A direct current method data acquisition system and method

Abstract

The application discloses a direct current method data acquisition system and method, which comprises a power supply, a measuring host, an electrode converter and a measuring cable. The power supply is used for providing power supply for the whole system. The electrode converter is connected with the measuring host. The measuring cable is connected with the electrode converter. Two ends of the measuring cable are respectively connected with first cables. Each measuring cable is connected with at least one second cable in series. A plurality of first electrodes are connected on the first cable. A plurality of second electrodes are connected on the second cable. The interval between two adjacent first electrodes connected on the first cable is greater than the interval between two adjacent second electrodes connected on the second cable. The application uses high-density electrical method equipment, connects the large electrode distance cable, simultaneously carries out the intermediate gradient profile measurement and the electric sounding measurement, guarantees the data density, reduces the boundary blind area range and increases the exploration depth.

Description

Technical Field

[0001] This invention relates to the field of geophysical exploration technology, specifically to a direct current resistivity data acquisition system and method. Background Technology

[0002] Electrical resistivity tomography (IRM) is one of the most widely used geophysical methods in geological exploration. The direct current method (DC method) is based on the electrical differences in underground rocks (ores). It involves artificially establishing a stable DC electric field underground and utilizing the transmission and distribution patterns of DC current to detect the structure and physical properties of underground geological materials. In DCM, a current of a certain magnitude and direction is applied to the surface or underground, and the electrical parameters of the underground medium are measured using two or more sets of electrodes. The variation patterns are analyzed to infer the conductivity and structural characteristics of the underground medium, thereby inferring the underground geological structure, stratigraphic properties, and hydrogeological conditions. This method is suitable for detecting geological bodies with large differences in underground resistivity, such as mineral deposits, rock masses, and groundwater layers.

[0003] Currently, DC resistivity tomography (DC tomography) typically employs high-density electrical resistivity equipment. This equipment deploys multiple sets of electrodes simultaneously, with automatic electrode movement controlled by a controller, enabling simultaneous resistivity depth measurement and profile measurement. It boasts high measurement efficiency and high data density. However, limitations in array length and equipment type restrict exploration depth (conventional high-density electrical resistivity instruments can only connect a limited number of electrodes with fixed spacing, resulting in limited exploration depth). This is especially true for devices like the intermediate gradient method, which uses a large electrode spacing, where the AB length is limited, significantly reducing exploration depth. While the array length can be extended using multiple series cables, this method is always limited by the equipment's load-bearing capacity, and most electrodes are underutilized, leading to low implementation efficiency and unsatisfactory results.

[0004] Furthermore, conventional high-density electrical resistivity tomography is limited by its working methods, which restricts its exploration depth and spatial resolution, making it difficult to achieve high-resolution imaging of deep targets, especially in complex geological environments where exploration faces numerous challenges.

[0005] Furthermore, current DC electrical resistivity tomography (EDT) is primarily two-dimensional. In practical engineering, geological structures and target bodies typically exhibit complex three-dimensional spatial distributions. Two-dimensional EDT struggles to accurately reflect the spatial location and morphology of anomalies, making geological interpretation of these anomalies challenging. Three-dimensional EDT, however, can effectively address these issues. When using high-density EDT equipment for three-dimensional EDT, parallel or mesh-like survey lines are typically used. These lines collect data independently and without correlation, resulting in a lack of spatial correlation and effectively creating "pseudo-three-dimensional" exploration that fails to accurately reflect the spatial location and morphology of anomalies. Summary of the Invention

[0006] The purpose of this invention is to overcome at least one defect in the prior art and provide a DC electrical resistivity tomography data acquisition system and method. It utilizes existing high-density electrical resistivity tomography equipment, connects to a large-pitch cable, and simultaneously performs intermediate gradient profile measurement and electrical sounding measurement. While ensuring data density, it reduces the boundary blind zone and increases the exploration depth.

[0007] The technical solution of this invention is implemented as follows: This invention discloses a DC electrical resistivity data acquisition system, including a power supply, a measurement host, an electrode converter, and a measuring cable. The power supply is used to provide power to the entire system. The electrode converter is connected to the measurement host, and the measuring cable is connected to the electrode converter. Each end of the measuring cable is externally connected to a first cable. Each measuring cable is composed of at least one second cable connected in series. A plurality of first electrodes are connected to the first cables, and a plurality of second electrodes are connected to the second cables. The interval between two adjacent first electrodes connected to the first cables is greater than the interval between two adjacent second electrodes connected to the second cables.

[0008] In some embodiments, the measurement host is a high-density electrical resistivity meter;

[0009] or / and,

[0010] The first cable is a large-pitch cable;

[0011] or / and,

[0012] The second cable is a centralized cable.

[0013] In some embodiments, the two ends of the test cable are respectively connected to the first cable through a cable connector. When the test cable is composed of multiple second cables connected in series, two adjacent second cables are connected in series through a cable connector. The electrode converter is connected to the cable connector.

[0014] In some embodiments, the spacing between two adjacent first electrodes is n times the spacing between two adjacent second electrodes, where n>1.

[0015] This invention discloses a method for acquiring DC resistivity data, comprising the following steps:

[0016] Step 1: Lay out the measuring cable along the measuring line, connect the measuring cable to the electrode converter, connect the electrode converter to the measuring host, and connect the two ends of the measuring cable to the first cable. Each measuring cable is composed of at least one second cable connected in series. Several first electrodes are connected to the first cable, and several second electrodes are connected to the second cable.

[0017] Step 2: Use the two first electrodes as power supply electrodes AB and the two second electrodes as measuring electrodes MN. The measuring electrodes MN are located between the power supply electrodes AB. Determine the initial power supply electrode spacing and the measuring electrode spacing.

[0018] Step 3: Keeping the distance between the power supply electrodes and the distance between the measuring electrodes constant, measure point by point along the measuring line to complete one middle step sweep measurement;

[0019] Step 4: If the data does not meet the exploration depth requirements, the electrode spacing of the power supply electrodes is increased by equal distances, and Step 3 is repeated to perform the mid-step sweep measurement until the data meets the exploration depth requirements. The measurement is then completed, and multiple sets of mid-step sweep data at different depths are obtained.

[0020] In some embodiments, the DC electrical resistivity data acquisition method of the present invention further includes step 5: processing and inverting multiple sets of intermediate gradient scan data at different depths to finally obtain a DC electrical resistivity result profile at a greater depth.

[0021] In some embodiments, in step 2, the electrode spacing of the measuring electrode is 1 to 2 electrode spacings, and the electrode spacing of the power supply electrode ranges from 3 to 5 times the exploration depth.

[0022] In some embodiments, in step 3, the measurement point corresponding to the measurement data is the midpoint of the measurement electrode MN, and the specific calculation formula for the depth Z of the measurement point is: n≤3, Z=0.18AB; 3<n≤10,Z=0.19AB;n> 10, Z = 0.25; where n is the interval coefficient.

[0023] In some embodiments, in step 3, the measurement point location corresponding to the measurement data is the midpoint of the measurement electrode MN, and the specific formula for calculating the depth of the measurement point is:

[0024]

[0025] Where α is the proportionality coefficient. The proportionality coefficient α is determined empirically, based on the distance between the measuring electrodes and the distance between the power supply electrodes.

[0026] In some embodiments, after step 4 is completed, the electrode spacing of the measuring electrodes is changed, and steps 3-4 are repeated.

[0027] In some embodiments, after step 4 is completed, the measuring cable is moved parallel to the side measuring line, and steps 2-4 are repeated to obtain three-dimensional measurement data.

[0028] The present invention has at least the following beneficial effects: The DC electrical resistivity data acquisition system and method proposed in this invention are based on existing high-density electrical resistivity equipment, with an external first cable, and simultaneously perform intermediate gradient profile measurement and electrical sounding measurement. Compared with traditional acquisition methods, it improves the density and breadth of data acquisition, reduces the data blind zone range of the boundary area, and enhances the penetration of conductive strata. While maintaining shallow resolution, it enhances the vertical extension of anomalies and can increase the exploration depth by 2 to 4 times. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of a DC electrical resistivity data acquisition system provided in one embodiment of the present invention;

[0031] Figure 2 A flowchart illustrating the workflow of a DC electrical data acquisition method according to an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the electrode arrangement provided in one embodiment of the present invention;

[0033] Figure 4 A schematic diagram of electrode arrangement provided for another embodiment of the present invention;

[0034] Figure 5 A flowchart illustrating the workflow of a DC electrical data acquisition method according to another embodiment of the present invention;

[0035] Figure 6 The following are spatial distribution diagrams of data for a hybrid device provided in another embodiment of the present invention: (a) is a spatial distribution diagram of data for a dipole-dipole and intermediate-ladder hybrid device; (b) is a spatial distribution diagram of data for a positive and negative tripolar, intermediate-ladder, and intermediate-ladder depth sounding hybrid device; and (c) is a spatial distribution diagram of data for an intermediate-ladder and intermediate-ladder depth sounding hybrid device.

[0036] Figure 7 This is a schematic diagram for measuring a polar distance of a and an interval coefficient of n;

[0037] Figure 8 This is a schematic diagram of a series of polar distance measurements and the corresponding interval coefficient sequence. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" or "several" means two or more.

[0041] Electrical resistivity tomography (ERT) is one of the most widely used geophysical exploration methods in geological exploration. It is a geophysical exploration method that utilizes the differences in electrical properties of underground rocks (ores) to artificially establish a stable underground direct current electric field. By using two or more sets of electrodes to measure the electrical parameters of the underground medium and analyze their variation patterns, it can solve related geological problems.

[0042] Currently, DC electrical resistivity exploration typically employs high-density electrical resistivity equipment, which deploys multiple sets of electrodes at once and automatically moves the electrodes via a controller, simultaneously achieving resistivity depth measurement and profile measurement. It features high measurement efficiency and high data density.

[0043] Direct current methods include resistivity profiling, resistivity depth measurement, charging method, and excited polarization method.

[0044] The resistivity sounding method is based on the electrical differences of underground rocks (minerals). It artificially establishes a stable DC electric field underground and observes and analyzes the resistivity variation of rock (mineral) layers at different depths in the vertical direction at the same measuring point by gradually increasing the power supply and the electrode spacing.

[0045] The resistivity profiling method is based on the electrical differences of underground rocks (minerals). It involves artificially establishing a stable DC electric field underground, keeping the electrode spacing constant, and observing point by point along the survey line to analyze the variation law of the resistivity of the rock (mineral) layer in the horizontal direction within a certain depth range.

[0046] The high-density electrical resistivity method is based on the electrical differences of underground rocks (minerals). It artificially establishes a stable DC electric field underground and uses electrode array technology to simultaneously measure resistivity depth and resistivity profile, thereby obtaining the resistivity distribution law of underground rock (mineral) layers in two or three dimensions.

[0047] In addition, the central gradient array method is a commonly used and important method in DC resistivity tomography. This method keeps the power supply electrode stationary at the distance from AB and the distance between the measuring electrodes MN constant. It moves point by point along the survey line within the middle 1 / 2 to 1 / 3 of AB, observes the potential difference between MN, and calculates the apparent resistivity value at each measuring point (midpoint of MN). Its exploration depth is approximately 1 / 6 of the length of AB. When using high-density resistivity tomography equipment, the exploration depth is limited by the working array length. To address this problem, this invention increases the array length by using an external large-pole cable, while avoiding the addition of ineffective electrodes, to achieve multi-pole central gradient depth sounding, thereby enabling rapid data acquisition and analysis.

[0048] like Figure 7 The measured polar distance is 'a', and the interval coefficient is 'n'. Customizing the measured polar distance series and corresponding interval coefficient sequences refers to selecting different values ​​of 'a' and 'n' for data acquisition as needed. For example, 'a' and 'na' can be multiples of the basic track spacing in an arithmetic sequence, such as... Figure 8 As shown, one example is that the distance between the measuring electrodes P1 and P2 is set sequentially in multiples of the channel pitch [1 to 5]. Corresponding to each measurement sequence, the distance between the power supply electrodes C1 and C2 is set in multiples of the channel pitch as {1 to 6}, {6 to 11}, {11 to 16}, {16 to 21}, and {21}. The values ​​of a and n in this invention are selected as needed and are not limited to the above example.

[0049] Example 1

[0050] See Figures 1 to 4This invention provides a DC electrical resistivity data acquisition system, including a power supply, a measurement host, an electrode converter, and a measuring cable. The power supply provides power to the entire system. The electrode converter is connected to the measurement host, and the measuring cable is connected to the electrode converter. Each end of the measuring cable is externally connected to a first cable. Each measuring cable is formed by connecting at least one second cable in series. A plurality of first electrodes are connected to the first cables, and a plurality of second electrodes are connected to the second cables. The interval between two adjacent first electrodes connected to the first cables is greater than the interval between two adjacent second electrodes connected to the second cables.

[0051] The electrode converter is connected to the cable connector between the second cable and the second cable. Preferably, the electrode converter is connected to the intermediate cable connector.

[0052] In some embodiments, the measuring host is a high-density electrical resistivity meter; the first cable is a large-pitch cable; and the second cable is a conventional cable, such as a centralized cable.

[0053] In some embodiments, the two ends of the test cable are respectively connected to the first cable through a cable connector. When the test cable is composed of multiple second cables connected in series, two adjacent second cables are connected in series through a cable connector. The electrode converter is connected to the cable connector.

[0054] The first electrodes connected by the two first cables are arranged symmetrically.

[0055] In some embodiments, the spacing between two adjacent first electrodes is n times the spacing between two adjacent second electrodes, that is, the electrode spacing of a large-pitch cable is n times the electrode spacing of a conventional cable (n>1). n is generally taken as an integer.

[0056] The power supply for this invention can be a battery box. The high-density electrical resistivity tomography (EP tomography) instrument can utilize existing commercially available high-density EP instruments. The electrode converter is connected to the high-density EP instrument and is controlled by the instrument. The battery box is connected to the electrode converter to provide a stable current to the measurement system. Conventional cables are directly connected to the high-density EP instrument or other conventional cables, while large-pitch cables are connected to the conventional cables at the end of the array. Cable connectors are used to connect conventional cables in series, as well as conventional cables and large-pitch cables. Electrodes are used to measure underground potential and current.

[0057] In some embodiments, the high-density electrical resistivity meter host supports a series centralized cable connection, which can connect no less than 4 cables and supports custom acquisition parameters.

[0058] In some embodiments, the electrode converter is controlled by the high-density electrical resistivity instrument host, which in turn controls the power supply and measurement of the measuring electrodes.

[0059] In some embodiments, the conventional cable is a centralized cable, and several electrodes can be connected to the cable. Multiple conventional cables can be connected together through the cable connector to form a test line cable.

[0060] In some embodiments, multiple conventional cables connected in series are connected to an electrode converter to form a conventional measurement arrangement.

[0061] In some embodiments, the large-pitch cable can be a centralized cable, on which several power supply electrodes can be connected. The large-pitch cable is connected to the two conventional cables at the end of the conventional measurement arrangement described above via a cable connector.

[0062] In some embodiments, the electrodes connected to the conventional cable and the large-pitch cable are evenly spaced, except that the spacing between the electrodes connected to the large-pitch cable is n times that of the electrodes connected to the conventional cable.

[0063] Example 2

[0064] See Figures 1 to 4 This invention discloses a direct current resistivity data acquisition method, comprising the following steps:

[0065] Step 1: Lay out the measuring cable along the measuring line, connect the measuring cable to the electrode converter, connect the electrode converter to the measuring host, and connect the two ends of the measuring cable to the first cable. Each measuring cable is composed of at least one second cable connected in series. Several first electrodes are connected to the first cable, and several second electrodes are connected to the second cable.

[0066] Step 2: Use the two first electrodes as power supply electrodes AB and the two second electrodes as measuring electrodes MN. The measuring electrodes MN are located between the power supply electrodes AB. Determine the initial power supply electrode spacing and the measuring electrode spacing.

[0067] Step 3: Keeping the distance between the power supply electrodes and the distance between the measuring electrodes constant, measure point by point along the measuring line to complete one middle step sweep measurement;

[0068] Step 4: If the data points do not meet the exploration depth requirements, the electrode spacing of the power supply electrodes is increased by equal distances, and Step 3 is repeated to perform the mid-step sweep measurement until the data points meet the exploration depth requirements. Once the measurement is completed, multiple sets of mid-step sweep data at different depths are obtained.

[0069] In some embodiments, the DC electrical resistivity data acquisition method of the present invention further includes step 5: processing and inverting multiple sets of intermediate gradient scan data at different depths to finally obtain a DC electrical resistivity result profile at a greater depth.

[0070] In some embodiments, in step 2, the electrode spacing of the measuring electrode is 1 to 2 electrode spacings, and the electrode spacing of the power supply electrode ranges from 3 to 5 times the exploration depth.

[0071] In some embodiments, in step 3, the measurement point location corresponding to the measurement data is the midpoint of the measurement electrode MN, and the specific formula for calculating the depth Z of the measurement point is:

[0072] n≤3, Z=0.18AB;

[0073] 3 <n≤10,Z=0.19AB;

[0074] When n>10, Z=0.25;

[0075] Where n is the isolation coefficient (i.e., the interval coefficient), and AB is the electrode spacing of the power supply electrodes.

[0076] In other embodiments, in step 3, the measurement point corresponding to the measurement data is the midpoint of the measurement electrode MN, and the specific formula for calculating the depth of the measurement point is:

[0077]

[0078] Where α is the proportionality coefficient. The proportionality coefficient α is determined empirically, based on the distance between the measuring electrodes and the distance between the power supply electrodes.

[0079] In some embodiments, after step 4 is completed, the electrode spacing of the measuring electrodes is changed, and steps 3-4 are repeated.

[0080] In some embodiments, after step 4 is completed, the measuring cable is moved parallel to the side measuring line, and steps 2-4 are repeated to obtain three-dimensional measurement data.

[0081] The process of Example 2 will be described in detail below through specific examples.

[0082] Step 1: Lay out several conventional cables along the survey line according to the task requirements, and connect large-pitch cables at the end of the arrangement, and connect the high-density electrical resistivity meter main unit, electrode converter, battery box, electrodes, etc. in sequence;

[0083] Step 2: Designate the pair of electrodes in the large-pitch cable that are closest to the conventional cable as the power supply electrodes AB, and designate the pair of electrodes in the conventional cable that are close to each other as the measurement electrodes MN.

[0084] Step 3: Keeping the positions of the power supply electrode AB and the distance between the measuring electrode MN unchanged, move the measuring electrode MN synchronously from one end of the arrangement to the other end, measure point by point, and complete one mid-step gradient scan measurement.

[0085] Step 4: Gradually increase the distance between the power supply electrodes AB at equal intervals, and repeat Step 3 to perform mid-gravity surface scanning measurement to obtain multiple sets of mid-gravity surface scanning data at different depths;

[0086] Step 5: Process and invert the data collected by the above methods to finally obtain a more in-depth DC electrical resistivity tomography profile.

[0087] Furthermore, after step 4 is completed, the distance of the measuring electrode MN can be changed, and the above measurement steps can be repeated to obtain more measurement data.

[0088] Furthermore, after step 4 is completed, the conventional cable can be moved to a parallel side test line, and the above measurement steps can be repeated to obtain three-dimensional measurement data.

[0089] In step 2, the setup of the power supply and measuring electrodes can be automatically completed by the high-density electrical resistivity tomography (EDT) instrument. The electrode switching in subsequent steps can also be automatically completed by the high-density EDT instrument. In step 2, the electrodes in the large-pitch cable are always used as power supply electrodes, and the electrodes in the conventional cable are always used as measuring electrodes. In step 2, the distance between the measuring electrodes MN is generally selected as 1 to 2 electrode pitches, and the distance between the power supply electrodes AB is generally selected as 3 to 5 times the exploration depth.

[0090] This invention is based on existing high-density electrical resistivity tomography equipment, with external large-pitch cables, and simultaneously performs intermediate gradient profile measurement and electrical sounding. Compared with conventional acquisition devices and methods, it can reduce the range of boundary blind zones and increase exploration depth while ensuring data density.

[0091] Example 3

[0092] See Figure 5 This invention discloses a three-dimensional direct current resistivity data acquisition method, comprising the following steps:

[0093] Step 1: Design several parallel survey lines in the survey area according to the task requirements, namely the first survey line, the second survey line, the third survey line, etc.

[0094] Step 2: Lay out the first measuring line cable and the second measuring line cable respectively, and connect the first cable to both ends of the first measuring line cable located on the first measuring line. Connect the electrode converter to the measuring host. Connect the first measuring line cable and the second measuring line cable to the electrode converter. The first measuring line cable and the second measuring line cable are formed by connecting at least one second cable in series. A plurality of first electrodes are connected on the first cable and a plurality of second electrodes are connected on the second cable. The interval between two adjacent first electrodes connected on the first cable is greater than the interval between two adjacent second electrodes connected on the second cable.

[0095] Step 3: Collect multi-pole mid-gradient depth sounding data on the first survey line to obtain multi-pole mid-gradient depth sounding data;

[0096] The first measuring line is used as the power supply measuring line, and the second measuring line is used as the measurement measuring line. A series of measurement pole spacings and corresponding interval coefficient sequences are defined, and data is collected from the first and second measuring lines by the line mixing device.

[0097] Disconnect the first cable, customize the measurement pole spacing series and the corresponding interval coefficient sequence, and perform data acquisition of the mixing device on the first measurement line;

[0098] Step 4: When there are more than 2 survey lines, move the first survey line cable from the first survey line to the third survey line, disconnect the first cable at both ends of the first survey line cable, and connect the first cable to both ends of the second survey line cable located at the second survey line at this time. Perform multi-pole mid-step depth sounding data acquisition on the second survey line to obtain multi-pole mid-step depth sounding data.

[0099] The second measuring line is used as the power supply measuring line, and the third measuring line is used as the measurement measuring line. A series of measurement pole spacings and corresponding interval coefficient sequences are customized, and data acquisition of the inter-line mixing device is performed on the second and third measuring lines.

[0100] Disconnect the first cable, customize the measurement pole spacing series and the corresponding interval coefficient sequence, and perform data acquisition of the mixing device on the second measurement line;

[0101] When there are more than 3 survey lines, the second survey line cable is moved from the second survey line to the fourth survey line, and the first cable at both ends of the second survey line cable is disconnected. At this time, the first cable is connected to both ends of the first survey line cable located on the third survey line. Multi-pole mid-step depth sounding data is collected on the third survey line to obtain multi-pole mid-step depth sounding data.

[0102] Disconnect the first cable, customize the measurement pole spacing series and the corresponding interval coefficient sequence, and perform data acquisition of the mixing device on the third measurement line;

[0103] The third measuring line is used as the power supply measuring line, and the fourth measuring line is used as the measurement measuring line. A series of measurement pole spacings and corresponding interval coefficient sequences are defined, and data acquisition of the inter-line mixing device is carried out on the third and fourth measuring lines.

[0104] This process is repeated (i.e., rolling survey line measurement) until data collection for all survey lines is completed.

[0105] In some embodiments, the three-dimensional DC electrical resistivity data acquisition method of the present invention further includes step 5: after completing the data acquisition of all survey lines, according to the abnormal data distribution characteristics, horizontally arrange connecting survey lines and supplement the data acquisition of mixed devices within or between lines.

[0106] Based on the characteristics of abnormal data distribution, horizontal connecting survey lines are arranged to supplement the data collection of mixed devices within or between lines. Specifically, based on the profile of the measurement data, the location of suspected anomalies is identified, and multiple horizontal connecting survey lines (perpendicular or oblique to the parallel survey lines) are arranged at the location to conduct densified measurements. The horizontal connecting survey lines can also be used to conduct mixed device measurements within or between lines according to the longitudinal survey lines.

[0107] In some embodiments, multi-pole gradient sounding data acquisition is performed on the i-th survey line, specifically including:

[0108] S1: Use the two first electrodes as power supply electrodes AB and the two second electrodes as measuring electrodes MN. The measuring electrodes MN are located between the power supply electrodes AB. Determine the initial power supply electrode spacing and the measuring electrode spacing.

[0109] S2: Keeping the power supply electrode spacing and the measuring electrode spacing constant, measure point by point along the i-th measuring line to complete one middle ladder sweep measurement;

[0110] S3: Change the electrode spacing of the power supply electrodes AB, repeat step S2 to perform mid-gradient surface scanning measurement, and obtain multi-electrode spacing mid-gradient depth measurement data, i.e., multiple sets of mid-gradient surface scanning data at different depths.

[0111] In some embodiments, after step S3 is completed, the distance of the measuring electrode MN can be changed, and steps S2 to S3 can be repeated to obtain more measurement data.

[0112] In some embodiments, the multi-pole gradient depth acquisition on the i-th survey line further includes: processing and inverting multiple sets of gradient scanning data at different depths to finally obtain a DC electrical resistivity tomography profile at a greater depth.

[0113] The data processing in this invention generally includes: removing "flying points" and terrain correction. Inversion refers to calculating the subsurface true resistivity profile from the measured apparent resistivity profile, which is the final result.

[0114] Taking the multi-pole gradient depth sounding data acquisition on the first survey line as an example, it specifically includes:

[0115] S1: Use the two first electrodes as power supply electrodes AB and the two second electrodes as measuring electrodes MN. The measuring electrodes MN are located between the power supply electrodes AB. Determine the initial power supply electrode spacing and the measuring electrode spacing.

[0116] S2: Keeping the power supply electrode spacing and the measuring electrode spacing constant, measure point by point along the first measuring line to complete one middle ladder sweep measurement;

[0117] S3: Change the electrode spacing of the power supply electrodes AB, repeat step S2 to perform mid-gradient surface scanning measurement, and obtain multi-electrode mid-gradient depth measurement data.

[0118] In some embodiments, data acquisition of the mixing device is performed on the i-th measurement line, specifically including: customizing the measurement pole spacing series and the corresponding interval coefficient sequence, and performing data acquisition of the mixing device within the i-th measurement line.

[0119] In some embodiments, data acquisition of the inter-line mixing device is performed on the Nth and N+1th measurement lines, where N is a positive integer. Specifically, this includes: using the Nth measurement line as the power supply measurement line and the N+1th measurement line as the measurement measurement line, defining a series of measurement pole distances and corresponding interval coefficient sequences, and performing data acquisition of the inter-line mixing device on the Nth and N+1th measurement lines.

[0120] When collecting data from the inter-line mixing device on the Nth and N+1th measurement lines, the first cable can be disconnected and the second electrode of the Nth measurement line can be used as the power supply electrode. Alternatively, when collecting data from the inter-line mixing device on the Nth and N+1th measurement lines, the first cable can be kept connected and the first electrode or / and the second electrode of the Nth measurement line can be used as the power supply electrode.

[0121] Taking the data acquisition of the inter-line mixing device on the first and second measuring lines as an example, the specific steps include: using the first measuring line as the power supply measuring line and the second measuring line as the measurement measuring line, defining a series of measurement pole distances and corresponding interval coefficient sequences, and then acquiring data of the inter-line mixing device on the first and second measuring lines.

[0122] In some embodiments, the setup of the power supply electrode and the measurement electrode can be automatically completed by the high-density electrical resistivity meter host, and the electrode switching in subsequent steps can also be automatically completed by the high-density electrical resistivity meter host. Customizing the measurement electrode spacing series and the corresponding interval coefficient sequence can be automatically completed by the high-density electrical resistivity meter host.

[0123] In some embodiments, when performing mid-gradient surface scanning measurements, the distance between the measuring electrode MN is generally selected as 1 to 2 electrode distances, and the distance between the power supply electrode AB is generally selected as 3 to 5 times the exploration depth.

[0124] In some embodiments, the hybrid device is a combination of at least two devices, including but not limited to: Wenner Alpha (WN_α), Wenner Beta (WN_β), Wenner Gamma (WN_γ), Wenner-Schlumberger (WS), pole-pole (PP), gradient (GD), dipole-dipole (DPDP), pole-dipole (PDP), and positive and negative tripolar devices. The hybrid device is determined according to the task requirements and implementation effect.

[0125] The power supply provides power to the entire system. The electrode converter is connected to the measurement host. The first and second measuring cables are connected to the electrode converter. The first and second measuring cables are formed by connecting at least one second cable in series. The two ends of the first or second measuring cable are respectively connected to a first cable. A plurality of first electrodes are connected to the first cable, and a plurality of second electrodes are connected to the second cable. The interval between two adjacent first electrodes connected to the first cable is greater than the interval between two adjacent second electrodes connected to the second cable.

[0126] In some embodiments, the measuring host is a high-density electrical resistivity meter; the first cable is a large-pitch cable; and the second cable is a conventional cable, such as a centralized cable.

[0127] In some embodiments, the two ends of the first test cable or the second test cable are respectively connected to the first cable through a cable connector. When the test cable is composed of multiple second cables connected in series, two adjacent second cables are connected in series through a cable connector. The electrode converter is connected to the cable connector.

[0128] The first electrodes connected by the two first cables are arranged symmetrically.

[0129] In some embodiments, the spacing between two adjacent first electrodes is n times the spacing between two adjacent second electrodes.

[0130] The power supply for this invention can be a battery box. The high-density electrical resistivity meter main unit can utilize existing commercially available high-density electrical resistivity instruments. The electrode converter is connected to the high-density electrical resistivity meter main unit and is controlled by it for measurement. The battery box is connected to the electrode converter to provide a stable current to the measurement system. Conventional cables are directly connected to the high-density electrical resistivity meter main unit or other conventional cables. Large-pitch cables are connected to conventional cables at the end of the array. Cable connectors are used to connect conventional cables in series, as well as conventional cables and large-pitch cables. Electrodes are used to measure underground potential and current.

[0131] In some embodiments, the high-density electrical resistivity meter host supports a series centralized cable connection, which can connect no less than 4 cables and supports custom acquisition parameters.

[0132] In some embodiments, the electrode converter is controlled by the high-density electrical resistivity instrument host, thereby controlling the electrodes for power supply and measurement.

[0133] In some embodiments, the conventional cable is a centralized cable, and several measuring electrodes can be connected to the cable. Multiple conventional cables can be connected together through the cable connector to form a measuring cable.

[0134] In some embodiments, multiple conventional cables connected in series are connected to an electrode converter to form a conventional measurement arrangement.

[0135] In some embodiments, the large-pitch cable is a centralized cable, on which several power supply electrodes can be connected. The large-pitch cable is connected to the two conventional cables at the end of the conventional measurement arrangement described above via a cable connector.

[0136] In some embodiments, the electrodes connected to the conventional cable and the large-pitch cable are evenly spaced, except that the spacing between the electrodes connected to the large-pitch cable is n times that of the electrodes connected to the conventional cable.

[0137] The process of Example 3 will be described in detail below through specific examples.

[0138] See Figure 5 A three-dimensional direct current resistivity data acquisition method includes the following steps:

[0139] Step 1: Design several survey lines in parallel in the survey area according to the task requirements, including survey lines I, II, and III.

[0140] Step 2: Lay out two high-density measurement line cables, I and II, and connect large-pitch cables to both ends of the I measurement line cable. Then connect the high-density electrical resistivity meter main unit, electrode converter, battery box, electrodes, etc. in sequence.

[0141] Step 3: Set the electrode in the large-pitch cable of measurement line I as the power supply electrode AB, and set the electrode in the conventional cable of measurement line I as the measuring electrode MN. Keep the position of the power supply electrode AB unchanged and the distance of the measuring electrode MN unchanged. Move the measuring electrode MN synchronously from one end of the arrangement to the other end, measure point by point, and complete one mid-step sweep measurement.

[0142] Step 4: Change the distance between the power supply electrodes AB and repeat step 3 to perform mid-gradient surface scanning measurement to obtain multi-pole mid-gradient depth measurement data for rapid data analysis.

[0143] Step 5: Disconnect the large-pole-gap cable, customize the measurement pole-gap series and the corresponding interval coefficient sequence, and collect data from the mixing device within measurement line I;

[0144] Step 6: Use measurement line I as the power supply measurement line and measurement line II as the measurement measurement line. Define the measurement pole spacing series and the corresponding interval coefficient sequence, and collect data from the mixed device between measurement lines I and II.

[0145] Step 7: Move the high-density cable of survey line I to survey line III, and connect large-pitch cables to both ends of the cable of survey line II;

[0146] Step 8: Repeat steps 3 to 7 to complete the data acquisition of multi-pole depth sounding within the line, data acquisition of the mixing device within the line, and data acquisition of the mixing device between lines;

[0147] Step 9: Based on the abnormal distribution characteristics of the data, arrange the connecting survey lines horizontally and supplement the data collection of mixed devices within or between the lines;

[0148] Step 10: Complete the acquisition of three-dimensional high-density electrical resistivity tomography (EDT) data. Figure 6 The following are spatial distribution diagrams of the data of the hybrid device provided in the embodiments of the present invention: (a) is a spatial distribution diagram of the data of the dipole-dipole and intermediate ladder hybrid device; (b) is a spatial distribution diagram of the data of the positive and negative tripolar, intermediate ladder and intermediate ladder sounding hybrid device; and (c) is a spatial distribution diagram of the data of the intermediate ladder and intermediate ladder sounding hybrid device.

[0149] The main measuring instrument is a high-density electrical resistivity meter; the first cable is a large-pole cable; and the second cable is a centralized cable.

[0150] In step 3, the setting of the power supply electrode and the measuring electrode can be completed automatically by the main unit of the high-density electrical resistivity instrument. The electrode switching work in subsequent steps can also be completed automatically by the main unit of the high-density electrical resistivity instrument.

[0151] In step 3, the electrodes in the large-pitch cable are always used as power supply electrodes, and the electrodes in the conventional cable are always used as measurement electrodes.

[0152] In step 3, the distance between the measuring electrode MN is generally selected as 1 to 2 electrode distances, and the distance between the power supply electrode AB is generally selected as 3 to 5 times the exploration depth.

[0153] After step 4 is completed, the distance of the measuring electrode MN can be changed, and steps 3 to 4 can be repeated to obtain more measurement data.

[0154] In steps 5 and 6, the custom measurement pole spacing series and the corresponding interval coefficient sequence can be automatically completed using the high-density electrical resistivity meter host.

[0155] Furthermore, in steps 5 and 6, in some embodiments, the hybrid device is a combination of at least two devices, including but not limited to: Wenner Alpha (WN_α), Wenner Beta (WN_β), Wenner Gamma (WN_γ), Wenner-Schlumberger (WS), pole-pole (PP), gradient (GD), dipole-dipole (DPDP), pole-dipole (PDP), and positive and negative tripolar devices. The hybrid device is determined according to the task requirements and implementation effect.

[0156] When using high-density electrical resistivity tomography (EPT) equipment for exploration, observations are typically conducted using a limited number of given device types. The measurement electrode spacing and interval sizes are relatively fixed, resulting in limited data acquisition, limited exploration depth, and the existence of blind zones. To address this issue, a custom series of measurement electrode spacings and corresponding interval coefficient sequences are used for multi-device combined observations. Compared to conventional devices, this approach enriches the data volume, effectively improves spatial resolution and exploration depth, and reduces blind zones.

[0157] The present invention proposes a three-dimensional DC electrical resistivity tomography (DCEP) data acquisition device and method. By using conventional high-density DCEP equipment, external large-pole-gap cables, a defined composite device, and rolling acquisition of multi-line data, three-dimensional DCEP exploration can be achieved. This can effectively increase the penetration of conductive strata, and the exploration depth is increased by 2 to 4 times compared with traditional methods. While maintaining near-surface resolution, it can effectively increase the lateral resolution in the direction perpendicular to the survey line. Furthermore, rapid data analysis can be achieved by using multi-pole-gap gradient sounding data.

[0158] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for acquiring DC resistivity data, characterized in that, Includes the following steps: Step 1: Lay out the measuring cable along the measuring line, connect the measuring cable to the electrode converter, connect the electrode converter to the measuring host, and connect the two ends of the measuring cable to the first cable. Each measuring cable is composed of at least one second cable connected in series. Several first electrodes are connected to the first cable, and several second electrodes are connected to the second cable. The interval between two adjacent first electrodes connected to the first cable is greater than the interval between two adjacent second electrodes connected to the second cable. Step 2: Use the two first electrodes as power supply electrodes AB and the two second electrodes as measuring electrodes MN. The measuring electrodes MN are located between the power supply electrodes AB. Determine the initial power supply electrode spacing and the measuring electrode spacing. Step 3: Keeping the power supply electrode spacing and the measuring electrode spacing constant, measure point by point along the measurement line to complete one mid-gradient surface measurement; the measurement point corresponding to the measurement data is the midpoint of the measuring electrode MN, and the specific calculation formula for the depth Z of the measurement point is: n≤ 3, Z = 0.18AB; 3 < n≤10, Z = 0.19AB; n>10, Z = 0.25; where n is the interval coefficient and AB is the power supply electrode spacing; Step 4: If the data does not meet the exploration depth requirements, the electrode spacing of the power supply electrodes is increased by equal distances, and Step 3 is repeated to perform the mid-gradient sweep measurement until the data meets the exploration depth requirements. The measurement is completed, and multiple sets of mid-gradient sweep data at different depths are obtained. After step 4 is completed, move the measuring cable parallel to the side measuring line and repeat steps 2-4 to obtain three-dimensional measurement data.

2. The DC resistivity data acquisition method as described in claim 1, characterized in that: It also includes step 5: processing and inverting multiple sets of intermediate gradient scan data at different depths to finally obtain a DC electrical resistivity tomography profile at a greater depth.

3. The DC resistivity data acquisition method as described in claim 1, characterized in that: In step 2, the electrode spacing of the measuring electrode is 1 to 2 electrode distances, and the electrode spacing of the power supply electrode is 3 to 5 times the exploration depth.

4. The DC resistivity data acquisition method as described in claim 1, characterized in that: After completing step 4, change the electrode spacing of the measuring electrodes and repeat steps 3-4.

5. A DC resistivity data acquisition system, characterized in that: The system includes a power supply, a measurement host, an electrode converter, and a measuring cable. The power supply provides power to the entire system. The electrode converter is connected to the measurement host. The measuring cable is connected to the electrode converter. Each end of the measuring cable is connected to a first cable. Each measuring cable is composed of at least one second cable connected in series. Several first electrodes are connected to the first cables. Several second electrodes are connected to the second cables. The interval between two adjacent first electrodes connected to the first cables is greater than the interval between two adjacent second electrodes connected to the second cables. The DC electrical resistivity data acquisition system is used to implement the DC electrical resistivity data acquisition method as described in any one of claims 1 to 4.

6. The DC resistivity data acquisition system as described in claim 5, characterized in that: The main measuring instrument is a high-density electrical resistivity meter; or / and, The first cable is a large-pitch cable; or / and, The second cable is a centralized cable.

7. The DC resistivity data acquisition system as described in claim 5, characterized in that: The two ends of the test cable are connected to the first cable through cable connectors. When the test cable is composed of multiple second cables connected in series, two adjacent second cables are connected in series through cable connectors. The electrode converter is connected to the cable connectors.

8. The DC resistivity data acquisition system as described in claim 5, characterized in that: The interval between two adjacent first electrodes is n times the interval between two adjacent second electrodes, where n>1.

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