Well direct current perspective detection method

Abstract

The invention discloses a well-to-well direct current perspective detection method, which relates to the technical field of exploration and comprises the following steps: S1, measuring a potential value generated by a secondary site; s2, according to a potential value data distribution rule generated by the secondary site, analyzing to obtain an interface position of each stratum; and S3, according to the potential value data generated by the secondary site and the corresponding emission point power supply position and measurement observation point position information, calculating the apparent resistivity value of each stratum by adopting a resistivity method apparent resistivity calculation formula. Position information of a power supply of an emission point, position information of a measurement observation point and potential value data generated by a secondary site are acquired, then the interface position of each stratum is analyzed and obtained according to a distribution rule of potential values generated by the secondary site, and the apparent resistivity of each stratum is calculated and obtained by using an apparent resistivity calculation formula of a resistivity method. Therefore, the exploration purpose is achieved, and high accuracy is achieved.

Description

Technical Field

[0001] The invention relates to the field of exploration technology, in particular to a well direct current electric perspective detection method. Background Art

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

[0003] Single-hole resistivity logging can obtain the resistivity of each layer of ore (rock) at the logging location through measurement by a microelectrode system in the well. The test range is limited to the inside of the electrode system, and the measurement area is limited. Moreover, during the measurement process, the size of the well diameter, the wellbore, and the changes in mud concentration will affect the measurement results. In particular, when there is intrusion, filling material or unevenness on the well wall, the measurement results may be distorted.

[0004] Well resistivity CT is a type of double-hole test method. It arranges electrodes in two boreholes and collects data according to the set working device (such as quadrupole, tripole, and dipole). The data is then inverted and reconstructed to obtain the apparent resistivity value of the ore (rock) between the two wells. The interpretation of the results should refer to the comprehensive analysis of drilling coring and single-hole logging data. Affected by the existing reconstruction algorithm, the results of measuring the apparent resistivity value after tomography are not unique, the detection results have multiple solutions, and there are many false anomalies in the profile, which brings great difficulties to the interpretation of the results; moreover, the reconstruction algorithm has a certain stability and fault tolerance. For small or weak anomalies between wells, it has little disturbance to the normal field, and the weak anomalies cannot be reproduced after iterative calculation of the data. Summary of the invention

[0005] The object of the present invention is to provide a well-to-well direct current electric perspective detection method in view of the problems existing in the above-mentioned single-hole resistivity logging and well-to-well resistivity CT, which utilizes the potential value generated by the secondary field to achieve the purpose of stratigraphic stratification through data processing, and obtains the apparent resistivity of each stratum, and has high accuracy and wide applicability.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for direct current perspective detection of a well, comprising the following contents:

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

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

[0010] Step S3, based on the potential value data generated by the aforementioned secondary field, and the corresponding information on the location of the transmitting point power source and the location of the measurement observation point, the resistivity method apparent resistivity calculation formula is used to calculate the apparent resistivity value (electrical characteristics) of each stratum.

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

[0012]

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

[0014] Measurement of the potential value generated by the secondary field:

[0015] In one scheme, in step S1, the potential value generated by the secondary field is measured by a monopole power supply method. Specifically, first, a power supply electrode is arranged in well 1 as a transmitting point power supply, and a number of measurement observation points are arranged in well 2 from top to bottom. Then, the transmitting point power supply position and 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 obtained by measuring the measuring electrode, and the position information of each measurement observation point is obtained at the same time.

[0016] In another scheme, in step S1, the potential value generated by the secondary field is measured by a bipolar power supply method. Specifically, first, two power supply electrodes are arranged in well 1 as a transmitting point power supply, and a number of measurement observation points are arranged in well 2 from top to bottom. Then, the transmitting point power supply position and 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 obtained by measuring the measuring electrodes, and the position information of each measurement observation point is obtained at the same time.

[0017] In another scheme, in step S1, the potential value generated by the secondary field is measured by the common pole measurement method. Specifically, first, a common pole electrode is arranged in well 1 as an emission point power supply, and a number of measurement observation points are arranged in well 1 from top to bottom. A common pole electrode is arranged in well 2 as an emission point power supply, and a number of measurement observation points are arranged in well 2 from top to bottom. Then, the position of the emission 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 emission point power supply is obtained by measuring with a common pole electrode in another well, and the position information of each measurement observation point is obtained at the same time.

[0018] Analysis of the distribution law of potential values ​​generated by the secondary field:

[0019] In one scheme, in step S2, the distribution law of the potential value data generated by the secondary field is as follows: the potential value generated by the secondary field is gradually distributed, specifically, the potential value is maximum at the interface position and gradually decreases on both sides of the interface as it moves away from the interface, or the potential value is minimum at the interface position and gradually increases on both sides of the interface as it moves away from the interface.

[0020] The specific process of interface analysis and judgment of each layer is as follows:

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

[0022]

[0023]

[0024] Where I is the power supply current at the transmitting point; ρ1 is the resistivity of medium 1 (stratum 1); ρ2 is the resistivity of medium 2 (stratum 2); and The distance between the observation point (x, y, z) measured in medium 1 and the mirror image point of the emission point source about the interface The distance between the observation point (x, y, z) and the transmitting point power source in medium 2

[0025] According to the calculation formula of the potential value generated by this primary field, we can know the size of the potential value generated by this secondary field. Combined with the position data (position information) of the measurement observation point, it is the distribution law of the potential value data generated by this secondary field. Based on this, the potential value data generated by the aforementioned secondary field are analyzed to obtain the interface position of each stratum.

[0026] In this way, according to the gradual distribution of the potential value data generated by the secondary field, the interface position of each layer of the formation is analyzed. The gradual distribution of the secondary potential value is that the interface position is the maximum value and gradually decreases as it moves away from the interface, or the interface position is the minimum value and gradually increases as it moves away from the interface; the interface position can be obtained by analysis.

[0027] In another scheme, the specific process of analyzing and judging the interface of each stratum is as follows: according to the calculation formula of the potential value generated by the secondary field, the rate of change of the potential value generated by the secondary field is derived, and it can be known that the rate of change of the potential value generated by the secondary field, combined with the position data of the measurement observation point, is the distribution law of the potential value data generated by the secondary field. Based on this, the potential value data generated by the aforementioned secondary field is analyzed to obtain the interface position of each stratum. Among them, the distribution of the rate of change of the potential value generated by the secondary field is that it tends to be straightly distributed in various places on both sides of the interface and convexly changes at the interface position. These data tend to be straightly distributed in various places on both sides of the interface, and change abruptly at the interface position. The interface position can be obtained by analysis based on this; compared with the aforementioned gradual distribution law of potential value size, it is easier to distinguish and has better anti-interference performance.

[0028] In another scheme, the above two schemes can be combined, and the above two potential value distribution law analyses and judgments on the interface position can be used together, and then the two interface positions obtained by analysis (the interface position obtained according to the above potential value gradual distribution and the interface position obtained according to the above potential value change rate distribution) can be compared with each other to verify the analysis results, otherwise the analysis can be repeated to serve as a mutual confirmation.

[0029] Due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0030] The present invention acquires the power source location information of the transmitting point, the location information of the measuring observation point and the potential value data generated by the secondary field, and then analyzes the interface position of each layer according to the distribution law of the potential value generated by the secondary field, and calculates the apparent resistivity of each layer using the resistivity method apparent resistivity calculation formula, thereby achieving the exploration purpose with high accuracy. The detection method can be extended and applied to geotechnical engineering survey, resource investigation, slope stability monitoring, earth-rock dam leakage monitoring, pollution source investigation and other aspects, and has great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flow chart of the detection method of the present invention.

[0032] Figure 2 It is a schematic diagram of the electric field parameters of the calculation point power supply in the second layer of dielectric.

[0033] Figure 3 It is a distribution diagram of the potential generated by the primary generating field of the present invention.

[0034] Figure 4 yes Figure 3 Distribution diagram of the potential change rate curve generated by the secondary field.

[0035] Figure 5 This is another potential distribution diagram generated by the secondary field of the present invention.

[0036] Figure 6 This is another potential distribution diagram generated by the secondary field of the present invention.

[0037] Figure 7 It is a layout diagram of point power sources and observation points of the present invention.

[0038] Figure 8 It is a schematic diagram of a simulation example model of the present invention.

[0039] Fig. 9 yes Figure 8 The relationship between the potential value generated by the point source in the second layer of medium and the position of the observation point.

[0040] Fig.10 yes Figure 8 A curve showing the relationship between the rate of change of the potential value generated by a point source in the secondary field of the second-layer medium and the position of the observation point. DETAILED DESCRIPTION

[0041] The specific implementation of the invention is further described below with reference to the accompanying drawings.

[0042] Example

[0043] See also Figure 1 As mentioned above, a well DC electric perspective detection method of the present application includes steps S1-S3, a specific scheme has a combination of monopolar power supply method measurement and the potential value data generated by the secondary field, a gradual distribution law analysis and judgment feature, another specific scheme has a combination of monopolar power supply method measurement and the potential value data generated by the secondary field, a change rate change distribution law analysis and judgment feature, another specific scheme has a combination of monopolar power supply method measurement and the potential value data generated by the secondary field, a gradual change and its change rate change distribution law analysis and judgment feature, another specific scheme has a combination of bipolar power supply method measurement and the potential value data generated by the secondary field, etc., according to the above description and combined with actual conditions to form a number of specific scheme applications, which will not be described one by one here. The following will take some feature combination schemes as an example to explain in detail from the perspective of scheme design, law analysis and experimental demonstration.

[0044] Starting from the conductive electric field established by a point source in different media, this application proposes a well direct current electric perspective detection technology based on the basic theory of the direct current resistivity method, and forms a detection method that can be used in practice and has good detection effects. Data collection, data processing and results interpretation can all be maturely implemented and verified, and can solve many geological problems, such as isolated rocks, karst, goaf, rock-soil interface investigations, etc. This application is a supplement and update to the geophysical exploration method in wells, with high accuracy and wide applicability. It will be explained in detail below.

[0045] (I) The process of establishing the electric field of a point source in a two-layer medium and the process of formula derivation:

[0046] In time domain electrical exploration, the active source direct current method uses electrodes A and B to supply direct current to the area being explored, and the conductive current field in the ground is quickly established. In the process of building a field from scratch, according to the basic theory of electromagnetic field, this short process includes unstable transient electromagnetic induction fields and unstable conductive current fields. After the τ moment (usually a few microseconds), the induced electromagnetic field disappears and the conductive current field tends to be stable. At this time, the primary current field is established.

[0047] According to the law of conservation of electric charge, during a field building process, the conduction charge will not suddenly disappear in the medium, nor will it appear out of nothing. To illustrate the field building process, the following is an example of a two-dimensional space with two layers of medium:

[0048] like Figure 2 As shown, there are two partitioned uniform media in an infinite region, the resistivity of medium 1 is ρ1, the resistivity of medium 2 is ρ2, the interface between the two media is S, and there is a point power source (emitting point power source) A(+I) in medium 1. Before the primary field is stable (t<τ), the initial electric field intensity, initial current density and potential at any position in medium 1 are recorded as: The initial electric field intensity, initial current density and potential at any position in medium 2 are recorded as: The superscript of the symbol is the medium number where the measuring point is located, and the subscript "0" is the initial field.

[0049] Before the stable electric field is established, that is, when the electric field is just applied at point A, at time T→0, the basic boundary conditions of the electric field are met at the interface, that is, the voltage is equal and the normal component of the electric field is continuous, as shown in the following formula:

[0050]

[0051] From the differential form of Ohm's law we can get:

[0052]

[0053] Substituting equations (3) and (4) into equation (2), we obtain:

[0054]

[0055] Write (5) in proportional form:

[0056]

[0057] Equation (6) shows that the current density on both sides of the interface S is not equal and is inversely proportional to the corresponding resistivity. Assuming ρ1<ρ2, we can get:

[0058]

[0059] That is to say, the current density in medium 1 is greater than that in medium 2, which is shown in the figure as a large density of electric line in the low resistance area and a small density of electric line in the high resistance area.

[0060] In order to achieve balance of the electric fields on both sides of the interface S, the current in medium 1 will flow through the S surface to medium 2. According to the law of conservation of electric charge, the current flowing out of the interface is equal to the reduction of the charge in the interface, as shown below:

[0061]

[0062] Among them, q s is the free charge surface density on the interface. Substituting (8) into (7) yields:

[0063] q s >0

[0064] In the process of establishing the electric field, as time t increases, driven by the electric field, more free positive charges gradually accumulate on the interface. When time t→∞, the electric field reaches a stable state, and the charge on the interface reaches a saturated state, that is, the surface charge density no longer changes with time t. The reason why the electric field can eventually reach stability in an infinite region is that the positive charges accumulated on the interface will generate secondary fields in medium 1 and medium 2 respectively according to Coulomb's law. We temporarily call it the surface charge field (subpotential field). The secondary field generated by the surface charge field in medium 1 is abbreviated as The secondary field generated in medium 2 is simply expressed as The secondary field generated by the surface charge is superimposed on the original initial field, balancing the electric field magnitudes on both sides of the interface and achieving final equilibrium.

[0065] Therefore, in medium 1, the potential (total potential) at the observation point (measurement observation point) M1 is the superposition of the normal field and the secondary field:

[0066]

[0067] Similarly, the potential value of observation point M2 in medium 2 can be written as:

[0068]

[0069] Among them, the total field and It can be obtained by connecting the Laplace equation or using the mirror method, and It can be obtained by the method of obtaining the electromotive force based on the point charge of the quasi-static field. This basic content will not be repeated. After the above solution and substituting it into equations (9) and (10), the subpotential field values ​​generated by the surface charge field in medium 1 and medium 2 are finally obtained as follows:

[0070] The subpotential field potential value of the observation point for point power supply observation in medium 1 is:

[0071]

[0072] The subpotential field potential value of the observation point for point power supply observation in medium 2 is:

[0073]

[0074] Where I is the current intensity 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 interface reflection coefficient is The distance between the measured observation point (x, y, z) and the mirror image point of the point source about the interface in medium 1 The distance between the measured observation point (x, y, z) and the point source in medium 2 The transmitting point power source is taken as the origin in one well, and the measuring observation point (x, y, z) is in another well, and the position information of the transmitting point power source and the measuring observation point can be obtained when they are arranged.

[0075] (II) Analysis of the distribution law of the potential value generated by the secondary field (surface charge field) in the two-layer medium

[0076] In order to illustrate the distribution characteristics of the surface charge field of the emission point power source in two media (two strata), a practical example is given below.

[0077] Assume point A as the origin, h = 20m, ρ1 = 10Ω·m, ρ2 = 1000Ω·m, I = 1A, 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 the convenience of analysis, assume that all observation points are located on the z-axis, at this time y = 0, x = 0; Figure 3 As shown in the figure, this is the distribution law of the potential value generated by the surface charge field.

[0078] Figure 3As shown in the figure, the potential generated by the surface charge field is symmetrical about the interface S (z = 20m), and the potential values ​​are all positive. This is because q s >0 is the potential generated by positive charge. The smaller the distance from the surface charge concentration area, the greater the potential. The maximum value appears at the interface S. The maximum value calculation formula can be derived from formula (12) as follows:

[0079]

[0080] The farther away from the interface S, the smaller the potential value. It is easy to calculate from formulas (11) and (12) that the potential value is 0 at infinity. In order to more clearly reflect the position of the interface, the second derivative of the calculated potential value can be calculated, such as Figure 4 As shown, this is the curve characteristic after taking the second derivative of the calculated potential value.

[0081] exist Figure 4 It is easier to distinguish the location of the interface S, especially in the presence of interference data, the potential value change rate curve is more meaningful for reference.

[0082] Let's take another practical example to illustrate. According to the same analysis process as above, the distribution law of surface charge field potential when ρ1 and ρ2 are different values ​​is calculated. The other parameters are the same as the previous example. When ρ1 = 1000Ω·m, ρ2 = 10Ω·m, the distribution law of potential value is as follows: Figure 5 shown.

[0083] like Figure 5 As shown, since the values ​​of ρ1 and ρ2 are exchanged, the charge accumulated on the interface S is negative, so the generated potential is naturally negative, and the minimum potential is also generated at the interface S.

[0084] Let's take another practical example to illustrate. The other parameters are the same as the previous example. When ρ1 = 10Ω·m and ρ2 = 10Ω·m, the potential value distribution law is as follows Figure 6 shown.

[0085] like Figure 6 As shown, since the values ​​of ρ1 and ρ2 are equal, there is no interface S at this time. In other words, there is no interface with electrical difference in space, so there is no accumulated charge, and the potential generated is naturally 0, which also illustrates the correctness of the calculation formula.

[0086] 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, taking the interface position as the maximum value, it gradually decreases on both sides of the interface as the distance from the interface increases, or taking the interface position as the minimum value, it gradually increases on both sides of the interface as the distance from the interface increases. The distribution of the change rate of the potential value generated by this secondary field is that it tends to be flat at each location in the strata on both sides of the interface and bulges at the interface position (bulging and increasing or bulging and decreasing).

[0087] (III). Design of the DC electroscopic detection technology for well-to-well

[0088] 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.

[0089] 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 Figure 7 (b) shows, 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 interface position is analyzed, and then the apparent resistivity is calculated, thus forming the well-to-well DC electroscopic observation method.

[0090] 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 electroscopic detection is divided into three types:

[0091] (1). Bipolar power supply method: As Figure 7 (a) shows, 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 media with different resistivities; a 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 1 finite number (such as 2 or 3, etc.) of measuring electrodes can be arranged from top to bottom at each observation point position in 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 strata is obtained through result superposition; then, using the basic principle of the resistivity method (the above formula (14)), the apparent resistivity data between the two dipoles can be calculated, and based on this, the resistivity magnitudes of each stratum can be determined. This data has high accuracy, strong stability, is not affected by algorithms, and has no false anomalies, etc.

[0092] (2) Unipolar power supply method: Figure 7 As shown in (b), electrode A is placed in well 1 as a point power source, and measuring electrode M is placed in well 2 (if there is only one well, it can also be placed only in well 1). Several measuring points are arranged in sequence from top to bottom. In actual measurement, measuring electrodes can be directly arranged at each observation point for simultaneous measurement, or more than one finite number (such as 2 or 3, etc.) of measuring electrodes can be arranged from top to bottom at each observation point in each segment for measurement. The measurement data is analyzed and processed according to the distribution law of the potential value data generated by the secondary field mentioned above in the present application, and then the resistivity method (the above formula (14)) is used to calculate the apparent resistivity data, and the well formation distribution (interface position) and the resistivity of each formation are also obtained.

[0093] (3) Common-pole measurement method: Figure 7 As shown in (c), a common electrode A (power supply electrode A, also known as measuring electrode M1) is placed in well 1, and a common electrode B (power supply electrode B, also known as measuring electrode M2) is placed in well 2. Several measuring points are arranged in sequence from top to bottom. In actual measurement, measuring electrodes can be directly arranged at each observation point for simultaneous measurement, or more than one limited number (such as 2 or 3) of measuring electrodes can be arranged from top to bottom at each observation point of each segment for measurement (for example, measuring points 1 and 2 are 1 segment, and measuring points 3 and 4 are 2 segments). 2 segments, etc., two measuring electrodes are arranged at measuring points 1 and 2, and then moved down to segment 2 and arranged at measuring points 3 and 4, and so on). During data acquisition, the power supply voltage and loop current between the two are recorded simultaneously. The potential value data distribution law generated by the secondary field mentioned above in the present application is analyzed and processed to obtain the position of the well-to-well stratum interface; 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)). This value more directly reflects the electrical characteristics of the medium, and the resistivity of each layer is determined based on it.

[0094] (IV) Practical effects of DC detection technology in wells

[0095] In order to check the effect of DC detection in wells, a practical simulation was carried out. Figure 8 As shown, there are two layers of medium, the upper medium resistivity is ρ1 = 50Ω·m, ρ2 = 1000Ω·m, the left is well 1, the right is well 2, a point power source is placed in well 1, the coordinates are (-10, 0, -16), the current is 1A, the interface S is located in the middle (x, y, 0), so the point power source is 16m away from the interface, the observation point is located in well 2, the first point coordinates are (10, 0, -16), and the distance between two adjacent observation points is 1m (the smaller the distance, the more accurate). The second method mentioned above, the monopolar power supply method, is used for data acquisition and processing.

[0096] like Fig. 9 As shown in , it is the total potential field curve at the observation point. From the stable field potential diagram, it can be seen that when the observation point and the power point are in the same medium, the potential is relatively high and changes greatly. When the observation point crosses the interface, the potential value becomes smaller and the rate of change is smaller. When the point power source and the observation point are both in medium 1, the initial field is dominant, 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 secondary field strength generated by the surface charge remains unchanged, so the change speed slows down. From Fig. 9 The interface is judged to be at the 0m position, thus achieving the purpose of locating the interface.

[0097] like Fig.10 As shown in the figure, the secondary potential generated by the surface charge field in the medium is extracted, and then the rate of change is calculated to obtain the change curve. It can be seen that there is an abrupt change at one position while the two sides tend to be smooth. The place with a larger rate of change is the interface between the two media, which is consistent with the set model.

[0098] It can be seen that the above verification test shows that the detection method of the present application has accurate and reliable solution results.

[0099] As mentioned above, the technology proposed in the present invention acquires the power source location information of the transmitting point, the location information of the measuring observation point and the potential value data generated by the secondary field, and then analyzes the interface position of each layer according to the distribution law of the potential value generated by the secondary field, and calculates the apparent resistivity of each layer using the resistivity method apparent resistivity calculation formula, thereby achieving the exploration purpose. It is a direct measurement method for the resistivity (or conductivity) of the medium. The measurement data does not need to undergo complex approximate calculations, 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 existing single well and well-to-well resistivity (CT) tomography, which is mainly manifested in the following aspects:

[0100] (1) The purpose of single-hole resistivity logging is to use a micro-gradient electrode system device to measure the resistivity of ore (rock) in a small area of ​​the well wall to achieve the purpose of geological stratification. Generally, the detection range is less than 10 cm, which cannot achieve a large-scale detection around the well and is greatly affected by the measurement environment. The well-to-well direct current detection technology proposed in the present invention also achieves the purpose of stratification, and the detection range covers the distance between wells.

[0101] (2) Well resistivity (CT) tomography can achieve the purpose of measuring the dielectric resistivity between wells, but based on the existing research level, it is well known that its detection results are of low reliability and low resolution. This technology has always been a hot topic in the industry research, all with the goal of improving exploration accuracy. The well DC detection technology of the present invention changes the data acquisition method and data source segmentation, and focuses on using the information segment that can distinguish the boundary. It not only achieves the problem of dielectric stratification and resistivity measurement between wells, but also greatly improves the credibility of the results through direct measurement and calculation, and also enhances the perception of circumference.

[0102] This detection method is a new geophysical exploration technology that can be widely applied to geotechnical engineering investigation, resource survey, slope stability monitoring, earth-rock dam leakage monitoring, pollution source investigation, etc., and has great application prospects.

[0103] It should be pointed out that the examples of the above-mentioned embodiments can be preferably combined with one or more of them according to actual needs, and multiple examples use a set of drawings to illustrate the combined technical features, which will not be described one by one here.

[0104] The above description is a detailed description and illustration of the preferred embodiments of the present invention, but these descriptions are not intended to limit the scope of protection required by the present invention. All equivalent changes or modified modifications achieved under the technical teachings suggested by the present invention should fall within the scope of patent protection covered by the present invention.

Claims

1. A method for direct current perspective detection of a well, characterized in that: Includes the following: Step S1, measuring the potential value generated by the secondary field: 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 and obtaining the potential value generated by the secondary field at each measuring observation point corresponding to the transmitting point power supply; Step S2, analyzing and obtaining the interface position of each layer according to the distribution law of the potential value data generated by the aforementioned secondary field; Step S3, based on the potential value data generated by the aforementioned secondary field, and the corresponding information on the power supply location of the transmitting point and the location of the measuring observation point, the apparent resistivity value of each stratum is calculated using the resistivity method apparent resistivity calculation formula.

2. A method for direct current perspective detection of a well according to claim 1, characterized in that: In step S2, the potential value data distribution law generated by the secondary field is as follows: the potential value generated by the secondary field is gradually distributed, specifically, the potential value is maximum at the interface position and gradually decreases on both sides of the interface as it moves away from the interface, or the potential value is minimum at the interface position and gradually increases on both sides of the interface as it moves away from the interface.

3. A method for direct current perspective detection of a well according to claim 2, characterized in that: In step S2, the specific process of analyzing and judging the interface of each layer is as follows: The calculation formula for determining the potential value generated by the secondary field at each measurement observation point corresponding to the power supply at the emission point is as follows: Where I is the power supply current at the emission point; ρ1 is the resistivity of medium 1; ρ2 is the resistivity of medium 2; and The distance between the observation point (x, y, z) measured in medium 1 and the mirror image point of the emission point source about the interface The distance between the observation point (x, y,)z and the transmitting point power source in medium 2 According to the calculation formula of the potential value generated by the primary field, the size of the potential value generated by the secondary field can be known. Combined with the location information of the measurement observation point, it is the distribution law of the potential value data generated by the secondary field. Based on this, the potential value data generated by the aforementioned secondary field are analyzed to obtain the interface position of each stratum.

4. A method for direct current perspective detection of a well according to claim 3, characterized in that: The specific process of analyzing and judging the interface of each stratum is as follows: according to the calculation formula of the potential value generated by the secondary field, the derivative is performed to obtain the rate of change of the potential value generated by the secondary field. It can be known that the rate of change of the potential value generated by the secondary field, and then combined with the position data of the measurement observation point, it is the distribution law of the potential value data generated by the secondary field. Based on this, the potential value data generated by the aforementioned secondary field are analyzed to obtain the interface position of each stratum; wherein, the distribution of the rate of change of the potential value generated by the secondary field is that it tends to be flat at various locations on both sides of the interface and convexly changes at the interface position.

5. A method for direct current perspective detection of a well according to claim 1, characterized in that: In step S3, the resistivity method apparent resistivity calculation formula of each layer is as follows: Where ρ1 is the apparent resistivity of medium 1; V MN Refers to the potential difference between two measurement observation points M and N in medium 1; I is the current strength of the transmitting point power supply; AM refers to the distance from the transmitting point power supply A to the measurement observation point M, BM refers to the distance from the transmitting point power supply B to the measurement observation point M, AN refers to the distance from the transmitting point power supply A to the measurement observation point N, BN refers to the distance from the transmitting point power supply B to the measurement observation point N. When there is only one transmitting point power supply A, the position of the transmitting point power supply B is set to infinity.

6. A method for direct current perspective detection of a well according to claim 1, characterized in that: In step S1, the potential value generated by the secondary field is measured by a monopole power supply method. Specifically, first, a power supply electrode is arranged in well 1 as a transmitting point power supply, and a plurality of measurement observation points are arranged in well 2 from top to bottom. Then, the transmitting point power supply position and 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 obtained by measuring the measuring electrode, and the position information of each measurement observation point is obtained at the same time.

7. A method for direct current perspective detection of a well according to claim 1, characterized in that: In step S1, the potential value generated by the secondary field is measured by a bipolar power supply method. Specifically, first, two power supply electrodes are arranged in well 1 as a transmitting point power supply, and a number of measurement observation points are arranged in well 2 from top to bottom. Then, the transmitting point power supply position and 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 obtained by measuring the measuring electrodes, and the position information of each measurement observation point is obtained at the same time.

8. A method for direct current perspective detection of a well according to claim 1, characterized in that: In step S1, the potential value generated by the secondary field is measured by a common-pole measurement method. Specifically, first, a common-pole electrode is arranged in well 1 as a transmitting point power source, and a number of measurement observation points are arranged in well 1 from top to bottom. A common-pole electrode is arranged in well 2 as a transmitting point power source, and a number of measurement observation points are arranged in well 2 from top to bottom. Then, the position of the transmitting point power source 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 source is obtained by measuring with a common-pole electrode in another well, and the position information of each measurement observation point is obtained at the same time.

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