A method for extracting information on thickness of a prospecting target layer based on CSAMT

Abstract

The application provides a CSAMT-based method for extracting thickness information of a prospecting target layer. The method comprises the following steps: obtaining original data by conducting CSAMT measurement; generating a two-dimensional inversion resistivity section according to the original data; combining with the resistivity parameter characteristics of rocks and ores, establishing an interpretation mark of the prospecting target layer in the two-dimensional inversion resistivity section; according to the interpretation mark, drawing the top interface and the bottom interface of the prospecting target layer in the two-dimensional inversion resistivity section, and reading the corresponding elevation data; calculating the thickness data of the prospecting target layer corresponding to each measuring point according to the elevation data; establishing the plane position and the thickness information data of the prospecting target layer of each measuring point; and drawing a thickness contour plan of the prospecting target layer. The application can project the thickness information of the prospecting target layer in the CSAMT two-dimensional inversion resistivity section to a plane, realize the display of the thickness of the prospecting target layer on the plane, and provide a basis and a reference for mineral resource exploration.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ore-prospecting target layer thickness information extraction, in particular to a CSAMT-based ore-prospecting target layer thickness information extraction method. BACKGROUND

[0002] Mineral resources are a very important natural resource, and also an indispensable material basis for the survival and development of human society. With the development of society and the continuous progress of science and technology, the demand for mineral resources by mankind has gradually increased. Although China has a rich variety of mineral resources and a high total amount, the per capita share is very small, which is difficult to meet the needs of China's economic development. In recent years, the state has continuously increased investment in mineral resource exploration to identify the distribution and potential reserves of mineral resources.

[0003] The controllable source audio magnetotelluric method (CSAMT) has the characteristics of strong anti-interference ability and high work efficiency, and can identify stratum structure, ore-prospecting target layer, and fault structure and other geological problems related to mineralization in mineral exploration, providing an important basis for exploration deployment, accelerating the progress of China's ore-prospecting process, and improving exploration efficiency. In particular, quickly identifying the thickness of the concealed target layer (ore body) plays a key role in guiding the deployment of later-stage projects.

[0004] At present, the interpretation content of CSAMT measurement data is mostly for the stratum structure, fault structure, and top interface burial depth and bottom interface burial depth of the target layer of a single survey line, and lacks related content specifically for the target layer thickness information extraction process and method, especially the target layer thickness distribution characteristics in the plane, so that the development of the target layer in the plane in the survey area cannot be understood as a whole and intuitively, and ultimately the basis and reference for mineral resource exploration cannot be accurately provided. SUMMARY

[0005] The purpose of the present application is to provide a CSAMT-based ore-prospecting target layer thickness information extraction method, to provide a new ore-prospecting target layer thickness information extraction method, and to provide a basis and reference for mineral resource exploration.

[0006] The present application is implemented as follows:

[0007] A CSAMT-based ore-prospecting target layer thickness information extraction method, comprising the following steps:

[0008] a. Conducting CSAMT measurement to obtain the original data of each survey point on each survey line in the survey area, including the coordinate information (including the plane position information (i.e. plane coordinates) and elevation information) of each survey point in the survey area and the CSAMT original data;

[0009] b. Data processing of the obtained original data, including static displacement correction, far zone data selection, terrain correction, and two-dimensional inversion;

[0010] c. According to the result of inversion, a two-dimensional inversion resistivity section of each survey line is drawn;

[0011] d. Collect, count and analyze the logging resistivity data of the survey area and surrounding boreholes, and extract the resistivity difference between the target layer and the upper and lower rock layers;

[0012] e. According to the resistivity difference between the target layer and the upper and lower rock layers, an interpretation mark of the target layer is established in the two-dimensional inversion resistivity section;

[0013] f. According to the interpretation mark of the target layer, the top and bottom boundaries of the target layer are drawn in the two-dimensional inversion resistivity section of each survey line;

[0014] g. The top and bottom boundary elevation information of the target layer of each survey point of each survey line is read;

[0015] h. According to the read top and bottom boundary elevation information of the target layer of each survey point of each survey line, the thickness information data of the target layer of each survey point of each survey line is calculated;

[0016] i. The thickness of the target layer of each survey point is matched with its plane position, and a matching relationship between the plane position of all survey points in the survey area and the thickness information data of the target layer is established;

[0017] j. According to the established matching relationship between the plane position of all survey points in the survey area and the thickness information data of the target layer, a thickness contour plane map of the target layer is drawn.

[0018] The step a of obtaining the original data includes the plane coordinates, elevation information and CSAMT original data of each survey point.

[0019] The static displacement correction and far zone data selection in step b are performed by Astatic software, and the terrain correction and inversion processing are performed by SCS2D inversion software.

[0020] The calculation of the thickness of the target layer in step h is based on the difference between the top and bottom boundary elevations of the target layer read in step g.

[0021] The plane position of the survey point in step i is the plane coordinates of each survey point obtained in step a, and the thickness information of the target layer is the thickness information data of the target layer calculated in step h.

[0022] The present application establishes a systematic method for extracting the thickness information of the target layer based on CSAMT, which can project the thickness information of the target layer in the CSAMT two-dimensional inversion resistivity section onto the plane, realize the display of the thickness of the target layer on the plane, and provide basis and reference for mineral resource exploration. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a method flowchart of the present application.

[0024] Figure 2 is a frequency-apparent resistivity and frequency-phase difference double logarithmic curve of CSAMT single measurement point raw data in an embodiment of the present application.

[0025] Figure 3 is a comparison chart before and after static displacement correction and far zone data selection processing in an embodiment of the present application.

[0026] Figure 4 is a two-dimensional inversion resistivity section generated by data processing in an embodiment of the present application.

[0027] Figure 5 is an interpretation mark chart of the ore-prospecting target layer in a two-dimensional inversion resistivity section in an embodiment of the present application.

[0028] Figure 6 is an interpretation chart of the top and bottom interfaces of the ore-prospecting target layer in an embodiment of the present application.

[0029] Figure 7 is a thickness contour plan of the ore-prospecting target layer in an embodiment of the present application. DETAILED DESCRIPTION

[0030] In combination Figure 1 , the method for extracting thickness information of an ore-prospecting target layer based on CSAMT provided by the present application comprises the following steps:

[0031] S1, CSAMT measurement is carried out to obtain standardized raw data. There are multiple survey lines in each survey area, and there are multiple measurement points on each survey line. The standardized raw data comprises coordinate information and CSAMT raw data of each measurement point. The coordinate information of each measurement point is obtained by using a handheld GPS and comprises longitude, latitude and altitude. The CSAMT raw data of each measurement point comprises apparent resistivity and phase difference data corresponding to the frequency of each measurement point, which can be represented by a frequency-apparent resistivity and frequency-phase difference double logarithmic curve, as shown in the following figure: Figure 2 The horizontal axis is frequency, the left vertical axis is apparent resistivity, the right vertical axis is phase difference, the solid line in the figure is the frequency-apparent resistivity double logarithmic curve, and the dashed line is the frequency-phase difference double logarithmic curve.

[0032] S2, the raw data is processed, specifically including static displacement correction, far zone data selection, terrain correction and two-dimensional inversion.

[0033] (1) Astatic.exe software provided by Zonge Company is used to perform static displacement correction processing and far zone data selection on the raw data of each survey line, Figure 3The contrastive graph before and after the static displacement correction and the far zone data selection processing: the Cagniard resistivity of the No. 176 measuring point before the processing is in the form of vertical strip, and the effect of the near surface electrical inhomogeneity is effectively eliminated after the processing, so that the useful information is reflected more obviously and clearly.

[0034] The far zone data refers to the data remaining after the near zone data is removed. The near zone data is characterized in the following two aspects: the Cagniard resistivity value on the double logarithmic graph of resistivity-frequency rises in the form of 45° straight line from high frequency to low frequency, and is independent of the geoelectric characteristics; the impedance phase tends to 0.

[0035] (2) The terrain correction and the two-dimensional inversion processing are performed by using the SCS2D inversion software.

[0036] S3, the inversion result obtained in step S2 is used to generate the final two-dimensional inversion resistivity section, as shown in FIG. 3, the horizontal coordinate is the planar distance corresponding to the measuring point, the vertical coordinate is the elevation corresponding to the measuring point, and the value of the contour line is the inversion resistivity value corresponding to the planar distance and the elevation of the measuring point. Figure 4

[0037] S4, the well logging resistivity data of the survey area and the surrounding drilling holes are collected, counted and analyzed, and the resistivity difference between the target layer and the upper and lower rock layers is extracted. Figure 5 According to the analysis, the layer A is the upper rock layer of the target layer, and is a relatively medium-high resistivity layer; the layer B is the target layer, and is a relatively low resistivity layer with discontinuous medium resistivity layer in the middle and upper part; and the layer C is the lower rock layer of the target layer, and is a relatively high resistivity layer. The target layer and the upper and lower rock layers have obvious resistivity difference.

[0038] S5, according to the resistivity difference between the target layer and the upper and lower rock layers, a typical target layer interpretation mark is established in the two-dimensional inversion resistivity section of the survey area, as shown in FIG. 4. Figure 5 The medium-high resistivity layer at the top of the section is the layer A, the low resistivity layer in the middle of the section is the target layer B, and the high resistivity layer at the bottom of the section is the layer C.

[0039] S6, according to the interpretation basis of the target layer established in step S5, the top and bottom boundaries of the target layer are drawn in the two-dimensional inversion resistivity section, and the top and bottom boundary interpretation graph of the target layer corresponding to the two-dimensional inversion resistivity section is generated, as shown in FIG. 5. Figure 6

[0040] S7, according to the top and bottom boundaries of the target layer drawn in step S6, the top and bottom boundary elevation information of the target layer of each measuring point of each measuring line is read from the two-dimensional inversion resistivity section.​​

[0041] S8, the absolute value of the difference between the top interface and the bottom interface elevation information data of each measuring point of each measuring line read according to step S7 is the thickness value of the ore-prospecting target layer of the measuring point.

[0042] S9, the thickness of the ore-prospecting target layer of each measuring point of each measuring line is matched with the plane coordinates (longitude, latitude) to establish a matching relationship between the plane position and the thickness information data of the ore-prospecting target layer of all measuring points in the survey area.

[0043] S10, the plane position and the thickness information data of the ore-prospecting target layer of all measuring points in the grid survey area are used to draw the thickness contour map of the ore-prospecting target layer, and finally Figure 7 .

[0044] The staff used the method to conduct a survey experiment in the Bayingebi Basin survey area, Figure 7 is the thickness contour map of the ore-prospecting target layer obtained in the survey area by the method. The CSAMT ore-prospecting target layer thickness information extraction method projects the CSAMT two-dimensional inversion resistivity section ore-prospecting target layer thickness information onto the plane to realize the display of the ore-prospecting target layer thickness on the plane, and provides a basis and reference for mineral exploration in the survey area.

Claims

1. A method for extracting information on the thickness of a prospecting target layer based on CSAMT, characterized in that, The method comprises the following steps: a. CSAMT measurement is carried out to obtain original data of each measuring point of each measuring line in the survey area; b. The obtained original data is processed, including static displacement correction, far zone data selection, terrain correction and two-dimensional inversion; c. According to the inversion result, a two-dimensional inversion resistivity section of each measuring line is drawn; d. Well logging resistivity data of the survey area and surrounding drill holes are collected, counted and analyzed to extract resistivity difference of the ore-prospecting target layer and upper and lower rock layers; e. According to the resistivity difference of the ore-prospecting target layer and upper and lower rock layers, an interpretation mark of the ore-prospecting target layer is established in the two-dimensional inversion resistivity section; f. According to the interpretation mark of the ore-prospecting target layer, the top and bottom boundaries of the ore-prospecting target layer are drawn in the two-dimensional inversion resistivity section of each measuring line; g. The top and bottom boundary elevation information data of the ore-prospecting target layer of each measuring point of each measuring line are read; h. According to the read top and bottom boundary elevation information data of the ore-prospecting target layer of each measuring point of each measuring line, the thickness information data of the ore-prospecting target layer of each measuring point of each measuring line are calculated; i. The thickness information data of the ore-prospecting target layer of each measuring point are matched with the plane position to establish a matching relationship between the plane position of all measuring points in the survey area and the thickness information data of the ore-prospecting target layer; j. According to the established matching relationship between the plane position of all measuring points in the survey area and the thickness information data of the ore-prospecting target layer, a thickness contour plane map of the ore-prospecting target layer is drawn.

2. The method for extracting information on the thickness of a target layer based on CSAMT for prospecting according to claim 1, characterized in that, The original data of each measuring point of each measuring line obtained in step a. contains plane coordinates, elevation information and CSAMT original data of each measuring point.

3. The method for extracting information on the thickness of a target layer based on CSAMT for prospecting according to claim 1, characterized in that, In step b, static displacement correction and far zone data selection are carried out by Astatic software, and terrain correction and two-dimensional inversion are carried out by SCS2D inversion software.

4. The method for extracting information on the thickness of a target layer based on CSAMT according to claim 1, characterized in that, In step h, the thickness of the ore-prospecting target layer is calculated according to the absolute value of the difference between the top and bottom boundaries of the ore-prospecting target layer read in step g.

5. The method for extracting information on the thickness of the target layer based on CSAMT according to claim 2, characterized in that, The plane position of the measuring point in step i is the plane coordinates of each measuring point obtained in step a.

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