring points, the solid cross symbol indicates the position of the known point, and the solid point symbol indicates the position of the measuring point.

Detailed ways:

The present invention will be further described below with reference to FIG. 1 , FIG. 2 , and FIG. 3 in conjunction with specific embodiments.

As shown in Figure 3, it is necessary to carry out natural electric field exploration using the new method of diurnal variation correction proposed by the present invention for 36 measuring points in the exploration area in Figure 3. The specific steps are as follows:

1) Select two electrical equipment for measuring natural electric field, first perform the consistency test of the two electrical equipment, control the system difference of the two instruments within the error range or obtain the system difference of the two instruments, use one of the electrical methods The instrument is used as the benchmark, and the measurement results of the other instrument are systematically corrected.

2) In the exploration area, choose a known point where the geological conditions are basically known and the interference of the human electric field is small. Deploy an electrical equipment that measures the total field of the natural electric field through two measuring electrodes; in order to improve the stability of the natural electric field signal at the known points , the measurement electrodes used on the known point O are non-polarized electrodes, and the distance between the two measurement electrodes is 50 meters; according to the time interval of one measurement per minute, measure the natural electric field of the known point O at different times and corresponding frequencies The signal U _O (t,f) and the acquisition time of each measurement of the natural electric field and the frequency of the natural electric field signal are recorded to form the time series data of the natural electric field signal of the known point O.

3) Arrange 36 measuring points numbered 1 to 36 in the exploration area. When the electrical method equipment on the known point O starts to collect the natural electric field data, another electrical method equipment for measuring the total natural electric field will be used. Two measuring electrodes arranged at each measuring point collect the natural electric field data collection of each measuring point, wherein the distance between the two measuring electrodes at each measuring point is 20 meters; the natural electric field of 36 measuring points is recorded Data U _n (T _n , f) (n=1, 2, 2....36), where T _n (n=1, 2, 2....36) is the moment when natural electric field data is collected for each measuring point, f is the frequency of the natural electric field signal of the corresponding measuring point; the electrical equipment of the natural electric field on each measuring point uses copper electrodes as the measuring electrodes, which can reduce the difficulty of field work and improve the work efficiency; the electrical equipment of the natural electric field of the measuring point The instrument parameters are the same as those of the electrical equipment for the natural electric field at the known point O, but the time interval for data collection by the two electrical equipment can be different; Then stop the natural electric field data acquisition at the known point O.

4) According to the natural electric field data collection time T _n (n=1, 2, 2....36) and the corresponding frequency of the 36 measuring points in step 3), the natural electric field signal of the known point O obtained from step 2) is The time series data selects the natural electric field signal U _O (T of the known point O at the same collection time T _n (n=1, 2, 2....36) and the same frequency as the natural electric field data of the corresponding measuring point in step 3). _n , f) (n=1, 2, 2....36), for the acquisition time T _n (n=1, 2, 2....36) obtained in step 3), the natural electric field of the measuring point corresponding to the same frequency Data U _n (T _n , f) (n=1,2,2....36) adopts F _n (f)=(U _n (T _n ,f)-U _O (T _n ,f))*50/ (U _O (T _n ,f)*20) formula is calculated to obtain the F _n ( _f ) data of the corresponding frequency of the corresponding measuring point; ) data to carry out systematic error correction to eliminate the systematic errors between different instruments and further improve the exploration effect; the F _n (f) data of all measuring points processed in the above way eliminates the fact that the excitation source signal strength of the natural electric field is different at different times, The data changes caused by different human electric field interference increase the comparability of the natural electric field data of the measuring points in the entire survey area, thereby improving the exploration effect and exploration accuracy.

5) Combine the known geological conditions of the known points, analyze and interpret the F _n (f) data of the corresponding measuring points, and judge the geological conditions of the corresponding measuring points; obtain the geological stratification and electrical properties of the known points. According to the geological information such as the geoelectric cross-section of the known points, combined with the F _n (f) data of all the measuring points, the geological layers and geological anomalies of all the measuring points are divided . When the F _n (f) of a certain frequency of a certain measuring point is equal to or close to 0, it means that the electrical characteristics reflected by the frequency of the measuring point are the same as those reflected by the corresponding frequency of the known point O Or similar; if the F _n (f) of a certain frequency of a certain measuring point is obviously greater than 0, it indicates that the electrical characteristics reflected by the frequency of the measuring point are relative to the electrical characteristics reflected by the corresponding frequency of the known point O In terms of characteristics, there is a high-resistance anomaly response, and the greater the difference, the greater the high-resistance anomaly trend; if the F _n (f) of a certain frequency at a certain measuring point is significantly less than 0, it indicates that the frequency of the measuring point is not the same. Compared with the electrical characteristics reflected by the corresponding frequency of the known point O, the electrical characteristics of the reaction show a low-resistance abnormal response, and the greater the difference, the greater the low-resistance anomaly trend; The geological anomalies of , are comprehensively judged and interpreted based on the geological characteristics of the known point O.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the present invention.

Claims (1)

1. a natural electric field diurnal variation correction method, its concrete steps are as follows: a) Select a known point where the geological conditions are basically known and the human electric field interference is small, and an electrical equipment for measuring the natural electric field is arranged to measure the natural electric field signal and record the natural electric field signal of a certain time period and certain frequency of the known point according to a certain time interval Each time the natural electric field is measured at the acquisition time, the natural electric field signal time series data U _O (t,f) of the known point is formed, and the natural electric field measurement pole distance L _O of the known point is recorded; where t represents the acquisition time, and f represents The frequency of the natural electric field signal, o is the number of the known point; b) Use other electrical equipment for measuring natural electric field in the exploration area to measure the natural electric field data U _n (T _n , f) of the measuring points in the exploration area; where T _n is the data collection time; n is a natural number, representing different The number of the measuring point; f represents the frequency of the natural electric field signal and is the same as the frequency value in step a); and record the natural electric field measurement pole distance L _n of the corresponding measuring point; c) According to the natural electric field data acquisition time T _n and the frequency parameter of the measurement point in step b); wherein n is a natural number, representing the number of different measurement points; the time series data of the natural electric field signal of the known point obtained from step a) From U _O (t,f), select the natural electric field signal U _O (T _n ,f) of the known point at the same acquisition time T _n and the same frequency as the natural electric field data of the corresponding measuring point in step b). ) The natural electric field data U _n (T _n , f) at the same acquisition time T _n and the same frequency obtained at the measuring point adopts the formula F _n (f)=(U _n (T _n ,f)-U _O (T _n , f))*L _O /(U _O (T _n ,f)*L _n ) is calculated to obtain the F _n (f) data of the corresponding measuring points and corresponding frequencies after the daily variation correction; d) Combined with the known geological conditions of the known points, map, analyze and interpret the F _n (f) data of all frequencies of all the measuring points, and judge the geological conditions of all the measuring points.