Method for eliminating influence of roadways and terrains on apparent resistivity in direct-current exploration

Abstract

The invention discloses a method for eliminating the influence of roadways and terrains on the apparent resistivity in direct-current exploration. The method comprises the following steps of establishing a model according to a roadway shape, the roadway cutting depth, topographic relief elevation and the like; taking the minimum value of the formation resistivity of an exploration area as the resistivity of a uniform half-space containing the roadways and the terrains; putting a power supply electrode at a corresponding position in the model according to the type of the adopted device for direct-current exploration and the electrode distribution mode; performing one-time three-dimensional numerical simulation every time the power supply electrode moves, obtaining potential response of a background field, and interpolating to obtain potential difference between receiving electrodes as potential difference of the background field; deducing an apparent resistivity formula from a potential formula of a point current source in the horizontal uniform self-space; and subtracting the potential difference of the background field from the measured potential difference to obtain potential different without the influence of the roadways and the terrains, and substituting the potential difference into an apparent resistivity formula of a current source in an underground self-space to obtain the relative apparent resistivity. The method can be widely applied to direct-current resistivity exploration projects.

Description

technical field [0001] The invention belongs to the field of electrical and electromagnetic prospecting, and in particular relates to a technology for eliminating the influence of tunnels and topography on apparent resistivity in DC resistivity prospecting. Background technique [0002] Apparent resistivity is one of the important methods for interpretation of electrical prospecting data. In the detection of underground and surface direct current methods, the apparent resistivity distortion affected by the roadway and terrain is often mixed with the abnormality of geological targets, leading to interpretation errors and even misjudgments. The roadway effect is a distortion of the normal distribution of the constant current field, which is related to various factors such as the device form, the pole layout method, the degree of terrain undulation, the geometric shape of the roadway, and the conductivity of the formation. This effect is nonlinear with the change of the power ...

AI Technical Summary

Problems solved by technology

[0004] 1. In the underground and ground direct current method detection, the apparent resistivity distortion affected by the roadway and terrain is often mixed with the abnormality of the geological target, resulting in interpretation errors or even misjudgments;

[0005] 2. The impact of the roadway is related to various factors such as the device type, the pole layout method, the degree of terrain undulation, the geometric shape of the roadway, and the conductivity of the formation, and it changes nonlinearly with the distance between the power supply and the electrode. It is difficult to find the influencing factors to achieve correction;

[0006] 3. The usual method of correcting the influence of terrain by ratio is difficult to determine the uniform half-space resistivity value for simulating pure terrain response. When the underground electrical structure becomes complex, the accuracy of this correction method is reduced, and even wrong results are obtained;

[0007] 4. If relying entirely on 3D numerical inversion including roadways and topography, apparent resistivity, an essential component of data interpretation, will be missing

Moreover, the 3D inversion itself still has problems such as instability and high non-uniqueness;

[0008] 5. The original underground and surface DC apparent resistivities are derived from the potential formula of the current source on the surface of the uniform half space and the potential formula of the current source in the uniform full space, respectively, and cannot be used universally

For underground exploration close to the ground, the original apparent resistivity derived from the potential formula of the current source in uniform full space has a large error

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