A method of well-to-well direct current perspective detection

Abstract

This invention discloses a method for wellbore direct current radiometric exploration, relating to the field of exploration technology. The method includes: Step S1, measuring the potential values ​​generated by a secondary field; Step S2, analyzing the distribution patterns of the potential values ​​generated by the secondary field to determine the interface locations of various strata; Step S3, calculating the apparent resistivity values ​​of each stratum based on the potential value data generated by the secondary field, along with the corresponding power source location and measurement observation point location information, using the apparent resistivity calculation formula of the resistivity method. This invention achieves its exploration objective by collecting and acquiring power source location information, measurement observation point location information, and potential value data generated by the secondary field. It then analyzes the distribution patterns of the potential values ​​generated by the secondary field to determine the interface locations of various strata and calculates the apparent resistivity of each stratum using the apparent resistivity calculation formula of the resistivity method. This method has high accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of exploration technology, in particular to a well-to-well direct current perspective detection method. BACKGROUND

[0002] According to the number of boreholes used, borehole exploration is divided into single-hole testing method and double-hole testing method.

[0003] Single-hole resistivity logging measures the resistivity of ores (rocks) in each layer at the logging position through a micro-electrode system in the well, and the testing range is limited to the inside of the electrode system, the measurement area is limited, and during the measurement process, the size of the well diameter, the wellbore, and the change in mud concentration have an impact on the measurement results, especially when there are intruding or filling materials on the well wall or unevenness, the measurement results may be distorted.

[0004] Well-to-well resistivity CT is a kind of double-hole testing method, which arranges electrodes in two boreholes, collects data according to the set working device (such as four-pole, three-pole, and two-pole), and after data inversion and reconstruction, the apparent resistivity value of the ores (rocks) between the two wells is obtained, and the analysis of the results needs to be comprehensively analyzed with drilling core and single-hole logging data. Influenced by the existing reconstruction algorithm, the measured apparent resistivity value after tomographic imaging is not unique, the detection results have multiple solutions, there are many false anomalies in the profile, which brings great difficulty to the interpretation of the results; moreover, the reconstruction algorithm has certain stability and fault tolerance, and for small or weak anomalies between the wells, the disturbance to the normal field is small, and after iterative calculation of the data, the weak anomalies cannot be reproduced. SUMMARY

[0005] The purpose of the present application is to solve the problems of single-hole resistivity logging and well-to-well resistivity CT, and to provide a well-to-well direct current perspective detection method, which uses the potential value generated by the secondary field, processes the data to achieve the purpose of stratigraphic layering, and obtains the apparent resistivity of each layer, which has high accuracy and wide applicability.

[0006] To achieve the above purpose, the technical solution adopted by the present application is:

[0007] A well-to-well direct current perspective detection method, comprising the following contents:

[0008] Step S1, measuring the potential value generated by the secondary field (surface charge field): arranging a transmitting point power supply and a plurality of measurement observation points in well 1 and well 2 respectively, setting the current intensity I of the transmitting point power supply, and measuring the potential value generated by the secondary field at each measurement observation point corresponding to the transmitting point power supply;

[0009] Step S2, according to the data distribution rule of the potential value generated by the secondary field, analyzing to obtain the position of the interface of each layer;

[0010] Step S3, according to the potential value data generated by the secondary place and the corresponding transmitting point power supply position and the measured observation point position information, the apparent resistivity calculation formula of the resistivity method is used to calculate the apparent resistivity value (electrical characteristic) of each stratum.

[0011] In step S3, the conventional apparent resistivity calculation formula of the resistivity method is used for calculation, that is, the apparent resistivity calculation formula of the resistivity method of each stratum is as follows:

[0012]

[0013] Wherein, ρ1 is the apparent resistivity of medium 1 (stratum 1); V MN The potential difference of two measured observation points M and N in medium 1; I is the current intensity of the transmitting point power supply; AM is the distance from the transmitting point power supply A to the measured observation point M, BM is the distance from the transmitting point power supply B to the measured observation point M, AN is the distance from the transmitting point power supply A to the measured observation point N, and BN is the distance from the transmitting point power supply B to the measured observation point N. When there is only one transmitting point power supply A, the transmitting point power supply B is defined as infinite.

[0014] For the potential value measurement of the secondary place:

[0015] In one scheme, in step S1, the potential value generated by the secondary place is measured by the single-pole power supply method. Specifically, first, a power supply electrode is arranged in well 1 as a transmitting point power supply, and a plurality of measured observation points are arranged in well 2 from top to bottom, then the transmitting point power supply position and the current intensity I are set, and the potential value generated by the secondary place at each measured observation point corresponding to the transmitting point power supply is measured by the measuring electrode, and the position information of each measured observation point is obtained.

[0016] In another scheme, in step S1, the potential value generated by the secondary place is measured by the double-pole power supply method. Specifically, first, two power supply electrodes are arranged in well 1 as transmitting point power supplies, and a plurality of measured observation points are arranged in well 2 from top to bottom, then the transmitting point power supply position and the current intensity I are set, and the potential value generated by the secondary place at each measured observation point corresponding to the transmitting point power supply is measured by the measuring electrode, and the position information of each measured observation point is obtained.

[0017] In another scheme, in step S1, the potential value generated by the secondary field is measured by the common electrode measurement method. Specifically, first, a common electrode is arranged in well 1 as a transmitting point power supply, and a plurality of measurement observation points are arranged in well 1 from top to bottom; a common electrode is arranged in well 2 as a transmitting point power supply, and a plurality of measurement observation points are arranged in well 2 from top to bottom; then, the position of the transmitting point power supply in one well and the current intensity I are set, and the potential value generated by the secondary field at each measurement observation point corresponding to the transmitting point power supply is measured by the common electrode in the other well, and the position information of each measurement observation point is obtained.

[0018] Analysis of the distribution rule of the potential value generated by the secondary field:

[0019] In one scheme, in step S2, the distribution rule of the potential value generated by the secondary field is as follows: the potential value generated by the secondary field gradually changes, specifically, the position of the boundary surface is the maximum value, and gradually decreases on both sides of the boundary surface away from the boundary surface, or the position of the boundary surface is the minimum value, and gradually increases on both sides of the boundary surface away from the boundary surface.

[0020] The specific process of analyzing and determining the boundary surface of each stratum is as follows:

[0021] The calculation formula of the potential value generated by the secondary field at each measurement observation point corresponding to the transmitting point power supply is as follows:

[0022]

[0023] Wherein, I is the current of the transmitting point power supply; ρ1 is the resistivity of medium 1 (stratum 1); ρ2 is the resistivity of medium 2 (stratum 2); and the boundary surface reflection coefficient is The distance between the measurement observation point (x, y, z) in medium 1 and the mirror point of the transmitting point power supply about the boundary surface The distance between the measurement observation point (x, y, z) in medium 2 and the transmitting point power supply

[0024] According to the calculation formula of the potential value generated by the secondary field, the potential value generated by the secondary field can be known, and combined with the position data (position information) of the measurement observation point, the distribution rule of the potential value data generated by the secondary field is obtained, and the boundary surface position of each stratum is obtained by analyzing the potential value data generated by the secondary field.

[0025] In this way, according to the gradual change of the potential value data generated by the secondary field, the boundary surface position of each layer of the stratum is obtained. The gradual change of the potential value is that the position of the boundary surface is the maximum value, and gradually decreases to the stratum on both sides away from the boundary surface, or the position of the boundary surface is the minimum value, and gradually increases to the stratum on both sides away from the boundary surface; and the boundary surface position can be obtained by analysis.

[0026] In another scheme, the specific interface analysis process of each stratum is as follows: the rate of change of the potential value generated by the secondary site is obtained by derivation according to the potential value calculation formula of the secondary site, and the rate of change of the potential value generated by the secondary site is combined with the position data of the measurement observation point, that is, the potential value data distribution law generated by the secondary site, and the interface position of each stratum is obtained by analyzing the potential value data generated by the secondary site. The distribution of the rate of change of the potential value generated by the secondary site is that the potential value generated by the secondary site is respectively distributed flat on both sides of the interface and changes convexly at the interface position. These data are respectively distributed flat on both sides of the interface and change abruptly at the interface position, and the interface position can be obtained by analysis; compared with the gradual distribution law of the potential value, it is easier to distinguish and has better anti-interference performance.

[0027] In another scheme, the two schemes can be combined, the two potential value distribution laws for analyzing and judging the interface position are used together, and then the two interface positions obtained by analysis (the interface position obtained according to the gradual distribution of the potential value and the interface position obtained according to the change distribution of the rate of change of the potential value) are compared with each other to verify the analysis result, otherwise re-analyze, which plays a mutual verification role.

[0028] Due to the adoption of the above technical scheme, the present application has the following beneficial effects:

[0029] The present application acquires the position information of the power supply of the emission point, the position information of the measurement observation point and the potential value data generated by the secondary site, and then analyzes the interface position of each stratum according to the potential value distribution law generated by the secondary site, and calculates the apparent resistivity of each stratum by using the apparent resistivity calculation formula of the resistivity method, so as to achieve the exploration purpose, which has high accuracy. The detection method can be applied to geotechnical engineering investigation, resource investigation, slope stability monitoring, soil and rock dam leakage monitoring, pollution source investigation and the like, and has great application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is the flow chart of the detection method of the present application.

[0031] Figure 2 is the schematic diagram of the electric field parameter of the calculation point power supply in two-layer medium of the present application.

[0032] Figure 3 is the potential value distribution diagram of the primary site of the present application.

[0033] Figure 4 is the potential value distribution diagram of the secondary site of the present application. Figure 3 is the potential change rate curve distribution diagram of the secondary site of the present application.

[0034] Figure 5 is the potential size distribution map of the secondary field generated by the present application.

[0035] Figure 6 is the potential size distribution map of the secondary field generated by the present application.

[0036] Figure 7 is the layout of the point power supply and observation point of the present application.

[0037] Figure 8 is the simulation example model schematic diagram of the present application.

[0038] Figure 9 is Figure 8 is the potential value generated by the point power supply in the two-layer medium and the position curve of the observation point.

[0039] Figure 10 is Figure 8 is the potential value generated by the point power supply in the two-layer medium and the position curve of the observation point. DETAILED DESCRIPTION

[0040] The specific implementation of the application will be further described below in combination with the drawings.

[0041] EMBODIMENT

[0042] Referring to Figure 1 As described above, the well-to-well direct current perspective detection method of the present application includes steps S1-S3, and a specific scheme has a combination of single-pole power supply method measurement and secondary field generated potential value data size gradual change distribution rule analysis and judgment characteristics, another specific scheme has a combination of single-pole power supply method measurement and secondary field generated potential value data change rate change distribution rule analysis and judgment characteristics, another specific scheme has a combination of single-pole power supply method measurement and secondary field generated potential value data size gradual change and its change rate change distribution rule analysis and judgment characteristics, and another specific scheme has a combination of bipolar power supply method measurement and secondary field generated potential value data size gradual change distribution rule analysis and judgment characteristics, etc. can be combined to form several specific schemes according to the foregoing description combined with actual conditions, which will not be described one by one. The following will take some feature combination schemes as examples to explain in detail from the scheme design, rule analysis and test demonstration.

[0043] The application is based on the establishment of conductive electric field of point source in different media and the basic theory of direct current resistivity method, and proposes a well-to-well direct current perspective detection technology, and forms a detection method which can be used in practice and has good detection effect. The data acquisition, data processing and result interpretation can be realized and verified, which can solve many geological problems such as boulder, karst, goaf and rock-soil interface investigation. The application is a supplement and update of well geophysical exploration method, and has high accuracy and wide applicability. The following will be described.

[0044] (1) The establishment process and formula derivation process of electric field of point power supply in two-layer media

[0045] In time domain electrical exploration, active source direct current method is to supply direct current to the area to be explored by electrodes A and B, and the conductive current field in the ground is quickly established. In the process of building from nothing to something, according to the basic theory of electromagnetic field, in this short process, there is an unstable transient electromagnetic induction field and an unstable conductive current field. After τ time (usually several microseconds), the induced electromagnetic field disappears, and the conductive current field tends to be stable, and the primary current field is established at this time.

[0046] According to the law of conservation of electric charge, in the process of building the primary field, the conductive charge will not suddenly disappear in the medium, nor will it come from nothing. In order to explain the process of building the primary field, the following takes two-dimensional space two-layer medium as an example to explain:

[0047] As shown in Figure 2 , there are two kinds of uniform media in the infinite area, the resistivity of medium 1 is ρ1, the resistivity of medium 2 is ρ2, and the interface of the two media is S. There is a point power supply (transmitting point power supply) A (+I) in medium 1. Before the primary field is stable (t<τ), the initial electric field intensity, initial current density and potential of any position in medium 1 are respectively: The initial electric field intensity, initial current density and potential of any position in medium 2 are respectively: Where the upper index of the symbol is the medium number where the measuring point is located, and the lower index "0" is the initial field.

[0048] Before the stable electric field is established, that is, when T→0, at the interface, the basic boundary conditions of electric field are satisfied, that is, the voltage is equal and the electric field normal component is continuous, as shown in the following formula:

[0049]

[0050] From the differential form of Ohm's law, we can get:

[0051]

[0052] Substitute (3) and (4) into (2) to get:

[0053]

[0054] Write (5) in proportional form:

[0055]

[0056] (6) shows that the current density on both sides of the interface S is not equal, and is inversely proportional to the size of the corresponding resistivity. Assuming ρ1< ρ2, we get:

[0057]

[0058] That is, the current density in medium 1 is greater than that in medium 2, which is manifested in the figure as a large power line density in the low resistance area and a small power line density in the high resistance area.

[0059] In order to achieve balance on both sides of the interface S, the current in medium 1 will flow through S to medium 2. According to the law of conservation of electric charge, the current flowing out of the interface is equal to the decrease in charge in the interface, which is shown as follows:

[0060]

[0061] Where q s is the surface charge density on the interface, and (8) is substituted into (7) to easily know:

[0062] q s > 0

[0063] During the establishment of the electric field, with the increase of time t, the charge gradually accumulates more free positive charge on the interface under the driving of the electric field. When time t→∞, the electric field reaches a stable state, and the charge on the interface reaches a saturation state, that is, the surface charge density no longer changes with time t. The reason why the electric field eventually reaches stability in the infinite region is that the positive charge accumulated on the interface will generate a secondary field in medium 1 and medium 2 according to Coulomb's law, which we temporarily call the surface charge field (secondary potential field). The secondary field generated by the surface charge in medium 1 is simply denoted as The secondary field generated in medium 2 is simply denoted as The secondary field generated by the surface charge superimposes the original initial field, balancing the electric field values on both sides of the interface, and reaching the final balance.

[0064] Therefore, in medium 1, the potential (total potential) at observation point (measurement observation point) M1 is the superposition of the normal field and the secondary field:

[0065]

[0066] Similarly, the potential value of the observation point M2 in the medium 2 can be written as:

[0067]

[0068] where the total field and can be obtained by solving Laplace equation or using mirror method, and can be obtained by the method of calculating the electromotive force according to the point charge in the quasi-electrostatic field, and the basic content will not be repeated. After the above solving and substituting into equations (9) and (10), the numerical value of the secondary potential field generated by the surface charge field in medium 1 and medium 2 is as follows:

[0069] The potential value of the observation point of the point source observed in the medium 1 is:

[0070]

[0071] The potential value of the observation point of the point source observed in the medium 2 is:

[0072]

[0073] where I is the current intensity of the transmitting point source; ρ1 is the resistivity of medium 1 (formation 1); ρ2 is the resistivity of medium 2 (formation 2); the interface reflection coefficient The distance between the measurement observation point (x, y, z) and the mirror point of the point source about the interface in the medium 1 The distance between the measurement observation point (x, y, z) and the mirror point of the point source about the interface in the medium 2 where the transmitting point source is taken as the origin in one well, and the measurement observation point (x, y, z) is in another well, and the position information of the transmitting point source and the measurement observation point can be obtained when they are arranged.

[0074] (II) Analysis of the distribution law of the potential value generated by the secondary field (surface charge field) in the two-layer medium

[0075] In order to illustrate the distribution characteristics of the surface charge field of the transmitting point source in two media (two formations), an actual example is given as follows.

[0076] Let A point be the origin, h = 20 m, ρ1 = 10 Ω·m, ρ2 = 1000 Ω·m, I = 1 A, therefore, according to equations (11) and (12), the potential value generated by the surface charge field at any position in medium 1 and medium 2 can be calculated. For ease of analysis, it is assumed that all observation points are located on the z-axis, that is, y = 0, x = 0; as shown in FIG. 2, it is the distribution law of the potential value generated by the surface charge field. Figure 3

[0077] Figure 3 ​The potential generated by the surface charge field is symmetrical at the interface S (z = 20 m) and the potential values are all positive, because q s > 0 is the potential generated by the positive charge, the smaller the distance from the surface charge concentration area, the greater the potential, and the maximum value appears at the interface S. The maximum value calculation formula can be derived from formula (12) as follows:

[0078]

[0079] The farther away from the interface S, the smaller the potential value. From formula (11) and (12), it is easy to calculate that the potential value at infinity is 0. In order to more obviously reflect the position of the interface, the second derivative of the calculated potential value can be taken, as shown in Figure 4 , which is the curve characteristics after taking the second derivative of the calculated potential value.

[0080] In Figure 4 , it is easier to distinguish the position of the interface S, especially in the presence of interference data, the potential value rate curve is more meaningful.

[0081] The following is another practical example to illustrate that according to the same analysis process as described above, the potential distribution law of the surface charge field when ρ1 and ρ2 are different values. The remaining parameters are the same as in the previous example. When ρ1 = 1000 Ω·m and ρ2 = 10 Ω·m, the potential value distribution law is as shown in Figure 5 .

[0082] As shown in Figure 5 , because the values of ρ1 and ρ2 are exchanged, the charge concentrated on the interface S is negative, so the potential generated is naturally negative, and the minimum potential also occurs at the interface S.

[0083] The following is another practical example to illustrate that the remaining parameters are the same as in the previous example. When ρ1 = 10 Ω·m and ρ2 = 10 Ω·m, the potential value distribution law is as shown in Figure 6 .

[0084] As shown in Figure 6 , because the values of ρ1 and ρ2 are equal, there is no interface S, that is, there is no electrically different interface in space, and there is no charge concentration, so the potential generated is naturally 0, which also illustrates the correctness of the calculation formula.

[0085] Therefore, the distribution law of the potential value data generated by this secondary field is as follows: The magnitude of the potential value generated by this secondary field changes gradually. Specifically, the position of the interface is the maximum value, and on both sides of the interface, it gradually decreases as the distance from the interface increases, or the position of the interface is the minimum value, and on both sides of the interface, it gradually increases as the distance from the interface increases. The distribution of the change rate of the potential value generated by this secondary field is that on both sides of the interface, the formation at each location tends to be flat and bulges at the interface position (bulging and increasing or bulging and decreasing).

[0086] (III). Design of the DC electrogeophysical logging technology

[0087] The above simulations in (I) and (II) are a forward calculation and reasoning process, which is to analyze the variation law of the potential field in a determined electrical structure. Then, given the variation law of the potential value generated by this secondary field, the electrical structure characteristics of the medium can also be inversely deduced and analyzed.

[0088] In order to simplify the analysis process in the above simulations in (I) and (II), it is assumed that y = 0 and x = 0. When y ≠ 0 and x = 0, as shown in (b) of Figure 7 , it is the situation where the observation point deviates from the A pole by a certain distance in the horizontal direction. If the position where the A point is located is defined as the position of Well 1, and another Well 2 is arranged deviating from the A point, and a number of observation points are arranged successively from top to bottom in Well 2. According to the above distribution law, the position of the interface is analyzed, and then the apparent resistivity is calculated, thus forming the DC electrogeophysical logging observation method.

[0089] Based on the principle of solving the potential field of the surface charge field in different media and the distribution law of the potential value data generated by this secondary field, the data acquisition (measuring the potential value generated by this secondary field at the observation point) of the DC electrogeophysical logging is divided into three types:

[0090] (1). Bipolar power supply method: As shown in (a) of Figure 7 , two electrodes A and B are arranged in Well 1 as the power supply dipole. The distance r between the two points is as small as possible, preferably satisfying r << d, where d is the thickness of the medium with different resistivity; the measuring electrode M is arranged in Well 2, and a number of measuring points are arranged successively from top to bottom. In actual measurement, the measuring electrodes can be directly arranged at each observation point position for simultaneous measurement, or more than one finite number (such as 2 or 3, etc.) of measuring electrodes can be arranged successively from top to bottom at each observation point position of each segment for measurement. The data layer combinations collected are respectively applied to the above distribution law of the potential value data generated by this secondary field to obtain each component interface, and then the overall distribution of the well-to-well formation is obtained through result superposition; then, based on the basic principle of the resistivity method (the above formula (14)), the apparent resistivity data between the two dipoles can be calculated, and accordingly, the resistivity magnitudes of each formation can be determined. This data has high accuracy, strong stability, is not affected by algorithms, and has no false anomalies, etc.

[0091] (2), single pole power supply method: as shown in (b) in Figure 7 , the A electrode is arranged in the well 1 as a point power supply, and the measurement electrode M is arranged in the well 2 (if there is only one well, it can also be arranged only in the well 1), and several measurement points are arranged from top to bottom in turn, and in actual measurement, the measurement electrode can be directly arranged at each observation point position respectively and measured at the same time, or one or more limited number (such as 2 or 3, etc.) measurement electrodes can be arranged from top to bottom in each segment at each observation point position to measure, and the measurement data is analyzed and processed through the potential value data distribution law of the secondary field generated by the above formula (14), and then the apparent resistivity data is calculated by the resistivity method (the above formula (14)), and the well-well formation distribution (interface position) and the resistivity of each formation are obtained.

[0092] (3), common pole measurement method: as shown in (c) in Figure 7 , the common pole electrode A (as the power supply electrode A, and the measurement electrode M1) is arranged in the well 1, and the common pole electrode B (as the power supply electrode B, and the measurement electrode M2) is arranged in the well 2, and several measurement points are arranged from top to bottom in turn, and in actual measurement, the measurement electrode can be directly arranged at each observation point position respectively and measured at the same time, or one or more limited number (such as 2 or 3, etc.) measurement electrodes can be arranged from top to bottom in each segment at each observation point position to measure (for example, measurement points 1 and 2 are 1 segment, measurement points 3 and 4 are 2 segment, etc., two measurement electrodes are arranged at measurement points 1 and 2, and then moved to 2 segment to be arranged at measurement points 3 and 4, and so on), and the power supply voltage and loop current between the two are recorded at the same time during data collection, and the well-well formation interface position is obtained by analyzing and processing the potential value data distribution law of the secondary field generated by the above formula (14); the true resistivity value at the corresponding depth between the wells is calculated by Ohm's law and the resistivity method (the above formula (14)), which more directly reflects the electrical characteristics of the medium, and the resistivity of each layer is determined accordingly.

[0093] (Four), practical effect of well-well direct current detection technology

[0094] In order to check the effect of well-well direct current detection, verification is carried out through practice simulation. As shown in Figure 8 , two-layer medium, the upper medium resistivity is ρ1=50Ω·m, ρ2=1000Ω·m, the left is well 1, and the right is well 2, a point power supply is placed in well 1, the coordinates are (-10, 0, -16), the current size is 1A, the interface S is located in the middle (x, y, 0), so the distance between the point power supply and the interface is 16m, and the observation point is located in well 2, the first point coordinate is (10, 0, -16), and the distance between the adjacent two observation points is 1m (the smaller the distance, the more accurate). The second method of single pole power supply method is used for data collection and processing.

[0095] As Figure 9 shown, is the total potential field curve at the observation point. As can be seen from the stable field potential diagram, when the observation point and the power point are in one medium, the potential is relatively high and changes greatly, when the observation point crosses the interface, the potential value becomes small and the change rate is small. When the point power source and the observation point are in medium 1, the initial field dominates, and the secondary field generated by the surface charge is relatively weak. When crossing the interface to medium 2, the effect of the initialization field is weakened, but the strength of the secondary field generated by the surface charge is unchanged, so the change speed becomes slow. From Figure 9 it can be judged that the interface is at the position of 0m, and the purpose of interface positioning is achieved.

[0096] As Figure 10 shown, the secondary potential generated by the surface charge in the medium is extracted, and then the change rate is calculated to obtain the change curve. It can be seen that there is a position with abrupt change and both sides tend to be flat, and the place with large change rate is the position of the interface between the two media, which is consistent with the set model.

[0097] It can be seen from the above verification test that the detection method of the application is accurate and reliable.

[0098] As described above, the technology proposed by the application acquires the position information of the transmitting point power source, measures the position information of the observation point, and obtains the potential value data generated by the secondary field, and then analyzes the interface position of each stratum according to the potential value distribution law generated by the secondary field. The apparent resistivity of each stratum is calculated by using the apparent resistivity calculation formula of the resistivity method, so as to achieve the exploration purpose. It is a direct measurement method of medium resistivity (or conductivity), and the measurement data does not need to go through complex approximate calculation, and the mathematical operation process is simple. As long as the measurement data is true and reliable, the result is stable and reliable, which makes up for the technical problems of the existing single well and well resistivity (CT) tomography, mainly in the following aspects:

[0099] (1) The purpose of single-hole resistivity logging is to measure the resistivity of a small range of ore (rock) on the well wall by using a micro-gradient electrode system device to achieve the purpose of geological layering. The detection range is less than 10cm, which cannot achieve large-scale detection around the well, and is greatly affected by the measurement environment; the well-to-well direct current detection technology proposed by the application also achieves the purpose of layering, and the detection range covers between the wells.

[0100] (2) Well-well resistivity (CT) tomography can achieve the purpose of measuring the medium resistivity between wells, but based on the existing research level, it is well known that the reliability of the detection results is low, and the resolution is low. This technology has always been a research hotspot in the industry, and the goal is to improve the exploration accuracy. The well-well direct current detection technology of the present application changes the data acquisition method and data source segmentation, and focuses on using the information segment that can distinguish the boundary. Not only can it achieve the problem of medium layering and resistivity measurement between wells, but also greatly improve the reliability of the results through direct measurement and calculation, and enhance the perception ability of the winding.

[0101] This detection method is a new geophysical exploration technology, which can be widely applied to geotechnical engineering investigation, resource investigation, slope stability monitoring, soil and rock dam leakage monitoring, pollution source investigation and other aspects, and has great application prospect.

[0102] It should be pointed out that the examples of the above-mentioned embodiments can be preferred one or more than two combinations according to actual needs, and a set of combined technical features is used for the description of multiple examples, which will not be described one by one here.

[0103] The above description is a detailed description and example of the preferred embodiment of the present application, but these descriptions are not used to limit the scope of the patent protection required by the present application. Any equivalent changes or modifications made under the technical guidance of the present application should belong to the scope of the patent protection covered by the present application.

Claims

1. A method of borehole direct current perspective detection, characterized in that, The method comprises the following steps: Step S1, measuring the potential value generated by the secondary place: arranging a transmitting point power supply and a plurality of measuring observation points in well 1 and well 2 respectively, setting the current intensity I of the transmitting point power supply, and measuring the potential value generated by the secondary place at each measuring observation point corresponding to the transmitting point power supply; Step S2, analyzing the position of the interface of each formation according to the distribution rule of the potential value generated by the secondary place; Step S3, calculating the apparent resistivity value of each formation by using the apparent resistivity calculation formula of the resistivity method according to the potential value generated by the secondary place and the position information of the transmitting point power supply and the measuring observation point corresponding thereto; In step S2, the distribution rule of the potential value generated by the secondary place is as follows: the potential value generated by the secondary place gradually changes, specifically, the position of the interface is the maximum value, and gradually decreases on both sides of the interface away from the interface, or the position of the interface is the minimum value, and gradually increases on both sides of the interface away from the interface; In step S2, the specific process of analyzing and judging the position of the interface of each formation is as follows: The calculation formula of the potential value generated by the secondary place corresponding to the transmitting point power supply is as follows: wherein, is the secondary potential field potential value of the observation point observed in medium 1 for the point source observation; is the secondary potential field potential value of the observation point observed in medium 2 for the point source observation; I is the transmitting point source current; p1 is the resistivity of medium 1; p2 is the resistivity of medium 2; is the boundary reflection coefficient is the distance between the observation point (x, y, z) and the mirror point of the transmitting point source with respect to the boundary in medium 1 is the distance between the observation point (x, y, z) and the transmitting point source in medium 2 According to the calculation formula of the potential value generated by the secondary place, the potential value generated by the secondary place can be known, and the rate of change of the potential value generated by the secondary place can be obtained by derivation, that is, the rate of change of the potential value generated by the secondary place, and the position data of the measuring observation point, that is, the distribution rule of the potential value generated by the secondary place, and the position of the interface of each formation is analyzed according to the potential value generated by the secondary place; wherein the distribution of the rate of change of the potential value generated by the secondary place is that the potential value generated by the secondary place gradually changes on both sides of the interface.

2. A method of borehole DC perspective logging according to claim 1, characterized in that: In step S3, the apparent resistivity calculation formula of the resistivity method of each formation is as follows: wherein, p1 is the apparent resistivity of medium 1; V MN denotes the potential difference between two measurement observation points M and N in medium 1; I is the current intensity of the transmitting power source; AM denotes the distance from the transmitting power source A to the measurement observation point M, BM denotes the distance from the transmitting power source B to the measurement observation point M, AN denotes the distance from the transmitting power source A to the measurement observation point N, and BN denotes the distance from the transmitting power source B to the measurement observation point N, and when there is only one transmitting power source A, the position of the transmitting power source B is set to be infinitely far away.

3. A method for borehole-to-borehole direct current perspective investigation according to claim 1, characterized in that: In step S1, the potential value generated by the secondary place is measured by the single-pole power supply method, specifically, first, a power supply electrode is arranged in well 1 as a transmitting point power supply, and a plurality of measuring observation points are arranged in well 2 from top to bottom, then the position of the transmitting point power supply and the current intensity I are set, and the potential value generated by the secondary place at each measuring observation point corresponding to the transmitting point power supply is measured by a measuring electrode, and the position information of each measuring observation point is obtained.

4. A method for borehole DC perspective logging according to claim 1, characterized in that: In step S1, the potential value generated by the secondary place is measured by the double-pole power supply method, specifically, first, two power supply electrodes are arranged in well 1 as transmitting point power supplies, and a plurality of measuring observation points are arranged in well 2 from top to bottom, then the position of the transmitting point power supply and the current intensity I are set, and the potential value generated by the secondary place at each measuring observation point corresponding to the transmitting point power supply is measured by a measuring electrode, and the position information of each measuring observation point is obtained.

5. The method of claim 1 wherein: the well is a borehole. In the step S1, the potential value generated by the secondary field is measured by the common electrode measurement method. Specifically, first, the common electrode is arranged in the well 1 as a transmitting point power supply, and a plurality of measurement observation points are arranged in the well 1 from top to bottom. The common electrode is arranged in the well 2 as a transmitting point power supply, and a plurality of measurement observation points are arranged in the well 2 from top to bottom. Then, the position of the transmitting point power supply and the current intensity I in one well are set, and the potential value generated by the secondary field at each measurement observation point corresponding to the transmitting point power supply is measured by the common electrode in the other well, and the position information of each measurement observation point is obtained.

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